By converting wind energy into electricity, wind turbines reduce the environmental impact of power generation. Wind energy is currently the most developed of a number of renewable energy technologies, with more than 1,000 terrestrial wind turbines already operating across the UK, producing around one quarter of one percent of the country’s energy.
Our advice on wind energy includes information on evaluating the impact of offshore and onshore wind turbine projects on the historic environment.
This guidance is aimed at anyone who is developing a wind energy project which may affect any aspect of the historic environment.
It is also aimed at those involved in strategic planning for renewable energy, as well as those who decide on specific applications, including local authority planners and their advisers on the historic environment.
Wind turbines can be deployed individually, to power a single site or installation, but are most commonly grouped together as ‘wind farms’ to provide power to the national grid.
The energy output from turbines has increased dramatically over the past decade from 200 KW to 3 MW, and 5 MW turbines are currently being evaluated for use in the seas around England.
Their greater energy yield means that the number of turbines needed to produce a given amount of energy has been reduced by at least a factor of five.
Over the same period, however, the tower height and rotor diameter of turbines has doubled. Large modern terrestrial wind turbines have rotor diameters ranging up to 65 metres.
Towers range from 25 to 80 metres in height and, when a blade is vertical, some of the larger modern wind turbines can reach a total height in excess of 100 metres.
Larger-scale wind energy developments are also becoming increasingly common as turbine ratings increase. In 2003, around a third of completed developments were above the 50MW threshold, and wind farms may now include up to 24 turbines and cover a total area of around one square kilometre.
Offshore wind generation
As technical advances improve its cost effectiveness, offshore wind generation is beginning to play an increasingly important role in achieving renewable energy targets.
By 2006, the installation rate for offshore generation over took that of onshore. To date, wind energy developments have occurred in clusters off the north west coast, off the Wash embayment and off the outer Thames estuary.
Offshore wind farms are generally large installations. Current turbine hub heights range from 40 to 100 metres and rotor diameters from 44 to 110 metres, with turbines likely to increase further in size and capacity from 3.6MW up to 8MW.
Although this increase in scale could increase the visual impact of offshore installations when seen from the land, fewer should be needed and improvements in foundation design and the transmission of electricity, should mean that they can be sited further out to sea.
However, the offshore survey programmes that accompany these developments must be conducted in a way that supports archaeological analysis given that what we know about the historic environment further offshore is limited.
These surveys could greatly increase our knowledge of submerged and buried prehistoric environments, as well as historic shipwrecks and aircraft lost at sea.