A civilization built on renewable resources, such as the products of forestry and agriculture, is by this fact alone superior to one built on non-renewable resources, such as oil, coal, metal, etc. This is because the former can last, while the latter cannot last. The former co-operates with nature, while the latter robs nature. The former bears the sign of life, while the latter bears the sign of death.
E. F. Schumacher 1911-1977
Renewable energy will never run out, is freely available and causes no pollution. Over the last few decades renewable power was dominated by large hydro schemes and energy from waste projects, but the opportunity for further expansion in these industries is limited. Solar heat and power, biomass, wave and tide, are all likely to play important roles in the future, but wind is the technology best placed to make a significant contribution to Government targets up to 2010.
How Does Wind Energy Work?
Modern wind turbines capture the wind in the same way that traditional windmills used to, except that instead of turning grindstones or water pumps the rotor is used to turn a generator that produces electricity. The electricity generated by modern turbines is sold into the local electricity grid which forms part of the national grid. The same grid that is used to supply electricity to homes and industries throughout the UK.
How Long Does a Turbine Last?
A wind turbine generator is designed for approximately a 20 year lifetime. After this period moving components such as the blades, gearbox and generator can be replaced or refurbished.
How Much Electricity Does A Wind Turbine Produce?
Over a year the output of one 600 kW wind turbine will produce enough electricity to power between 400 to 500 average households. Even though occasionally the wind doesn’t blow, a turbine will be generating around 70% of the time. The five wind turbines at Harlock Hill and the four turbines at Haverigg generate electricity equivalent to the annual consumption of around 3000 average households.
Wind Turbine Glossary
Anemometer: Measures the wind speed and transmits wind speed data to the controller.
Blades: Most turbines have either two or three blades. Wind blowing over the blades causes the blades to “lift” and rotate.
Brake: A disc brake which can be applied mechanically, electrically, or hydraulically to stop the rotor in emergencies.
Controller: The controller starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and shuts off the machine at about 65 mph. Turbines cannot operate at wind speeds above about 65 mph because their generators could overheat.
Gear box: Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about 30 to 60 rotations per minute (rpm) to about 1200 to 1500 rpm, the rotational speed required by most generators to produce electricity. The gear box is a costly (and heavy) part of the wind turbine and engineers are exploring “direct-drive” generators that operate at lower rotational speeds and don’t need gear boxes.
Generator: Usually an off-the-shelf induction generator that produces 50-cycle AC electricity.
High-speed shaft: Drives the generator.
Low-speed shaft: The rotor turns the low-speed shaft at about 30 to 60 rotations per minute.
Nacelle: The rotor attaches to the nacelle, which sits atop the tower and includes the gear box, low and high-speed shafts, generator, controller, and brake. A cover protects the components inside the nacelle. Some nacelles are large enough for a technician to stand inside while working.
Pitch: Blades are turned, or pitched, out of the wind to keep the rotor from turning in winds that are too high or too low to produce electricity.
Rotor: The blades and the hub together are called the rotor.
Tower: The tower supports the nacelle and is most often a steel cylinder with an internal access ladder which provides access for maintenance and repairs. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity.
Transformer: At the base of the tower there is a transformer that alters the voltage of the electricity generated so that it can be fed into the local electricity network.
Wind direction: The turbines at Harlock Hill and Haverigg are “upwind” turbines, so-called because they operate facing into the wind. Other turbines are designed to run “downwind”, facing away from the wind.
Wind vane: Measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind.
Yaw drive: Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into the wind as the wind direction changes. Downwind turbines don’t require a yaw drive, the wind blows the rotor downwind.
Yaw motor: Powers the yaw drive.
For more technical information on wind energy visit the BWEA website and download briefing sheets on the following:
Wind Energy Technology
Benefits of Wind Energy
Wind Energy and the 10% Target
Wind Power and Intermittency: The Facts
Small Wind Energy Systems
Low Frequency and Wind Turbines