Unsustainable, conventional methods of power generation utilise the maximum energy density of primary energy sources such as uranium, coal, oil and gas in spatially highly concentrated plants with downstream network structures for power distribution. This type of generation results in enormously high operating costs for the primary energy, as well as even greater economic follow-up costs for the disposal of radioactive waste and the terrible damage that climate change causes due to the released CO2. In addition, based on the second law of thermodynamics, only approximately 25% of the primary energy is thermally converted to electricity, 75% simply raises the surrounding temperature as pure heat. Being responsible for the future means that this type of power generation must be stopped as rapidly as possible and replaced by climate-neutral processes.
PRINCIPLES OF PHOTOVOLTAICS (PV)
The entire global radiation of the sun falling on the earth is basically 10,000 times greater than the entire energy consumed by humankind! This is an extremely solid basis for a PV power supply.
As PV uses the natural solar radiation for generating power, it is relatively land-intensive. The solar constant is 1.367 kW/m2, i.e., global radiation vertical to the earth surface. In order to take into account all variables, particularly the radiation angle and the level of cloud cover, an evaluation period of one year is practical in order to sum up all energy contributions. Such an evaluation was implemented by the European Commission between 2001 and 2008, and the mean value obtained from these eight years was documented for Germany, Figure 1 . Figure 1 shows the recorded annual global radiation in kWh/m2 for every town in Germany, which gives a mean value of approximately 1,200 kWh/m2 across Germany. A good solar module, with the current 23% degree of efficiency, can generate the following annual amount of electricity: 1,200 x 0.23 = 280[kWh/m2]. This value provides us with a practical unit for further calculations applicable to Germany.
COMPLETE PV POWER SUPPLY IN GERMANY
In 2018, total power consumption in Germany was 527 TWh (Tera = 1012), based on an annual consumption per person of 7.2 MWh . A simple calculation determines the area required (AR) to generate this amount of power using PV:
AR = 527×1012/ 280×103[Wh /(Wh/m2)]
This area is equivalent to a square with an edge length of 43 km.
Germany covers an area of 357,000 km2, and the AR for a total PV power supply makes up just 0.53 % of that area. There should therefore be no rational obstacle against implementation. However, political decisions often follow very different criteria.
Next week, the follow-up PV page will show how power generation can be effectively and optimally configured with synergistic effects.
1. http://re.jrc.ec.europa.eu/pvgis/ (European Commission)
2. https://de.statista.com/statistik/daten/studie/164149/umfrage/netto-stromverbrauch-in-deutschland-seit-1999/ (Statista, online-portal for statistics)