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Heating - Solar air heater - Industrial / Canada
Case study assignment
You have been hired by an industrial manufacturer to prepare a preliminary feasibility study on its behalf. The manufacturer wants you to evaluate different energy efficiency options for the renovation of their plant. Plans include recladding the building's exterior to replace siding past its useful life, insulating the old building, and installing additional ventilation capacity to improve indoor air quality.
A solar air heating (SAH) ventilation system is being considered instead of conventional wall cladding and make-up air units. The system is being considered based on savings demonstrated in other industrial plants with SAH systems installed.
Site information
The plant is located in Montreal, Quebec, Canada. For aesthetic reasons, the client has requested that the collector be Rocky Gray and that the canopy be white. There are two walls suitable for collector installation, one wall facing 45º east of south and an adjacent wall facing 45º west of south. The total available collector area is 8,826 m² split evenly between the 2 orientations. The southern exposure of the building is about 10% shaded during the heating season.
The SAH system will be very large with numerous fan and ducting systems. The collector will service 116,000 m² of production and assembly area. The required total airflow capacity is 1,000,000 m³/h. Operation will be 24 hours a day, 365 days per year with a system designed to maximise energy savings. It is expected that the fans for the SAH system will not require more electricity than conventional rooftop make-up air equipment. The building is heated from mid-September to mid-May using 75% efficient gas heaters.
Due to the type and nature of the machinery, internal gains in the plant are high and a supply of cool ventilation air is necessary. The desired delivered air temperature is estimated to be 15 ºC while a delivered air temperature in excess of 20 ºC may cause overheating. Twelve metre high ceilings present a challenge for system installation, but cause surprisingly little air stratification: preliminary measurements indicate that there is only 1 ºC difference between floor and roof level air temperatures. The RSI value of the walls is estimated at about 1.0 (m²-ºC)/W. The ceiling RSI is about 1.5 (m²-ºC)/W.
Site information
Typical financial figures for the analysis are provided by the firm (income tax rate of 42.6%, inflation rate of 1.5%, debt ratio of 25%, fuel cost escalation rate of 3%, debt interest rate of 8%, discount rate of 8%, and a debt term of 5 years). The company needs to obtain financing, permits, and approvals for the renovation in any case, and therefore these need not be factored into the cost. The equipment will be depreciated at an accelerated rate of 30% on a declining balance basis. Natural gas prices are around $0.20/m³. The project life should be 20 years.
Since the building is already being renovated, we can assume some credits for costs that would have been associated with the planned retrofit. There will be an incremental cost to install a SAH system versus a conventional system. The installed cost of the collector material will be about 65% higher than conventional cladding. Fan and ducting material costs are approximately 5% lower, however, due to the type of duct used within the building. Development costs will be minimal.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
Real project
Results
In 1994, Canadair requested that Natural Resources Canada and Enermodal Engineering Limited prepare a feasibility study of installing a solar air heating (SAH) system at their industrial facility in Montreal, Quebec, Canada. The building needed renovating and plans included recladding of the building's exterior to replace siding past its useful life, insulating the old building and installation of additional ventilation capacity to improve indoor air quality. The objective of the feasibility study was to determine the financial viability of a SAH system compared with the original renovation plans.
The original study proved that it would be cost-effective to install a SAH system at the 116,000 m2 Canadair plant. The retrofit installation had a 1.7-year payback. As a result of this study, Canadair went ahead with the installation of a SAH system instead of conventional wall cladding and make-up air units. The decision was also influenced by savings demonstrated in other plants with SAH systems.
System description
The Canadair system is unique in several ways. First, the installation is a hybrid of industrial SAH systems and commercial SAH systems. One half of the installed capacity operates like a typical industrial SAH system: fans with recirculation dampers adjust the temperature of the ventilation air by varying the ratio of solar-heated fresh air to air drawn from the ceiling level. The other half of the system, functioning like a typical commercial SAH system, uses gas-fired make-up air heaters to raise the temperature of the solar-heated fresh air, when necessary. Second, the installation uses custom air handlers with centrifugal fans and air filters rather than the more typical stand-alone vane-axial fans. Third, the collector is installed on one wall facing 40º east of south and on an adjacent wall facing 50º west of south. Fourth, the exhaust fans are operated by a thermometer at the ceiling. This reduces the heat lost from the building and provides destratification savings. Finally, the collector is Rocky Gray rather than black and the canopy is white rather than dark. The canopy is not part of the collector itself but acts as a manifold ensuring good distribution of airflow across the entire collector area. In this application, it also serves as an architectural highlight.
Lessons learned
The big picture
The Canadair facility is the largest solar ventilation air heating system in the world. This project showed that solar heating can achieve large energy savings in an industrial facility at a payback acceptable to industrial customers.
Photo
Industrial building - Solar air heater, Quebec, Canada
References
Case study assignment
You have been hired by an industrial manufacturer to prepare a preliminary feasibility study on its behalf. The manufacturer wants you to evaluate different energy efficiency options for the renovation of their plant. Plans include recladding the building's exterior to replace siding past its useful life, insulating the old building, and installing additional ventilation capacity to improve indoor air quality.
A solar air heating (SAH) ventilation system is being considered instead of conventional wall cladding and make-up air units. The system is being considered based on savings demonstrated in other industrial plants with SAH systems installed.
