Wind power
When one thinks of alternative power sources, wind power usually comes to mind. The UK has about 35% of the potential economic wind resource of the whole of Europe. The advantages are that there are no fuel costs, no pollution, low maintenance, long lifetimes and few decommissioning problems. The disadvantages are the high installation costs, visual impact, noise and inefficiency. There is a theoretical maximum of 60% efficiency at which a wind turbine can work. Modern turbines are close to this limit but the wind does not blow at the best speed all of the time and the turbines average about 35% of what they could achieve at maximum output. Grant systems have meant that other European countries generate more wind power than the UK.
To produce enough energy to contribute to the National Grid a wind generator needs to be in a particularly windy area (wind speeds averaging over 7 metres per second) and at least 45 metres high. There also needs to be good access to the site for the huge vehicles necessary to transport materials. About 600 sq km of the Greater Exmoor area has been identified as having suitable wind conditions, with the potential for producing up to 85MW, about 5 times the area’s needs, but the environmental impact of such large structures would be unacceptable. Proposals for two small wind farms just outside of the National Park boundary have been turned down because of their potential impact on the landscape. Somerset has an estimated potential of generating 148MW but this is reduced to 71MW when protected areas such as the National Park are taken out of the equation. However, there are plans for a large 33MW wind farm next to the nuclear power station at Hinkley Point.
There is probably greater planning potential for offshore wind power installations in the UK. The policy of Exmoor National Park Authority is that ‘small is beautiful’ and, whilst each planning application is taken on its own merits, there is a presumption against large scale wind farms and in favour of smaller units. The main problem even with smaller units is the visual intrusion. If the turbines are hidden out of sight, they are generally in positions where they cannot work efficiently, so a compromise has to be reached. There are seven small wind generators within the National Park. Each serves one or two premises as a back up supply. The National Park Authority's generator at Pinkery produces up to 6kW and this combines with up to 4kW from a photovoltaic roof.
Wind turbine at Pinkery
The National Park Authority installed the wind generator at Pinkery in 2001. Funding came from the Authority, Western Power Distribution, Department of Environment, Transport and the Regions and the Rural Development Agency under a scheme that was intended to connect remote farm to mains electricity. The problems of connecting Pinkery to the mains unobtrusively and sustainably were considered too great and renewable energy was considered to be a viable option.
The turbine is made by Proven. Whilst it is hidden from most views, it is far enough from obstacles to allow the wind to pass unhindered from the most common wind directions. It has a simple downwind design that naturally aligns itself to the wind direction and the rotor baldes have a 'passive pitching' mechanism linked to wind speed, which means that they furl back if the wind speed gets too great. The turbine does not have a gearbox, resulting in less noise and less maintenance. The tower is lowered with a winch every 6 months to grease the moving parts. An information board between the centre and the turbine explains simply to the public how the turbine works.
Information board near the wind turbine at Pinkery
An underground cable takes the DC electricity to the centre's generator building. There the electricity goes either to be stored in batteries or, if the batteries are fully charged, to heat water in the centre. Two inverters take power from the battery bank and convert it into usable domestic AC electricity at 230V. If the battery volvage drops below a certain level, the diesel generator is started automatically. Dials in the generator building show wind generator output and battery voltage. Installation of the system meant that use of the diesel generator dropped from an average of 105 hours a week to 5 hours a week.
Batteries and inverters at Pinkery
Input/output control box at Pinkery
Inverter at Pinkery
The National Park Authority has provided grants for wind power through its Sustainable Development Fund and other funds:
A cottage at Frogwell Lodge, Skilgate, was given a grant for a wind generator to supplement its diesel generator in lieu of a grant for connection to the mains. During the foot and mouth outbreak the neighbouring landowners were reluctant to permit access for a long spur from the mains. Objections from local residents resulted in the turbine being kept out of public sight but in the location being less suitable for efficient use of the wind. The set up is similar to that at Pinkery, with a 5.8kW generator. The scheme cost £17,500.
Wind generator at Frogwell Lodge