Sunday, April 26, 2009
Saturday, April 25, 2009
Power Production from a Moderate -Temperature Geothermal Resource
ABSTRACT
Organic Rankine Cycle power production from low temperature resources has inherently a low thermal efficiency. Low efficiency requires increased power plant equipment size (turbine, condenser, pump and boiler) that can become cost prohibitive. The use of ORC power plant hardware derived from air-conditioning equipment overcomes this cost problem since air-conditioning hardware has a cost structure almost an order of magnitude smaller than that of traditional power generating equipment.
Using the HVAC derivative concept a low-cost 200 kW ORC power plant has been developed as a derivative of a standard 350 ton air-conditioning equipment. The corresponding PureCycleTM200 product was introduced in 2004. It uses waste heat exhaust gases and air-cooled condenser equipment. This paper describes the extension of this ORC development work towards power production from moderate-temperature geothermal resources.
1. BACKGROUND (ORIGIN OF THE IDEA)
Compressors in HVAC and refrigeration installations are known to start running in reverse after system shut-down unless special provisions are in place to prevent that. Reverse operation can be detrimental for certain type of positive displacement compressors, e.g. scroll and screw compressors, requiring a check valve in the compressor discharge line to prevent reverse rotation. Turbo-compressors, such as the centrifugal compressors used on water-cooled chillers, can easily be designed to handle temporary reverse rotation following system shut-down. After system shutdown pressure equalization takes place between the condenser and the evaporator. During that process refrigerant flashes/boils in the condenser and condenses in the evaporator, temporarily reversing the original design roles of these heat exchangers with heat now being rejected to the chilled water loop and extracted from the cooling tower water loop. Figure 1 compares the normal operation of the refrigeration or vapor compression cycle with its operation during pressure equalization.
The rotational speed of the turbo-compressor is immediately reversed after shutdown. The time required for pressure equalization depends on the amount of refrigerant charge in the condenser and evaporator relative to the size of the compressor and whether or not the cooling tower and chilled water pumps are stopped. Pressure equalization takes typically place within half a minute. One of the qualification tests a water-cooled chiller centrifugal compressor has to go through during its development phase is the sudden power failure test. Since the heat transfer between refrigerant and water is reversed during pressure equalization, the entering condenser water is temporarily cooled down and the water entering the cooler/evaporator is temporarily warmed up. Figure 2 compares chiller behavior at normal operating conditions versus that after shut down during pressure equalization.
During the development of the 19XR centrifugal chiller, which uses a compressor with a discrete passage diffuser as opposed to the vaneless diffuser concept used on previous designs, high reverse rotational speed was observed after shutdown. Reverse rotational speeds up to 75% of the original speed were now seen. The explanation for this phenomenon is that the discrete diffuser passages introduced for better pressure recovery in the diffuser and therefore higher compressor efficiency act as perfect turbine nozzles during pressure equalization. This observation triggered the idea to actually use this compressor as a turbine. Figure 3 shows how the impeller/pipe diffuser combination of a centrifugal compressor can act as the perfect nozzle/rotor combination for a radial inflow turbine when flow direction and rotor speed are reversed.
2. THE COST ADVANTAGE OF USING AIR-CONDITIONING EQUIPMENT FOR POWER GENERATION
Thanks to equipment standardization and high-volume production, air-conditioning and refrigeration equipment is available at a cost of around $ 200 - $ 300 per kW electric motor input. For example, the cost of a 1500 kW centrifugal chiller with a 300 kW electric motor varies, depending on options, from $ 60,000 to $ 90,000. The equipment cost of multi-megawatt conventional power generation equipment is an order of magnitude higher ($ 1,200 – 1,500 per kW generator output). Even higher cost is encountered for smaller (100 to 2000 kW) distributed power generation equipment. Reciprocating engines are the exception at $ 500 per kW, but these engines have emission problems and suffer from high maintenance costs.
Industrial processes generate large amounts of waste heat. Waste-heat-driven steam power plants are often not economical, especially for capacities below 5 MW and for low-temperature waste-heat streams. In those cases waste heat power recovery has been attempted with Organic Rankine Cycle (ORC) machines. Due to high cost of the equipment, the penetration of this technology has been limited to specific niche markets such as geothermal. Moreover, most ORC applications have been heavily subsidized. The reason for high equipment cost is that current ORC systems utilize low-volume power equipment hardware. Waste heat power recovery systems are inherently limited in thermal efficiency due to the relatively low temperature of waste heat. Consequently, a waste heat power generating ORC system requires larger capacity components (boiler, condenser, turbine and pump) for equivalent power output than conventional fuel fired power generation equipment. This causes high overall system cost. Efforts to improve the ORC cost structure by focussing on thermal efficiency enhancements have not been successful in bringing the system cost down to a level that would allow a large market penetration. The absence of fuel cost means that the economically correct metric to be used for waste-heat power recovery systems is its cost per unit of power generating capacity ($/kWel). Better efficiency is only beneficial as far as it results in lower equipment/installation cost since the waste heat is free.
3. R-245fa, THE ENABLING REFRIGERANT FOR AIR-COOLED ORC SYSTEMS
Given the lower cost structure of HVAC equipment versus power generating equipment, and the apparently good turbine action of the centrifugal compressor during power outages, it was decided to design an ORC system using HVAC hardware to the maximum extend possible. Only minor equipment modifications - not fundamentally affecting the equipment - were allowed. For example, modifying equipment to achieve higher cycle efficiency by going to higher boiler temperatures was only allowed if the resulting improvement in efficiency would result in a lower-cost overall product without too much additional development work.
Air-conditioning equipment is only cost effective if it is used to its full design capability. Temperature/working fluid combinations that result in a turbine power output less than the power input of the existing compressor would not fully utilize the potential of this compressor hardware during turbine operation and would therefore result in higher equipment cost per unit power delivered. Conversely, temperature/working fluid combinations that result in a turbine power output higher than the power input of the corresponding compressor hardware would exceed the mechanical limits (e.g. gear and shaft torque limits and bearing loading limits) of the original compressor design. Modifications to overcome those limits were only allowed if the net cost per unit power delivered would reduce, again without too much additional development work.
In order to preserve the cost advantage of the HVAC compressor as an ORC turbine it was found that the maximum temperature and pressure the turbine is seeing should be within the capabilities of the existing compressor housing. Moreover, to take full advantage of the given compressor hardware in turbine operation the power density of the turbine should be equal to that of the compressor. This allows unaltered use of the electrical and mechanical components of the centrifugal compressor. In other words, if a 200 kW compressor is used in an ORC application, the pressure-flow characteristics of the working fluid in the ORC system have to result in a 200 kW turbine output. Using R-134a, the working fluid used for the chiller application, as working fluid for the ORC application, would result in unacceptably high operating pressures requiring major redesign. Therefore, a lower-pressure working fluid is required for the higher- temperature operational regime of the organic Rankine cycle.
The non-flammable and non-toxic refrigerants promoted in the past as attractive fluids for organic Rankine cycle systems [1] have all been outlawed because of their ozone layer depletion potential. The HFC refrigerants introduced during the last decade to replace the CFC and HCFC refrigerants, such as R-134a, R-407C and R410A, have relatively low critical temperatures resulting in low ORC cycle efficiencies [2]. These refrigerants also would result in very high evaporator and turbine inlet pressures. This only leaves flammable and sometimes also highly toxic hydrocarbon fluids, such as pentane and toluene, as the fluids currently used on ORC installations. Apart from the flammability and toxicity issues, these fluids would, If applied to existing HVAC compressor hardware, fail to achieve the required turbine power density given their low vapor density at moderate temperature levels. These fluids would need larger turbine and condenser equipment than is available in the HVAC industry.
4. EXISTING INSTALLATIONS
Three 200 kW power producing installations using different waste heat sources have been in operation since January 2004. The exhaust heat of an Pratt and Whitney FT12 gas turbine is used as heat input source for the organic Rankine cycle in East-Hartford, CT. A second installation uses the heat from a landfill flare in Austin, TX while the exhaust heat from three Jenbacher reciprocating engines powers the third installation in Danville, IL. Figure 5 shows pictures of these installations.
After successful continuous operation since January 2004, the ORC product has been offered for sale in the US in August 2004. UTCPower sells the product under the PureCycleTM200 trademark name, in close cooperation with Carrier Corporation.
5. LOWER TEMPERATURE ORC APPLICATIONS
Cost-effective ORC operation requires a minimum temperature difference between evaporator and condenser saturation temperatures of about 50K or 100 0F. If air-cooled condensers are used, as in the PureCycleTM200 system, nominal condenser saturation temperatures of around 35 0C or 100 0F are encountered. As a result evaporator/boiler saturation temperatures from 90 to 120 0C (200 –250 0F) are required for cost-effective ORC operation.
Lower saturated condenser temperatures enable power recovery from lower temperature heat sources utilizing ORC technology. These lower temperature applications increase the similarity between existing air-conditioning equipment and ORC hardware. If the operating temperatures of the ORC system approach those of the air-conditioning system the unit was derived from, the original refrigerant used the corresponding centrifugal chiller becomes the preferred working fluid for the organic Rankine cycle at these temperature levels. R-245fa is the working fluid that at the normally higher ORC condenser and evaporator saturation temperatures achieves power-density similarity with a conventional R-134a centrifugal chiller. R-245fa would result in lower power output for the same turbine at reduced evaporator/condenser temperatures due to the lower densities and pressures. To obtain power density similarity at these lower saturation temperatures between compressor and turbine operation the original centrifugal chiller refrigerant R-134a should be used as ORC working fluid. Figure 6 shows side-by-side conventional chiller operation and low temperature ORC operation utilizing the same working fluid.
6. CONCLUSIONS
1. An Organic Rankine Cycle (ORC) turbine has been developed as a derivative of an existing centrifugal compressor with a discrete passage diffuser used on water-cooled chillers.
2. In order to operate at the higher temperature levels required for ORC duty when using engine exhaust or flare heat as heat input into the ORC unit, a lower pressure refrigerant was required to keep working pressures at acceptable levels.
3. Power density matching between compressor and turbine operation is needed for cost-effective utilization of existing compressor hardware as a radial inflow turbine. This can be achieved by switching from R-134a for HVAC compressor operation to R-245fa for ORC turbine operation when encountering higher temperature waste heat sources.
5. For moderate geothermal resource temperatures the power producing ORC system can use the original refrigerant used in centrifugal chillers at its working fluid, increasing the similarity between HVAC and ORC equipment. Such a unit is currently under construction for testing at Chena Hot Springs in the near future.
4. The cost advantage of HVAC equipment over power generation equipment allows an economically viable product despite the inherently (= second law of thermodynamics) low thermal efficiency of low temperature waste heat power recovery.
7. REFERENCES
1. Smith, I.K., The Choice of Working Fluids for Power Recovery from Waste Heat Streams, Transactions by the Institute of Marine Engineers of Conference on Organic Fluids for Waste Heat Recovery in Ships and Industry, pp. 8-18, January 7-8, 1981.
2. Brasz, L.J., Bilbow, W.M., Ranking of Working Fluids for Organic Rankine Cycle Applications, paper R068 presented at the 10th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, Indiana, July 12-15, 2004.
3. Zhong, B., Bowman, J.M., Williams, D., HFC-245fa: An Ideal Blowing Agent for Integral Skin Foam, Paper presented at the International Conference and Exposition Polyurethanes Expo 2001, Columbus, Ohio, September 30 - October 3, 2001.
4. Zyhowski, Sr, G.J., Spatz, M.W., Yana Motta, S. An Overview of the Properties and Applications of HFC-245fa, Paper presented at the Ninth International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, Indiana, July 16-19, 2002.
5. Brasz, J.J., Transforming a Centrifugal Compressor into a Radial Inflow Turbine, paper C060 presented at the 17th International Compressor Engineering Conference at Purdue, West Lafayette, Indiana, July 12-15, 2004.
Organic Rankine Cycle power production from low temperature resources has inherently a low thermal efficiency. Low efficiency requires increased power plant equipment size (turbine, condenser, pump and boiler) that can become cost prohibitive. The use of ORC power plant hardware derived from air-conditioning equipment overcomes this cost problem since air-conditioning hardware has a cost structure almost an order of magnitude smaller than that of traditional power generating equipment.
Using the HVAC derivative concept a low-cost 200 kW ORC power plant has been developed as a derivative of a standard 350 ton air-conditioning equipment. The corresponding PureCycleTM200 product was introduced in 2004. It uses waste heat exhaust gases and air-cooled condenser equipment. This paper describes the extension of this ORC development work towards power production from moderate-temperature geothermal resources.
1. BACKGROUND (ORIGIN OF THE IDEA)
Compressors in HVAC and refrigeration installations are known to start running in reverse after system shut-down unless special provisions are in place to prevent that. Reverse operation can be detrimental for certain type of positive displacement compressors, e.g. scroll and screw compressors, requiring a check valve in the compressor discharge line to prevent reverse rotation. Turbo-compressors, such as the centrifugal compressors used on water-cooled chillers, can easily be designed to handle temporary reverse rotation following system shut-down. After system shutdown pressure equalization takes place between the condenser and the evaporator. During that process refrigerant flashes/boils in the condenser and condenses in the evaporator, temporarily reversing the original design roles of these heat exchangers with heat now being rejected to the chilled water loop and extracted from the cooling tower water loop. Figure 1 compares the normal operation of the refrigeration or vapor compression cycle with its operation during pressure equalization.
