What Are Solar Thermal Panels?
You probably know that solar energy can be turned into electricity by using solar panels, but there’s another popular application to the sun’s power. Solar thermal technologies, in fact, turn sunlight into heat instead of power and were actually the first solar energy products to be commercialized.
Just like solar PV, solar thermal panels help you reduce your carbon footprint and save on your monthly bills by covering your heating needs using a completely free, renewable energy source.
Benefits of Solar Thermal Panels
While solar photovoltaic panels are much more popular and you’ve probably heard about all of their benefits, you should know that solar thermal panels also come with great advantages:
They are actually more efficient than PV, because heat waves carry more energy than sunlight, and because there is no process of transformation into electricity.
They are cheaper and thus have a shorter payback period than PV panels.
They work in cold climates, overcast weather and strong wind, and incorporate an energy storage system.
Most systems come with a 5-10 year warranty but they last much longer up to 25 years. Moreover, they require little to no maintenance, so the only expense you'll have to worry about is the installation cost.
Solar thermal panels can help you save up to 600 kg of carbon dioxide emissions in a year.
How Do Solar Thermal Panels Work?
Solar thermal panels or solar collectors are devices that are mounted on your roof to absorb the sun’s heat and use it to heat up water, stored in a cylinder. The liquid flowing through the panels is a mix of water and antifreeze. The main purposes of this technology are space and water heating, and they’re a very popular solution for swimming pool heating. There are two main types of solar thermal panels:
Flat-plate collectors: these devices look very much like solar PV panels. They are composed of a dark absorbing surface, a transparent cover, a heat insulating backing and, most importantly, a fluid that transports heat from the absorber to a water tank. The absorber can be made of different materials, namely polymers, copper, aluminium or steel. Copper is the most expensive, but it’s also a better, more durable conductor. Polymer collectors are indicated for colder climate since materials such as silicon are much more freeze-tolerant than metal.
Evacuated (or vacuum) tube collectors: unlike solar panels, these collectors are made up of several glass tubes through which the transfer fluid flows. These systems are more efficient than flat-plate panels, especially in cold climates, but lose efficiency in warm weather due to the risk of overheating. That is because vacuum tubes avoid heat loss, while flat panels tend to lose some heat. The evacuated tube structure, with gaps between the tubes, allows snow to fall down and thus minimizes its impact on efficiency since the lack of radiated heat makes it impossible for the snow to melt.