Technologies - Wind
How Does Wind Energy Work?
- The wind blows on the blades and makes them turn.
- The blades turns a shaft inside the nacelle (the box at the top of the turbine)
- The shaft goes into a gearbox which increases the rotation speed enough for...
- The generator, which uses magnetic fields to convert the rotational energy into electrical energy. These are similar to those found in normal power stations.
- The power output goes to a transformer, which converts the electricity coming out of the generator at around 700 Volts (V) to the right voltage for distribution system, typically 33,000 V.
- The national grid transmits the power around the country.
Instruments to measure the wind speed and direction are fitted on top of the nacelle. When the wind changes direction motors turn the nacelle, and the blades along with it, around to face the wind. The nacelle is also fitted with brakes, so that the turbine can be switched off in very high winds, like during storms. This prevents the turbine being damaged. All this information is recorded by computers and transmitted to a control centre, which means that people don't have to visit the turbine very often, just occasionally for a mechanical check. This is often done by local firms.
The real situation is more complicated, with many wind turbines, more voltages, different types of generators and safety systems, but this is a good guide to the basics
Source: http://www.bwea.com/energy/how.html
Small Scale Wind Generation
Most small wind turbines generate direct current (DC) electricity. Systems that are not connected to the national grid require battery storage and an inverter to convert DC electricity to AC (alternating current - mains electricity).
Wind systems can also be connected to the national electricity grid. 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 may be able to be exported to the grid and sold to the local electricity supply company.
There are two types of wind turbines:
- Mast mounted - which are free standing and located near the building(s) that will be using the electricity.
- Roof mounted - which can be installed on house roofs and other buildings.
Benefits
Wind power is a clean, renewable source of energy which produces no carbon dioxide emissions or waste products.
In the UK we have 40% of Europe's total wind energy
Is it suitable for my home?
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 1 - 6 kilowatts). Uses range from very small turbines supplying energy for battery charging systems (e.g. on boats or in homes), to turbines on wind farms supplying electricity to the grid.
You should consider the following issues if you're thinking about small scale wind. An accredited installer will be able to provide more detailed advice.
- Wind speed increases with height so it's best to have the turbine high on a mast or tower.
- Generally speaking the ideal site is a smooth top hill with a flat, clear exposure, free from excessive turbulence and obstructions such as large trees, houses or other buildings.
- Small scale wind power is particularly suitable for remote off grid locations where conventional methods of supply are expensive or impractical.
Please note that the electricity generated at any one time by a wind turbine is highly dependent on the speed and direction of the wind. The windspeed itself is dependent on a number of factors, such as location within the UK, height of the turbine above ground level and nearby obstructions. Ideally, you should undertake a professional assessment of the local windspeed for a full year at the exact location where you plan to install a turbine before proceeding. In practice, this may be difficult, expensive and time consuming to undertake. Therefore we recommend that, if you are considering a domestic building mounted installation and electricity generation is your main motivation, then you only consider a wind turbine under the following circumstances:
- The local annual average windspeed is 6 m/s or more. An approximate figure for your location can be checked on the BERR website
- There are no significant nearby obstacles such as buildings, trees or hills that are likely to reduce the windspeed or increase turbulence
If you are in any doubt, please consult a suitably qualified professional.
Planning issues such as visual impact, noise and conservation issues also have to be considered. System installation normally requires permission from the local authority, so it's important to always check with your local authority about planning issues before you have a system installed.
Costs and savings
Roof mounted
These cost from £1,500.The amount of energy and carbon that roof top micro wind turbines save depends on several things including size, location, wind speed, nearby buildings and the local landscape. At the moment 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 up to 100 wind turbine installations; the results of this activity will help to provide further information for householders considering this technology.
Mast mounted
Larger systems in the region of 2.5kW to 6kW would cost between £11,000 - £19,000 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 22.5 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: http://www.energysavingtrust.org.uk/generate_your_own_energy/types_of_renewables/microwind
Large Scale Onshore Wind Generation
Large scale wind operates in exactly the same way as small scale - it just a matter of size. Large scale projects can be single or multiple turbines but all are mounted on turbine towers.
Offshore Wind Generation
As with onshore wind, offshore operates in the same way. Offshore turbines are mounted on turbine towers using a variety of foundations types depending on the water depth. Most shallow water projects use monpile foundations. Turbine size is usually 3.6 MW or 5MW.