Wind is the largest of the non-hydro renewable energies. It has undergone a dramatic series of improvements over the past two decades.
The first known electrical generators powered by wind were more or less simultaneously invented in 1887 by James Blyth, Scottish, and Charles Brusch, American. Wind was soon supplanted by hydrodams and then fossil fuel burner power plants as an energy source for electricity generation. Since the 1970s, however, the older technology of wind has experienced a resurgence as a contender for the much-needed clean renewable energy for the transition economy.
Wind currently powers single figure percentages of most countries’ electricity generation capacities, but this is likely to change as the technology proves its efficiency and cost competitiveness.
Wind turbine design has seen a steady increase in size, efficiency, and consequently output and reliability ratings. Denmark has been a leading research pioneer, given its perennial strong wind resources. Between 1983 and 1987, it operated the first large-scale experimental installation, the GROWIAN, which had a tower height of 100 meters and rotor (x2) length of 50.2 m (lee-side of tower). It had a rating of 3.0MW, a record for the time, and was expected to produce 12 GWh per year. The many technical problems it had caused the project to be abandoned.
In the 1980s, USA-made turbines had three rotor blades, without blade angle adjustment, and had only a maximum of two fixed speeds.
The Electricity Feed-in Act (Stromeinspeisungsgesetz StrEG 1991) and the Renewable Energy Sources Act (Erneuerbare-Energien-Gesetz EEG 2000) have been instrumental in promoting wind energy in Germany. Thanks to these initiatives, German wind turbine manufacturers are now world leaders. Approximately every decade, the average nominal output of the new wind turbines installed in Germany has increased by 1 MW. In 1990 it was 164kW (Ø <50m), in 2000 1MW (Ø 60-90m), in 2009 already 2MW. Offshore wind turbines are typically equipped with 3-MW class power ratings, and the trend is towards 3.6-6MW (up to Ø 170m).
Through Repowering old installations are being replaced by more powerful wind turbines. As a result, in wind parks sometimes the number of installations can drop, while the installed power and yield increases.
The power density of the wind ω is proportional to the square of the wind speed υ and the air density ρ: ω = ½ρ⋅υ2
Germany has strong winds in the north of the country, and by joining forces with Denmark, it is developing efficient, powerful wind parks offshore in the North and Baltic Seas.
Germany generated 8.1 TWh of power offshore in 2015, about 10% of its total wind output, or 1.3% of total domestic electricity demand.
Offshore wind is a growing sector of renewable energy. Turbines with 80m radius and over 6MW peak power potential (compared to more typically 2.5MW onshore) can be erected in large arrays offshore on continental shelves, such as in the North Sea. In 2016 offshore wind provided around 10% of Germany’s wind power, but this proportion is likely to increase rapidly.
The world’s most powerful wind turbine power plant (2nd from left) (E112 from Enercon GmbH) is 6 megawatts, rotor diameter of 114m and hub height 124m. It is located at the Offshore wind energy test field in Cuxhaven, Germany. The two prototypes on the right (5M from Repower AG) are of the multimegawatt class. The test field operated by DEWI-OCC for offshore prototypes is located directly on the river Elbe.
Gode Wind: Altogether 176 wind turbines with a capacity of 760 MW (average of 4.3MW each) were erected and started production in 2017 at three locations in the North Sea. A delay at the start of construction was due to still unresolved issues related to the grid connection and the construction of the necessary electrical power lines through the Wattenmeer. At the “Gode Wind” III site, 7 MW wind turbines are to be tested.