Solar radiation in Central Europe brings approximately 1000 kWh/m2 a. The sun is essential for the loop of nature and outnumbers the total energy need of the whole world by a factor of 10,000. The solar reserves will last for the coming four billion years. If we analyse the gifts of nature and physics per square meter from the viewpoint of the final consumer or according to the demand-side management, we note different heights of precipitation depending on the location, an annual increase in biomass and solar radiation. These three energy sources can be transformed into kWh/m2 as follows:
• Hydropower: With precipitation in Central Europe, nature makes a water gift per square meter of «1m height (1 m2 x 1 m) i. e. 1 m3 of water « 11 of water per m2. If this ton of water is poured from a height of 400 m on a turbine, we get 1 kWh per year.
• Biomass: The annual increase of biomass in plants in Central Europe corresponds to an energy amount of 2 kWh/m2 a.
• Photovoltaic: The optimally integrated PV installation of SES-SIG in Geneva produces a total of 585,000 kWh/a on a surface of 3395 m2. This corresponds to 172 kWh/a, per square meter. a For additional floors, facade collectors produce between 70 and 130 kWh/m2a (depending on the
aAn energy-efficient average apartment or business building needs between 25 and 40 kWh/m2a. On a sunny roof in Central Europe, there is therefore four times more energy than averagely needed per year. Or in other words: a roof produces enough energy to completely supply four to five floors energetically. For additional floors, facade collectors produce between 70 and 130 kWh/m2a (depending on the PV cells).
PV cells.)3 In Central Europe, a complete renewable energy supply is therefore feasible and undoubtedly possible.
In their study, Jacobson and Deluchi from the University of Stanford compare today’s energy need of 11.5 TW with renewable energy reserves amounting to 580 TW for solar energy, 40-85 TW for wind energy and 2 TW for hydropower. b If we look at these physical facts, how can we still talk of electricity or energy gaps? Either the so-called "energy experts” just ignore physics and the outstanding performance of building technology in Central Europe, or they need to fill in their "expert gaps” with the help of an expect for psychiatry.