My life has been strongly linked to solar energy. Since 1997, I am working at the Fraunhofer Institute for Solar Energy Systems in Freiburg and I am contributing to the science and engineering of photovoltaics with highest conversion efficiencies. We are using III-V compound semiconductors, tailored to absorb light in different wavelength ranges. By stacking several of these absorbers on top of each other, the solar-electric conversion efficiency of sunlight into electricity can be as high as 47.6 %.
There is by far sufficient amount of solar energy available on this planet to serve our human needs but the density is low and we need large areas of solar collectors. Photovoltaics is an efficient way to harvest this energy of the sun directly and convert it into electric power which is a valuable and useful energy source. Photovoltaics is a decentralized approach to generate electricity close to the consumer. It can be used nearly everywhere on this planet. Today, local electricity generation by photovoltics can be as cheap as 5-10 €cent/kWh in Germany and 2-5 €cent/kWh in the most sunny places of the world. Everyone can build a PV system - on your own roof, by investing into a community system or an investment fund.
When the sun is not shining there is usually sufficient amount of renewable energy available in the form of wind, biomass, geothermal and water. A mixture of these resources fits very well to the consumption profile for most of the year. Additionally, solar electricity can be converted into hydrogen or methane to store the energy for times where there is a lack of renewable energy production. The technology is available, it can be locally produced and it allows to become 100 % independent of energy imports.
My first investment into renewable energies was in 2002 with a 3.000 € share in 6 windmills which were installed on the mountains surrounding Freiburg. I was so happy to see the towers grow out of the black forrest and finally the rotors were moving gently in the wind. At night red flashlights indicate the position of each windmill and they can be seen from a far distance. For me they are directing me home from my travels abroad. I can see some of the windmills from my house and I always know what my money is doing. With 10.714 kWh of clean electricity per year my investment of only 3000 € is producing the electricity of 4 family households. This shows that even with a small investment you can make a difference. I see my money moving every day and it makes me very happy!
I have to admit that this investment was not without controversy and it has never created high revenues. The predicted forecasts could not be met due to several low wind years. Ecologists were initially fighting against the installations and predicted that bats would be killed by the rotors. Others claimed that the Black Forrest picture would be destroyed. I think we should be honest to ourselves living in a highly industrialized world. We are all consuming huge amounts of energy and it has to come from somewhere. Seeing a rotating windmill or a solar power plant reminds us that we should be cautious not to waste energy. But for me they are also a sign of hope that we can rely on a safe and renewable energy source for our society.
Finally after this first investment I have learned that the South of Germany is not the best wind region and I invested again into a wind park in North-East Germany: Enertrag Windwerk I. For me it is still incredible but my second investment actually produces 123.000 kWh of electricity per year which is enough to power more than 40 households! Or in other words, dividing the 2015 German primary energy demand of 13335 PJ (=3,7E15 Wh) by 81,2 Mio citisen results in 45.000 kWh per capita. Then the windpark delivers approximately the full primary energy demand of my family. This calculation of course reminds us that most of the energy spending is outside of our homes and we have to work on better energy efficiency.
If you do not want to invest yourself, here are two suggestions where you can buy renewable electricity in Germany and support the energy transition: Elektrizitätswerke Schönau, Greenpeace Energy