By Brooke Cupelli 

 

The industry for clean energy continues to innovate and grow as the demand for clean energy steadily rises. The shift away from fossil fuels, and towards clean electricity, continues to expedite the research focussed on “electricity systems powered with clean sources, [including] hydropower, wind, solar, and nuclear.” [4] The benefits of clean energy range from reductions in greenhouse gas emissions to economic growth of industry and individual household savings. Additionally, the potential of “a healthy, safe and liveable environment for all Canadians” bolsters the clean energy sector and demonstrates its intrinsic value to our collective future. [4] 

With moving water (i.e., hydroelectricity) providing 61.7 percent of Canada’s generated electricity (2022), it is currently the most salient source of renewable energy for Canada. [2] Further, “Canada is the third largest producer of hydroelectricity in the world.” [2] Although hydro maintains its immense contribution to the renewable energy sector, “wind energy and solar [photovoltaics (PV)] are the fastest growing sources of electricity in Canada.” [2] With clean energy sectors advancing rapidly, solar energy is continuing to evolve. Solar thermal air collection is a burgeoning field in Canada, with Canada leading the “solar air collector development and commercialization” sector globally. [3]

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What is Solar Thermal Air Collection? 

Solar thermal air collectors (solar air collectors, solar hot air collectors, thermal air collectors) are devices, similar to traditional solar panels, with a core function of capturing solar energy (sunlight) and converting said energy into heat. Solar panels use PV cells to convert solar energy into electricity. The greatest difference between traditional solar panels and solar thermal air collectors is the use of circulated hot air to generate heat and electricity, rather than PV cells creating an electrical current. Solar thermal air collectors are vital in both application and utilization of solar-thermal technologies. [7] Solar thermal air collectors are highly efficient mechanisms made to heat the “internal working medium—air.” [7] After these “solar thermal technologies… [convert] solar radiation into heat, [they use] pumps or fans to actively transfer the heat” to a designated area. [3] In their standard form, they operate under four parameters: absorbing/ capturing sunlight, transferring this sunlight to heat air within the collector, circulating air to mobilize the heat via a fan mechanism, and finally, distributing the output air. With multiple variants, “the key component of any active solar-system is the solar collector.” [3] Regardless of variation, this component can be found absorbing radiant solar energy, resulting in usable heat being transmuted. The absorber “is usually made up of material of high thermal conductivity…[and] is coloured black to enable” maximum radiation absorption. [6] Installing solar air collectors vertically on a south-facing wall is most efficient and successful, capitalizing on optimal sun exposure. Vertical installation accounts for times when the sun is at a lower angle (ex. during the winter). Solar air collectors are most commonly used for heating, drying, and energy stores. Additionally, they can be used for dehumidification systems and ventilation systems. [7]  

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Common Types of Solar Thermal Air Collectors  

The infrastructure of solar thermal air collectors has advanced and continues to develop, with much of this progress originating in Canada. There are various types of solar air “collectors used in solar energy conversion.” [3] With different applications and desired outcomes, as well as different temperature requirements, solar thermal air collectors vary in form and function. Commonly categorized into three types of collectors, these variations can be classified as: the flat-plate solar thermal air collector, the evacuated tube solar thermal air collector, and the concentrated solar thermal air collector. [4] 

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Flat-Plate Solar Thermal Air Collectors

Implied by its name, this collector uses a flat-plate made of plastic or unglazed metal (i.e., the absorber plate does not have a cover and remains exposed to the air). These collectors are used for low-temperature applications, most frequently applying to “residential pool heating and ventilation air heating for commercial and industrial buildings.” [3] Flat-plate collectors are the most common solar thermal air collectors in Canada. With an “estimated 544,000 m2 solar air collectors operating in Canada,” from 2007 to current day, 97 percent of them are flat-plate collectors. [3] Flat-plate unglazed plastic collectors hold the highest percentage, at 71 percent, with a primary usage of residential pool heating. The secondary use comes from air heating commercial buildings, at 26 percent, utilizing flat-plate unglazed perforated collectors. [3] 

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Evacuated Tube Solar Thermal Air Collectors

Evacuated tube collectors can be placed into two subcategories: glazed flat-plate and vacuum tube collectors. The glazed flat-plate has a coated absorber plate or a glass cover over the plate. The vacuum tube collector has multiple tubes running from one end to the other, with a similar material makeup to the glazed flat-plate. With the ability to produce midrange temperatures, the application of the evacuated tube air collector is most commonly “domestic hot water and space heating/ cooling.” [3] With only 3 percent of Canada’s solar air collector utilization remaining, after accounting for flat-plate usage, the current impact of this technology in Canada is minimal. 

