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Heating - Solar air heater - Institutional / Canada (St-Hubert Airport)
Case study assignment
You have been hired by the facility manager of a federal government research centre to evaluate a bid from a contractor for a proposed solar air heating (SAH) system at the facility. An extension to the existing building is to be built and this presents a good opportunity to incorporate a renewable energy technology into the structure. The SAH system is to preheat the fresh air supply for the pilot plant part of the new extension. Your study will be used in support of an application to a federal government incentive, which can provide an incentive of 25% of the purchase and installation costs of the system, up to a maximum refund of $80,000.
Site information
The Centre is in the town of Varennes, Quebec, just east of Montreal. The closest weather station is at the airport in St-Hubert. The extension will include a 597-m² pilot plant, as depicted in the figure. The pilot plant will be occupied from 7:00 AM to 6:00 PM, 5 days a week.
Case study assignment
You have been hired by the facility manager of a federal government research centre to evaluate a bid from a contractor for a proposed solar air heating (SAH) system at the facility. An extension to the existing building is to be built and this presents a good opportunity to incorporate a renewable energy technology into the structure. The SAH system is to preheat the fresh air supply for the pilot plant part of the new extension. Your study will be used in support of an application to a federal government incentive, which can provide an incentive of 25% of the purchase and installation costs of the system, up to a maximum refund of $80,000.
Site information
The Centre is in the town of Varennes, Quebec, just east of Montreal. The closest weather station is at the airport in St-Hubert. The extension will include a 597-m² pilot plant, as depicted in the figure. The pilot plant will be occupied from 7:00 AM to 6:00 PM, 5 days a week.
There is 192 m² of south facing plant wall area available for the installation of the SAH system, with roughly 5% shaded during the season of use. The design airflow rate for the plant has been estimated at 18,740 m³/h. The maximum and minimum delivered air temperatures are 15°C and 21°C respectively and potential building temperature destratification is estimated at 8°C. The RSI value for the ceiling is 2.9 m²-°C/W and the walls are about ½ that amount.
The heating system for the building is fired by natural gas and has a seasonal efficiency of 80%. Heating is not required during the summer season, which for the Montreal region generally extends from the last week of May through the middle of September. The SAH system is expected to last 30 years.
Financial information
The facility manager provides typical financial parameters for the analysis: inflation of 2.5%, fuel cost escalation rate of 3% and a social discount rate of 3%. The incremental cost of the SAH system will be paid out of a budget allotted for this purpose. The price of energy for the Centre is $0.05/kWh for electricity and $0.28/m³ for natural gas.
The total cost proposed in the contractor's bid is as follows:
Solar air heating collectors: $23,000
Installation of collectors: $23,000
Installation of ducting with insulation, bypass damper and controls: $42,300
Total: $88,300
Given that this is a fixed-price bid from the contractor it is not necessary to estimate the detailed projects costs, but rather simply use the values above as-is. Some credits for conventional cladding material and installation are probably available, but likely low on a cost/m² basis given the potential size of the solar collector. A credit for both the fan and ducting material and installation can be estimated at about $15,000. It can be assumed that there are no incremental annual or periodic costs.
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
Results
In 1997 a solar air heating (SAH) system was installed on the south-facing wall of the second phase of the CANMET Energy Technology Centre - Varennes (CETC-Varennes). The federal research centre is located in the municipality of Varennes, Quebec, just east of Montreal. A large extension was being added to the existing building and this provided an excellent opportunity to consider the implementation of a renewable energy technology into the building structure. For more information, view the RETScreen Video (2:02 minutes).
The solar air heating system has operated without problems since that time. For example, on sunny winter days, when the temperature outside is around -5°C, the increase in temperature through the solar collector is about 10°C.
System description
The SAH system collector area is 192 m². It was installed on the entire south-facing wall of the pilot plant. A canopy or a bypass damper were not directly integrated in the solar collector. Instead, a bypass damper was installed on the north-facing plant wall because that is where the fresh air supply for the ventilation system is located.
A federal government incentive provided an incentive equal to 25% of the total system cost (or $22,075).
Lessons learned
The solar air heating system is a simple and proven technology. The most cost-effective installations occur where the cost of the solar collector cladding is partially offset by avoiding the need for conventional cladding; this is the case in new construction or where renovations are planned. The air within high-ceiling industrial buildings is often thermally stratified, with warm air near the ceiling and cool air near the floor. SAH systems, when integrated with a suitable fresh air distribution system (e.g. fabric ducts), can generate additional energy savings by destratifying the interiors of these buildings.
