Wind Turbines

A highly visible form of harnessing renewable energy and to date probably the most hotly debated!

Putting aside some more exotic designs, the majority of installed turbines are horizontal axis models. They fall broadly into the small scale, 1kw or less, and up to 20kw, any larger are commercial units and more likely to be installed on wind farms.

The smaller units are intrinsically less efficient and, except in exceptional cases, are only suitable for producing ‘off grid’ power which typically is fed into heavy duty batteries to provide more constant (although still limited) power. Surplus energy can also be ‘saved’ as heat produced in a thermal store by a suitable heating element. The electricity can also be converted to mains power by use of an inverter.

This expense and trouble may be warranted where electrical loads are small or occasional and connection to mains supply is impractical or expensive.

For turbine of 1kw or more, depending on the site (urban sites rarely work due to turbulent wind), there can be a case for connecting the output to the grid to become partially or fully self sufficient. The necessary approved connection equipment adds considerably to the capital cost and therefore a careful site survey is a pre-requisite for successful installation.

A grid connected turbine can export surplus electricity in return for which the electrical supplier will pay the generator a negotiable tariff rate plus a ‘top up’ ROC subsidy – the latter arises under statute compelling electricity producers to increase their quote of renewable energy delivered to the end user.

Capital grants may be available whilst the production subsidy may amount to 10p/kwH. From April 2010 in the UK a new regime of ‘Feed-in Tariffs’ may potentially yield much higher returns on exported electricity which will lower the threshold (turbine size, average wind speed) for economic viability.

Considerations

• Building mounted - rarely going to work
  
• The turbine must be high – the higher the better even for small turbine
  
• Noise – poor design usually the culprit
  
• Planning consent – visibility and perception of excessive noise the obvious obstacles
  
• Wind Profile – there are good, bad and hopeless sites; know which yours is.
  
• Self-sufficiency – to make 4,700kwH/year (average domestic consumption), unless it is a very good site, you could be looking at a 5kw or 10kw turbine. These are very big machines (7-8m rotor diameter) and installed, grid connected can cost £25-£30k… For a site survey or further information please call or email.