Here’s my latest offering for Our Green Earth. I really enjoyed researching and writing this one and learnt a lot about the viability of wind-generated electricity in the UK. I hope you do too!
[Edit 3rd December 2010: Sadly, Our Green Earth no longer exists but the owner has very kindly handed back copyright of my articles to me. Here, for your reading pleasure, is A Guide to Residential Wind Turbines…]
A Guide to Residential Wind Turbines
Love them or hate them, wind turbines are here to stay. The Environment Agency aims to help the UK generate 15% of its electricity by using renewable, sustainable and clean sources of energy by the year 2020 (1) and one of the ways that it intends to meet this target is through the use of wind.
Wind Farms in the UK
Wind farms are a relatively common sight in the UK nowadays, with 260 operational wind farms around the country, comprising 2718 individual turbines generating enough energy for over 2 million homes (2). This handy map shows the locations of these wind farms, plus those under construction and those given the go-ahead for construction. Although many people complain about the “blot on the landscape” that wind turbines create and the noise that they make, to me it seems logical that we should be utilising this free, non-polluting energy resource to reduce our fossil fuel consumption and lower our carbon footprint. Technology improves all the time and today’s wind turbines are quieter and more efficient than ever before.
Residential Wind Turbines
Commercial wind farms generate electricity that is then fed into the national power network, the National Grid. The Energy Saving Trust however estimates that approximately 800,000 homes in the UK are well placed to benefit from the generation of their own “off the grid” wind-powered electricity by installing smaller scale residential wind turbines. In addition, many more homes could reduce their reliance on grid energy (and their electricity bills!) by around 25% by supplementing their homes with a domestic turbine (3).
How Does A Residential Turbine Work?
Residential turbines work in much the same way as a large commercial-scale turbine, but on a much smaller scale. The plastic or fibreglass rotor blades are designed in a very similar way to aircraft wings in order to provide “lift”. Because of the angling of the blades, they spin rather than rise upwards and do so at potentially very high speeds. Contrary to what some might think, adding more or wider blades will in fact not increase spin speed since airflow over the blades needs to be kept smooth; too many blades, or blades that are too big would create turbulence that would actually reduce the rotational speed (4).
The rotation of the turbine’s blades drives a permanent magnet alternator, or generator, which in turn spins a coil of wire inside a magnet to generate electricity. This electricity can be fed into the grid system or, since wind speed is rarely consistent, the electricity can be stored in batteries for later use (4).
Location Location Location
In July 2009, the Energy Saving Trust published a report on the findings of a survey in which 712 homes around the UK who were already using either a free-standing or building-mounted residential turbine, were monitored for 1 year. Parameters including wind speed, turbine efficiency and electrical power were measured in order to determine whether or not small-scale wind-generated electricity is a viable alternative to fuel-generated power. The results of the study showed that wind-drive electricity generation is a worthwhile investment for some, but not all people (5).
Unsurprisingly, wind turbines were found to be most beneficial to homes in rural, open locations with few topographical features such as hills, mountains or trees to get in the way of air flow. The free-standing turbines of many homes in high wind-speed areas of rural Scotland were found to operate at more than 30%, which is in fact consistent with the efficiency of some large-scale commercial turbines and generates some 18,000 kWh of electricity. Building-mounted turbines in urban or suburban areas were significantly less effective (5).
Installing your own wind turbine
Domestic wind turbines cost somewhere in the region of £1500 to buy and install so before considering to buy one, it is wise to thoroughly research whether or not a wind turbine would be a wise investment for you. To generate enough electricity to be financially viable, wind speeds in your area need to average at 5 m/s, but ideally much more. The Energy Saving Trust has a clever little wind-speed predicting tool here, but also recommends that if you are serious about investing in wind power, you should use an anemometer to measure your wind speed for at least 3 months. If your area has a low average wind speed, alternative solutions may be better for you so investigate maximising the energy efficiency of your home instead (5).
If your home would be suitable to host a turbine, there are several things that need to be taken into consideration. Firstly, at present, there is no industry standard for manufacturers of home turbines, so makes and models may vary considerably in their efficiency as well as cost. The Energy Efficiency Trust recommends that customers only purchase turbines from suppliers accredited under the Microgeneration Certification Scheme, but acknowledges that guidelines for turbine specifications need to be established (5).
Buy Back Schemes
Home turbines need to be properly erected and sited in an unobstructed location to work most efficiently. If you are lucky enough to live in an area where your turbine may generate more electricity than you actually need, many energy companies offer a “buy back” scheme where you can sell your excess energy back to the National Grid. In the Energy Saving Trust survey, those people who were most satisfied with their turbines were unsurprisingly those who had seen the greatest savings in their energy bills, although some concern was expressed as to the real benefit of these schemes in their present state. Finally, you should always remember that wind is highly variable and cannot always be relied upon (5). A plan B is highly recommended!
- Location, Location, Location: Domestic small-scale wind field trial report, Energy Saving Trust, July 2009