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Concentrated Solar Thermal Air Collectors

Similar to the Evacuated Tube collectors, concentrated solar air collectors are not currently making a measurable impact on Canadian clean electricity (accounting for the remaining 3 percent cited above). With the ability to maintain the highest temperature applications, they hold great potential but are not highly commercialized currently. Concentrated collectors work by focusing “sunlight onto a much smaller area,” usually by utilizing mirrors or lenses for accurate positioning. [3] These collectors broaden the functionality of the solar air collector with “applications such as industrial process heat, absorption cooling, and large-scale solar thermal power applications to generate steam for electricity generation.” [3]
 

Efficiency and Importance 

Solar air collectors are a vital resource for clean energy generation. With the consistent goal of high efficiency, solar energy continues to grow and improve for a better future. With solar power generation being variable and determined by environmental factors (i.e., available sunlight), there are natural barriers to face. [1] But, with solutions like energy stores, the reliability of solar power is improved. [1] 

With continued research in the realm of efficiency, modifications to absorber plates are proving to elevate the potential of the collectors. [7] The use of solar-thermal energy is underutilized in the clean energy sector. As an easily available renewable energy, source with large reserves and significant application potential, solar thermal energy can aid in meeting long-term sustainability goals. [3, 7]  

CanmetENERGY (based in Ottawa) is responsible for the majority of Canada’s research and development of solar thermal technologies. With technological advances, practical applications, and measurable accomplishments, CanmetENERGY is growing the solar thermal sector in Canada and beyond. [3] 

Solar electricity accounts for less than 1 percent of Canada’s electricity production (2022), demonstrating how the solar sector has vast untapped potential. With many obstacles facing the energy sector, renewable clean energy is the remedy. Combating energy shortages, issues of low efficiency, and remedying the detrimental polluting of our environment are paramount to the future of our planet. Further utilization of technology, such as solar thermal air collectors, will aid in the transition to a clean and sustainable collective future for all.
 

References

1. Bettle, L. (2025). Challenges in Grid Supply and Demand Management with Increased Adoption of Wind and Solar Energy. Lark Scientific. https://www.larkscientific.org/in-depth-research/challenges-in-grid-supply-and-demand-management 

2. Canada (Natural Resources). (2024, December 20). About Renewable Energy Canada. Natural Resources Canada. https://natural-resources.canada.ca/energy-sources/renewable-energy/about-renewable-energy-canada 

3. Canada (Natural Resources). (2025, May 7). Solar Thermal. Natural Resources Canada. https://natural-resources.canada.ca/energy-sources/renewable-energy/solar-thermal 

4. Canada (Services). (2025, March 14). Canada’s Clean Electricity Future. Canada.ca. https://www.canada.ca/en/services/environment/weather/climatechange/climate-plan/clean-electricity.html 

5. Ikem, I., Ibeh, M., & John, U. (2017, January). Estimating the efficiency of okra drying mixed-mode solar dryer. International Journal of Engineering Research. 6. 250. 10.5958/2319-6890.2017.00013.7.

6. Mund, C., Kumar Rathore, S., & Kumar Sahoo, R. (2021, September 25). A review of solar air collectors about various modifications for performance enhancement. ScienceDirect. https://doi.org/10.1016/j.solener.2021.08.040 

7. Zhang, J., & Zhu, T. (2022, November 18). Systematic review of solar air collector technologies: Performance evaluation, structure design and application analysis. ScienceDirect. https://doi.org/10.1016/j.seta.2022.102885