Wind turbines are moved by the wind and convert this kinetic energy directly into electricity by spinning a generator. Usually they use blades like the wing of a plane to turn a central hub which is connected through a series of gears (transmission) to an electrical generator. The generator is similar in construction to the generators used in traditional fossil fuel power plants.
Wind resources are best along coastlines and on hills, but usable wind resources can be found in most other areas as well. As a power source wind energy is less predictable than solar energy, but it is also typically available for more hours in a given day. Wind resources are influenced by the ground surface and obstacles at altitudes up to 100 metres.
The wind energy is thus much more site specific than solar energy. In hilly terrain, for example, two places are likely to have the exact same solar resource. But it is quite possible that wind resource can be different at both places because of site condition and different exposure to the prevailing wind direction. In this regard, wind turbine planning must be considered more carefully than solar technology. Wind energy follows seasonal patterns that provide the best performance in the winter months and the lowest performance in the summer months. This is just the opposite of solar energy. For Denmark conditions of a PV plant has a production per month varying between 18% in January and 100% in July. The wind power plant produces 55% in July and 100% in January. For this reason small wind and solar systems work well together in hybrid systems. These hybrid systems provide a more consistent year-round output than either wind-only or PV-only systems.
It is important to know that the amount of wind power generated is proportional to the density of air, area swept by the rotor blades of the wind turbine, and to the cube of the wind speed.
Common Misconceptions about Wind Energy
1. Developers of wind farms make profits from public subsidies
There are no direct subsidies for wind farms or other forms of renewable energy. Until 2000 there was a scheme that encouraged the use of non-fossil fuels for the generation of electricity (referred to as NFFO). This was first introduced to support nuclear power. In the 1990?s it was used to support the generation of electricity from wind-power through a series of auctions. Since 2001 suppliers of electricity have been obliged to buy a percentage of their supplies from renewable sources, or pay a surcharge equivalent to 3p/kWh for each kWh shortfall. Some part of this surcharge can therefore be used to buy electricity from renewable sources and could be regarded as an indirect subsidy. It is regarded by the Government as necessary to ensure that renewable energy develops even when it is not directly cost-competitive with existing fossil fuel sources. (The alternative, of taxing fossil fuels to reflect their environmental costs, has been ruled out because of the impacts on fuel poverty and the competitiveness of UK industry).
2. The problems in California were caused by expensive wind energy
In 2000 the state of California experienced serious shortages of electricity production with several power companies filing for bankruptcy because they had to pay more for wholesale electricity than they were permitted to charge their retail customers. This situation arose due to a shortage of production capacity (largely because of difficulties in obtaining planning permission for new capacity), shortages of gas supply capacity and a peculiar set of regulations. It had nothing to do with wind energy.
3. The intermittency of wind energy causes serious problems for supply
In Great Britain the national grid system links all electricity production with all electricity consumers and it is managed so as to achieve a balance between supply and demand on a continuous basis. Electricity demand varies significantly from moment to moment. Certain events, such as a commercial break in a popular TV programme, or high powered locomotives disconnecting from the system, can cause very large increases or decreases in demand. These are accommodated by running a number of power stations at below full capacity (so called spinning reserve) so that a sudden increase in demand can be met by increased output and a decrease in demand met by reducing the output of other power stations. Whilst renewable energy contributes less than 10% of the total electricity supply its contributions are largely lost in the random fluctuations in demand. The company operating the grid has estimated that it can accommodate intermittent sources of up to 20% of total supply with its current regime. To increase the proportion of intermittency above 20% is feasible but would incur additional costs and perhaps some storage technologies.
4. Wind-power cannot replace other power stations.
The argument here is that on days when there is no wind blowing the required electricity has to be generated by non-wind power stations, so even when we have a lot of wind turbines we will also still need all the existing power stations. This is broadly correct, though the days when there is no wind across the entire UK are extremely rare. In general, if wind generators are spread from the north of Scotland to the south of England the availability of the wind broadly evens itself out. This ?evening out? might be further enhanced by the new electricity links being built to Europe.
The main point is that benefits of wind energy do not come from reducing the number of conventional power stations, but from reducing the burning of fossil fuel?it is this that generates the carbon dioxide which aggravates climate change. It is regarded as quite likely that if the contribution of renewable electricity increases then a number of the older power stations will be kept on as an emergency reserve for the few days a year when demand is at its peak and there is a significant drop in wind.
5. Wind power is expensive and will not become any cheaper
All technologies cost a lot more when new than when they are mature. There are many reasons for this?the most important being that the producers learn how to engineer the product better, increases in scale which reduce costs, and a steady stream of technological improvements. Between 1980 and 1995 the average cost of wind generated electricity in Europe decreased to about one tenth and it is expected to decrease by a similar amount over the next few decades. Similar relationships between costs and production apply in most industries. The PIU Energy Review concluded that by about 2020 wind energy was likely to be the cheapest form of electricity generation available.
6. Wind turbines do not repay the energy required to build them
All electricity generating equipment requires significant amounts of energy for its production and assembly. For example iron ore has to be converted to iron, then steel and then fabricated into pipes, machinery and bearings. The energy required to produce facilities power stations is sometimes referred to as their ?embodied energy? and this is included in the ?life cycle? cost analyses. Not only does this include the energy to produce the components, but also the energy to dispose or recycle them. There is no universally agreed method of calculating these life cycle costs, so the results vary from one author to another. However there is one feature of all the analyses of alternative methods of power production that stands out, namely that wind power is fastest to repay the investment of embodied energy. It takes only a few months of operation (including the 30% intermittency factor) for a wind turbine to pay for itself in energy terms.
7. Wind-turbines will destroy tourism in Wales
There are several issues wrapped up in this assertion. First it assumes that there will be a very large number of wind turbines erected in Wales. Secondly it assumes that these will either be so numerous, or so sited, that they will be visible in all or most of the most favoured tourist areas. Finally it assumes that tourists dislike wind turbines sufficiently for the sight of them to overcome their attraction to the beauty of Wales.
The total number of on-shore wind turbines possible in Wales will be limited by many factors, not least the requirement to exclude them from National Parks and areas of outstanding beauty or scientific interest. In the first part of its Review of Energy Policy the Economic Development Committee published a number of scenarios of renewable energy deployment in Wales. The option with the greatest contribution from on-shore wind would require about 200 extra turbines.
There is no objective evidence available as to whether wind turbines increase or decrease tourist interest in an area. There have been several different surveys in other areas which generally report that the majority of people are not influenced one way or another by the presence of wind farms. The most recent surveys, carried out by MORI in Scotland and reported recently in The Times, concluded that ?Nine out of ten tourists visiting some of Scotland?s top beauty spots say the presence of wind farms makes no difference to the enjoyment of their holiday, and twice as many people would return to an area because of the presence of a wind of a wind farm than would stay away?. Whether the same is true in Wales remains to be established.
8. Wind turbines are bad for bird populations
Whilst there have undoubtedly been a number of bird deaths associated with wind turbines the total number is not large. The Royal Society for the Protection of Birds Cymru has not raised this as an issue in its submission to the Committee. They point out that a wind farm location needs to be sensitive to migration paths and at-risk habitats. However their overall message is that global warming presents the greatest risk to bird species and that all forms of renewable energy should be welcomed to help reduce climate change.
 The information for this section is taken from the Review of Energy Policy in Wales: Renewable Energy?Final Report. The National Assembly for Wales? Economic Development Committee (January 2003).
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Last Updated (Monday, 02 November 2009 14:43)