Photo
Solar Air Heating System on the CANMET Energy Technology Centre - Varennes, Quebec, Canada
References
The heating system for the building is fired by natural gas and has a seasonal efficiency of 80%. Heating is not required during the summer season, which for the Montreal region generally extends from the last week of May through the middle of September. The SAH system is expected to last 30 years.
Financial information
The facility manager provides typical financial parameters for the analysis: inflation of 2.5%, fuel cost escalation rate of 3% and a social discount rate of 3%. The incremental cost of the SAH system will be paid out of a budget allotted for this purpose. The price of energy for the Centre is $0.05/kWh for electricity and $0.28/m³ for natural gas.
The total cost proposed in the contractor's bid is as follows:
Solar air heating collectors: $23,000
Installation of collectors: $23,000
Installation of ducting with insulation, bypass damper and controls: $42,300
Total: $88,300
Given that this is a fixed-price bid from the contractor it is not necessary to estimate the detailed projects costs, but rather simply use the values above as-is. Some credits for conventional cladding material and installation are probably available, but likely low on a cost/m² basis given the potential size of the solar collector. A credit for both the fan and ducting material and installation can be estimated at about $15,000. It can be assumed that there are no incremental annual or periodic costs.
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 cladding material credit is relatively low. This reflects the relatively small size of the collector compared to the total wall area of the building. The small collector has higher unit costs, while the unit costs for the conventional cladding material are based on the much larger wall area of the new building extension.
- The cladding labour credit is relatively low compared with the collector installation cost. It has been assumed that the contractor who installs the solar cladding will be different from the one that installs the rest of the cladding. Thus, the unit labour costs for the solar cladding are those for a small project, while the unit labour costs for the rest of the cladding are those for the relatively large job of installing the cladding for the entire building.
- No additional fan was required for this installation, so a relatively high fan and ducting material credit has been given. However, it is assumed that some changes will be required particularly in the configuration of the ducting to accommodate the SAH system, thus making the fan and ducting installation somewhat more expensive than for the base case.
- It is not necessary to define the base case electricity system for the greenhouse gas analysis as the base case heating system fuel type is natural gas (i.e. not electricity), and also due to the fact that the incremental fan power is equal to zero, so there is no additional electricity required in the proposed case heating system.
Results
In 1997 a solar air heating (SAH) system was installed on the south-facing wall of the second phase of the CANMET Energy Technology Centre - Varennes (CETC-Varennes). The federal research centre is located in the municipality of Varennes, Quebec, just east of Montreal. A large extension was being added to the existing building and this provided an excellent opportunity to consider the implementation of a renewable energy technology into the building structure. For more information, view the RETScreen Video (2:02 minutes).
The solar air heating system has operated without problems since that time. For example, on sunny winter days, when the temperature outside is around -5°C, the increase in temperature through the solar collector is about 10°C.
System description
The SAH system collector area is 192 m². It was installed on the entire south-facing wall of the pilot plant. A canopy or a bypass damper were not directly integrated in the solar collector. Instead, a bypass damper was installed on the north-facing plant wall because that is where the fresh air supply for the ventilation system is located.
A federal government incentive provided an incentive equal to 25% of the total system cost (or $22,075).
Lessons learned
- In summer, fresh air is drawn in via the bypass damper located on the north facing wall just at the ventilation air handling unit, allowing the supply of cooler air. Unfortunately, the pressure drop is higher through the solar collector than the bypass damper. The fresh air supply ventilation system is therefore more complicated to balance. To correct this, additional flow restriction will be added on the bypass damper side.
- The installation of the SAH collector did not add to the time required to construct the extension. However, dealing with the contractors and trades people who were not familiar with this innovative technology did prove to be challenging.
The solar air heating system is a simple and proven technology. The most cost-effective installations occur where the cost of the solar collector cladding is partially offset by avoiding the need for conventional cladding; this is the case in new construction or where renovations are planned. The air within high-ceiling industrial buildings is often thermally stratified, with warm air near the ceiling and cool air near the floor. SAH systems, when integrated with a suitable fresh air distribution system (e.g. fabric ducts), can generate additional energy savings by destratifying the interiors of these buildings.
Photo
Solar Air Heating System on the CANMET Energy Technology Centre - Varennes, Quebec, Canada
References
- Choinière, Daniel, "Personal communication," CANMET Energy Technology Centre - Varennes, 2000.
- Hosatte, Pierre, "Personal communication," TN Conseil, 2000.