The rotational speed of the turbo-compressor is immediately reversed after shutdown. The time required for pressure equalization depends on the amount of refrigerant charge in the condenser and evaporator relative to the size of the compressor and whether or not the cooling tower and chilled water pumps are stopped. Pressure equalization takes typically place within half a minute. One of the qualification tests a water-cooled chiller centrifugal compressor has to go through during its development phase is the sudden power failure test. Since the heat transfer between refrigerant and water is reversed during pressure equalization, the entering condenser water is temporarily cooled down and the water entering the cooler/evaporator is temporarily warmed up. Figure 2 compares chiller behavior at normal operating conditions versus that after shut down during pressure equalization.
During the development of the 19XR centrifugal chiller, which uses a compressor with a discrete passage diffuser as opposed to the vaneless diffuser concept used on previous designs, high reverse rotational speed was observed after shutdown. Reverse rotational speeds up to 75% of the original speed were now seen. The explanation for this phenomenon is that the discrete diffuser passages introduced for better pressure recovery in the diffuser and therefore higher compressor efficiency act as perfect turbine nozzles during pressure equalization. This observation triggered the idea to actually use this compressor as a turbine. Figure 3 shows how the impeller/pipe diffuser combination of a centrifugal compressor can act as the perfect nozzle/rotor combination for a radial inflow turbine when flow direction and rotor speed are reversed.
2. THE COST ADVANTAGE OF USING AIR-CONDITIONING EQUIPMENT FOR POWER GENERATION
Thanks to equipment standardization and high-volume production, air-conditioning and refrigeration equipment is available at a cost of around $ 200 - $ 300 per kW electric motor input. For example, the cost of a 1500 kW centrifugal chiller with a 300 kW electric motor varies, depending on options, from $ 60,000 to $ 90,000. The equipment cost of multi-megawatt conventional power generation equipment is an order of magnitude higher ($ 1,200 – 1,500 per kW generator output). Even higher cost is encountered for smaller (100 to 2000 kW) distributed power generation equipment. Reciprocating engines are the exception at $ 500 per kW, but these engines have emission problems and suffer from high maintenance costs.
Industrial processes generate large amounts of waste heat. Waste-heat-driven steam power plants are often not economical, especially for capacities below 5 MW and for low-temperature waste-heat streams. In those cases waste heat power recovery has been attempted with Organic Rankine Cycle (ORC) machines. Due to high cost of the equipment, the penetration of this technology has been limited to specific niche markets such as geothermal. Moreover, most ORC applications have been heavily subsidized. The reason for high equipment cost is that current ORC systems utilize low-volume power equipment hardware. Waste heat power recovery systems are inherently limited in thermal efficiency due to the relatively low temperature of waste heat. Consequently, a waste heat power generating ORC system requires larger capacity components (boiler, condenser, turbine and pump) for equivalent power output than conventional fuel fired power generation equipment. This causes high overall system cost. Efforts to improve the ORC cost structure by focussing on thermal efficiency enhancements have not been successful in bringing the system cost down to a level that would allow a large market penetration. The absence of fuel cost means that the economically correct metric to be used for waste-heat power recovery systems is its cost per unit of power generating capacity ($/kWel). Better efficiency is only beneficial as far as it results in lower equipment/installation cost since the waste heat is free.
3. R-245fa, THE ENABLING REFRIGERANT FOR AIR-COOLED ORC SYSTEMS
Given the lower cost structure of HVAC equipment versus power generating equipment, and the apparently good turbine action of the centrifugal compressor during power outages, it was decided to design an ORC system using HVAC hardware to the maximum extend possible. Only minor equipment modifications - not fundamentally affecting the equipment - were allowed. For example, modifying equipment to achieve higher cycle efficiency by going to higher boiler temperatures was only allowed if the resulting improvement in efficiency would result in a lower-cost overall product without too much additional development work.
Air-conditioning equipment is only cost effective if it is used to its full design capability. Temperature/working fluid combinations that result in a turbine power output less than the power input of the existing compressor would not fully utilize the potential of this compressor hardware during turbine operation and would therefore result in higher equipment cost per unit power delivered. Conversely, temperature/working fluid combinations that result in a turbine power output higher than the power input of the corresponding compressor hardware would exceed the mechanical limits (e.g. gear and shaft torque limits and bearing loading limits) of the original compressor design. Modifications to overcome those limits were only allowed if the net cost per unit power delivered would reduce, again without too much additional development work.
In order to preserve the cost advantage of the HVAC compressor as an ORC turbine it was found that the maximum temperature and pressure the turbine is seeing should be within the capabilities of the existing compressor housing. Moreover, to take full advantage of the given compressor hardware in turbine operation the power density of the turbine should be equal to that of the compressor. This allows unaltered use of the electrical and mechanical components of the centrifugal compressor. In other words, if a 200 kW compressor is used in an ORC application, the pressure-flow characteristics of the working fluid in the ORC system have to result in a 200 kW turbine output. Using R-134a, the working fluid used for the chiller application, as working fluid for the ORC application, would result in unacceptably high operating pressures requiring major redesign. Therefore, a lower-pressure working fluid is required for the higher- temperature operational regime of the organic Rankine cycle.
The non-flammable and non-toxic refrigerants promoted in the past as attractive fluids for organic Rankine cycle systems [1] have all been outlawed because of their ozone layer depletion potential. The HFC refrigerants introduced during the last decade to replace the CFC and HCFC refrigerants, such as R-134a, R-407C and R410A, have relatively low critical temperatures resulting in low ORC cycle efficiencies [2]. These refrigerants also would result in very high evaporator and turbine inlet pressures. This only leaves flammable and sometimes also highly toxic hydrocarbon fluids, such as pentane and toluene, as the fluids currently used on ORC installations. Apart from the flammability and toxicity issues, these fluids would, If applied to existing HVAC compressor hardware, fail to achieve the required turbine power density given their low vapor density at moderate temperature levels. These fluids would need larger turbine and condenser equipment than is available in the HVAC industry.
4. EXISTING INSTALLATIONS
Three 200 kW power producing installations using different waste heat sources have been in operation since January 2004. The exhaust heat of an Pratt and Whitney FT12 gas turbine is used as heat input source for the organic Rankine cycle in East-Hartford, CT. A second installation uses the heat from a landfill flare in Austin, TX while the exhaust heat from three Jenbacher reciprocating engines powers the third installation in Danville, IL. Figure 5 shows pictures of these installations.
After successful continuous operation since January 2004, the ORC product has been offered for sale in the US in August 2004. UTCPower sells the product under the PureCycleTM200 trademark name, in close cooperation with Carrier Corporation.
5. LOWER TEMPERATURE ORC APPLICATIONS
Cost-effective ORC operation requires a minimum temperature difference between evaporator and condenser saturation temperatures of about 50K or 100 0F. If air-cooled condensers are used, as in the PureCycleTM200 system, nominal condenser saturation temperatures of around 35 0C or 100 0F are encountered. As a result evaporator/boiler saturation temperatures from 90 to 120 0C (200 –250 0F) are required for cost-effective ORC operation.
Lower saturated condenser temperatures enable power recovery from lower temperature heat sources utilizing ORC technology. These lower temperature applications increase the similarity between existing air-conditioning equipment and ORC hardware. If the operating temperatures of the ORC system approach those of the air-conditioning system the unit was derived from, the original refrigerant used the corresponding centrifugal chiller becomes the preferred working fluid for the organic Rankine cycle at these temperature levels. R-245fa is the working fluid that at the normally higher ORC condenser and evaporator saturation temperatures achieves power-density similarity with a conventional R-134a centrifugal chiller. R-245fa would result in lower power output for the same turbine at reduced evaporator/condenser temperatures due to the lower densities and pressures. To obtain power density similarity at these lower saturation temperatures between compressor and turbine operation the original centrifugal chiller refrigerant R-134a should be used as ORC working fluid. Figure 6 shows side-by-side conventional chiller operation and low temperature ORC operation utilizing the same working fluid.
6. CONCLUSIONS
1. An Organic Rankine Cycle (ORC) turbine has been developed as a derivative of an existing centrifugal compressor with a discrete passage diffuser used on water-cooled chillers.
2. In order to operate at the higher temperature levels required for ORC duty when using engine exhaust or flare heat as heat input into the ORC unit, a lower pressure refrigerant was required to keep working pressures at acceptable levels.
3. Power density matching between compressor and turbine operation is needed for cost-effective utilization of existing compressor hardware as a radial inflow turbine. This can be achieved by switching from R-134a for HVAC compressor operation to R-245fa for ORC turbine operation when encountering higher temperature waste heat sources.
5. For moderate geothermal resource temperatures the power producing ORC system can use the original refrigerant used in centrifugal chillers at its working fluid, increasing the similarity between HVAC and ORC equipment. Such a unit is currently under construction for testing at Chena Hot Springs in the near future.
4. The cost advantage of HVAC equipment over power generation equipment allows an economically viable product despite the inherently (= second law of thermodynamics) low thermal efficiency of low temperature waste heat power recovery.
7. REFERENCES
1. Smith, I.K., The Choice of Working Fluids for Power Recovery from Waste Heat Streams, Transactions by the Institute of Marine Engineers of Conference on Organic Fluids for Waste Heat Recovery in Ships and Industry, pp. 8-18, January 7-8, 1981.
2. Brasz, L.J., Bilbow, W.M., Ranking of Working Fluids for Organic Rankine Cycle Applications, paper R068 presented at the 10th International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, Indiana, July 12-15, 2004.
3. Zhong, B., Bowman, J.M., Williams, D., HFC-245fa: An Ideal Blowing Agent for Integral Skin Foam, Paper presented at the International Conference and Exposition Polyurethanes Expo 2001, Columbus, Ohio, September 30 - October 3, 2001.
4. Zyhowski, Sr, G.J., Spatz, M.W., Yana Motta, S. An Overview of the Properties and Applications of HFC-245fa, Paper presented at the Ninth International Refrigeration and Air Conditioning Conference at Purdue, West Lafayette, Indiana, July 16-19, 2002.
5. Brasz, J.J., Transforming a Centrifugal Compressor into a Radial Inflow Turbine, paper C060 presented at the 17th International Compressor Engineering Conference at Purdue, West Lafayette, Indiana, July 12-15, 2004.
EVAPORATIVE COOLING CYCLE FOR SOLAR AIR CONDITIONING AND HOT WATER HEATING
ABSTRACT
Using excess summer heat from solar collectors to drive
desiccant cooling systems is often proposed. A two wheel
desiccant system using solar heat for desiccant
regeneration is typically discussed. The two wheel system
uses a desiccant wheel that is “matched” with a heat
exchanger wheel. The heat exchanger recycles heat for
the desiccant regeneration and improves system
efficiency. These systems are generally limited to
delivering warm dry air or cool humid air in most parts of
the US.
A newly patented desiccant cooling cycle creates two dry
air streams. This new cycle uses indirect evaporative
cooling of one air stream to cool the second stream.
Additional direct evaporative cooling allows cool and dry
air to be delivered to the building. Regeneration exhaust
heat can provide water heating. Combining the system
with a new solar air heating system should provide a
significant solar heating, cooling, and hot water delivery
system.
1. BACKGROUND
Low temperature heating dominates all residential,
commercial, and industrial end uses of energy within
buildings. Nearly 61% of the energy used across all
sectors of the economy is for low temperature heating
uses. These heating end uses include space heating,
industrial process heating, water heating, boiler heating,
and clothes drying.
The second greatest energy end use is for cooling.
Another 13% of all building energy end use is for
refrigeration or space cooling. In the late 1990's, the
combination of all heating and cooling energy end uses cost
US consumers nearly $180 billion per year.
Most of this energy use requires the consumption of fossil
fuels. In most cases, the energy conversion devices, such as
boilers or electric heat pumps, operate at low efficiency
compared to the fuel they consume. In almost all fossil
energy heating and cooling systems, the conversion from the
primary fuel (gas, oil, coal, etc.) to heating or cooling is done
at less than 100% efficiency. This is often described as a
coefficient of performance of less than 1.0. (COP < style="font-weight: bold;">3. DEVELOPMENT OF AN INTEGRATED SOLAR
DESICCANT EVAPORATIVE COOLING CYCLE
With the solar, desiccant, and evaporative cooling industries
each targeting different geographic or technological
problems, there has been little joint development. Solar
thermal work is concentrated on flat plate water heating
systems, which are generally not cost effective for space
heating applications. In general, the northern climates, with
high heating needs, are where solar space heating could
deliver the greatest value, but thi is also where minimal
cooling energy is required in the summer. Evaporative
cooling is targeted to the dry southwest. Desiccant cooling is
targeted to the humid southeast.
