Do solar heating systems continue to provide heat even when the sun is not shining?
On a cloudy day when there is little or no direct sunlight, there may still be 200W/m² of solar radiation light falling on the solar collector. This is sufficiently intense to be usefully collected by solar collectors. While the highest amounts of monthly solar radiation are obviously experienced in the summer months, there is enough radiation coming from the sun in spring, autumn and winter to make a very useful contribution to a household’s energy needs. A properly sized system can be expected to provide the following: • 80 – 90% of all summer hot water needs. • 40 – 50% of spring and autumn hot water needs. • 10 – 15% of winter hot water needs.
