We often hear about photovoltaic solar collectors. They’re the best-known and most widespread solar technology for producing electricity from sunlight. But there’s another, lesser-known type of solar collector: thermal collectors.
They are used to heat or preheat air or water. This reduces the energy consumption of heating systems and their greenhouse gas (GHG) emissions. This solution harnesses solar radiation, an unlimited, renewable and completely free energy source.
How do solar thermal collectors work?
- To preheat air, a vertical or sharply slanted panel is generally used. This allows for better capture of solar radiation in winter, when the sun is lower. It also prevents the panel from being covered by snow.
- To preheat water, a panel tilted between 30 and 60 degrees is used to optimize production throughout the year.
In both cases, the operation is essentially the same. The panel captures heat using an absorber, which transfers the heat to a heat transfer fluid in the tubes. The fluid then warms the air (which is directed into the house via ducts) or water (which is routed to a storage tank to preheat the water inside).
How a residential solar hot water heater works
Heating vs. preheating: What’s the difference?
Heating a home entirely with solar energy involves installing a complex system to capture, store and distribute heat continuously. However, preheating air or water requires a relatively simple and more affordable infrastructure. Preheating is an efficient solution that can significantly reduce backup energy needs by only covering the last few degrees.
Good to know
Montréal gets 1,580 hours of sunlight a year, compared to 1,251 hours for Paris and 1,131 hours for Berlin,1 the capital of a solar energy leader. That means there’s real potential for developing this resource in Quebec!
The effectiveness of solar thermal collectors depends more on the level of sunlight and the panels’ orientation than on the temperature. In other words, the more sunshine there is, the more efficient they are, whether it’s hot or cold.
