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Everyone has experienced it in the summer: a simple garden hose left in the sun will provide a few litres of hot water when it is emptied. How can this system be improved?
Painting the hose black is a first step. In fact, a black object emits virtually no light, and therefore absorbs most of the energy to turn it into heat.
However, this accumulated heat will nevertheless radiate in the infrared towards the outside of the pipe. The role of glazing helps to retain this energy.
A simple ordinary glazing is enough to stop the infrared radiation and allows this thermal radiation to be stored in the sensor enclosure, while allowing visible sunlight to enter.
On the back of the sensor that does not need to be transparent, insulation (with conventional insulation) helps to retain heat.
Once the solar radiation has been converted into heat, it must be brought to where it needs to be stored. It is the role of the heat-carrying fluid that circulates in the panel. Cold at the entrance of the circuit, it gradually heats up in the panel, and at the exit of the sensor, it allows to evacuate the heat to where it needs to be consumed (example: the solar water heater, solar pool).
The first application of solar thermal remains its use to obtain hot sanitary water. Easy to implement with moderate investment and work, the solar water heater allows many homes on our planet to significantly reduce their heating needs and cover nearly 70% of the use of hot water. For passive houses, it is even possible to meet 100% of its needs!
In France, for a conventional dwelling it is considered that a solar water heater can cover about 70% of its energy needs with the sun. The remaining 30% can be brought either by electrical resistance, by a gas-fired water heater, or by a boiler used to heat the home.
Generally the need for extra energy takes place mainly in the winter months, and more occasionally in the half-season.s.