Background: what wind, water & co can (should)

Electricity from wind and sun, heat from biomass or directly from the earth. Renewable energies are supposed to free people from dependence on coal and oil. Which advantages and disadvantages do the individual "renewables" have? And how important is it almost ten years after the Renewable Energy Sources Act came into force? An overview.

By Yannick Christmann, ARD-aktuell

According to the Federal Environment Ministry, the use of renewable energies in 2008 prevented the emission of more than 110 million tons of carbon dioxide. However, this is only a small part of the total C02 emissions: According to estimates, in Germany in 2008 this was almost 750 million tons.

But by 2020 wind power, bioenergy, hydropower, solar energy and geothermal energy are to increase their share of the energy demand in Germany to 18 percent according to the plans of the federal government. That would be almost twice as much as it is today. In 2050, the share of renewable energies should even be half.

In order for this expansion to be successful, the state gives preference to "renewables" over fossil fuels: The providers are guaranteed a fixed remuneration regardless of the current electricity price. This is prescribed by the Renewable Energy Sources Act (EEG), which came into force in 2000 under the red-green federal government and was expanded again in 2008.

Wind power: successful, expandable, unpopular

The number one supplier of electricity among renewables has so far been wind turbines: Last year wind energy accounted for 6.6 percent of total electricity consumption in Germany. This proportion is expected to increase sharply in the coming years. Existing wind turbines on land are to be replaced by larger, more powerful systems. However, many citizens’ initiatives by residents are resisting this so-called repowering. That is why the industry is also relying on wind farms on the high seas. The first German offshore wind farm alpha ventus comprises twelve wind turbines and is located in the North Sea, 45 kilometers north of the island of Borkum.

Biomass: versatile heat source

In second place behind wind power is the generation of electricity from biomass. Your advantage: In contrast to weather-dependent wind power, it is reliably available around the clock. It is also particularly versatile: In addition to electricity, heat and fuel are obtained from liquid manure, wood or rapeseed. Among the renewable energies, biomass is by far the most important heat source – with a share of 94 percent last year.

Third place in electricity production goes to hydropower. In Germany, however, their potential is largely exhausted. Hydropower is particularly useful in pumped storage power plants. If more electricity is produced than consumed, the excess energy is used to pump water into a reservoir. However, this storage potential is also limited.

Solar energy: a lot of funding, little electricity

Solar energy is most strongly promoted in Germany. Those who produce electricity with photovoltaic systems and feed it into the grid receive the highest remuneration. There are grants for solar thermal systems for heat generation. Despite high growth rates, the contribution of solar energy to energy demand in Germany is still relatively small. Last year, the share of photovoltaic systems in gross electricity consumption was just 0.7 percent.

Just like solar energy, geothermal energy can also be used by private households. A heat pump system in the house then provides heating and hot water. So-called geothermal power plants can also produce electricity from geothermal energy. However, this requires drilling deep into the earth’s interior. This harbors risks: Several earthquakes occurred in Landau in the Palatinate. In spite of this, the federal government intends to further increase the previously low share of geothermal energy in electricity production in the coming years.

Smart networks for the future

In order to further increase the share of renewable energies, it is not only crucial how the potential of the individual energy sources can be better developed. The existing infrastructure of the energy networks must also be adapted in order to guarantee a reliable supply: after all, solar energy and wind power are dependent on the weather. Sometimes they deliver too much and sometimes less energy than is currently needed. The Federal Ministry of Economics is therefore promoting research to develop energy transmission paths into "smart grids". These intelligent networks should precisely record the energy demand in order to coordinate production, storage and consumption.