Solar thermal: definition and technological and economic considerations.
Solar thermal recovers heat from the sun with a fluid that circulates in the panels. In mainland France, the solar thermal represents over 55 000m² panels.
Principle of operation
The purpose of a solar thermal panel is to transmit the heat emitted by the sun to a secondary water circuit. The sun's rays pass through the glass, inside an absorbent plate which aims to capture infrared rays. Behind this hot plate passes a water circuit which recovers this heat.
Subsequently this circuit supplies a secondary circuit that can power a home or domestic water heating.
The circulation of water can be done by simple physical phenomenon, hot water is less dense than cold water. This is why in the diagram hot water is always above cold water.
- high efficiency (up to 80%): up to 1200 W / m² of calories can be recovered in France with (the best solar panels and the best sunshine).
- allows water to be heated "for free" after return on investment, which can be interesting for communities that would like to control their expenses such as very energy-consuming swimming pools.
- an inexhaustible source of energy but be careful, the installations wear out ... especially if the assembly was done in a hurry,
- huge development potential.
- generally limited to domestic hot water heating unless you have a low temperature underfloor heating
- solar thermal energy remains an expensive energy compared to heating by fossil fuels because of fairly heavy investments (from 500 to 1500 € per m2 installed),
- fairly long return on investment (a return of 10 to 15 years is not uncommon),
- lifetime of the panels is generally limited to 20 years,
- some panels are very sensitive and can be damaged by certain weather conditions (hail, frost, etc.),
- billing equipment in many cases,
- development "controlled" by subsidies and various aids (double-edged sword).
Principle of a solar thermal panel for domestic hot water.
Conclusions: high potential but an energy that is still expensive.
Solar is one of the oldest "renewable" energies. Prehistoric men already used it to dry their fish, for example.
Today it is once again on the front of the stage with the exhaustion of fossil fuels and global warming and its development potential is very important since it is very rarely exploited.
Finally, to conclude, we would still add a word about state subsidies.
If they make it possible to democratize solar energy, conversely they also allow an overbilling of the installations (the subsidies are given only on the most expensive installations) ...