Wind Turbines

With a good site, a wind generator provides an extremely effective means of generating electricity.  However, the siting of a wind turbine is key, as even a small increase in wind can give a large increase in output.

Siting a turbine

The power available to a turbine is related to the wind speed cubed - so even a small increase in wind can give a large increase in output.  Consequently, the selection of a wind turbine site and tower height are key to ensure good performance.  Wind speed increases with height, hence an increase in tower height can yield a significant improvement in turbine performance

Turbulence reduces power output and also increases wear and tear on the machine.  To minimise effects, the turbine should be mounted away from and above obstructions such as buildings or trees, paying attention to prevailing winds. A common rule of thumb is that the turbine should be placed away from an obstacle at a distance of a least 10 times the obstacle’s height, or   alternatively mounted on a tower over 2 times the height of the obstacle.

Buildings, trees (and the growth of trees), cliff faces and other natural obstacles need consideration as they will all act to slow and disrupt wind flow.  The ideal site of a smooth rounded hilltop may not be available and practical issues such cable routing, planning will all influence site selection.

 

Grid connected wind turbines

A grid-connected system links the wind turbine to the existing mains electricity supply so that wind energy is utilised when it is available and exported when there is a surplus.

With domestic or smaller scale systems, the wind turbine is linked to the grid via a "grid-connect" inverter. This device transforms the electricity generated by the turbine into mains voltage AC, synchronised precisely with the voltage and frequency of the grid. The inverter also performs various safety functions, constantly monitoring the grid and switching off in the event of a fault or major fluctuation in supply.

The output of the inverter is connected directly to a fuse box – feeding wind generated electricity into the buildings conventional electricity supply. Electricity generated by the turbine is used within the building first with any surplus fed into the grid.

Stand-alone systems

Stand-alone wind systems are simple to install and provide an effective source of electricity to locations with no mains supply. Small DC systems are common for applications such as boats, caravans and outbuildings where low voltage DC lights and appliances are used. Larger systems utilise a stand-alone inverter to provide AC power from the battery bank. Wind power, from larger machines, can also be used directly for heating - with all power generated fed directly to immersion or storage heaters.