Electric storm

Two projects to research and harness wind energy look set to put windfarms on the European map as a signficant source of power. Niall Firth reports.


Lately, it would seem as though expert opinion over the UK‘s energy future has been heading irrepressibly towards the rebirth of the nuclear option. One of the arguments for this is that as laudable as renewables are, they cannot produce enough power to fill the UK‘s energy gap if our reliance on fossil fuels were to be reduced. However, two projects in Europe are set to tackle this argument head on by committing huge amounts of money, resources and technology to thinking big about the future of offshore windfarms.

Last month the EU’s largest-ever wind energy research project kicked off in Brussels. Involving more than 100 wind energy specialists from throughout Europe, UpWind brings together academia, industry and various research organisations to look at the design and engineering issues that surround the next generation of giant wind turbines to be built some time after 2010.

Led by the European Wind Energy Association (EWEA) the project was launched after pressure from the wind energy sector following what it perceived as a lack of emphasis on renewable technologies in the EU’s latest raft of Framework 6 proposals.

The sector responded by establishing a think-tank, led by EWEA, calling for the inclusion of an integrated project for wind energy in the third call of FP6. UpWind is the result, with a budget of around £28m — just over half of which is funded by the EU.

According to Jos Beurskens, the project’s co-leader who works at the Energy Research Centre of the Netherlands, it is crucial for Europe to look closely at the design problems that giant wind turbines may pose in the future.

‘If you take a big machine, leave it as it is, but just make everything bigger then the internal stresses increase linearly with the increase in scale. This means that there will be an upper limit on how big a wind turbine can be. The question is: where is that limit? These are the boundaries that need to be explored in this project, particularly for offshore applications,’ he said.

While the existing largest wind turbines are approaching 5MW in power, the UpWind project is predicated on future giant wind turbines being able to produce upwards of 20MW. To do this, a number of engineering challenges will have to be addressed. Despite the continued work by manufacturers and researchers in developing new materials that have a better stress-to-mass ratio, as well as improved flexibility to decrease fatigue loading, Beurskens said that the project will involve starting again from scratch in looking at the fundamental design of a large wind turbine.

‘We decided to look at everything that is involved in designing these machines of the future,’ he said. ‘We have divided the machine into different parts and disciplines, and will bring it all together again into an updated design methodology for giant turbines. It’s a big and complicated project.’

One of the new technologies that UpWind will look at using in turbine development is Lidar technology to measure windspeed at high altitudes. While Lidar, which measures distances with a laser, is currently used in a number of varied applications this will be the first time it will feature in such an environment. It will provide information regarding turbulence in the rotor plane, which has until now been difficult to measure accurately.

As turbines become larger this type of data will be invaluable to engineers, said Beurskens. The project will also be used to verify the accuracy of existing software that is used to develop wind turbines. ‘As turbines become bigger the aerodynamics and the “aero-elastic” properties of the turbines change,’ said Beurskens. ‘We really don’t know if the codes we have been using until now are good enough for really big machines.’

Of the handful of UK institutions that are part of the consortium, energy consultants Garrad Hassan is heavily involved in the project while researchers from Salford, Bristol and Edinburgh universities will also be collaborating with their European colleagues.

The second new development that will gladden the heart of renewable energy advocates everywhere is a proposed project by Irish renewable energy company Airtricity. Last week Airtricity outlined its proposals to MPs in Westminster for a £22bn 10GW offshore wind energy project to be stationed in the North Sea between the UK, Netherlands and Germany. Consisting of around 2,000 large 5MW turbines it would be the largest offshore windfarm in European waters and would provide power for around eight million homes, it is claimed.

The project, nicknamed Supergrid, is being developed by Airtricity in conjunction with global power group ABB and is designed to be able to deliver wind-generated power throughout Europe via a subsea electricity network. The concept is the combination of an offshore meshed grid that networks the participating countries and the windfarms together, instead of just connecting the wind turbines to the nearest point of land, as is currently the case.

When it is operational the high-voltage network will have access to wind energy at all times as the unique network of power cables will allow the power transmission to be aggregated. This means that if there is more wind in one section of the grid than another the power can still be shared equally across the grid. Airtricity’s Chris Veal, director of the Supergrid project, outlined his company’s ambitious plan: ‘Interconnecting the countries in western Europe so the power levels can be smoothed out will make wind power a far more reliable source of energy,’ he said. ‘This will also help to create a single European market for renewable power as it can be traded and shared between the countries.’

The crucial technology that makes the Supergrid concept possible is the DC transmission technology that was developed by ABB. According to Veal, using conventional AC cabling for power transmission over long distances is not possible. This is because over long distances the reactive power required to charge the cable increases to a point where it takes up the bulk-carrying capacity of the cable. This leaves less capacity for the power that is to be transmitted.

Until recently conventional high-voltage DC technology has only been used for point- to-point transmission connections, using a two-ended cable. Veal said: ‘This new technology enables meshed networks so you can have multi-terminal points with one in the UK, one in the Netherlands and a windfarm terminal in the middle. This is what has made the Supergrid possible.’

The proposed 10GW windfarm is envisaged as being only the first step towards a larger western European supergrid while Airtricity’s ambitions also extend to developing similar networked windfarms as far afield as China.

Construction of the first stage of the supergrid will begin towards the end of 2010, and Veal believes that projects of this kind will do a great deal for the credibility of wind energy as a power source for the future. ‘While wind power has a lot of benefits that the others don’t in terms of its sustainability, Supergrid brings us into the mainstream and makes wind power comparable in size with other existing power technologies,’ he said.