Onshore or Offshore?

Whilst looking at the UK's cuts to renewable energy subsidies in my last post, I noticed that the UK's attitude to wind energy was highlighted in many articles.

This year, onshore wind energy became the cheapest form of electricity production in the UK, with 60% of wind power being produced onshore. However, despite this, gaining approval for a new onshore wind farms is difficult; a recent report by the think tank the Fabian Society (2015), showed that 6 out of 10 onshore wind farm proposals were rejected in 2014, with the rate of rejection doubling since the coalition government came into power in 2010.

In June this year, ontaining approval became even more difficult. This is because of the government's introduction of new planning rules which state that, in England, wind farms with over 50MW of installed capacity must also be approved at local authority level to ensure that local residents are supportive of the new development.

RenewableUK, the trade association representing wind power, expressed concerns about the additional delay this would cause. In September this year alone, the Department of Energy & Climate Change rejected plans for four significant wind farms to be built in Mid-Wales.

Controversial Placement of Wind Turbines in Cumbria
Source: Telegraph 

So why is offshore favoured over onshore? 

Although onshore wind farms are cheaper, offshore turbines are typically exposed to faster wind speeds and are able to be installed lower to the ground due to the difference in the turbulent air layer above the sea compared to the land. These benefits are discussed by Esteban et al. (2011), in their  paper on offshore wind power.

Another key issue with onshore turbines is wildlife mortality. Although bird mortality is associated with both onshore and offshore wind farms, onshore wind farms have the additional impact of killing large numbers of bats. A study by Berwald et al. (2008), states that over 90% of bat deaths caused by wind turbines are a result of barotrauma (damage to the lungs caused by the rapid reduction of pressure when nearing the turbines), of which mammals are more susceptible than birds.

Source: Countryside Learning

There are however, certain environmental impacts that are specific to offshore turbines. One of the greatest concerns is the noise created from pile-driving to create the foundations of the turbines. Thomsen et al. (2006), states that this noise can lead to hearing impairment and alterations in normal behaviour patterns of a number of marine species including salmon, herring, cod and dab. Another study by Bailey et al. (2010), looked at the impact of the construction of two turbines in the North-East of Scotland. Their results concluded that permanent hearing damage would have occurred in cetaceans and pinnipeds within 5m and 20m, respectively, of the pile-driving. Two other species highlighted in the study were Bottlenose Dolphins and Minke Whales whose behavioural responses would have been impacted if they were within circa 50km of the pile-driving.

The noise pollution of onshore wind farms is also of concern, but unlike offshore wind farms, the impact is primarily on residents living in the vicinity of the turbines. They create both mechanical sounds from the generators as well as noise from the movement of blades and this sound increases with wind speed.

However, the primary reason for the preference of offshore wind farms by the public is aesthetics. A study by Jones & Eiser (2010), analysed local residents opinions on a number of proposed offshore and onshore wind farm sites. They found that offshore sites were far better received with the majority giving aesthetic impact on the environment as the reason for their preference.

The public opinion of onshore wind farms is influenced heavily by visual impacts and noise pollution and with local authorities now involved in the approval process of new onshore developments (of which the local residents play a major role), this form of wind power is unlikely to expand easily. It can be presumed that offshore wind farms will receive far greater support and we are likely to see increased development in this area. One of the key benefits of offshore is the ability to build wind farms with a greater number of turbines which therefore greatly increases capacity. Although they are more expensive, the cost is likely to continue to decrease with increased investment in this area.

Although there are clearly environmental impacts of both offshore and onshore wind turbines, the number of species impacted by fossil fuel consumption will be far more significant. With advancing technology aimed at limiting the number of wildlife fatalities from wind farms, including an ultrasonic 3D whistle aimed at preventing bats from flying into turbines, the environmental impacts of wind power is likely to decrease.

I really do believe that the positives of wind power (both onshore and offshore) vastly outweigh the negatives and feel it should be fully supported by the government, the public and environmentalists.