Site information
The plant is located in Montreal, Quebec, Canada. For aesthetic reasons, the client has requested that the collector be Rocky Gray and that the canopy be white. There are two walls suitable for collector installation, one wall facing 45º east of south and an adjacent wall facing 45º west of south. The total available collector area is 8,826 m² split evenly between the 2 orientations. The southern exposure of the building is about 10% shaded during the heating season.
The SAH system will be very large with numerous fan and ducting systems. The collector will service 116,000 m² of production and assembly area. The required total airflow capacity is 1,000,000 m³/h. Operation will be 24 hours a day, 365 days per year with a system designed to maximise energy savings. It is expected that the fans for the SAH system will not require more electricity than conventional rooftop make-up air equipment. The building is heated from mid-September to mid-May using 75% efficient gas heaters.
Due to the type and nature of the machinery, internal gains in the plant are high and a supply of cool ventilation air is necessary. The desired delivered air temperature is estimated to be 15 ºC while a delivered air temperature in excess of 20 ºC may cause overheating. Twelve metre high ceilings present a challenge for system installation, but cause surprisingly little air stratification: preliminary measurements indicate that there is only 1 ºC difference between floor and roof level air temperatures. The RSI value of the walls is estimated at about 1.0 (m²-ºC)/W. The ceiling RSI is about 1.5 (m²-ºC)/W.
Site information
Typical financial figures for the analysis are provided by the firm (income tax rate of 42.6%, inflation rate of 1.5%, debt ratio of 25%, fuel cost escalation rate of 3%, debt interest rate of 8%, discount rate of 8%, and a debt term of 5 years). The company needs to obtain financing, permits, and approvals for the renovation in any case, and therefore these need not be factored into the cost. The equipment will be depreciated at an accelerated rate of 30% on a declining balance basis. Natural gas prices are around $0.20/m³. The project life should be 20 years.
Since the building is already being renovated, we can assume some credits for costs that would have been associated with the planned retrofit. There will be an incremental cost to install a SAH system versus a conventional system. The installed cost of the collector material will be about 65% higher than conventional cladding. Fan and ducting material costs are approximately 5% lower, however, due to the type of duct used within the building. Development costs will be minimal.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
- The velocity of the wind hitting the solar collector has a significant influence on the estimated energy delivered by the solar air heating system. Obstacles such as other buildings, trees and fences will typically attenuate, but in some cases even intensify, the wind speed hitting the solar collector. In this case, a 0.70 wind sheltering coefficient is assumed (this was done by multiplying each of the wind speed values by 0.70 in the climate data section of the Start worksheet).
- Fans and ducting labour costs are high due to the complicated nature of the installation.
- If the collector is installed on 2 or more walls with different orientations, an average orientation should be used. Since the solar air heating (SAH) model does not differentiate between east and west, the sign of the azimuth of each contributing wall should be ignored.
Real project
Results
In 1994, Canadair requested that Natural Resources Canada and Enermodal Engineering Limited prepare a feasibility study of installing a solar air heating (SAH) system at their industrial facility in Montreal, Quebec, Canada. The building needed renovating and plans included recladding of the building's exterior to replace siding past its useful life, insulating the old building and installation of additional ventilation capacity to improve indoor air quality. The objective of the feasibility study was to determine the financial viability of a SAH system compared with the original renovation plans.
The original study proved that it would be cost-effective to install a SAH system at the 116,000 m2 Canadair plant. The retrofit installation had a 1.7-year payback. As a result of this study, Canadair went ahead with the installation of a SAH system instead of conventional wall cladding and make-up air units. The decision was also influenced by savings demonstrated in other plants with SAH systems.
System description
The Canadair system is unique in several ways. First, the installation is a hybrid of industrial SAH systems and commercial SAH systems. One half of the installed capacity operates like a typical industrial SAH system: fans with recirculation dampers adjust the temperature of the ventilation air by varying the ratio of solar-heated fresh air to air drawn from the ceiling level. The other half of the system, functioning like a typical commercial SAH system, uses gas-fired make-up air heaters to raise the temperature of the solar-heated fresh air, when necessary. Second, the installation uses custom air handlers with centrifugal fans and air filters rather than the more typical stand-alone vane-axial fans. Third, the collector is installed on one wall facing 40º east of south and on an adjacent wall facing 50º west of south. Fourth, the exhaust fans are operated by a thermometer at the ceiling. This reduces the heat lost from the building and provides destratification savings. Finally, the collector is Rocky Gray rather than black and the canopy is white rather than dark. The canopy is not part of the collector itself but acts as a manifold ensuring good distribution of airflow across the entire collector area. In this application, it also serves as an architectural highlight.
Lessons learned
- Using two sides of the building dramatically increases the area available for collector installation.
- The lighter collector colour did not significantly decrease performance.
- Using high-efficiency fans will ensure that the system is at least as efficient as a make-up air unit, resulting in zero incremental fan power.
The big picture
The Canadair facility is the largest solar ventilation air heating system in the world. This project showed that solar heating can achieve large energy savings in an industrial facility at a payback acceptable to industrial customers.
Photo
Industrial building - Solar air heater, Quebec, Canada
References
- Carpenter, Stephen, "Personal communication," Enermodal Engineering Limited, 2000.
- Kokko, John, "Personal communication," Enermodal Engineering Limited, 2000.
- Natural Resources Canada, Performance Assessment of the World's Largest Solarwall, September 1997.
