Sunlight and Heat

The brilliance of solar technology

How does a solar system work? The sun is not only a source of light,but it is also a source of heat. That is why the water in a garden hoselying in the sun will heat up - more so in a dark hose than in a light-coloured one. This basic principle is used by solar technology to gene- rate heat directly. However, the garden hose is replaced by a coated"reception surface" (the absorber) that receives (or absorbs) the solarenergy and converts it into heat. This heat is transferred to a fluid flo- wing through the absorber. This fluid is a non-toxic water/antifreeze mixture which prevents the fluid from freezing in winter. To increase the yield (or efficiency) of the usable solar energy, theabsorber is installed in a well-insulated housing with a glass cover. Such a unit is known as a flat plate collector.In vacuum tube collectors, the absorber is located in a vacuum. As weknow from thermos flasks, a vacuum has excellent thermal insulation properties.

Heat from the roof to the tap

Since sunshine and the need for hot water do not always coincide, a home storage tank is required to store the heat delivered from the collector.When the collector temperature climbs over the storage tank tempe-rature, the solar controller starts a circulation pump which brings the heated liquid down to the heat exchanger of the storage tank. In theheat exchanger, the fluid transfers the heat to cold drinking or servicewater, then it flows back into the collector. The water in the storage tank heats up, and radiates heat which can then be used by the enti- re household. When the sun supplies less energy in the spring,autumn or during the winter months, the water is heated via the upperheat exchanger of the storage tank using the conventional heating system.This combination of collector, storage tank, controller and solar stati-on (pump) is called a solar (or thermal) heating system.

Yearly total of global irradiation; Ireland and UK

750 kWh/m
2 1100 kWh/m
2 4