Despite the differences in geographic, technological, and
economic conditions that favor the limited separate use of
individual technologies, there is a potential to draw together
the best characteristics of each of these super efficient
technologies into one super efficient system. The combined
solar desiccant evaporative system can provide a significant
portion of the space heating, hot water heating and space.
4. NEW TECHNOLOGIES
Recent patents in each technology (Refs. 1 & 2) have
overcome some of the problems holding back greater
deployment. Tests of these new technologies in the past 4
years indicate that workable systems can be deployed.
These systems have shown the technical capacity to
deliver solar heating and desiccant cooling with indirect
and direct evaporative cooling. Specifically, these new
technologies include the solar thermal tile system shown
in Figures 3 and 4 and the NovelAire desiccant
evaporative cooling cycle
The solar thermal tile system is a mid temperature air
heating collector. It is designed to function as the weather
tight roof of a building or as a rack mounted solar
collector on low sloped roofs or in ground mounted
applications. It is designed to be installed at a cost
comparable to high quality slate and tile roofing, which is
substantially less expensive than existing mid temperature
collectors. As a result, the system can be economically
installed to handle the larger space heating loads, even
with the seasonal reduction in productivity during the
summer months.
Stagnation tests show that the systems can achieve
internal air temperatures of greater than 200 degrees F (94
C) and more than 130F (72 C) above ambient
temperature. An air flow test with an early prototype
showed outlet air temperatures of 160 -180 F (71-82 C)
are possible. Higher temperatures are expected with
optimal orientation, improved materials such as selective
surface absorbers, and optimal air flow.
One version of the NovelAire desiccant evaporative cooling
cycle is shown in Figure 5. The cycle uses excess air passing
through the desiccant wheel to create excess dry air to
support the evaporative cooling process. After leaving the
desiccant wheel (B), the hot dry air is cooled in the supply
side of a heat exchanger (C). The warm dry air is then split
into two air streams. The first stream (C-CX-CY) supports an
indirect evaporative cooling of the second stream (C-C’).
This cools the second stream without adding any humidity at
state point C’. The final direct evaporative cooling stage from
point C’ to D can adjust the temperature and humidity to any
point on the line CD.
The regeneration side of the NovelAire cycle begins by
recovering heat via the exhaust side of the heat exchanger.
The heat transfer in the supply side of the heat exchanger
is from the full air stream with excess dry air. This is
more air flow than the reduced volume air which actually
enters the building and returns as exhaust. As a result, the
smaller volume of exhaust air from the building is not
sufficient, by itself, to cool the full excess air flowin the
heat exchanger. Therefore, the initial cooling of the
exhaust side of the heat exchanger is from a stream of
outside air at state point A.
This outside air flow, passing through the first stage of the
heat exchanger, cools the hottest air entering at state point
B on the supply side. The outside air is then exhausted
back to the atmosphere. Then, the exhaust air from within
the building, passes through the second stage of the heat
exchanger. The exhaust air further cools the supply air to
state point C, while the exhaust air heats to state point G.
The exhaust air is then heated from state point G to I by
an external heat source, such as gas heat, shown in Figure
5. The high temperature exhaust is then used to regenerate
the desiccant and exhausted to the atmosphere at state
point J.
The obvious difference in the psychometric is that the
final cooling line C’ D is moved to a cooler temperature
than the “2 wheel limit line”. This allows cool dry air to
be introduced to the building to overcome the internal and
external heating and humidity loads that a traditional 2
wheel systems can not handle.
What is not obvious from the psychometrics is that the
gas heating of the smaller exhaust air stream must be
increased to regenerate the larger volume of desiccant in
the larger wheel. The larger wheel is required to dry the
excess air required by the cycle.
NovelAire constructed and tested a desiccant evaporative
cooling system in the mid 1990s. Patent documentation
(Ref. 2) from 1998 provides an example calculation for a
cycle that would produce 5.4 tons of cooling (64 MJ) with
a COP of about 0.92. If the system were solely dependent
on natural gas or other traditional energy source, then
other cooling technologies, such as compression
refrigeration, would generally be more cost effective.
However, if large volumes of low cost solar heated air are
available, then the economics can swing in favor of the
solar desiccant evaporative cooling cycle. In addition,
because the COP of the solar thermal system is much
higher that for natural gas combustion (~4 for solar vs. 1
max. for gas) the COP of the integrated cooling systems
can be greatly increased.
The efficiency of the system is further improved by using the
high temperature waste heat from any of the available air
streams involved in the desiccant regeneration. These air
streams from the heat exchanger exhaust or from the
desiccant wheel exhaust are between 45 and 70 degrees C
(112-158 F). By using this heat source to heat water for
domestic use, the system increases its productivity, with
essentially no additional primary energy being used.
5. INTEGRATING THE NEW TECHNOLOGIES
There are several ways to integrate the two technologies. One
version of the integrated cycle is shown in Figure 6.
The cycle shown includes:
1) a solar thermal tile system,
2) a NovelAire desiccant evaporative cooling systems,
3) one additional evaporative cooling system between
state points E and F, and
4) a hot water heating system using the waste heat from
the desiccant regeneration at state point J.
The psychometrics of the integrated cycle are shown in
Figure 7. The increased cooling for the heat exchanger by
the building air can be seen from the change in state point
temperature from E to F. The first stage cooling of the heat
exchanger from A to L can also be seen.
The particular integrated cycle shown in Figure 7 does not
use recovered heat from the heat exchanger for desiccant
regeneration. Instead, the excess solar heated air from the
solar thermal tile roof is used as the primary heating source
for desiccant regeneration. (An alternative cycle could
introduce air from point L into the solar thermal tile roof
system.)
Supplemental gas heat, as shown in Figure 7, is used to
support desiccant regeneration during cloudy days, and
possibly early evening cooling hours, or other hours when
solar heating is not 100% effective at delivering cool dry
air for cooling or dehumidification. With minor
adaptation, the supplemental gas heat can also provide the
peak space heating required during the coldest winter
days.
The hot water heating systems uses waste heat from the
desiccant regeneration to heat water via an air-to-water
heat exchanger. During the rest of the year, solar heated
air from the thermal tile roof would be ducted to the same
air- to-water heat exchanger for hot water production.
Because the solar heating system would provide an air to
water heat exchanger for domestic water heating in nonsummer
months, there is little added cost for the heat
recovery for water heating. The only added cost would be
the duct work and dampers to bypass the desiccant
regeneration when cooling is not required.
6. EXPECTED PERFORMANCE
The solar thermal tile roof has been demonstrated to reach
stagnation temperatures of 200+ deg. F. (93+ C) and 130
F (72 C) above ambient. Even though delivered air
temperatures would be somewhat below the 200 degree F
(93 C) temperature, these outlet conditions are adequate
to support desiccant regeneration.
However, there is a significant likelihood of
raising collector outlet temperatures using
several routine measures that were not
incorporated in the original stagnation tests.
For example, the solar thermal tile test
section used painted absorber plates instead
of selective surfaces. No anti- reflective
coatings were used on the tiles. The
collector was at a slope of 20 degrees from
the horizontal, an angle that would roughly
equal a roof pitch of 4 in 12. The sun was at
an angle of 37 degrees below perpendicular
to the collector. Given improvements in any
of these test conditions, the collector would
likely sustain higher delivered air
temperatures. These higher temperatures are
comparable to other mid temperature air
heating collectors which were widely
researched in the late 1970s and early 1980s.
The higher temperatures would also provide
additional desiccant regeneration capacity
and greater cooling. Finally, because the
output of the solar thermal tile system is
heated air, it is compatible with the air
drying of the desiccants. This eliminates the temperature drop
from a water-to-air heat exchanger that would be required for
a liquid based system.
Reference 3 described the economics of the solar thermal tile
system. The analysis indicated that the 600 sq ft. (56 sq. m.)
solar thermal tile system used for heating only, could save
$655 per year when competing against $9 per million BTU
delivered natural gas. Under these conditions, the system
showed a 10 year payback for space heating and water
heating and handled 56 % of the total space heating and hot
water load for a 2000 sq. ft. (186 sq. m.) house in a Boston,
MA climate.
The analysis has been extended to the integrated system and
evaluated based on climate conditions for Charlotte, NC.
Charlotte has both heating and air conditioning loads. The
600 sq. ft. (56 sq. m.) system would deliver energy cost
savings as shown in Figure 8. The total energy savings across
the year would be 116 gigajoules (110 million Btu) and only
28 gigajoules (26 million Btu) of fan power would be
required. The system would handle 87 % of the annual
household heating, cooling, and hot water energy load as
derived from EIA data from 1993 (Ref. 4). The system would
save $847 per year with gas at $9 per million Btu
($8.86/gigajoule) and electricity at $.0785 per KWHR.
In the summer months, the system would handle 100% of the
cooling load of the 2000 sq ft. (186 sq. m.) house. These
calculations assume a collector efficiency of 35% even during
summer cooling with high collector operating temperatures.
However, if the collector operating temperatures reduce
efficiency to only 20%, the system still handles 81% of
the seasonal cooling load. Throughout the year, the
systems would handle 74% of the space heating load and
75% of the water heating load, for a total of 87% of the
entire heating and cooling load.
However, if the collector operating temperatures reduce
efficiency to only 20%, the system still handles 81% of
the seasonal cooling load. Throughout the year, the
systems would handle 74% of the space heating load and
75% of the water heating load, for a total of 87% of the
entire heating and cooling load.
7. ADDITIONAL RESEARCH
Additional research is recommended in the following
areas:
1) Evaluate alternative solar tile roof components to
establish the most cost effective summer outlet
temperature for the solar roof when supporting desiccant
regeneration.
2)Prepare a desiccant wheel that is optimized to the outlet
temperatures of the solar roof.
3) Assemble the components in an operational prototype
and test for cooling performance in a suburban setting
8. REFERENCES
(1) U.S. Patent 5,651,226 to Archibald dated July 29, 1997.
(2) U.S. Patent 5,758,508 to Belding, et.al. dated June 2,
1998.
(3) John Archibald, Building Integrated Solar Thermal
Roofing Systems; History, Current Status, and Future
Promise, Proceedings of the ASES Annual Conference,
American Solar Energy Society, 1999 Report on Solar Water
Heating Quantitative Survey Dec 1997-Sept 1998, Focus
Marketing Services, NREL report SR-550-26484, April 1999
(4) Energy Information Administration, Household Energy
Consumption and Expenditures 1993, October 1995.
Using excess summer heat from solar collectors to drive
desiccant cooling systems is often proposed. A two wheel
desiccant system using solar heat for desiccant
regeneration is typically discussed. The two wheel system
uses a desiccant wheel that is “matched” with a heat
exchanger wheel. The heat exchanger recycles heat for
the desiccant regeneration and improves system
efficiency. These systems are generally limited to
delivering warm dry air or cool humid air in most parts of
the US.
A newly patented desiccant cooling cycle creates two dry
air streams. This new cycle uses indirect evaporative
cooling of one air stream to cool the second stream.
Additional direct evaporative cooling allows cool and dry
air to be delivered to the building. Regeneration exhaust
heat can provide water heating. Combining the system
with a new solar air heating system should provide a
significant solar heating, cooling, and hot water delivery
system.
1. BACKGROUND
Low temperature heating dominates all residential,
commercial, and industrial end uses of energy within
buildings. Nearly 61% of the energy used across all
sectors of the economy is for low temperature heating
uses. These heating end uses include space heating,
industrial process heating, water heating, boiler heating,
and clothes drying.
The second greatest energy end use is for cooling.
Another 13% of all building energy end use is for
refrigeration or space cooling. In the late 1990's, the
combination of all heating and cooling energy end uses cost
US consumers nearly $180 billion per year.
Most of this energy use requires the consumption of fossil
fuels. In most cases, the energy conversion devices, such as
boilers or electric heat pumps, operate at low efficiency
compared to the fuel they consume. In almost all fossil
energy heating and cooling systems, the conversion from the
primary fuel (gas, oil, coal, etc.) to heating or cooling is done
at less than 100% efficiency. This is often described as a
coefficient of performance of less than 1.0. (COP < style="font-weight: bold;">3. DEVELOPMENT OF AN INTEGRATED SOLAR
DESICCANT EVAPORATIVE COOLING CYCLE
With the solar, desiccant, and evaporative cooling industries
each targeting different geographic or technological
problems, there has been little joint development. Solar
thermal work is concentrated on flat plate water heating
systems, which are generally not cost effective for space
heating applications. In general, the northern climates, with
high heating needs, are where solar space heating could
deliver the greatest value, but thi is also where minimal
cooling energy is required in the summer. Evaporative
cooling is targeted to the dry southwest. Desiccant cooling is
targeted to the humid southeast.
Despite the differences in geographic, technological, and
economic conditions that favor the limited separate use of
individual technologies, there is a potential to draw together
the best characteristics of each of these super efficient
technologies into one super efficient system. The combined
solar desiccant evaporative system can provide a significant
portion of the space heating, hot water heating and space.
4. NEW TECHNOLOGIES
Recent patents in each technology (Refs. 1 & 2) have
overcome some of the problems holding back greater
deployment. Tests of these new technologies in the past 4
years indicate that workable systems can be deployed.
