March 10, 2008

Energy- Offshore Wind

Wind Farms can be located in 3 different zones.

How do wind turbines work?

1 Rotor Blades, which are shaped like airplane wings attach to a hub and can be up to 150 feet long.
2 Pitch drive Rotates blades to reduce lift when wind speeds become too great.
3 Nacelle Encloses components.
4 Brake Acts as a backup to the pitch drive.
5 Low-Speed Shaft Attaches to the rotor.
6 Gear Box The rotor turns the low-speed shaft at speeds ranging from 20-400 rpm. Transmission gears increase the speed to the 1,200-1,800 rpm required by most generators to produce electricity.
7 High-Speed Shaft Attaches to the Generator.
8 Generator Converts energy into electricity.
9 Heat Exchanger Cools generator.
10 Controller Computer system runs tests, adjusts, turbine.
11 Anemometer Measures wind speeds.
12 Wind Vane Detects wind direction.
13 Yaw Drive Keeps rotor facing into the wind.
14 Towe

On Shore vs. Off Shore

Historically, wind power has been developed on land. But the interest has now been directed towards the sea. Particularly coastal areas with water depths of between 5 and 15 m. Here the output is up to 50% higher than on land and the visual and noise pollution is greatly reduced.

Also areas that have sufficient land for large scale wind operations such as middle America are less efficient as power supply locations as they are located far away from city centers where most of the population lives. Since 30% of all energy produced is lost in it’s transportation sighting power sources close to population hubs is key. Off shore sites tend to be closer to large cities than vast unused expanses of land.

How do Off Shore wind farms work?

Piles (1) are driven into the seabed. Erosion protection, similar to sea defenses, are placed at the base to prevent damage to the sea floor. The top of the foundation is painted a bright color to make it visible to ships and has an access platform to allow maintenance teams to dock.

The blades (2) rotate around a horizontal hub, which is connected to a shaft inside the nacelle (3). This shaft, via a gearbox, powers a generator to convert the energy into electricity. Sub sea cables (4) take the power to an offshore transformer (5) which converts the electricity to a high voltage (33kV) before running it back 5 -10 miles to connect to the grid at a substation on land (6).

London Array

A proposed offshore wind farm, to be built off the Kent and Essex coasts, in the outer Thames Estuary.

A consortium called London Array Limited is developing the project. The company comprises the following three partners: Shell WindEnergy, E.ON and DONG Energy.

The project will consist of up to 341 turbines which would have a capacity of 1,000 MW of electricity. This is enough to meet the electricity needs of 750,000 homes or roughly 1/4 of the homes in the greater London area.

The project would contribute significantly to the Government’s target for renewable energy – providing around 10% of their target for 10% wind energy by2010.

The turbines will range between 3MW and 7MW in electrical capacity, depending on when they are installed. The hub heights will be between 85m and 100m above sea level, and the total turbine height won’t be greater than 175m.

The wind turbines will typically begin generating electricity at a minimum wind speed of 7mph, with full power being achieved from 29mph. They would begin to shut down at wind speeds greater than 56mph.


Wind Energy Systems Technology (WEST)

Offshore oil drilling sites are being retrofitted for wind power.

Normally returned to shore only to rust, old drilling platforms, refurbished by a local startup, will return to sea for the wind. The first will carry wind-monitoring equipment as well as radar for tracking migratory birds. Those that follow will be topped by windmills.

The turbines will be tested 18-square-mile area roughly 10 miles off the coast of Galveston, Texas, where the first offshore wind farm in the US is under construction.

The project, at only $240 million and 150 megawatts of peak output—enough to power 45,000 homes— is modest. But what allows them to compete with larger more established projects is their reuse of materials. Not only are they reusing old oil industry infrastructure, but in the event of a hurricane they decided to outfit their windmills with hydraulic lifts scavenged from oil-industry machinery; the system would lower the turbines in the event of a squall.

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