Wind Farms – How are they made?

Wind power is a hot topic at the moment.

Many see it as a path out of the current energy crisis and are calling for increased investment into this renewable source of energy.

Of course, wind power has gone from strength to strength over the last few years, and has many merits that other renewable sources don’t.

As an energy source, it is truly limitless – as the industry has grown there has been downwards supply pressure exerted on the costs of developing new wind installations.

But, how on earth do new wind farms take shape?

Do they just… appear?

Installation is a lengthy process, with several steps along the way from development and engineering, to construction, and finishing with operation.

In this article we will go through some of the ways that off-shore and on-land wind farms are set up (as well as some incredible facts about the industry).

Step One

One of the questions that many people ask is ‘how do you decide where to put a wind turbine?’

This is truly the first step of wind farm development. Firstly, a site must be identified and the available wind resources of the area determined. Measurements like wind speed, temperature, pressure, and humidity are all important. Around a year’s worth of data must be collected to give a decent indication of the average wind speed.

The wind resource is dictated by several factors. Things like geographical and topographical features can affect the energy potential of wind, altering the speed and kinetic energy available to be harvested.

Onshore sites generally have more obstacles in the way which alter the wind. At sea, wind speeds are higher and more consistent which usually translates into greater energy production – helping offshore wind to flourish.

There is the obvious problem of overcoming logistical and engineering challenges when it comes to offshore sites. Sites must be resilient to harsh sea conditions, especially strong winds and rough seas.

Step Two

Once a site is found, construction can begin in earnest.

The design of the site and turbine must be finished and standardised. The choice of materials and model is consistent across windfarms.

The horizontal-axis wind turbine is seen very much as an industry standard, and the materials most commonly used during construction are steel and fibreglass. These materials offer the perfect blend of strength and stability, with steel being perfect for a stable tower and fibreglass being light enough to catch the wind but firm enough to tolerate high wind speeds.

As the turbine is being constructed, other work will be carried out to facilitate its installation. The will likely include preparing the foundations for the turbine to sit on as well as connecting the export cable to transport the generated electricity away from the site.

Step Three

As onshore turbines sit on concrete foundations, getting these just right is crucial. Depending on a number of factors like soil quality, water retention by the soil, and the weight and height of the turbine; the depth of the foundations can vary. Good foundations provide the stability needed for turbines, which due to their height experience extreme stress from the force of the wind.

Currently, these foundations are seen to be suitable, but in the future it may be the case that foundations for onshore turbines need to take up less space but offer the same support.

Offshore turbines are a little more complex. Turbines are either fixed or floating.

For fixed foundations, a single steel monopile is driven into the sea bed. This single leg is suitable for supporting wind turbines in depths of up to thirty meters. Alternative methods use a steel jacket structure, similar to electricity pylons, which are suitable for depths of up to fifty meters.

In either scenario, the structures have to be driven deep into the seabed. Monopiles can reach up to six meters in diameter so that the wide foundation can support tall turbines. Steel jacket structures have four smaller legs which also provide additional stability in deeper waters. Fixed foundations are very practical up until around 50 meters, but beyond this costs start to seriously skyrocket and the process of fixing the foundations to the seabed becomes more difficult.

This has created the need for exploration into floating foundations in deeper waters. Such foundations could be used to take offshore wind energy to water depths beyond fifty meters, with The Hywind project in Scotland currently trialling floating foundations at depths up to 120 meters.

In both cases, the structures are driven deep into the seabed. Monopiles can be up to six metres in diameter, with the wide foundation to support tall turbines. Steel jacket structures have four smaller legs, providing additional stability in deeper waters.

There are a number of different floating platform designs; a semi-submersible platform, a spar-buoy system, and tension-leg platforms. All of these designs are fixed to the seabed using tethers or anchors.

Semi-submersible platforms are buoyant structures which are anchored to the seabed, with the weight of the wind turbine counteracting the buoyancy – giving stability. Spar-buoys use cylindrical structures filled with ballast submerged below the surface of the water, with the turbine atop the structure being lighter than the weight of the ballast, creating buoyancy. Tension leg platforms are semi-submersible structures anchored to the seabed with tensioned mooring lines and have already been proven by the petroleum industry who have used floating rigs to exploit undersea oil and gas wells for years.

In all of these examples, the turbine sits atop the floating foundation and must be able to withstand incredibly hostile conditions. This places stress on the anchors and mooring lines.

Step Four

Now comes the time to put the pieces together both literally and figuratively. As the groundwork has been done, the turbine must now be transported ready for construction. Turbine blades and towers need to be transported to the site where they can be assembled and tested.

Once foundations are complete, the component parts of an onshore turbine are put together over the course of a few days. Usually, this can take two cranes with one lifting and the other stabilising parts. The tower is erected first, then the nacelle (which houses the generator and other moving parts of the turbine) is attached to the top. The blades are individually attached to the hub before lifting it up and fitting it to the nacelle.

Of course, offshore construction requires much more logistical manoeuvring, however. The turbine must be transported by ship to the site and assembled piece by piece. Specialist ships are needed to carry such heavy loads, as well as cranes to hoist parts into place. Working at sea makes everything more difficult, but the same steps are followed.

Once construction is complete, the turbine undergoes testing to ensure that everything is operating as it should. Once testing is finished, the turbine is ready to generate and feed electricity to the grid.

Astonishing facts about wind power

Windmills have been used since around 2000 B.C and were first develop in Persia and China. Ancient mariners used wind power to sail to and colonise distant lands, and farmers used it to pump water and increase farming yield.

The first ‘modern’ wind turbine was built in Vermont, USA, in the 1940’s. The Smith-Putnam wind turbine was built in 1941 and was one of the world’s first megawatt-sized wind turbines connected to the local electrical distribution system. The turbine operated for a whole 1100 hours before a blade failed due to war-time material shortages. It remained the largest wind turbine ever built until 1979.
The largest wind turbine in the world is in Hawaii, standing over 20 stories tall and has blades the length of a football field.
Wind energy is mostly harvested by wind turbines. The average size of onshore turbines these days is around 2.5 to 3 MW with blades about 50 meters in length. Blades are spun by the wind which transfers motion to a shaft connected to a generator which produces electricity.
The average onshore wind turbine can power more than 1,500 EU households. An average offshore wind turbine of 3.6MW can power more than 3,312 average EU households.
Wind power is unique in that it does not use any water. It is expected that wind power will save around 30 trillion bottles of water in the U.S by 2030.

The largest wind turbines can harness enough energy to power 600 UK homes. These turbines form wind farms and hundred are arranged in lines in windy spots (like ridges).
A small back-garden turbine could easily power a small business or home. Many wind farm provide rental income to rural communities where they are situated, providing a useful revenue stream.
Smaller wind turbines can be used to charge batteries or as backup power. These can be connected to the electric grid through your power provider or it can stand alone (off-grid). They can be installed on the roof of a home where there is a suitable wind resource, often around 1-2 kW in size.
The wind energy industry is growing exponentially. Global generation quadrupled from 2000 to 2006, which if maintained would mean wind could met a third of global energy demands by 2050.
Germany, Spain, China, and the USA are all world leaders in wind energy capacity.

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