These systems have shown the technical capacity to
deliver solar heating and desiccant cooling with indirect
and direct evaporative cooling. Specifically, these new
technologies include the solar thermal tile system shown
in Figures 3 and 4 and the NovelAire desiccant
evaporative cooling cycle
The solar thermal tile system is a mid temperature air
heating collector. It is designed to function as the weather
tight roof of a building or as a rack mounted solar
collector on low sloped roofs or in ground mounted
applications. It is designed to be installed at a cost
comparable to high quality slate and tile roofing, which is
substantially less expensive than existing mid temperature
collectors. As a result, the system can be economically
installed to handle the larger space heating loads, even
with the seasonal reduction in productivity during the
summer months.
Stagnation tests show that the systems can achieve
internal air temperatures of greater than 200 degrees F (94
C) and more than 130F (72 C) above ambient
temperature. An air flow test with an early prototype
showed outlet air temperatures of 160 -180 F (71-82 C)
are possible. Higher temperatures are expected with
optimal orientation, improved materials such as selective
surface absorbers, and optimal air flow.
One version of the NovelAire desiccant evaporative cooling
cycle is shown in Figure 5. The cycle uses excess air passing
through the desiccant wheel to create excess dry air to
support the evaporative cooling process. After leaving the
desiccant wheel (B), the hot dry air is cooled in the supply
side of a heat exchanger (C). The warm dry air is then split
into two air streams. The first stream (C-CX-CY) supports an
indirect evaporative cooling of the second stream (C-C’).
This cools the second stream without adding any humidity at
state point C’. The final direct evaporative cooling stage from
point C’ to D can adjust the temperature and humidity to any
point on the line CD.
The regeneration side of the NovelAire cycle begins by
recovering heat via the exhaust side of the heat exchanger.
The heat transfer in the supply side of the heat exchanger
is from the full air stream with excess dry air. This is
more air flow than the reduced volume air which actually
enters the building and returns as exhaust. As a result, the
smaller volume of exhaust air from the building is not
sufficient, by itself, to cool the full excess air flowin the
heat exchanger. Therefore, the initial cooling of the
exhaust side of the heat exchanger is from a stream of
outside air at state point A.
This outside air flow, passing through the first stage of the
heat exchanger, cools the hottest air entering at state point
B on the supply side. The outside air is then exhausted
back to the atmosphere. Then, the exhaust air from within
the building, passes through the second stage of the heat
exchanger. The exhaust air further cools the supply air to
state point C, while the exhaust air heats to state point G.
The exhaust air is then heated from state point G to I by
an external heat source, such as gas heat, shown in Figure
5. The high temperature exhaust is then used to regenerate
the desiccant and exhausted to the atmosphere at state
point J.
The obvious difference in the psychometric is that the
final cooling line C’ D is moved to a cooler temperature
than the “2 wheel limit line”. This allows cool dry air to
be introduced to the building to overcome the internal and
external heating and humidity loads that a traditional 2
wheel systems can not handle.
What is not obvious from the psychometrics is that the
gas heating of the smaller exhaust air stream must be
increased to regenerate the larger volume of desiccant in
the larger wheel. The larger wheel is required to dry the
excess air required by the cycle.
NovelAire constructed and tested a desiccant evaporative
cooling system in the mid 1990s. Patent documentation
(Ref. 2) from 1998 provides an example calculation for a
cycle that would produce 5.4 tons of cooling (64 MJ) with
a COP of about 0.92. If the system were solely dependent
on natural gas or other traditional energy source, then
other cooling technologies, such as compression
refrigeration, would generally be more cost effective.
However, if large volumes of low cost solar heated air are
available, then the economics can swing in favor of the
solar desiccant evaporative cooling cycle. In addition,
because the COP of the solar thermal system is much
higher that for natural gas combustion (~4 for solar vs. 1
max. for gas) the COP of the integrated cooling systems
can be greatly increased.
The efficiency of the system is further improved by using the
high temperature waste heat from any of the available air
streams involved in the desiccant regeneration. These air
streams from the heat exchanger exhaust or from the
desiccant wheel exhaust are between 45 and 70 degrees C
(112-158 F). By using this heat source to heat water for
domestic use, the system increases its productivity, with
essentially no additional primary energy being used.
5. INTEGRATING THE NEW TECHNOLOGIES
There are several ways to integrate the two technologies. One
version of the integrated cycle is shown in Figure 6.
The cycle shown includes:
1) a solar thermal tile system,
2) a NovelAire desiccant evaporative cooling systems,
3) one additional evaporative cooling system between
state points E and F, and
4) a hot water heating system using the waste heat from
the desiccant regeneration at state point J.
The psychometrics of the integrated cycle are shown in
Figure 7. The increased cooling for the heat exchanger by
the building air can be seen from the change in state point
temperature from E to F. The first stage cooling of the heat
exchanger from A to L can also be seen.
The particular integrated cycle shown in Figure 7 does not
use recovered heat from the heat exchanger for desiccant
regeneration. Instead, the excess solar heated air from the
solar thermal tile roof is used as the primary heating source
for desiccant regeneration. (An alternative cycle could
introduce air from point L into the solar thermal tile roof
system.)
Supplemental gas heat, as shown in Figure 7, is used to
support desiccant regeneration during cloudy days, and
possibly early evening cooling hours, or other hours when
solar heating is not 100% effective at delivering cool dry
air for cooling or dehumidification. With minor
adaptation, the supplemental gas heat can also provide the
peak space heating required during the coldest winter
days.
The hot water heating systems uses waste heat from the
desiccant regeneration to heat water via an air-to-water
heat exchanger. During the rest of the year, solar heated
air from the thermal tile roof would be ducted to the same
air- to-water heat exchanger for hot water production.
Because the solar heating system would provide an air to
water heat exchanger for domestic water heating in nonsummer
months, there is little added cost for the heat
recovery for water heating. The only added cost would be
the duct work and dampers to bypass the desiccant
regeneration when cooling is not required.
6. EXPECTED PERFORMANCE
The solar thermal tile roof has been demonstrated to reach
stagnation temperatures of 200+ deg. F. (93+ C) and 130
F (72 C) above ambient. Even though delivered air
temperatures would be somewhat below the 200 degree F
(93 C) temperature, these outlet conditions are adequate
to support desiccant regeneration.
However, there is a significant likelihood of
raising collector outlet temperatures using
several routine measures that were not
incorporated in the original stagnation tests.
For example, the solar thermal tile test
section used painted absorber plates instead
of selective surfaces. No anti- reflective
coatings were used on the tiles. The
collector was at a slope of 20 degrees from
the horizontal, an angle that would roughly
equal a roof pitch of 4 in 12. The sun was at
an angle of 37 degrees below perpendicular
to the collector. Given improvements in any
of these test conditions, the collector would
likely sustain higher delivered air
temperatures. These higher temperatures are
comparable to other mid temperature air
heating collectors which were widely
researched in the late 1970s and early 1980s.
The higher temperatures would also provide
additional desiccant regeneration capacity
and greater cooling. Finally, because the
output of the solar thermal tile system is
heated air, it is compatible with the air
drying of the desiccants. This eliminates the temperature drop
from a water-to-air heat exchanger that would be required for
a liquid based system.
Reference 3 described the economics of the solar thermal tile
system. The analysis indicated that the 600 sq ft. (56 sq. m.)
solar thermal tile system used for heating only, could save
$655 per year when competing against $9 per million BTU
delivered natural gas. Under these conditions, the system
showed a 10 year payback for space heating and water
heating and handled 56 % of the total space heating and hot
water load for a 2000 sq. ft. (186 sq. m.) house in a Boston,
MA climate.
The analysis has been extended to the integrated system and
evaluated based on climate conditions for Charlotte, NC.
Charlotte has both heating and air conditioning loads. The
600 sq. ft. (56 sq. m.) system would deliver energy cost
savings as shown in Figure 8. The total energy savings across
the year would be 116 gigajoules (110 million Btu) and only
28 gigajoules (26 million Btu) of fan power would be
required. The system would handle 87 % of the annual
household heating, cooling, and hot water energy load as
derived from EIA data from 1993 (Ref. 4). The system would
save $847 per year with gas at $9 per million Btu
($8.86/gigajoule) and electricity at $.0785 per KWHR.
In the summer months, the system would handle 100% of the
cooling load of the 2000 sq ft. (186 sq. m.) house. These
calculations assume a collector efficiency of 35% even during
summer cooling with high collector operating temperatures.
However, if the collector operating temperatures reduce
efficiency to only 20%, the system still handles 81% of
the seasonal cooling load. Throughout the year, the
systems would handle 74% of the space heating load and
75% of the water heating load, for a total of 87% of the
entire heating and cooling load.
However, if the collector operating temperatures reduce
efficiency to only 20%, the system still handles 81% of
the seasonal cooling load. Throughout the year, the
systems would handle 74% of the space heating load and
75% of the water heating load, for a total of 87% of the
entire heating and cooling load.
7. ADDITIONAL RESEARCH
Additional research is recommended in the following
areas:
1) Evaluate alternative solar tile roof components to
establish the most cost effective summer outlet
temperature for the solar roof when supporting desiccant
regeneration.
2)Prepare a desiccant wheel that is optimized to the outlet
temperatures of the solar roof.
3) Assemble the components in an operational prototype
and test for cooling performance in a suburban setting
8. REFERENCES
(1) U.S. Patent 5,651,226 to Archibald dated July 29, 1997.
(2) U.S. Patent 5,758,508 to Belding, et.al. dated June 2,
1998.
(3) John Archibald, Building Integrated Solar Thermal
Roofing Systems; History, Current Status, and Future
Promise, Proceedings of the ASES Annual Conference,
American Solar Energy Society, 1999 Report on Solar Water
Heating Quantitative Survey Dec 1997-Sept 1998, Focus
Marketing Services, NREL report SR-550-26484, April 1999
(4) Energy Information Administration, Household Energy
Consumption and Expenditures 1993, October 1995.
The Winston Series CPC
The Winston Series CPCThe WINSTON SERIES CPC incorporates a geometrical concept, uses selective crystal
plating techniques and special anti reflective coatings to achieve high-energy efficiency
levels. The WINSTON SERIES CPC has a solid structure that provides excellent support for
its outer glass covering; its rigid design provides safety and reliability, even under harsh
winter conditions. With its mirrors reflecting the solar radiation onto the fluid tubes or
receivers, the WINSTON SERIES CPC has a cooler surface than conventional flat collectors.
The WINSTON SERIES CPC delivers more energy per square meter than competing solar
collectors and does so at unit prices that can facilitate cost effective applications for both
distributors and end users.
Applications:
- Domestic and Commercial water heating (Also as thermosiphonic system).
- Domestic space heating (Easily combined with existing systems).
- Air conditioning (in connection with single stage absorption machines).
- Swimming Pool and Spa Heating
- Possible building integrated utilization as a leak- proof roof due to its uniform structure.
Reliability of the Winston Series CPC Collector
1. Leakage through glass sealing into the housing.
The silicon-seal on each side of the glass ensures a reliable water proof seal.
2. Leakage from the flow tubes/ brazing.
Controlled process and individual testing of each collector (in pressure of 12 Bar/ 168
PSI) ensure efficient and problem- free sealing.
3. Selective coating of the flow tubes.
The electro-plate crystals of selective coating- and the semi-selective painted coatings are
stable and do not change its properties (quality) after many years of operation.
4. Anti- reflective coating of cover plate.
Special process ensures stability of the coating for many years.
5. Insulation.
The polyurethane insulation retains its performance for many years specifically due to the
low temperature that develops in the collector housing as a result of the CPC design.
Instructions for System Design
The system designer for the WINSTON SERIES CPC must observe the following:
1. Regulating the flow rate
For optimal performance use a control valve for each series of panels to ensure equal flow
rate. This requires special attention when a different number of panels are used in each
series of panels or all panels are not mounted on an equal level. To regulate the flow rate
through every collector in a panel, set the suitable flow rate.
2. Use an automatic air release valve (with rapid exhausting mechanism) and a safety
valve at the outlet of each series of panels.
3. Drain back option (freezing & over heating)
For the heat transfer liquid draining system, use a manifold construction that will allow the
heat transfer liquid to be completely drained from the collector. To ensure complete
draining of each series of panel, the collector array should be tilted and sloped at least ¼
per foot of collector. No air vents required.
4. If the CPC collector is used in an indirect or closed system, additives such as propylene
glycol should be used to avoid corrosion of any dissimilar metals in the solar loop/piping
and freeze protection.
5. Vertical positioning
For vertical positioning, the system should be operated with circulating pump of sufficient
size to force any trapped air out of the collector and maintain the recommended flow rate.
Instructions for Handling
General Instructions
1. Whenever handling the collector, be sure to wear gloves and clothes that fully protect
your skin.
2. Do not lift and handle the collector holding the inlet and outlet connection.
3. Do not scratch the glass panel.
4. The collectors should be stored in a place where they will not be exposed to direct
sunlight, rain, or snow.
