Solar thermal

Solar thermal technology harnesses the energy of the sun to heat water for domestic use or for space heating. And solar thermal technologies can be used also for cooling. Solar thermal systems collect heat and differ from solar photovoltaic (PV) systems, which generate electricity.

How it works

Solar collectors convert sunlight into heat and produce hot water for your home use. In larger systems, they can also help to heat your rooms. Thanks to a solar thermal system, a house can reduce its energy consumption by half and much reduce CO2 emissions. Most solar systems work in combination with a heater, for example a condensing boiler or a heat pump, which helps the solar thermal system when heat demand is high.

How is a solar system composed?

A solar heating system is composed of:

  • solar collectors (one or more), which are usually installed on the roof of the building;
  • a hot water tank, to store the water heated by the system;
  • a circuit with a fluid (frost and heat resistant), which delivers solar heat from the collectors to the hot water storage tank;
  • a heat exchanger, to transfer heat from the circuit to the hot water storage tank

There are two types of solar collectors: flat-plate collectors are the most common. Vacuum tube collectors – a heat pipe in an evacuated glass tube (vacuum) – can achieve high yields and temperatures. Because of their higher efficiencies, they require less surface area than flat-plate collectors.

Solar energy can be used to produce hot water and to top up a space heating system. In the latter case, the size of the collector surface is usually increased by a factor of about 2 to 2.5. The saving on fuel is somewhere between 10 % and 30 %, depending on the insulation levels of the building. In low energy buildings, solar systems can attain savings up to 50 %. Where solar heat is used to assist a space heating system, either a second storage tank (buffer store) or a combination storage can be used. Stratified tanks or cylinders are also available.

Where can you use a solar thermal system?

Solar thermal systems for hot water production and space heating are suitable for a great variety of residential and commercial buildings, in both retrofitting and new-build projects. Moreover, solar collectors can provide hot water for both open-air and indoor swimming pools. Some systems operate on the thermosiphon principle, using a heat-insulated storage tank above the collector; these are most common in southern countries. Solar assisted industrial process heating is still in its early stages but the potential is enormous.

Solar cooling

Solar thermally driven cooling systems – so-called solar air-conditioning – have a great potential, as the highest need for cooling goes hand-in-hand with the sun’s presence. Moreover, the widespread use of solar cooling could make an essential contribution to lowering the electricity demand peaks caused by traditional air-conditioning systems.


  • It introduces renewables within any heating system both in existing and in new buildings;
  • saves energy;
  • solar heat is available and free for everybody: low maintenance and operations costs;
  • long lifespan;
  • easy to use;
  • reduces CO2 emissions