Germany's Experience: How Effective Are Renewables, Really?

The past 10 years have been the decade of wind power. At the end of 1999, wind turbines generated 2,875 megawatts. By the end of 2008, that number had skyrocketed to 23,903.

The Principle

Wind is everywhere. Temperature differences in our atmosphere set gigantic masses of air in motion and the energy involved in those shifts can easily be captured with the help of rotor blades. Using the principle of electromagnetic induction, a generator can transform the circular motion of those rotors into electricity.

The rotors of the largest wind power facilities now reach a diameter of over 100 meters, and they are set on top of 200-meter-tall towers. Indeed, the height of the towers greatly increases efficiency because it allows turbines to take advantage of higher-speed and more consistent winds. Should these facilities achieve 40 percent efficiency, a single wind turbine can generate between two and five megawatts -- enough to supply electricity to 4,000 homes. One German company has manufactured a wind turbine that supplies six megawatts.

The Market

Germany now gets more of its energy from wind power than from hydro-electric sources. Last year, wind power supplied Germany with 7 percent of its electricity. In states like Saxony-Anhalt, Schleswig-Holstein and Mecklenburg-Western Pomerania, wind power's share was well over 30 percent. "State subsidies have really worked when it comes to wind power," Hubertus Bardt, an expert with the German Economic Institute in Cologne, told SPIEGEL ONLINE.

Wind power is relatively cheap. The EEG mandates that energy companies buy wind power for 9 cents per kilowatt-hour -- not much more than the price for conventional power on the electricity markets. "Wind power is the most economical of the renewable energies," says Bardt.

But the market is not immune. Higher steel prices have meant that the EEG has had to be altered to increase the amount paid for each kilowatt-hour of wind energy. "The fall in prices we have seen during the last decade has been unfortunately reversed," says Bardt.

The Potential

In one study, scientists calculated that wind power could produce many times the amount of energy needed globally. In theory, wind power could produce up to 1.3 million terawatt hours of energy per year -- against a global energy consumption of just 15,666 terawatt hours, according to the International Energy Agency. That's just 1.2 percent of the calculated potential of wind energy.

Experts believe that the wind energy branch is going to grow dramatically in the future -- primarily offshore. Offshore wind parks have the dual advantage that they take advantage of stronger sea winds and are not as disruptive as they are on land.

Offshore wind parks are generally several kilometres off the coast. The gigantic facilities are anchored to the sea floor, with large parks containing up to 100 generators. A high-tension cable can efficiently deliver the energy generated over long distances.

The German government foresees a capacity of 20,000 to 30,000 megawatts from wind parks in the North and Baltic Seas by 2030. Such an output would represent the equivalent of 20 to 30 nuclear power plants, assuming an optimal wind supply. The first of those parks, known as Alpha Ventus, located 45 kilometers off the coast near Borkum, has recently gone online. Its 12 wind turbines produce 60 megawatts -- enough to power 50,000 households.

On land, things don't look nearly as rosy. "In Germany, those areas with sufficient wind have already been built up," says Bardt. In addition, numerous citizens' groups have ramped up their protests to wind parks in recent years. One potential solution to this problem is known as "re-powering" -- a term meaning little more than re-equipping existing onshore wind parks with newer, more efficient turbines. The German Wind Energy Association thinks that re-powering has a huge potential and predicts that by 2020, a quarter of German electricity needs will be met with wind power.

But do wind parks have a negative effect on wildlife? While research by the nature conservancy group NABU has found that the number of birds killed by wind power generators is relatively small compared to those killed by automobile traffic, there is little data for offshore wind parks. A 2003 study by Germany's Federal Environment Agency looked at the risks of offshore parks for fish and birds, but was unable to produce reliable conclusions.

Wind power, though, has a potentially bigger problem: It is unreliable. The wind doesn't always blow, and when it does, it sometimes blows too hard for the facilities to harness it. Furthermore, there is as yet no good way to store excess energy produced by wind power, meaning that if strong winds are blowing at a time when consumers are using little electricity, much is wasted.

In addition, the wind blows stronger in northern Germany whereas the most energy is consumed in the west and the south of the country. New power lines stretching across the country are necessary -- which will drive up costs for the consumer. As a result, wind energy will remain just one element in Germany's energy mix. The hope is that long term the share will grow. Prices will go down as technology improves, and subsidies may soon be unnecessary. "In the next decade, wind energy will likely become economical," says Bardt.

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• Part 1: How Effective Are Renewables, Really?
• Part 2: Wind Power
• Part 3: Photovoltaic
• Part 4: Solar-Thermal Energy
• Part 5: Hydroelectric Power
• Part 6: Bioenergy
• Part 7: Geothermal Power