Instructions for Collector Assembly
1. During assembly, take special care not to drop heavy tools on the glass panel.
2. For securing a collector, be sure to use rubber gaskets or other appropriate cushioning
material.
Instructions for Installation
1. Install the panels on the roof; protect the glass panel with cardboard or other material.
Take special care not to damage or deform the collector. The installers on the roof should
use safety belts to prevent injury or damage.
2. Installing the panels on its stand / construction should be perform using the standard flush
mounting, or tilt mount hardware. Direct mounting to Uni-Strut is recommended (see
drawings on pages 13 & 14).
3. When handling the panel do not pull or push the enclosures, inlet and outlet tubes.
4. Do not release the safety belts until the panel is fixed on its stand.
5. Do not remove the special protective cover from the collector until the water system is
full and ready for operation.
6. Do not touch the inlet & outlet with bare hands. They may be extremely hot due to heat
absorption.
7. To prevent possible corrosion or reduced structural strength, do not locate the system in
the following places:
One) In the vicinity of a cooling tower
Solar Absorption Cooling
Efficient Use of Solar Energy
• Passive solar design of buildings with efficient
daylighting.
• Low temperature non-concentrating collectors for
low temperature end-use such as pool heating, hot
water, and space heating.
• Medium temperature moderately concentrating
collectors for thermo GS heat pump HVAC, 2E
absorption cooling, and process heat.
• High temperature concentrating tracking collectors
for CHP and process heat.
• High temperature concentrating tracking collectors
and PV for electric power production.
Wagner Project Specifications
• NYSERDA primary funding, $2.9M (2002 dollars)
• 320-ton Carrier hot water fired 1E absorption chiller
• 800 Sunmaster evacuated tube collectors with CPC
reflectors, 11,000 ft2 aperture, mounted on 22,000 ft2
platform
• 1900F - 2200F solar operating temperatures
• Medium temperature backup hot water boilers
• Provided heating/cooling/service hot water to two
campus buildings with 75,000 ft2 of floor area.
• Solar energy system averaged 55 man-hours per
Austin TX 30-Ton Solar 1E-Absorption Chiller,
2003
• 360 m2 aperture area of 180 ground-mounted Non-
Evacuated CPC collectors, 720 m2 gross horizontal
area
• Orientation: South, 200 slope
• Water HTF, 36 gpm, 520 Mbtu/hr peak output at
950C, filled system, over-temperature protected
• 2500 gallon SS pressurized thermal storage tank
• 30-ton Yazaki hot water fired 1E absorption chiller
• 13,000 ft2 pre-engineered steel single-story building
used for Austin Energy Sand Hill power plant
control center.
Solar Absorption vs Electric Chillers
• Accounting for the electrical grid energy losses,
the adjusted primary source fuel COP for electric
A/C units varies from 0.83 to 1.93, with an
average of 0.98.
• A hybrid solar/fuel 2E absorption chiller system
can produce an average cooling season solar
fraction of at least 60%, so that the net primary
source fuel COP is 3.0.
• Solar/fuel 2E absorption chiller systems will
consume one-third the average primary source
energy used for electric A/C in the US.
Sacramento, CA 20-Ton Solar 2-E Absorption HVAC
System, CEC Primary Funding, 1997
• 336 ICPC parallel collector tubes in three rows, filled
system, over-temperature protected
• 111 m2 Aperture Area, 156 m2 Gross Area, 186 m2
footprint
• Orientation South, Sloped at 280 (Latitude - 100)
• Water HTF, 40 gpm, 50 feet of water pressure drop, 220
Mbtu/hr peak heat output, 1770C maximum
• 1000 gallon stainless steel pressurized thermal storage tank
• 20-ton Sanyo-McQuay direct-fired 2E absorption chiller
modified to hot water fired at 1650C with tube-in-shell,
reverse-flow generator
• 8,000 ft2 single-story building used for print shop and
offices
ICPC Collector Highlights
• Evacuated Borosilicate glass tube with proprietary
non-imaging optics reflector inside.
• Proprietary selective coating on stainless steel
absorber tube with absorptivity ~98% and emissivity.
~6% over wide temperature range.
• Ten-tube modules anticipated.
• Vertical load of 6.7 lb/ft2.
• Flexible roof-mounting requirements.
Solar Energy System Highlights
• Roof-mounted ICPC evacuated tube collectors reduce
solar gain and reduce building cooling load.
• Approximately 50% of collectable solar energy
delivered to 2E absorption chiller at 3300F.
• Peak cooling energy per peak collectable solar energy
equals 60%.
• Non-tracking.
• Low maintenance and long life.
• Any suitable clean backup fuel including biofuels.
• 2E absorption chiller: high reliability, environmentally
friendly, average maintenance costs, full automatic
operation.
• System-ready for organic Rankine cycle (ORC) enginegenerator
when such equipment is available (30kW per
100 tons).
• Energy peak shaving.
• Insurance against rising energy costs.
• Summer: 100 tons of cooling and domestic hot
water heating.
• Winter: space and domestic hot water heating.
• Emissions annual reductions:
CO2 = 182,000 lb SO2 = 170 lb NOx = 240 lb
Dual Energy Source Absorption Chiller-
Heater
• Absorption chiller can be fired by natural gas,
LPG, fuel oil, hot water, steam, or hot thermal oil
• Newest units provide 1800F hot water for heating.
• Eliminates the need for separate backup energy
source for solar absorption HVAC system
• Lower capital costs and higher system efficiency
• Concept fully tested in 50-ton Yazaki 2E chiller
• Patent issued in 2006.
• Broad Air Conditioning Co. is now manufacturing
dual energy source 2E absorption chillers.
• Passive solar design of buildings with efficient
daylighting.
• Low temperature non-concentrating collectors for
low temperature end-use such as pool heating, hot
water, and space heating.
• Medium temperature moderately concentrating
collectors for thermo GS heat pump HVAC, 2E
absorption cooling, and process heat.
• High temperature concentrating tracking collectors
for CHP and process heat.
• High temperature concentrating tracking collectors
and PV for electric power production.
Wagner Project Specifications
• NYSERDA primary funding, $2.9M (2002 dollars)
• 320-ton Carrier hot water fired 1E absorption chiller
• 800 Sunmaster evacuated tube collectors with CPC
reflectors, 11,000 ft2 aperture, mounted on 22,000 ft2
platform
• 1900F - 2200F solar operating temperatures
• Medium temperature backup hot water boilers
• Provided heating/cooling/service hot water to two
campus buildings with 75,000 ft2 of floor area.
• Solar energy system averaged 55 man-hours per
Austin TX 30-Ton Solar 1E-Absorption Chiller,
2003
• 360 m2 aperture area of 180 ground-mounted Non-
Evacuated CPC collectors, 720 m2 gross horizontal
area
• Orientation: South, 200 slope
• Water HTF, 36 gpm, 520 Mbtu/hr peak output at
950C, filled system, over-temperature protected
• 2500 gallon SS pressurized thermal storage tank
• 30-ton Yazaki hot water fired 1E absorption chiller
• 13,000 ft2 pre-engineered steel single-story building
used for Austin Energy Sand Hill power plant
control center.
Solar Absorption vs Electric Chillers
• Accounting for the electrical grid energy losses,
the adjusted primary source fuel COP for electric
A/C units varies from 0.83 to 1.93, with an
average of 0.98.
• A hybrid solar/fuel 2E absorption chiller system
can produce an average cooling season solar
fraction of at least 60%, so that the net primary
source fuel COP is 3.0.
• Solar/fuel 2E absorption chiller systems will
consume one-third the average primary source
energy used for electric A/C in the US.
Sacramento, CA 20-Ton Solar 2-E Absorption HVAC
System, CEC Primary Funding, 1997
• 336 ICPC parallel collector tubes in three rows, filled
system, over-temperature protected
• 111 m2 Aperture Area, 156 m2 Gross Area, 186 m2
footprint
• Orientation South, Sloped at 280 (Latitude - 100)
• Water HTF, 40 gpm, 50 feet of water pressure drop, 220
Mbtu/hr peak heat output, 1770C maximum
• 1000 gallon stainless steel pressurized thermal storage tank
• 20-ton Sanyo-McQuay direct-fired 2E absorption chiller
modified to hot water fired at 1650C with tube-in-shell,
reverse-flow generator
• 8,000 ft2 single-story building used for print shop and
offices
ICPC Collector Highlights
• Evacuated Borosilicate glass tube with proprietary
non-imaging optics reflector inside.
• Proprietary selective coating on stainless steel
absorber tube with absorptivity ~98% and emissivity.
~6% over wide temperature range.
• Ten-tube modules anticipated.
• Vertical load of 6.7 lb/ft2.
• Flexible roof-mounting requirements.
Solar Energy System Highlights
• Roof-mounted ICPC evacuated tube collectors reduce
solar gain and reduce building cooling load.
• Approximately 50% of collectable solar energy
delivered to 2E absorption chiller at 3300F.
• Peak cooling energy per peak collectable solar energy
equals 60%.
• Non-tracking.
• Low maintenance and long life.
• Any suitable clean backup fuel including biofuels.
• 2E absorption chiller: high reliability, environmentally
friendly, average maintenance costs, full automatic
operation.
• System-ready for organic Rankine cycle (ORC) enginegenerator
when such equipment is available (30kW per
100 tons).
• Energy peak shaving.
• Insurance against rising energy costs.
• Summer: 100 tons of cooling and domestic hot
water heating.
• Winter: space and domestic hot water heating.
• Emissions annual reductions:
CO2 = 182,000 lb SO2 = 170 lb NOx = 240 lb
Dual Energy Source Absorption Chiller-
Heater
• Absorption chiller can be fired by natural gas,
LPG, fuel oil, hot water, steam, or hot thermal oil
• Newest units provide 1800F hot water for heating.
• Eliminates the need for separate backup energy
source for solar absorption HVAC system
• Lower capital costs and higher system efficiency
• Concept fully tested in 50-ton Yazaki 2E chiller
• Patent issued in 2006.
• Broad Air Conditioning Co. is now manufacturing
dual energy source 2E absorption chillers.
Energy Efficiency in Building Design and Construction
1.0 Introduction:
A study conducted by Energy Information
Administration, (EIA), U.S. Department of Energy
indicates that there is a visible trend across the globe
wherein the growth rate in total energy consumption
has been greater than the population growth rate.
In the developed countries the energy consumption
growth rate is only marginally higher compared to the
population growth rate. For example, in USA, energy
consumption is projected to grow at 1.3% while the
population growth rate is projected to grow at 0.8%.
In contrast, in developing countries like India population growth rate is expected to
grow at 1.3% while the energy consumption ra te is expected to grow at 4.3%.
This trend would strain the energy sector to a large extent.
The construction industry in the country is growing at a rapid pace and the rate of
growth is 10 % as compared to the world average of 5.2%. Hence energy efficiency
in the building sector assumes tremendous importance.
Commercial buildings are one of the major consumers of energy and are the third
largest consumers of energy, after industry and agriculture. Buildings annually
consume more than 20% of electricity used in India.
The potential for energy savings is 40 – 50% in buildings, if energy efficiency
measures are incorporated at the design stage. For existing buildings, the potential
can be as high as 20-25% which can be achieved by implementing house keeping and
retrofitting measures.
The incremental cost incurred for achieving energy efficiency is 5-8% vis-a-vis
conventional design cost and can have an attractive payback period of 2-4 years.
CII-Sohrabji Godrej Green Business Centre
LEED - Platinum Rated
63% Energy Savings
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
1.1 Typical Energy Consumption Pattern in Buildings:
Figure 1: Break-up of energy consumption in a building
Typical break-up of energy consumption in a building is as shown in Fig 1.
In a typical building, air conditioning is the highest consumer of energy followed by
lighting and other miscellaneous equipment. Therefore, if the initial design considers
energy efficiency measures in these areas, substantial energy savings can be realised.
2.0 Typical Energy Saving Approach In Buildings:
2.1 Orientation:
This is the f irst step to achieve energy efficiency. The
following measures can be adopted:
v Minimize exposure on the south and west
v Use simulation tools and techniques which can
help in designing the orientation to minimise
heat ingress and enhance energy efficiency.
2.2 Building Envelope:
Figure 2: Typical break-up of heat gain in a building
Wipro Technologies, Gurgaon
LEED – Platinum Rated
40% Energy Savings
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
Typical heat gain through the building envelope is shown in Fig.2
The following envelope measures can be considered:
v Select high performance glazing with low U-value, low Shading Coefficient and
high VLT (Visual Light Transmittance).
v Insulate the wall. The options for insulation materials can be - Extruded
polystyrene, Expanded polystyrene (thermocol), Glass wool e tc.,
v Brick wall with air cavity can also significantly reduce the heat ingress.
v Hollow blocks, Fly ash bricks and Autoclaved Aerated Concrete (AAC) Blocks
are also good insulators.
v The heat ingress through the roof can be as high as 12-15%. Insulating the
roof can substantially reduce the heat ingress.
v Consider shading devices for window openings.
