Solar energy
Solar panels producing hot water for domestic uses have been popular on Exmoor for many years. They have become more efficient in design, with modern vaccuum sealed units, but are still not competitive with heating from conventional fuels. Photovoltaic cells convert light energy into electricity. These are currently one of the most expensive renewable technologies but are often used where connection to main electricity is even more expensive, suiting remote properties in the National Park.
The most common use of solar energy on Exmoor is for domestic hot water. A typical system for this consists of a termal collector (which usually sits on a roof), a pre-heat tank, an electric pump with an electronic load controller and piping to connect to the hot water system. Solar radiation is absorbed by the collector and the heated fluid inside is then pumped to the pre-heat tank, which is in turn connected to the normal household hot water tank. The collectors generally do not have planning restrictions, except on Listed Buildings and in Conservation areas.
Another use of solar energy is in the form of Passive Solar Design. This suits new buildings, the orientation and design of which are contrived to capture, store and distribute solar energy, reducing the demand for light and heat and thereby reducing the building's energy demand. Many older Exmoor buildings face south for such reasons but, apart from meeting insulation standards, few new buildings incorporate Passive Solar Design, although this is to be encouraged through the National Park Authority's Design Guide. An example just outside of the National Park is a building for a playgroup in South Molton. This uses both passive and active solar features in a very energy efficient structure.
The development of photovoltaic electricity production in Britain has been slow. The feeling has been that Britain does not receive enough sunshine. This assumption, however, is not true and photovoltaic devices have become commonplace. Government grants are now helping to make larger structures more affordable. There are two main types of photovoltaic cells: crystalline and silicon based. The crystalline cells are more efficient but more expensive. The efficiency of the structure depends upon its orientation, angle and geographical location.On average in the UK the cells will produce 10-15% of their peak potential. A typical domestic installation will prevent about a tonne of carbon dioxide emission per year.
Building Integrated Photovoltaics are designed to be parts of building structure, such as roofs and walls. As the silicon film cells are semi-transparent they can be used as glazing and shading devices. This makes them more economical when used as part of a new structure. Exmoor National Park Authority has integrated photovoltaic tiles into the design of its new toilets at Tarr Steps. The building also uses conventional roof lights to save the need for electric lighting.
Tarr Steps toilets, with photovoltaic tiles on left hand side of roof and wooden shingles on right
A larger expanse of tiles was used on the Authority's hallways extension to its Pinkery Centre.
Alan Bailey, Head of the Pinkery Centre, demonstrates the photovoltaic roof, left
Residents at the centre can see both the amout of electricity produced by the photovoltaic roof and the wind generator on dials in the lounge.
Dial in lounge of Pinkery Centre showing energy output of photovoltaic roof, left, and wind turbine, right