Offshore wind farms

December 22, 2015

The Committee on Climate Change (CCC) has published its recommendations to the UK government regarding the UK’s fifth carbon budget, which is due to be made legally binding in June 2016. As the fifth carbon budget puts a limit on UK carbon emissions from 2028-32, it is planning for the UK’s future energy supply, and what different types of energy production will be most effective and efficient. The Committee’s current recommendation would limit the UK’s carbon emissions to 57% below 1990 levels.

In their 2011 report, the CCC calculated that offshore wind farms could generate over 400 TWh (Terawatt Hours) of electricity per year if placed in UK waters. This would fully supply the UK’s current electricity demand, giving us a country powered by 100% green energy.

Currently, an offshore wind farm costs almost twice as much as a newly built gas-fired power station. However, a detailed assessment commissioned by the CCC suggests that electricity generated by offshore wind could become economically competitive, if gas plants had to pay a tax based on their carbon emissions.

Wind turbines are surprisingly simple. The blades of the turbine are each shaped aerodynamically, so that when wind blows over them, they catch it and start spinning. The motion of the blades then passes into a shaft leading to a gearbox, which converts the speed of the rotations from 30-60 per minute to 1000-1800 per minute! The shaft coming out of the other side of the gearbox then connects to a generator – usually electromagnetic in some form – which produces electricity. The entire process has no waste, hazardous or otherwise, and is relatively cost-effective; each large 6 MW (Megawatt) wind turbine can power around 1300 homes. Once installed, turbines work continuously for around 25 years with regular maintenance. The closer to sea level the turbine is placed, the more force is exerted on the turbine and the more power it generates, as the air is “heavier” due to air pressure. Also, faster wind makes for faster rotation, meaning that the sea is the perfect place to put wind farms.

Everything has downsides, and wind turbines are no exception. Depending on where they’re placed, wind farms can have devastating impacts on bird and bat populations. The infrasound radiation from the turbines not only ruins bats’ navigational senses, it can also kill them if they get too close. The currents from turbines can stop birds from being able to fly properly, and change their migration routes. The blades themselves spin at up to 180 mph and so kill birds on impact, and the placement of the turbines can destroy habitats.

Wind turbines are, of course, reliant on the wind to generate electricity. This means that they do not tend to produce as much electricity as their energy rating would suggest. In fact, offshore wind turbines in the UK produce, on average, around 42% of their annual energy rating.

There is a great deal of contention regarding the potential negative health impacts of wind turbines. Some argue that the sound produced by wind turbines is quiet, and others that it is too loud for comfort, but the main debate regards infrasound radiation. “Wind-turbine syndrome” is the name given to a wide variety of symptoms (headaches, sleep problems, tinnitus, dizziness, nausea, etc) experienced by those who live around wind farms. Of course, these issues would not be present if the wind farms were placed at sea, away from populated areas.

Another important problem is in the anchoring of turbines to the seafloor. As it is, they have to be attached with huge metal piles and foundations dug deep into the seabed, which are heavy, expensive, and hard to reach for maintenance. However, floating wind turbine platforms are being swiftly developed. They will allow wind farms to be placed in deeper seas, with less damage to the underwater ecosystem.

Wind turbines must be considered as a viable solution to the UK’s energy crisis, in the knowledge that a little more research needs to be done. There are still some issues surrounding offshore wind farms, but they can all be solved with time and effort. The UK needs to make a huge decrease in emissions, and offshore wind farms could well play a vital part.

Photo by Statkraft: Sheringham Shoal Offshore Windfarm, North Norfolk, UK. This 317MW wind farm has been in operation since 2012.

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