2.3 Equipment & systems:
v Select chillers with high Coefficient of Performance
(CoP).
v Install Variable Frequency Drives (VFD) for supply &
return air fans and pumps.
v Select high efficiency cooling towers.
v Use high efficiency motors, transformers and pumps.
v Install Heat recovery wheels and economizers
v Consider night purging with ambient air to flush out
the heat trapped within the building during the day
v Adopt Controls & Building Management Systems for effective control
v Engage a Commissioning Authority to ensure that savings are realised once the
building becomes operational
2.4 Lighting:
v Design in such a way that the building gets maximum day lighting.
v Overall lighting power density can be designed as less as 1.0 W/sq.ft.
v Use daylight-cum-dimmer controls
v Install occupancy sensors
v Select energy efficient luminaires like CFL, T-5, LED, etc.,
ITC Green Centre, Gurgaon
LEED-Platinum Rated
45% Energy Savings
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
3.0 LEED India Rating System & Energy Efficiency:
The LEED (Leadership in Energy and Environmental
Design) green building rating system developed by the
US Green Building Council is now recognised as an
international rating system and followed by more than
24 countries. The LEED rating system has been
indigenized by the Indian Green Building Council to
suit the national context and priorities. Energy efficiency in design has been achieved
by a number of buildings in India by adopting the LEED India green building rating
system.
A LEED rated building consumes 30-50% lower energy as compared to a conventional
building. These buildings are designed to surpass the ASHRAE 90.1.2004 standards or
ECBC (Energy Conservation Building Code).
Energy performance of three ‘LEED Platinum’ ra ted buildings have been monitored for
about 3 years and energy savings achieved are shown in Table -1
Table – 1: Monitoring of energy savings in LEED rated buildings
Building
Built-up
Area
(Sq.ft)
Consumption
of
Conventional
Building
(kWh)
Consumption
of
LEED
Designed
Building
(kWh)
%
Reduction
Annual
Energy
Savings
(Rs in
Lakhs)
Wipro Technologies,
Gurgaon
1,75,000 48,00,000 31,00,000 40% 102
ITC Green Centre,
Gurgaon
1,70,000 35,00,000 20,00,000 45% 90
CII Godrej GBC,
Hyderabad
20,000 3,50,000 1,30,000 63% 9
The IGBC (Indian Green Building Council) has launched two rating programmes LEED
India NC (New Construction) and LEED India CS (Core & Shell). As on date, 195
projects with a built-up area of more than 110 million sq.ft. are registered for
rating. Thus far, 19 buildings have achieved the LEED ra ting in India.
NEG-Micon India (Pvt) Ltd, Chennai
LEED - Gold Rated
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
5
4.0 Challenges & Opportunities:
Achieving energy efficiency in building poses a number of challenges and at the same
time presents a host of opportunities. A few of them are discussed below:
4.1 Awareness & Training:
Incorporating energy efficiency measures at design
stage requires knowledge of the green building
concepts. There is now a need for skilled and
knowledgeable professionals who have deep
understanding of architecture and energy systems.
IGBC is addressing this through number of training
and awareness programmes all over the country. Thus
far, 3500 professionals have been trained on these
concepts.
Energy simulation programmes are excellent tools to design energy efficient buildings.
The tools typically used are Visual DOE, Energy Plus and Lumen Micro. As of now, the
number of trained professionals on these tools and techniques is scarce. IGBC is
facilitating training of professionals on these tools.
4.2 Availability of Materials, Equipment and Technologies:
The availability and affordability of materials/equipment which contribute to energy
efficiency is another major challenge. Tremendous potential exists for materials &
equipment like heat resistive paints, fly ash blocks, insulation materials, high
efficiency chillers, variable frequency drives, high efficiency cooling towers,
building management systems, lighting controls, BIPV (Building Integrated
Photo Voltaics), etc., New technologies like wind towers, geothermal systems etc.,
are gaining importance. The business opportunity for these products and technologies
in India expected to cross 25 billion USD / annum by 2010. To facilitate the
penetration of these products, IGBC has platforms like Green Building Congress,
Permanent Technology Centre in CII-Godrej GBC, Manufacturers meet, etc., to
showcase energy efficient products.
Grundfos Pumps India Ltd, Chennai
LEED - Gold Rated
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
6
4.3 Sustained Savings:
A building can have the best of materials,
equipment and systems in place at the design
stage; however, the building can sustain the
savings only if it is monitored on a continuous
basis.
LEED rated buildings use IPMVP (International
Performance Measurement and Verification
Protocol) to monitor and sustain the savings. Proper measurement & verification of
savings will help the building owner to fine-tune the base line and achieve high level
of savings.
Applying rating programmes like LEED EB (LEED for Existing Buildings) can help
buildings to sustain energy efficient practices over the life of the building.
4.4 National Codes and Standards:
Government of India has launched the ‘Energy Conservation Building Code
(ECBC)’ code. This code is voluntary and applicable to buildings or building
complexes that have a connected load of 500 KW or a contract demand of 600 KVA,
whichever is greater. This code addresses the minimum performance standards for
energy efficiency in a building covering building envelope, mechanical systems &
equipment, service hot water heating, interior & exterior lighting and electrical power
& motors. This is an excellent initiative which will enable design of high performance
buildings.
5.0 Conclusion:
With the tremendous growth the country is witnessing, energy efficiency in buildings
assumes paramount importance. The energy saving potential can be as high as 40-
50%, if addressed right at the design stage. The application of codes like ASHARE /
ECBC as a benchmark can help in designing high performance buildings. There exist
tremendous opportunities to introduce new materials, equipment and technologies
which can help enhance energy efficiency of buildings.
A study conducted by Energy Information
Administration, (EIA), U.S. Department of Energy
indicates that there is a visible trend across the globe
wherein the growth rate in total energy consumption
has been greater than the population growth rate.
In the developed countries the energy consumption
growth rate is only marginally higher compared to the
population growth rate. For example, in USA, energy
consumption is projected to grow at 1.3% while the
population growth rate is projected to grow at 0.8%.
In contrast, in developing countries like India population growth rate is expected to
grow at 1.3% while the energy consumption ra te is expected to grow at 4.3%.
This trend would strain the energy sector to a large extent.
The construction industry in the country is growing at a rapid pace and the rate of
growth is 10 % as compared to the world average of 5.2%. Hence energy efficiency
in the building sector assumes tremendous importance.
Commercial buildings are one of the major consumers of energy and are the third
largest consumers of energy, after industry and agriculture. Buildings annually
consume more than 20% of electricity used in India.
The potential for energy savings is 40 – 50% in buildings, if energy efficiency
measures are incorporated at the design stage. For existing buildings, the potential
can be as high as 20-25% which can be achieved by implementing house keeping and
retrofitting measures.
The incremental cost incurred for achieving energy efficiency is 5-8% vis-a-vis
conventional design cost and can have an attractive payback period of 2-4 years.
CII-Sohrabji Godrej Green Business Centre
LEED - Platinum Rated
63% Energy Savings
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
1.1 Typical Energy Consumption Pattern in Buildings:
Figure 1: Break-up of energy consumption in a building
Typical break-up of energy consumption in a building is as shown in Fig 1.
In a typical building, air conditioning is the highest consumer of energy followed by
lighting and other miscellaneous equipment. Therefore, if the initial design considers
energy efficiency measures in these areas, substantial energy savings can be realised.
2.0 Typical Energy Saving Approach In Buildings:
2.1 Orientation:
This is the f irst step to achieve energy efficiency. The
following measures can be adopted:
v Minimize exposure on the south and west
v Use simulation tools and techniques which can
help in designing the orientation to minimise
heat ingress and enhance energy efficiency.
2.2 Building Envelope:
Figure 2: Typical break-up of heat gain in a building
Wipro Technologies, Gurgaon
LEED – Platinum Rated
40% Energy Savings
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
Typical heat gain through the building envelope is shown in Fig.2
The following envelope measures can be considered:
v Select high performance glazing with low U-value, low Shading Coefficient and
high VLT (Visual Light Transmittance).
v Insulate the wall. The options for insulation materials can be - Extruded
polystyrene, Expanded polystyrene (thermocol), Glass wool e tc.,
v Brick wall with air cavity can also significantly reduce the heat ingress.
v Hollow blocks, Fly ash bricks and Autoclaved Aerated Concrete (AAC) Blocks
are also good insulators.
v The heat ingress through the roof can be as high as 12-15%. Insulating the
roof can substantially reduce the heat ingress.
v Consider shading devices for window openings.
2.3 Equipment & systems:
v Select chillers with high Coefficient of Performance
(CoP).
v Install Variable Frequency Drives (VFD) for supply &
return air fans and pumps.
v Select high efficiency cooling towers.
v Use high efficiency motors, transformers and pumps.
v Install Heat recovery wheels and economizers
v Consider night purging with ambient air to flush out
the heat trapped within the building during the day
v Adopt Controls & Building Management Systems for effective control
v Engage a Commissioning Authority to ensure that savings are realised once the
building becomes operational
2.4 Lighting:
v Design in such a way that the building gets maximum day lighting.
v Overall lighting power density can be designed as less as 1.0 W/sq.ft.
v Use daylight-cum-dimmer controls
v Install occupancy sensors
v Select energy efficient luminaires like CFL, T-5, LED, etc.,
ITC Green Centre, Gurgaon
LEED-Platinum Rated
45% Energy Savings
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
3.0 LEED India Rating System & Energy Efficiency:
The LEED (Leadership in Energy and Environmental
Design) green building rating system developed by the
US Green Building Council is now recognised as an
international rating system and followed by more than
24 countries. The LEED rating system has been
indigenized by the Indian Green Building Council to
suit the national context and priorities. Energy efficiency in design has been achieved
by a number of buildings in India by adopting the LEED India green building rating
system.
A LEED rated building consumes 30-50% lower energy as compared to a conventional
building. These buildings are designed to surpass the ASHRAE 90.1.2004 standards or
ECBC (Energy Conservation Building Code).
Energy performance of three ‘LEED Platinum’ ra ted buildings have been monitored for
about 3 years and energy savings achieved are shown in Table -1
Table – 1: Monitoring of energy savings in LEED rated buildings
Building
Built-up
Area
(Sq.ft)
Consumption
of
Conventional
Building
(kWh)
Consumption
of
LEED
Designed
Building
(kWh)
%
Reduction
Annual
Energy
Savings
(Rs in
Lakhs)
Wipro Technologies,
Gurgaon
1,75,000 48,00,000 31,00,000 40% 102
ITC Green Centre,
Gurgaon
1,70,000 35,00,000 20,00,000 45% 90
CII Godrej GBC,
Hyderabad
20,000 3,50,000 1,30,000 63% 9
The IGBC (Indian Green Building Council) has launched two rating programmes LEED
India NC (New Construction) and LEED India CS (Core & Shell). As on date, 195
projects with a built-up area of more than 110 million sq.ft. are registered for
rating. Thus far, 19 buildings have achieved the LEED ra ting in India.
NEG-Micon India (Pvt) Ltd, Chennai
LEED - Gold Rated
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
5
4.0 Challenges & Opportunities:
Achieving energy efficiency in building poses a number of challenges and at the same
time presents a host of opportunities. A few of them are discussed below:
4.1 Awareness & Training:
Incorporating energy efficiency measures at design
stage requires knowledge of the green building
concepts. There is now a need for skilled and
knowledgeable professionals who have deep
understanding of architecture and energy systems.
IGBC is addressing this through number of training
and awareness programmes all over the country. Thus
far, 3500 professionals have been trained on these
concepts.
Energy simulation programmes are excellent tools to design energy efficient buildings.
The tools typically used are Visual DOE, Energy Plus and Lumen Micro. As of now, the
number of trained professionals on these tools and techniques is scarce. IGBC is
facilitating training of professionals on these tools.
4.2 Availability of Materials, Equipment and Technologies:
The availability and affordability of materials/equipment which contribute to energy
efficiency is another major challenge. Tremendous potential exists for materials &
equipment like heat resistive paints, fly ash blocks, insulation materials, high
efficiency chillers, variable frequency drives, high efficiency cooling towers,
building management systems, lighting controls, BIPV (Building Integrated
Photo Voltaics), etc., New technologies like wind towers, geothermal systems etc.,
are gaining importance. The business opportunity for these products and technologies
in India expected to cross 25 billion USD / annum by 2010. To facilitate the
penetration of these products, IGBC has platforms like Green Building Congress,
Permanent Technology Centre in CII-Godrej GBC, Manufacturers meet, etc., to
showcase energy efficient products.
Grundfos Pumps India Ltd, Chennai
LEED - Gold Rated
Confederation of Indian Industry
CII-Sohrabji Godrej Green Business Centre
6
4.3 Sustained Savings:
A building can have the best of materials,
equipment and systems in place at the design
stage; however, the building can sustain the
savings only if it is monitored on a continuous
basis.
LEED rated buildings use IPMVP (International
Performance Measurement and Verification
Protocol) to monitor and sustain the savings. Proper measurement & verification of
savings will help the building owner to fine-tune the base line and achieve high level
of savings.
