Using renewable energy to heat is challenging in Western Canada as neither solar thermal nor air source heat pumps (ASHP) are very efficient at -30C. In addition, they most often have to compete with natural gas, which is relatively inexpensive in British Columbia, Alberta, and Saskatchewan, making the economics poor in many cases. However, there are circumstances where they can make sense. Industries which require heat in the summer, or rural areas which rely on propane, often 3-4 times the price of natural gas (NG), should consider using renewables to supplement or replace their fossil fuel usage.
Evacuated tube collector solar thermal (ETC ST) is the highest performing solar thermal technology and uses solar energy to heat a fluid within an evacuated tube. The vacuum chamber makes for better heat transfer and lower losses making this technology especially good for colder climates. The largest challenge with evacuated tube collectors is the unpredictable maintenance costs but a conservative estimate is 2% of the capital cost of the system annually. With solar thermal in Alberta, the economics are maximized when you can find applications which use heat in the summer, as this is when the majority of the heat is being generated.
Air source heat pumps use the same technology that’s in your fridge, air conditioner or geothermal heat pumps. They take the energy in the outdoor air and, using the refrigeration cycle, deposit that energy into the indoor space. The efficiency is measured as the Coefficient of Performance (COP) and is the output energy (in heat) divided by the input energy (electrical consumption). The COP varies greatly depending on the respective temperatures of the indoor and outdoor air. If the outdoor temperature is -30C and you’re trying to heat a room at 30C, the COP will be close to 1, whereas if you want to take outdoor air at 15C to heat a room at 20C, the COP can be over 5! While heat pumps are not a new technology, innovation continues to improve its efficiency. Most recently, Variable Compressor Speed Inverter (VCSI) Technology has the industry excited for the new potentials.
The application we found most recently is the beekeepers in Alberta who heat their honey rooms in the summer to keep the honey flowing. We did a brief analysis of a scenario where a room has to be heated to 37C throughout the summer and kept above freezing throughout the winter. The analysis assumed a retrofit where air source heat pump or evacuated tube collector solar thermal would offset a total of 66GJ/year fuel usage in the summer and 132GJ/year in the winter. Here’s a quick overview of the results:
| ETC ST | ASHP (Summer) | ASHP (Summer & Winter) | |
| Capital cost | $28,200 | $14,300 | $14,300 |
| Annual cash flow vs propane | $1,029 | $1,010 | $2,492 |
| Annual cash flow vs NG | – $161 | – $179 | – $1076 |