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Heating - Solar air heater - Gymnasium/exercise area / Canada
Case study assignment
A municipality in northern Canada has hired you to assess the feasibility of installing a solar air heating (SAH) system on a new recreation centre. The centre will include a gymnasium, curling rink, squash courts, fitness room, and miscellaneous meeting and change rooms.
Site information
The recreation centre planned for the town of Fort Smith, NWT, Canada, will require 9,000 m³/h of ventilation air. The fresh ventilation air will be mixed with building return air and distributed throughout the building using the conventional air handling system. The solar collector will not add any significant pressure drop to the system. The building is expected to be in use 14 hours a day, 7 days a week. The controls will be set to provide a delivered air temperature of 17 °C. When air heating is not required, the solar ventilation air damper will close and ventilation air will be taken in through a relief vent.
There will be 150 m² of unshaded southwest-facing wall area suitable for a SAH system. The client's architect has requested that the collector be dark grey. The building's walls will have an RSI value of 3.0 (m²-°C)/W. The SAH system will displace heat provided by a diesel-fired system with a 70% seasonal combustion efficiency.
Financial information
Typical financial figures for the analysis are provided by the client (inflation rate of 2%, debt ratio of 70%, fuel cost escalation rate of 3%, debt interest rate of 9%, discount rate of 9%, a debt term of 20 years, and a project life of 30 years). Financing will be provided by the client. Since the client is a municipality, it does not pay income tax. The current price of diesel fuel is $0.382/L.
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
The Town of Fort Smith, Northwest Territories, Canada, recently completed the design and construction of a new recreation centre. The centre includes a gymnasium, curling rink, squash courts, fitness room and miscellaneous meeting and change rooms. The building is used 14 hours a day and 7 days a week.
A study on the potential for solar-preheated ventilation systems showed that Canadian remote communities were a particularly attractive market for solar air heating (SAH) systems. Despite the short daylight hours in the middle of winter, the long heating season results in a high solar contribution. The high cost of energy in remote communities means that the payback period is often only a few years.
A monitoring system is recording the heat delivered by the SAH system at Fort Smith. This project is the first SAH system in a Canadian remote community, with a number of new systems installed since then. The solar system is serving as a preheat to a heat recovery ventilator (HRV).
System description
This collector is perforated grey metal cladding. Incident solar radiation warms the cladding. The outdoor air is heated as it is drawn through the perforations by the ventilation system. A channel behind the cladding serves to collect the heated air and direct it to an HRV.
A collector of 150 m² is mounted on the southwest wall of the building. This system supplies the ventilation air for the gymnasium only. The controls are set to provide a minimum of 50% outdoor air and a constant mixed air temperature (of ventilation air and recirculated air). The mixed air temperature is 17 °C. If the carbon dioxide concentration becomes too high or the mixed air temperature rises above 17 °C, the outdoor air ventilation rate can increase up to 100% of the system flow. When air heating is not required, the SAH damper closes and ventilation air is taken in through a relief vent (the wall-mounted hoods in the photograph).
The building owners selected the combined SAH/HRV system because of the high energy savings (62.2 MWh) and short payback (3 years). Although the 2 systems compete somewhat, they work well together in cold climates. The SAH ventilation system raises the supply air temperature to the HRV thereby reducing the need for HRV defrosting. The SAH system is operated at a lower than normal flow rate to achieve a high air temperature rise. It raises the air temperature so that for most of the year no additional air heating is required to achieve the desired mixed air temperature of
17 °C.
Lessons learned
The big picture
Canadian remote communities are a particularly attractive market for SAH systems. Despite the short daylight hours in the middle of winter, the long (9-month) heating season results in a high solar contribution. The high cost of energy in remote communities means that the payback period is often only a few years.
Photo
Fort Smith SAH System Under Construction, Northwest Territories, Canada
References
Case study assignment
A municipality in northern Canada has hired you to assess the feasibility of installing a solar air heating (SAH) system on a new recreation centre. The centre will include a gymnasium, curling rink, squash courts, fitness room, and miscellaneous meeting and change rooms.
Site information
The recreation centre planned for the town of Fort Smith, NWT, Canada, will require 9,000 m³/h of ventilation air. The fresh ventilation air will be mixed with building return air and distributed throughout the building using the conventional air handling system. The solar collector will not add any significant pressure drop to the system. The building is expected to be in use 14 hours a day, 7 days a week. The controls will be set to provide a delivered air temperature of 17 °C. When air heating is not required, the solar ventilation air damper will close and ventilation air will be taken in through a relief vent.