Applying rating programmes like LEED EB (LEED for Existing Buildings) can help
buildings to sustain energy efficient practices over the life of the building.
4.4 National Codes and Standards:
Government of India has launched the ‘Energy Conservation Building Code
(ECBC)’ code. This code is voluntary and applicable to buildings or building
complexes that have a connected load of 500 KW or a contract demand of 600 KVA,
whichever is greater. This code addresses the minimum performance standards for
energy efficiency in a building covering building envelope, mechanical systems &
equipment, service hot water heating, interior & exterior lighting and electrical power
& motors. This is an excellent initiative which will enable design of high performance
buildings.
5.0 Conclusion:
With the tremendous growth the country is witnessing, energy efficiency in buildings
assumes paramount importance. The energy saving potential can be as high as 40-
50%, if addressed right at the design stage. The application of codes like ASHARE /
ECBC as a benchmark can help in designing high performance buildings. There exist
tremendous opportunities to introduce new materials, equipment and technologies
which can help enhance energy efficiency of buildings.
THERMAL INSULATION OF ENERGY EFFICIENT BUILDINGS
Abstract:
Thermal insulation is the easiest and most effective energy efficient technologies available today. Thermal
insulating materials commonly used are flexible (mineral wool, glass fibre), loose fill, and spray. Using these
materials insulation techniques like stud walls with standard sheathing and cladding, stud walls with exterior
thermal sheathing and foundations like concrete foundation with exterior insulation, permanent wood foundation
renders good amount of efficient thermal insulation. But with the use of GRP, ACC and some insulating paints
thermal insulation can be increased to an optimum level. This paper includes the case study of residential
complex at Thatipur, Gwalior in which composite technique has been introduced.
1. Introduction
Over the past 30 years, rising power costs and energy conservation concerns have prompted the building industry
to improve the efficiency of newly built constructions. Since each site has its own unique climatic and
topographic characteristics, a considerate response to the site limitations which utilize the natural resources and
integrate them into the design will bring about an energy efficient building. The main goal of energy conscious
designer is to condition the interior environment to support a level of climate comfort acceptable to the users.
Efficient use of energy is important since global energy resources are finite and power generation using fossil
fuels (such as coal and oil) has adverse environmental effects.
Thermal insulation is a technique that minimizes the transfer of heat energy from inside to outside and viceversa,
of the building by reducing the conduction, convection and radiation effects. Insulation is the building
component which controls temperature directly, and indirectly affects the movement of moisture to and from
building spaces. Insulation in the building is maintained by thermal insulating material like flexible material,
loose fill and spray. Most common of these is Flexible. Insulating material used along with insulation technique
brings optimum insulation inside a building.
1.1 Review of Thermal Insulating Materials
The selection of thermal insulating materials depends up on their R & RSI values. Thermal resistance index
(RSI) is the resistance of an assembly to the transfer of heat and is given in units of m2•°C/W. The imperial
equivalent is R value expressed in units of ft2•h•°F/BTU. Insulation for the home has R-values usually in the
range of R-10 up to R-30. The following table shows R & RSI values of a few thermal insulating materials:
Table 1: RSI & R values of different insulating materials
Thickness Thermal Resistance
Sl. No.
Insulation Materials
mm inch
RSI
m2*°C/W
R
ft2*h*°F/BTU
low density 140 5-1/2 2.83 16
medium density 140 5-1/2 3.30 19
1.
Flexible
(mineral wool, glass
fibre) high density 140 5-1/2 3.93 22.5
glass fibre 100 4 2.00 11
mineral fibre 100 4 2.30 13
2.
Loose fill
cellulose fibre 100 4 2.50 12.5
polyurethane 100 4 4.1 23
isocyanurate 100 4 3.4 19
3.
Spray
cellulose fibre 100 4 2.4 13.5
Thermal Insulation of Energy Efficient Buildings 411
1.2 Review of Insulation Techniques
1.2.1 Stud Walls with Exterior Thermal Sheathing
The insulation of stud wall can be achieved by providing rigid or semi-rigid insulation panels that are nailed to
these walls using special nails with large plastic washers. In these types of wall, diagonal bracing is provided
which adds the rigidity to it (fig. 1).
1.2.2 Concrete Foundation with Exterior Insulation
Foundations wall enclosing heated space are insulated with rigid insulation boards made from polystyrene or
glass fiber installed vertically on the exterior of the wall. The above grade portion of the rigid insulation is
fastened to the sill plate or to the foundation wall with an adhesive. If the above grade portion is not covered by
the exterior cladding the exposed insulation is protected from mechanical damage with flashing and cement
parging on wire lath. Damp proofing is done before applying insulation.
Figure 1: Stud walls with exterior thermal sheathing Figure 2: Concrete foundation with exterior insulation
1.3 Insulation by Planning
In order to implement thermal insulation in the building, planning with proper orientation is essential. The
orientation should be such that it allows optimum amount of air and light to enter into the building. India
being a tropical country, efforts are directed to prevent entrance of excessive heat.
Following factors should be considered while planning a building:
• Total area covered by doors and windows should be as less as possible. Also they should be placed
according to seasonal wind direction.
• Use of sunshading devices (natural or artificial). The artificial sunshading devices like Louvers,
Overhangs, Screens proves to be effective.
• Longer outside walls should run in EW direction and shorter walls in NS direction.
• Provision of deep verandah in SW direction.
• Plantation of grass and shady trees around the building help in reducing the temperature of the building.
412 Advances in Energy Research (AER – 2006)
1.4 Review of Innovative Techniques
1.4.1 Autoclaved Aerated Concrete
AAC building blocks are manufactured conforming to IS 2185 having density
range of 551-600 kg/m³ and minimum compressive strength of 3N/mm². The
thermal insulating properties of these blocks is due to the closed air cell
structure and there increased level of thermal performance (K=0.16W/m deg.
K) leads to more comfortable living and efficient energy saving of air
conditioning.
1.4.2. Insulating Coatings
Thermal insulating coatings is a ceramic , insulating roof and exterior coating
which comprise of best in acrylic binder and ceramic/silica coating materials
which provide unequal resistance to adverse weather conditions and also
provide thermal insulation to the building. It attacks heat or cold penetration
before it enters the substrate. It has exceptional property of producing cross
linking structure which grows stronger over time thereby adhering and
bonding better to the substrate and also within itself providing it better
strength, longevity and flexibility.
1.4.3. Glass Reinforced Plastics (GRP)
GRP is a composite material or fiber reinforced plastic made of a plastic reinforced by the fine fibers made of
glass like graphite reinforced plastic. The applications of GRP in doors and windows are explained as follows:
1.4.3.1. GRP Windows
These are the new types of windows with narrower frames which give the
building a more elegant appearance and allow more light to enter the room.
The GRP material prevents thermal bridges and insulates so well that the Uvalue
of the total window structure is reduced to as low as 1.3 W/m2K which
is about 1.8 W/m2K in case of traditional windows. Moreover, windows can
not rot and require practically no maintenance and windows weigh 25% less
than traditional windows.
1.4.3.2. GRP Door Steps
Profiles of GRP prevent thermal bridges, reducing hest loss and condensation
problems. This simple solution can diminish heat loss by 20% or more, while
ensuring that residents are not exposed to the inconvenience of cold,
condensation and rot. The low, thin door step combines superior stiffness with
excellent thermal insulation properties. They are strong and durable solution.
2. Case Study
The site selected for the case study is located at Darpan Colony, Thatipur, Gwalior (M.P.) with Latitude-26°12'
N, Longitude- 76°18' E and Altitude-212 m above MSL. Following data shows the variation in various
environmental factors of the site:
2.1. Environmental Data
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean max.temp. 22 24 32.4 37.4 46 41.4 37.6 23.2 34.4 36.2 27 24
Mean min.temp. 3.2 10.9 15.8 18 25 29 28 26.4 22 16.3 14.2 8.5
Rainfall 20.8 23.6 12.9 9.7 67.6 186 169 14.2 2.0 8.6 2.0 8.6
Wind direction NW NW NW NW N N N NW NW NW NW NW
Thermal Insulation of Energy Efficient Buildings 413
2.2. Thermal Discomfort Index*
SEASON MONTH DISCOMFORT DURATION INDEX %
APRIL 21.5 1 21.5
HOT DRY MAY 23.5 1 23.5
JUNE 23.5 1 23.5
SEASONAL TOTAL 68.5 38
JULY 22.6 1 22.6
AUGUST 22.6 1 22.6
WARM HUMID SEPTEMBER 16.5 1 16.5
OCTOBER 18.1 1 18.1
SEASONAL TOTAL 73.0 34
DECEMBER -15.6 1 15.6
COLD DRY JANUARY -14.1 1 14.1
FEBRUARY -14.6 1 14.6
SEASONAL TOTAL 49.3 28
ANNUAL TOTAL 100
* Data used here are collected from M.P. Housing board (Gwalior)
• This table for thermal discomfort explains that hot season is much more important for thermal design than
cold season. Thus for thermal comfort techniques of insulation should be adopted.
• In the last twenty years there is an increase of 2°C in Gwalior and the summer duration is expanding. Thus
this increasing thermal discomfort should be cured so that occupants can enjoy the next coming years.
• Following figure shows the plan of the residential complex, which was built in yr 1992 by M.P. Housing
Board. In this case study we are estimating the approximate cost for thermal insulation of a single house of
this complex.
Figure 4: Plan of M.P. Housing Board residential complex
414 Advances in Energy Research (AER – 2006)
Figure 5.1: Ground floor plan Figure 5.2: First floor plan
Figure 5: Plan of single house
Table 2: Dimensions of different components of the house
GROUND FLOOR FIRST FLOOR
Verandah 2.8 x 1.5 Verandah 2.8 x 1.5
Drawing Room 3.1 x 3.9 Bed Room-I 3.1 x 3.9
Dining Room 3.7 x 2.5 Bedroom -Ii 3.7 x 2.5
Kitchen 3.0 x 2.4 Kitchen 3.0 x 2.4
Garage 3.1 x 4.5 Balcony 3.1 x 4.5
Toilet 2.0 x 1.5 Toilet 2.0 x 1.5
Wind Opening 1.2 x 1.0 Duct 1.2 x 1.0
(All dimensions in meter)
2.3. Observations: After studying all these, we suggest the following economic techniques for our site:
2.3.1. Insulation for Roof
• Average hours of solar radiations – 8.2 hours (9.7 hours/day in May, 6.4 hours/day in August).
• About 50-65% heat is transferred inside through roof, hence insulation of roof is essential.
• Figure 6 shows our suggestion, where we are using thermocol (1.5”), plywood (6mm), J-hooks, washers and
bolts. The bottom of the bolts should be covered with caps to give aesthetic view. This is a durable solution as
compared to the thermocol placed over the roof.
• Height of the topmost slab should be at least 3.10m
2.3.2. Insulation for Walls
• The walls directly exposed to sun radiations should be insulated by maintaining air gap.
• Cavity wall free from load should be constructed in front of the pre-existing wall. This technique is useful in
case of ground floor, because it may increase the load of the structures above the ground floor.
• ACC can be used (In case if they are economic).
• Honey comb the wall structure.
Figure 6: Iinsulation for roof Figure 7: Insulation for walls Figure 8: Insulation for windows
Thermal Insulation of Energy Efficient Buildings 415
2.3.3. Insulation for Windows & Door Steps
• GRP should be used (In case if they are economic).
• Provision of buffer zone at entry.
• Plantation on south and west sides.
• Provision of double glass window
• Proper overhang length of sunshade should be provided.
• Proper projection on south, east and west side.
• Construction of air tight door windows and ventilators by using rubber gaskets.
2.4. Estimation
S. No. Building component Area (m²) Material Details
Material Price/m² Cost
(Rs.)
Roof ( 1st Floor only)
Bed Room I 12.09
Bed Room II 9.25
Thermocol (1.5”
thick)
5
Kitchen 7.2
Verandah -
plywood
(6mmthick)
18
Balcony -
Staircase -
1.
Toilet 3
J-hooks
Washers,
bolts & caps
6 x 20
4510
Exterior walls Length in
running
meter
Ht.
Rear wall 11.1 3.1 34.41 x 2
Front wall
(verandah)
3 3.1 9.3 x 2
2.
*Deduction For Doors& windows 6.84 x 2
Cavity wall with
reinforcement in
cement mortar (1:4)
250
18435
3. Fully glazed Z- section window 10 x 1.8 - 950 17100
4. Flush doors 35 mm thick with all
necessary fittings
4 x(2 x
2.14)
- 900 15408
5. Synthetic enameled paint with putty
and priming
4 x 8.56 - 70 2400
Total 57853
Work Charge expenses (2%) 1157
GRAND TOTAL 59010
3. Conclusion
Thermal insulation is one of the important aspects which should be considered for the energy efficient building.
From the past 20 years data it is found that the temperature is increasing and thus thermal insulation is an
immediate need to be considered for occupant comfort. These days many techniques are being adopted for the
same. In this paper we have tried to emphasize on one of such technique by using the thermal insulating material
thermocol at the lower end of the roof along with plywood, bolts that are covered with caps to give your ceiling
an aesthetic look. The technique mentioned hereby is very economic, reliable and durable.
