Heating - Solar air heater - Commercial - Unglazed

Template assignment

Base Case

• Commercial building with a constant indoor temperature of 21°C
• Thermal resistance (R-value) of the walls is 1.5 m² - °C/W
• Design airflow rate is 7,200 m³/h
• The building ventilation is operating ten hours per day, seven days per week
• Natural gas heating with 70% efficiency
• Natural gas rate is $0.40/m³

Proposed case

• The base case natural gas heater is supplemented by a 80 m² unglazed, back-pass solar air heating collector that preheats the ventilation air
• The collector is mounted on a wall (slope of the collector is 90º) that faces 25º west of south
• The percentage of time that the heating ventilation system is used are as follows:

• The solar collector shading is 10% during the season of use
• Assume a 0.70 wind sheltering coefficient (this could be done by multiplying each of the wind speed values by 0.70 in the climate data section of the Start worksheet)
• The collector is black, with an absorptivity of 0.93 and performance factor of 0.70
• The collector does not increase ventilation fan energy requirements due to the buoyancy of the solar-heated air
• The incremental installed cost of the collector is around $130/m² for this installation
• Maintenance costs are the same as in the base case

Other opportunity

• A government incentive is applied to the installation cost of the solar collector

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.