Small Scale Wind Energy Generation

In the UK we have 40% of Europe's total wind energy. But it's still largely untapped and only 0.5% of our electricity requirements are currently
generated by wind power.
Wind power is proportional to the cube of the wind's speed, elatively minor increases in speed result in large changes in potential output.
Individual turbines vary in size and power output from a few hundred watts to two or three megawatts (as a guide, a typical domestic system would
be 2.5 - 6 kilowatts, depending on the location and size of the home).
Uses range from very small turbines supplying energy for battery charging systems (e.g. on boats or in homes), to turbines grouped on wind farms supplying
electricity to the grid.

Small scale wind and your home

Wind speed increases with height, generally speaking the ideal siting is a smooth-top hill with a flat, clear exposure, free from excessive turbulence and
obstructions. However, small-scale building-integrated wind turbines suitable for urban locations are currently being developed.

Knowledge of the local wind is critical to designing a wind energy system and predicting output. For domestic installations a good source of information on local
wind speeds is the NOABL database which can be accessed from the British Wind Energy Association.

You can also collect primary information by setting up your own monitoring mast to record wind speed. An ideal way of doing this is with an anemometer.
You can buy one online for around£120.
The amount of energy and carbon that micro wind turbines save depends a lot on a several things including size, location, wind speed, nearbybuildings
and the local landscape. At the moment (January 2007) there is not enough data from existing wind turbine installations to provide a figure of how
much energy and carbon could typically be saved. The Energy Saving Trust is monitoring several wind turbine installations; the results of this activity
will help to provide further information for householders considering this technology.
In the meantime, anyone considering installing a micro wind turbine should recognise that the savings achievable can only be determined with any certainty
by doing a detailed, site specific assessment. You should also satisfy yourself as to the structural suitability of any proposed installation, and that all
appropriate planning, electrical and other legal requirements have been complied with.
Issues such as visual impact, noise and conservation issues also have to be considered. System installation normally requires permission from the local authority.

Stand-alone or grid-connected system?
Small-scale wind power is particularly suitable for remote off-grid locations where conventional methods of supply are expensive or impractical. Most small
wind turbines generate direct current (DC) electricity. Off-grid systems require battery storage and an inverter to convert DC electricity to AC
(alternating current - mains electricity).

You also need a controller to divert power to another useful source (e.g. space and/or water heaters) when the battery is fully charged.

It's common to combine this system with a diesel generator for use during periods of low wind speeds. A combined wind and diesel system gives greater
efficiency and flexibility than a diesel only system. It allows the generator to be used at optimum load for short periods of time to charge batteries when there is
little wind, rather than by constant use at varying loads.

Wind systems can also be installed where there is a grid connection. A special inverter and controller converts DC electricity to AC at a quality and standard
acceptable to the grid. No battery storage is required. Any unused or excess electricity can be exported to the grid and sold to the local electricity supply company.

Cost and maintenance

Systems up to 1kW will cost around £3000 whereas larger systems in the region of 1.5kW to 6kW would cost between £4,000 - £18,000 installed.
These costs are inclusive of the turbine, mast, inverters, battery storage (if required) and installation, however it's important to remember that costs always vary
depending on location and the size and type of system.

Turbines can have a life of up to 20 years but require service checks every few years to ensure they work efficiently. For battery storage systems, typical battery
life is around 6-10 years, depending on the type, so batteries may have to be replaced at some point in the system's life.

Source of information is: The Energy Saving Trust January 2007.

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