The first law of thermodynamics defines: Energy can neither be produced nor destroyed, but only converted into other types of energy . From this it follows for us and our topic of circularity in the building industry that we must deal with the energy that the earth receives or has received, the solar radiation, and can feed our requirements from these. For Central Europe we can assume a solar radiation of 100 kWh/m²a  – however, when using energy we do not limit ourselves to the current solar radiation but also use stored solar radiation in the form of coal, oil, gas, biomass / wood and geothermal energy. Here it is only a question of how fast the energy flow is – several million years as with coal, oil and gas or only years or decades as with biomass / wood.
|Title of host publication||Circulariteit|
|Subtitle of host publication||Op weg naar 2050?|
|Publisher||TU Delft Open|
|Publication status||Published - 2018|