There will be 150 m² of unshaded southwest-facing wall area suitable for a SAH system. The client's architect has requested that the collector be dark grey. The building's walls will have an RSI value of 3.0 (m²-°C)/W. The SAH system will displace heat provided by a diesel-fired system with a 70% seasonal combustion efficiency.
Financial information
Typical financial figures for the analysis are provided by the client (inflation rate of 2%, debt ratio of 70%, fuel cost escalation rate of 3%, debt interest rate of 9%, discount rate of 9%, a debt term of 20 years, and a project life of 30 years). Financing will be provided by the client. Since the client is a municipality, it does not pay income tax. The current price of diesel fuel is $0.382/L.
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
- A high temperature rise design is preferable to standard operation or high efficiency designs because there is a lot of wall area available and the outdoor temperatures are very low.
- The cost of a feasibility study is prohibitive for a small project such as this one. The advantage of using RETScreen is that it is low cost.
- The maximum delivered air temperature is 17 ºC; heat at a temperature higher than this is rejected (and therefore wasted). In many SAH applications, heat at a temperature higher than the desired ventilation air temperature reduces the requirement for space heating and is not wasted. In the recreation centre, the fresh ventilation air is mixed with building return air. The existing control system would attribute higher temperatures in this mixed air to building heat gains, resulting in an air-conditioning load.
- For fans and ducting, the costs are equal to the credits. In new building construction such as this one, the fans and ducting can be designed to accommodate the SAH system at no additional cost.
- Annual operation & maintenance labour charges tend to be high due to the high labour costs in the remote community.
- Even though the average air temperature during the summer months is below the maximum delivered air temperature, the SAH system is not used. Daytime temperatures during the summer will be above the average, and ventilation air heating will be unnecessary.
Real project
Results
The Town of Fort Smith, Northwest Territories, Canada, recently completed the design and construction of a new recreation centre. The centre includes a gymnasium, curling rink, squash courts, fitness room and miscellaneous meeting and change rooms. The building is used 14 hours a day and 7 days a week.
A study on the potential for solar-preheated ventilation systems showed that Canadian remote communities were a particularly attractive market for solar air heating (SAH) systems. Despite the short daylight hours in the middle of winter, the long heating season results in a high solar contribution. The high cost of energy in remote communities means that the payback period is often only a few years.
A monitoring system is recording the heat delivered by the SAH system at Fort Smith. This project is the first SAH system in a Canadian remote community, with a number of new systems installed since then. The solar system is serving as a preheat to a heat recovery ventilator (HRV).
System description
This collector is perforated grey metal cladding. Incident solar radiation warms the cladding. The outdoor air is heated as it is drawn through the perforations by the ventilation system. A channel behind the cladding serves to collect the heated air and direct it to an HRV.
A collector of 150 m² is mounted on the southwest wall of the building. This system supplies the ventilation air for the gymnasium only. The controls are set to provide a minimum of 50% outdoor air and a constant mixed air temperature (of ventilation air and recirculated air). The mixed air temperature is 17 °C. If the carbon dioxide concentration becomes too high or the mixed air temperature rises above 17 °C, the outdoor air ventilation rate can increase up to 100% of the system flow. When air heating is not required, the SAH damper closes and ventilation air is taken in through a relief vent (the wall-mounted hoods in the photograph).
The building owners selected the combined SAH/HRV system because of the high energy savings (62.2 MWh) and short payback (3 years). Although the 2 systems compete somewhat, they work well together in cold climates. The SAH ventilation system raises the supply air temperature to the HRV thereby reducing the need for HRV defrosting. The SAH system is operated at a lower than normal flow rate to achieve a high air temperature rise. It raises the air temperature so that for most of the year no additional air heating is required to achieve the desired mixed air temperature of
17 °C.
Lessons learned
- This is the first SAH application in the far north and the system has operated reliably ever since.
- The combination of SAH and HRV means that almost no additional heating of ventilation air is required.
- The avoided cost of energy is relatively high because the displaced fuel is oil.
- One advantage of using a combined SAH/HRV system is that solar preheating of ventilation air will reduce the frequency for HRV defrosting and therefore improve the average heat recovery efficiency.
The big picture
Canadian remote communities are a particularly attractive market for SAH systems. Despite the short daylight hours in the middle of winter, the long (9-month) heating season results in a high solar contribution. The high cost of energy in remote communities means that the payback period is often only a few years.
Photo
Fort Smith SAH System Under Construction, Northwest Territories, Canada
References
- Kokko, John, "Personal communication," Enermodal Engineering Limited, 2000.