Reference
1. D B Mundra, Paper on AAC Building for Thermal Blocks for Reducing Air Conditioning Load in Buildings.
2. S. C. Rangwala, Building Construction, P-573 to 579
3. S. P. Bindra & Arora, Building Construction, P-801 to 814
4. Office: M.P. Housing Board, Sanjay Complex, Gwalior
5. www.mascotsingapore.com
6. www.cwc.com
7. www.fibreline.com
Thermal insulation is the easiest and most effective energy efficient technologies available today. Thermal
insulating materials commonly used are flexible (mineral wool, glass fibre), loose fill, and spray. Using these
materials insulation techniques like stud walls with standard sheathing and cladding, stud walls with exterior
thermal sheathing and foundations like concrete foundation with exterior insulation, permanent wood foundation
renders good amount of efficient thermal insulation. But with the use of GRP, ACC and some insulating paints
thermal insulation can be increased to an optimum level. This paper includes the case study of residential
complex at Thatipur, Gwalior in which composite technique has been introduced.
1. Introduction
Over the past 30 years, rising power costs and energy conservation concerns have prompted the building industry
to improve the efficiency of newly built constructions. Since each site has its own unique climatic and
topographic characteristics, a considerate response to the site limitations which utilize the natural resources and
integrate them into the design will bring about an energy efficient building. The main goal of energy conscious
designer is to condition the interior environment to support a level of climate comfort acceptable to the users.
Efficient use of energy is important since global energy resources are finite and power generation using fossil
fuels (such as coal and oil) has adverse environmental effects.
Thermal insulation is a technique that minimizes the transfer of heat energy from inside to outside and viceversa,
of the building by reducing the conduction, convection and radiation effects. Insulation is the building
component which controls temperature directly, and indirectly affects the movement of moisture to and from
building spaces. Insulation in the building is maintained by thermal insulating material like flexible material,
loose fill and spray. Most common of these is Flexible. Insulating material used along with insulation technique
brings optimum insulation inside a building.
1.1 Review of Thermal Insulating Materials
The selection of thermal insulating materials depends up on their R & RSI values. Thermal resistance index
(RSI) is the resistance of an assembly to the transfer of heat and is given in units of m2•°C/W. The imperial
equivalent is R value expressed in units of ft2•h•°F/BTU. Insulation for the home has R-values usually in the
range of R-10 up to R-30. The following table shows R & RSI values of a few thermal insulating materials:
Table 1: RSI & R values of different insulating materials
Thickness Thermal Resistance
Sl. No.
Insulation Materials
mm inch
RSI
m2*°C/W
R
ft2*h*°F/BTU
low density 140 5-1/2 2.83 16
medium density 140 5-1/2 3.30 19
1.
Flexible
(mineral wool, glass
fibre) high density 140 5-1/2 3.93 22.5
glass fibre 100 4 2.00 11
mineral fibre 100 4 2.30 13
2.
Loose fill
cellulose fibre 100 4 2.50 12.5
polyurethane 100 4 4.1 23
isocyanurate 100 4 3.4 19
3.
Spray
cellulose fibre 100 4 2.4 13.5
Thermal Insulation of Energy Efficient Buildings 411
1.2 Review of Insulation Techniques
1.2.1 Stud Walls with Exterior Thermal Sheathing
The insulation of stud wall can be achieved by providing rigid or semi-rigid insulation panels that are nailed to
these walls using special nails with large plastic washers. In these types of wall, diagonal bracing is provided
which adds the rigidity to it (fig. 1).
1.2.2 Concrete Foundation with Exterior Insulation
Foundations wall enclosing heated space are insulated with rigid insulation boards made from polystyrene or
glass fiber installed vertically on the exterior of the wall. The above grade portion of the rigid insulation is
fastened to the sill plate or to the foundation wall with an adhesive. If the above grade portion is not covered by
the exterior cladding the exposed insulation is protected from mechanical damage with flashing and cement
parging on wire lath. Damp proofing is done before applying insulation.
Figure 1: Stud walls with exterior thermal sheathing Figure 2: Concrete foundation with exterior insulation
1.3 Insulation by Planning
In order to implement thermal insulation in the building, planning with proper orientation is essential. The
orientation should be such that it allows optimum amount of air and light to enter into the building. India
being a tropical country, efforts are directed to prevent entrance of excessive heat.
Following factors should be considered while planning a building:
• Total area covered by doors and windows should be as less as possible. Also they should be placed
according to seasonal wind direction.
• Use of sunshading devices (natural or artificial). The artificial sunshading devices like Louvers,
Overhangs, Screens proves to be effective.
• Longer outside walls should run in EW direction and shorter walls in NS direction.
• Provision of deep verandah in SW direction.
• Plantation of grass and shady trees around the building help in reducing the temperature of the building.
412 Advances in Energy Research (AER – 2006)
1.4 Review of Innovative Techniques
1.4.1 Autoclaved Aerated Concrete
AAC building blocks are manufactured conforming to IS 2185 having density
range of 551-600 kg/m³ and minimum compressive strength of 3N/mm². The
thermal insulating properties of these blocks is due to the closed air cell
structure and there increased level of thermal performance (K=0.16W/m deg.
K) leads to more comfortable living and efficient energy saving of air
conditioning.
1.4.2. Insulating Coatings
Thermal insulating coatings is a ceramic , insulating roof and exterior coating
which comprise of best in acrylic binder and ceramic/silica coating materials
which provide unequal resistance to adverse weather conditions and also
provide thermal insulation to the building. It attacks heat or cold penetration
before it enters the substrate. It has exceptional property of producing cross
linking structure which grows stronger over time thereby adhering and
bonding better to the substrate and also within itself providing it better
strength, longevity and flexibility.
1.4.3. Glass Reinforced Plastics (GRP)
GRP is a composite material or fiber reinforced plastic made of a plastic reinforced by the fine fibers made of
glass like graphite reinforced plastic. The applications of GRP in doors and windows are explained as follows:
1.4.3.1. GRP Windows
These are the new types of windows with narrower frames which give the
building a more elegant appearance and allow more light to enter the room.
The GRP material prevents thermal bridges and insulates so well that the Uvalue
of the total window structure is reduced to as low as 1.3 W/m2K which
is about 1.8 W/m2K in case of traditional windows. Moreover, windows can
not rot and require practically no maintenance and windows weigh 25% less
than traditional windows.
1.4.3.2. GRP Door Steps
Profiles of GRP prevent thermal bridges, reducing hest loss and condensation
problems. This simple solution can diminish heat loss by 20% or more, while
ensuring that residents are not exposed to the inconvenience of cold,
condensation and rot. The low, thin door step combines superior stiffness with
excellent thermal insulation properties. They are strong and durable solution.
2. Case Study
The site selected for the case study is located at Darpan Colony, Thatipur, Gwalior (M.P.) with Latitude-26°12'
N, Longitude- 76°18' E and Altitude-212 m above MSL. Following data shows the variation in various
environmental factors of the site:
2.1. Environmental Data
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean max.temp. 22 24 32.4 37.4 46 41.4 37.6 23.2 34.4 36.2 27 24
Mean min.temp. 3.2 10.9 15.8 18 25 29 28 26.4 22 16.3 14.2 8.5
Rainfall 20.8 23.6 12.9 9.7 67.6 186 169 14.2 2.0 8.6 2.0 8.6
Wind direction NW NW NW NW N N N NW NW NW NW NW
Thermal Insulation of Energy Efficient Buildings 413
2.2. Thermal Discomfort Index*
SEASON MONTH DISCOMFORT DURATION INDEX %
APRIL 21.5 1 21.5
HOT DRY MAY 23.5 1 23.5
JUNE 23.5 1 23.5
SEASONAL TOTAL 68.5 38
JULY 22.6 1 22.6
AUGUST 22.6 1 22.6
WARM HUMID SEPTEMBER 16.5 1 16.5
OCTOBER 18.1 1 18.1
SEASONAL TOTAL 73.0 34
DECEMBER -15.6 1 15.6
COLD DRY JANUARY -14.1 1 14.1
FEBRUARY -14.6 1 14.6
SEASONAL TOTAL 49.3 28
ANNUAL TOTAL 100
* Data used here are collected from M.P. Housing board (Gwalior)
• This table for thermal discomfort explains that hot season is much more important for thermal design than
cold season. Thus for thermal comfort techniques of insulation should be adopted.
• In the last twenty years there is an increase of 2°C in Gwalior and the summer duration is expanding. Thus
this increasing thermal discomfort should be cured so that occupants can enjoy the next coming years.
• Following figure shows the plan of the residential complex, which was built in yr 1992 by M.P. Housing
Board. In this case study we are estimating the approximate cost for thermal insulation of a single house of
this complex.
Figure 4: Plan of M.P. Housing Board residential complex
414 Advances in Energy Research (AER – 2006)
Figure 5.1: Ground floor plan Figure 5.2: First floor plan
Figure 5: Plan of single house
Table 2: Dimensions of different components of the house
GROUND FLOOR FIRST FLOOR
Verandah 2.8 x 1.5 Verandah 2.8 x 1.5
Drawing Room 3.1 x 3.9 Bed Room-I 3.1 x 3.9
Dining Room 3.7 x 2.5 Bedroom -Ii 3.7 x 2.5
Kitchen 3.0 x 2.4 Kitchen 3.0 x 2.4
Garage 3.1 x 4.5 Balcony 3.1 x 4.5
Toilet 2.0 x 1.5 Toilet 2.0 x 1.5
Wind Opening 1.2 x 1.0 Duct 1.2 x 1.0
(All dimensions in meter)
2.3. Observations: After studying all these, we suggest the following economic techniques for our site:
2.3.1. Insulation for Roof
• Average hours of solar radiations – 8.2 hours (9.7 hours/day in May, 6.4 hours/day in August).
• About 50-65% heat is transferred inside through roof, hence insulation of roof is essential.
• Figure 6 shows our suggestion, where we are using thermocol (1.5”), plywood (6mm), J-hooks, washers and
bolts. The bottom of the bolts should be covered with caps to give aesthetic view. This is a durable solution as
compared to the thermocol placed over the roof.
• Height of the topmost slab should be at least 3.10m
2.3.2. Insulation for Walls
• The walls directly exposed to sun radiations should be insulated by maintaining air gap.
• Cavity wall free from load should be constructed in front of the pre-existing wall. This technique is useful in
case of ground floor, because it may increase the load of the structures above the ground floor.
• ACC can be used (In case if they are economic).
• Honey comb the wall structure.
Figure 6: Iinsulation for roof Figure 7: Insulation for walls Figure 8: Insulation for windows
Thermal Insulation of Energy Efficient Buildings 415
2.3.3. Insulation for Windows & Door Steps
• GRP should be used (In case if they are economic).
• Provision of buffer zone at entry.
• Plantation on south and west sides.
• Provision of double glass window
• Proper overhang length of sunshade should be provided.
• Proper projection on south, east and west side.
• Construction of air tight door windows and ventilators by using rubber gaskets.
2.4. Estimation
S. No. Building component Area (m²) Material Details
Material Price/m² Cost
(Rs.)
Roof ( 1st Floor only)
Bed Room I 12.09
Bed Room II 9.25
Thermocol (1.5”
thick)
5
Kitchen 7.2
Verandah -
plywood
(6mmthick)
18
Balcony -
Staircase -
1.
Toilet 3
J-hooks
Washers,
bolts & caps
6 x 20
4510
Exterior walls Length in
running
meter
Ht.
Rear wall 11.1 3.1 34.41 x 2
Front wall
(verandah)
3 3.1 9.3 x 2
2.
*Deduction For Doors& windows 6.84 x 2
Cavity wall with
reinforcement in
cement mortar (1:4)
250
18435
3. Fully glazed Z- section window 10 x 1.8 - 950 17100
4. Flush doors 35 mm thick with all
necessary fittings
4 x(2 x
2.14)
- 900 15408
5. Synthetic enameled paint with putty
and priming
4 x 8.56 - 70 2400
Total 57853
Work Charge expenses (2%) 1157
GRAND TOTAL 59010
3. Conclusion
Thermal insulation is one of the important aspects which should be considered for the energy efficient building.
From the past 20 years data it is found that the temperature is increasing and thus thermal insulation is an
immediate need to be considered for occupant comfort. These days many techniques are being adopted for the
same. In this paper we have tried to emphasize on one of such technique by using the thermal insulating material
thermocol at the lower end of the roof along with plywood, bolts that are covered with caps to give your ceiling
an aesthetic look. The technique mentioned hereby is very economic, reliable and durable.
Reference
1. D B Mundra, Paper on AAC Building for Thermal Blocks for Reducing Air Conditioning Load in Buildings.
2. S. C. Rangwala, Building Construction, P-573 to 579
3. S. P. Bindra & Arora, Building Construction, P-801 to 814
4. Office: M.P. Housing Board, Sanjay Complex, Gwalior
5. www.mascotsingapore.com
6. www.cwc.com
7. www.fibreline.com
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