Small and minor systems (housing, etc.)
Solar panels are usually mounted on the roof of the house.
Solar panels comprise an insulated box covered with glass. A heat absorber is placed inside the box to absorb solar energy. Insulation and glass minimise the heat loss, thereby ensuring that the absorption of solar energy is optimised. When the sunrays strike the solar panels through the glass and hit the absorber, heat is generated, which is circulated using a heat-resistant, non-freezing fluid.
The heat energy is thus transported away from the absorber and the heated liquid is carried to a hot-water tank, a storage tank or a separate heat exchanger to be used for domestic water and/or for space heating in combination with the conventional heating system of the home.
The hot-water tank has two coils, the bottom one for solar heating and the top one for central heating (if the solar panels do not produce enough heat, the top coil heats the top of the tank to make up the shortfall).
A conventional domestic water system consists of approximately 1 m2 of solar panel per person and a 40-70 litre hot-water tank per m2 of solar panel, providing up to 70% of the annual energy requirement for hot-water generation. Combined domestic water and space heating systems may be considerably larger, e.g. 9-18 m2, and may cover quite a significant portion of the overall heat energy requirements of the household.
Large-scale systems
Large solar panels to be used for e.g. district heating are mounted on the ground to admit as much solar irradiation as possible. In systems of this nature, solar panels typically cover an area of 5-20,000 m², providing a significant contribution to local heating supplies.
When the solar panels are mounted on the ground, they are virtually invisible – even from a short distance – but quite spectacular when seen from the air.
The effect of solar panels (both small-scale and large-scale) depends on:
- The tilt of the surface of the solar panels
- The orientation of the surface of the solar panels
- The geographical location of the system
- Shadow formation, if any
- Energy requirement, etc.
In Denmark, the estimated average energy yield per year is 500 kWh/m² of solar panel.