About Wind Energy

Wind energy or wind power is a fascinating subject for those who work within the industry, but equally, it is potentially of great interest to anyone. The creation of energy from “green” or renewable sources is of great interest to both individuals and for bodies such as the European Union, with countries such as Denmark and the Netherlands making great strides towards completely phasing out fossil fuels as a source of power.

Many people are interested to know how wind energy is harnessed or how power is generated. There are also questions surrounding whether wind power is free, where the original concept of harnessing the energy of wind comes from, and of course which wind farm is the largest.

How is Wind Power Harnessed?

Wind energy or power is created by harnessing the potential energy created by high winds. At its most basic level, this is done by wind turning purpose built wind blades which are connected to an axel which either directly or indirectly rotates a magnet surrounded by coils of copper wire. Rotating a magnet within a coil of copper wire induces an electric current within the wires, and that current can be harnessed to provide power either directly to a home or building, or to feed into a country’s national grid system.

To get the best results from this energy generation setup, the blades have to be large and designed with as much care as an aircraft’s wing, the turbines have to be as efficient as possible in converting rotational speed into electricity and the collection of wind turbines, or wind farm has to be located in an area known to consistently experience high winds.

Offshore wind projects are ideal for these purposes in that the temperature differences between land and sea consistently create areas of significantly different levels of air pressure, which induces air flow between their locations, which is better known as wind. Building turbines in shallower offshore locations allow wind farms to be removed from bird migration paths or nesting sites, away from aviation flight paths, and hopefully reasonably removed from impacting on a locations aesthetic beauty. Obviously it is not a perfect solution, but as a compromise it is a vast improvement over the use of fossil fuels and the cumulative effects of the by-products created in their combustion.

The US Department of the Interior and the US Department of Energy have collaborated together to produce some background information on wind energy for their Environmental Impact Statement. It’s a simple and concise guide which can be viewed here:

http://windeis.anl.gov/guide/basics/

The History of Wind Energy

There are many examples of very early wind based systems, and European windmills (smock towers) are probably the most recognisable examples of the exploitation of wind energy. There are still many examples of complete or partial wooden wind mills dotted around rural locations across Europe but at the height of the windmill’s success during the 1800’s we estimate the 200,000 or so towers boasted a combined 300 megawatts of generation capacity (or equivalent).

The First Windmill

The very first windmill is attributed to a Greek engineer Heron of Alexandria in the first century, which was believed to have powered a musical organ. Other very early windmills have been used for religious purposes, to pump water for irrigation projects, or to grind grain across the Middle East and Asia. Early windmills were typically based around a vertically mounted axel with vanes, built within an enclosure to ensure wind flow. The very first of the classic tower style windmill is reported to have been in Yorkshire (North England) in the 12th century.

If you would like to see more information on these systems we have included a link to Wikipedia’s resource page below:

https://en.wikipedia.org/wiki/Windmill

The Largest Offshore Wind Farm

Currently the largest offshore wind farm in the world is the London Array, where “largest” is defined by the installed generating capacity. It is tricky to define the physical foot print of a wind farm, as the allocated area is always larger than the area covered by towers, and a true assessment would also have to accommodate cable runs and substations. This would give a “size” advantage to more remotely installed wind farms, and given the purpose of a site is to provide electricity, installed capacity is a more relevant measure. Currently the Netherlands is working on 5 wind farms all of which are to be larger than the London Array in terms of capacity, and although these are equalled by other singular projects, their creation in combination should see Holland as the new host of the World’s largest offshore wind farm.

In the long-term the mantle of World’s largest offshore windfarm will inevitably revert back to the UK once DONG Energy’s Hornsea Project One comes online. Covering over 407 square kilometres, it is proposed to have a generating capacity of 1.2 gigawatts and be able to provide power to 1 million homes. The World’s largest wind farm is an onshore facility in China, boasting 6GW generating capacity; however, Hornsea 1 at 1.2GW rivals many onshore facilities which enjoy an advantage of being easier to construct on dry land. Given the engineering challenges in constructing offshore wind sites, DONG’s facility could hold the title of “World’s largest” for some time

Visit DONG’s site to see more information on this offshore mega-project:

http://www.hornseaprojectone.co.uk/en

To learn more about the London Array wind farm visit here:

http://www.londonarray.com/

Also, visit the Netherland’s Ministry for Economic Affairs to read more on wind farm projects such as Borssele:

https://www.government.nl/topics/energy-policy/news/2016/07/05/netherlands-offshore-wind-farm-borssele-cheapest-world-wide

Wind Power as a Free Resource

Wind power is of course free as a source of energy; however the investment required to create and install the required infrastructure is immense. Projects are typically estimated to cost in excess of €1 billion as the majority of new wind farms are substantial in size; however, as renewable energy subsidies are phased out, the price of generating electricity is dropping. This reflects innovations such as increased tower and blade size, bigger turbines, better efficiencies and economies of scale as more projects are built or planned.

