Offshore wind power is wind energy on the sea. No secrets here. However, offshore wind power is in many ways very different from wind power on land. I’m going to go through the most important differences in this article.
First of all, the wind power technology on land has had a much longer time maturing then what offshore wind power has, resulting in better optimized turbines, delivering cheaper energy (at the moment).
There are massive resources of wind energy available on the sea and they are also much more stable. This is what has sparked the interest in offshore wind power for many different countries when it comes to finding alternatives for the transition away from the non-renewable energy sources.
The foundations that these massive structures are built on are very different from what you will sea in wind turbines on land. These base structures can be divided into two categories, bases that are fixed and bases that are floating:
Fixed Base Offshore Wind Turbines
There are various types here, each with their own set of benefits and downsides.
A monopole is the most used base and consists of a pear that is drilled into the bottom. A typical monopole is 6 meters in diameter and can be used in depths up to 30 meters.
Tripods are drilled into to the bottom at three different places, between 10 and 20 meters into the surface. This allows for placing an offshore wind turbine on depths of 20 to 80 meters. There are two different types of tripod bases: Tripod piled structures and tripod suction caisson structures.
Gravity base structures were the first base types for offshore wind power. The foundation is most likely made of concrete, but some times steel are used. These bases are heavy enough to firmly hold the wind turbine at its place. Can be used in water anything from 20 to 80 meters deep
Steel jacket structures can also be the base of wind turbines at depths from 20 to 80 meters. These are widely used within the oil- and gas industry and are fixed to the bottom on four different places.
Floating Offshore Wind Turbines
By using floating wind turbines, we will be able to open up huge areas where the installation of offshore wind turbines previously wasn’t possible because of the water depth. In fact, the Hywind offshore wind turbine is expected to be able to be installed at depths up to 700 meters.
This is a picture of the transportation of the first prototype of the Hywind turbine, which now is installed in Karmøy, Norway for testing purposes.
A floating wind turbine will reduce some of the possibly environmentally and aesthetically conflicts a near-shore wind farm would have (not to speak of onshore wind farms)
The tower itself reaches 65 meters above the ocean surface, while the floating structure extends 100 meters below it, providing enough stability to harness the strong winds we can expect offshore on greater depths.
Massive Growth of Wind Farms
The growth of offshore wind farms has in the last few years been very impressive: Europe, with a current installed capacity of 2 396 MW has over 100.000 MW of projects currently in the construction or planning phase.
China finished their first offshore wind farm in 2010 with a total capacity of 102 MW. Several other projects on Chinese coastlines is expected to push this number to 20 000 MW within 2020, an increase of about 196 000%.
China is currently the leading investor in renewable energy (Read more about this in China: The Largest Investor in Clean, Green and Renewable Energy)
However, the growth in U.S. does not reflect the global market, and U.S has yet to install one offshore wind turbine, fleeting or fixed.
Learn more about wind power here: Wind Energy Pros and Cons