The sun
Every second, huge quantities of hydrogen in our sun are converted into helium, releasing unimaginable amounts of energy, some of which is radiated into space and reaches the Earth. In less than 9 minutes, more energy reaches the Earth's surface than can be used by the whole of mankind in a year.
Solar radiation determines the seasons and the weather
The seasons of the year are determined by the Earth's position in relation to the sun, the rotation of the earth gives us night and day, and the constant heating up and cooling down of land and water generates thermal air flows and therefore the weather.
The sun rays are more powerful than we might think
Germany is a country with cold winters and hot summers, but very rarely is the sky actually completely free of cloud cover. However, this is not altogether necessary to be able to utilise solar energy: even when it is cloudy, over 50% of radiation energy still reaches the earth and everywhere in Germany the annual mean generally has a value of 940 kWh/m2. Over the space of whole year, this corresponds to approximately 100 litres of heating oil per square meter of floor space - from Flensburg to Passau.