Photovoltaics (PV)

Photovoltaics (PV)

If one now thinks of the expansion of renewable energies, especially if one imagines a sixfold increase in the number of plants, this will not succeed only with the addition of wind power. Although the social support for wind energy and the associated wind turbines is broadly present, with a six-fold increase in the number of wind turbines, the acceptance would suffer greatly or even dwindle. Photovoltaics only provide a good 7% of energy in the current electricity mix in Germany[1]. This form of energy is widely accepted by the population, but this technology still faces many prejudices:

The most common prejudice is that the production of the solar modules would consume more energy than the modules will generate during their entire lifetime. This was even valid in the 1960s, because processes and materials from the very expensive microelectronics were used for the production of the first solar cells and photovoltaics as an independent branch of industry has developed later in the following four decades. Today, solar modules have an efficiency of more than 20% and return the energy for their production, set up at an average location in Germany, in about 2.5 years[2]. Most manufacturers today give a module warranty of 20-25 years. If you take this period, so a solar module pays back about 10 times as much energy as it required for its production!

Another prejudice is the seemingly high cost of photovoltaics. Also this was true until recently! The cost of PV modules[3] has fallen by about 97% since 1990, to about 3% [4]. So today (2019) each watt in terms of power of a PV module (Watt-peak or WP) will cost about 30 cents, in 1990 it was about 10 Euros. There is hardly any other industry that has achieved such a price reduction over a period of almost 30 years through mass production and innovation. The importance of a WP price of 30 cents is only clear when converted into a price per kWh of electricity generated. A large-scale plant with a PV output of 500 megawatts produces approx. 500 million kWh per year in Germany. The modules cost 30 cents per WP, that is 150 million Euros. The inverters, which feed the electricity generated into the grid, cost another 50 million Euros for such a system. For the installation and assembly, you can add depending on local circumstances about 100 million Euros. This plant will produce 500 million kWh annually, or 10 billion kWh, within 20 years. If you divide the cost of 300 million by the 10 billion kWh, costs per kWh come out of about 3 cents. It is therefore not surprising that large solar plants are already being built in Germany today and can successfully sell their electricity without any subsidies on the market. For example, In March 2019, a tender for tendered electricity was granted for a PV system, which supplies electricity to the grid for 3.9 cents per kWh[5]. No other available and scalable power generation technology can generate electricity at this price level, neither wind, coal nor nuclear. In addition to the lowest energy prices of PV compared to all other techniques, another advantage is that this electricity does not usually have to be transported over long distances, but can be generated regionally, essentially wherever it is consumed or charged into cars.

In Germany, a good 500 terrawatt hours (one terrawatt hour is one billion kilowatt hours) of electricity were consumed in 2018[6]. Half of this, around 250 TWh, might be generated in about 2019 with renewable energies. In order to get an idea of the area that would be necessary to generate not only twice as much green electricity in Germany as before, but 6 times as much (~1,500 TWh), to fulfill the energy requirements of all sectors such as industry and transport would result in the following calculation:

A modern solar panel has an efficiency of approx. 20% and generates approx. 200 watts per square meter at full solar radiation. With the average radiation power in the federal territory this will result in an annual production of 200 kilowatt hours per square meter. For the 1,500 terrawatt hours it required to have 7.5 billion square meters of area. Germany has an area of around[7] 360 billion m2, of which around 50% (around 180 billion m2) is agricultural land. For this reason, 4% of today's agricultural areas would be enough to generate three times the amount of electricity consumed in Germany today, or about six times the amount of green electricity generated in Germany today.


Firgure 1: On an area of only 2% of the federal territory, the entire amount of energy consumed in Germany can be generated by photovoltaics..


But that does not mean that these areas have to be lost to agriculture. There are already some examples of the so-called "Agro-Photovoltaics"[8], in which the solar modules are mounted above the agricultural land and below, partly shaded, agriculture is operated. This type of agriculture can proceed with less water, because of less evaporation under the shading. This may even result in higher crop yields for some plant species than would be the case without agro-photovoltaics. But the most important thing is that there is no conflict between energy production and food production with this strategy.


Firgure 2: Agro-photovoltaic system of the Hofgemeinschaft Heggelbach[9].
Agricultural production and energy production in the same place are not mutually exclusive.

Even biodiversity would receive a positive impetus, since the non-agricultural area in the area of the foundations and supports of the solar installations, which must be traversed by the tractors, insects and birds can find a home.

A massive expansion of photovoltaics as one of the mainstays of our energy supply brings with it the problem that solar panels generate significantly more electricity in summer than on short winter days. Now it is the case that the heating of buildings in Germany consumes relatively much energy in winter, while the consumption by air conditioning in summer is relatively low compared to the southern countries. In Spain and the south of France it is the other way round. Here in summer you need very large amounts of energy for air conditioning, in winter, however, little for heating. Electricity trading with the southern European countries with the respective seasonal surpluses would therefore be a very efficient and helpful way to deal with energy surpluses and deficits. It is also conceivable to convert part of the summer excess electricity into hydrogen or e-gas[10] in order to be able to use it in stationary fuel cells or gas-fired power plants in the winter to generate electricity.



[2] Page 39

[3] Here, the normalized prices for every watt of module power (Euro per Watt-Peak) are meant

[4] Page 9