How does a solar thermal system work?

In a period of profound change for the energy sector characterised by the energy transaction, many people are wondering what a solar thermal system is and what the advantages are. To give a precise definition of a solar thermal system, we should start with the two terms that characterise it: solar, because it is a system that makes it possible to harness the sun's energy and thermal, because it makes it possible to produce hot water and also to heat rooms, even if only partially.
Let us now go even deeper into the meaning  a solar thermal system to be installed in your home. It is a solution that can optimise energy efficiency and, in this way, reduce your energy costs. Its operation is based on thermal solar panels (or solar captors) that absorb the Sun's heat and convert it into thermal energy through a heat transfer fluid that in turn transfers the heat to a tank containing water for sanitary or heating use.

What is the difference between solar thermal and photovoltaic?

There is often confusion between solar photovoltaic and solar thermal energy, but in actual fact, they do not have much in common, except that they use solar radiation to produce energy. In fact, the two technologies are very different in terms of use, cost and durability. The main difference between solar thermal and solar photovoltaic energy that solar thermal panels produce hot water, whereas photovoltaic panels produce electricity.
But the differences between photovoltaic and solar thermal do not end there. So let's take a look at the main characteristics of the two different systems:

• The material constituting photovoltaic systems is mainly silicon combined with various chemical elements, glass and various structural components; solar thermal systems, on the other hand, consist of metal (aluminium, copper, steel) and glass;

• Photovoltaic systems have an average efficiency between 17% and 25%, while solar thermal systems can reach 80%;

• As far as tax benefits are concerned, photovoltaic systems can be deducted up to 50% while solar thermal systems can be deducted by up to 65%.

What are the advantages of using a solar thermal system?

The advantages of a solar thermal system are numerous and include economic, fiscal and environmental benefits. Let us see them in detail.

• Economic benefits: these mainly relate to the economic savings generated by the production of domestic hot water or heating using solar energy, with bill savings of up to 70%. In addition, the systems have a long service life, with reduced maintenance costs, and can be integrated with the existing system, also increasing the service life of the boiler because it is less stressed. Finally, with a solar thermal system your home can increase its energy efficiency class and its commercial value.

• Tax benefits: incentives for solar thermal systems offer tax relief of up to 65% on the expenses incurred for the installation of the system and VAT is reduced to 10%.

• Environmental benefits: the system harnesses the sun's energy, thus reducing the use of fossil fuels and emitting less CO2 into the environment.

What are the types of solar thermal systems?

There are two main categories of solar thermal systems: natural circulation systems, which are simpler and suitable for individual households; and forced circulation systems, in which hot water can be produced in large quantities with the help of a pump. Natural circulation solar thermal systems consist of a water storage tank placed above the solar captor. The heat transfer fluid contained in the tubes, once heated by solar energy, decreases in density and thus begins to rise upwards until it reaches the tank where the water is contained, heating it. Natural circulation solar thermal systems are small and more appropriate for domestic hot water production only. Among their advantages are their low cost, compact size and easy installation.

The forced-circulation solar thermal system, on the other hand, has an external water storage tank, located in a special technical compartment, separated from the solar captor and connected by piping. In this case, to circulate, the heat transfer fluid needs the “push” of an electric recirculation pump controlled by a control unit. Unlike natural circulation systems, the forced solar thermal system is of medium to large size and is used not only for the production of domestic hot water but also for water intended for space heating. In this case, even if the costs are higher, the advantages are considerable and concern the possibility of being energy independent, with considerable savings on the electricity bill.