Efficiency

Currently turbines work at about 60 per cent efficiency, so for every estimated megawatt of available of wind energy, 600 kilowatts of energy are recovered and transmitted to the power grid. Some power is lost through the collection of power at the substation (the system all the wind towers feed energy too) and again a little is lost to resistance across the length of cables needed to transmit power from the wind farm to the shore. It should be noted that there is a similar loss of power across any country’s national grid as power is distributed from generating sources to homes, and there is even a small loss of power within a home as electricity is distributed from the meter to the sockets.

Innovation

Efficiency will still increase, but in terms of systems, gearless turbines are closing in on their peak performance as are the blades as they approach their maximum useful size. Larger blades capture more wind energy and at optimal conditions probably rotate at about 170 mph at the blade’s tip (the tip of the blade is furthest from the hub and therefore is the fastest moving point). Blades can be increased in size, but that would increase weight adding to friction in the turbine. Larger blades would also need taller towers which would add to construction costs, where the structure would need bigger foundations and greater reinforcement. The most likely improvements in performance efficiency will come from lighter building materials (carbon fibre as a blade material is lighter than the current choice of fibre glass, but significantly more costly), so possibly we will see composite materials developed. Likewise optimising the location, facing and the blade’s ability to respond to changes in the flow of air are also potential areas in which performance can be enhanced.

Future Developments

One of the weaknesses of wind energy is its dependence on the weather to produce power. Lack of significant wind during peak demand, or high offshore winds during the summer when needs are low highlight the problems. Efficient energy storage can offset these problems, but the systems needed are under-developed or largely impractical. In South America some unused wind energy is used to power systems which pump water to higher altitude reservoirs. The electricity generated is effectively converted to potential energy in that water can be released to turn watermills and turbines when demand outstrips the wind farm’s ability to supply. It is an elegant system but it requires a lot of space and water to work effectively. Battery storage would and will be a more space-efficient way of storing un-needed electricity providing instant resources to respond to sudden demand. Systems are being developed to fill this need, such as the technologies being deployed by Statoil in Scotland to support its Hywind project, but they need to demonstrate measurable success for them to start to benefit from the cycle of efficiencies which come with mass production. In all likelihood, battery technologies will leap forward as mass storage and electric car systems are taken up in greater numbers, where they are sympathetic market areas.

Information on Statoil’s Hywind projects can be found on the company’s website (Hywind trial projects have been launched in different areas of the World) and a link to the parent page is provided below:

https://www.statoil.com/en/what-we-do/new-energy-solutions.html

Energy Sharing

In Northern America the US, Mexico and Canada have signed memorandums of understanding to cooperate in creating a continental energy network. Although this has been prompted primarily by the need to create pipeline infrastructure for oil transfer, the agreements include frameworks for providing cross border power, especially from renewable sources. Furthermore it sets out policies for sharing technologies and developments to enhance each country’s ability to support the other’s energy needs.

Similarly in Europe TenneT has created cross border infrastructure to support the electricity needs of both the Netherlands and Germany. There already exists a form of Northern Europe energy brokerage whereby the differing renewable energy sources can complement each other and offset undersupply during periods of higher demand. As renewable projects become more prevalent and move toward meeting 100 per cent of demand then this brokerage will harmonise and move closer to a watt for watt exchange system. At the moment however this is impossible as different energy sources have a differing price per kilowatt hour, so the exchange of power is not equal in generating costs. However, if Europe follows the models demonstrated by countries like Denmark and Holland, this will change.

Information from the US Energy Information Administration can be found here:

http://www.eia.gov/todayinenergy/detail.php?id=24972

And information about the work TenneT is performing within Europe can be found here (including its own concept project):

http://www.tennet.eu/news/detail/tennet-prepares-grid-system-for-growth-of-renewable-energy/

http://www.tennet.eu/news/detail/tennet-presents-hub-and-spoke-concept-for-large-scale-wind-energy-on-the-north-sea/

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