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The North Sea Supergrid

A Memorandum of Understanding on the EU supergrid was signed recently by ten European ministers from countries bordering the North Sea, covering the plan to develop an offshore electricity grid enabling interconnection between continental, offshore and British energy resources. In addition to allowing more trade in energy across the channel and North Sea, thus increasing energy security, it will also link up offshore wind projects (140GW are currently planned) and other variable renewables to pumped hydro storage facilities across the EU. That will help to balance the grid with power in and out, the wider geographical footprint averaging out local variations in renewable supply.

As the European Wind Energy Association put it in its new ‘Powering Europe’ report, ‘The grid plays a crucial role in aggregating the various wind power plant outputs installed at a variety of geographical locations, with different weather patterns. The larger the integrated grid - especially beyond national borders- the more pronounced this effect’.

However building supergrids will not be easy. Nature published a useful article on the supergrid (2 Dec 2010, Vol 468 pp 624-5) which highlighted some of the technical problems with High Voltage Direct Current (HVDC) links. They have to be used for long distance undersea grid links, since otherwise, with AC, the energy losses are too high. But it noted, there’s no such thing currently as circuit breakers for high-voltage DC. Power on AC grids can be disconnected relatively easily using circuit breakers, which fire off just at the point when the cyclic alternating current momentarily reaches zero. However you need milli- or even micro- second disconnection with DC. Nature reports that this sort of issue is being addressed in a 3 year €60m EU programme called TWENTIES, a consortium of 26 academic and industrial partners.

Ministers from the UK, Ireland, Belgium, Denmark, France, Germany, Luxembourg, the Netherlands, Norway and Sweden have agreed to start working on regulatory and technical issues, but of course cost is the big one- and who pays. Nature says that Germany is more interested in its Desertec Solar project, and France is presumably more focused on its proposed HVDC Transgreen links to North Africa. See my earlier Bog: http://environmentalresearchweb.org/blog/2010/08/only-connect—cspsupergrid-iss.html

However, these southern projects are still at the early planning stage, and given the spread of renewable capacity within the EU, there will be a growing need to balance variable renewables. So the more inter-connectors there are the better, and hopefully France and Germany will stay on board the North Sea project. Otherwise we may have to curtail, and waste, valuable output from some of our wind farms when the wind is high, but demand is low- especially if there is also a lot of inflexible nuclear on the grid.

In some locations this is already happening. For example, the Orkney Isles distribution company, supported by OFGEM, has introduced an active grid management system, which curtails output from their wind plants during high wind-low demand periods. This may be reasonable in isolated island areas with small local grids, where the cost of undersea grid links to the main land, to export occasional excess power, is very high, and it does mean that more/new renewable capacity can be added to supply a larger contribution at other times. And it certainly makes sense to use local resources to meet local needs as far as is possible. But as a national strategy this decoupling has its limits. Local grids have their place, and, in some locations local energy storage too e.g. via batteries or even hydrogen production, despite its cost. See for example the PURE wind-hydrogen project on the Shetlands: http://www.pure.shetland.co.uk/html/pure_project1.html. But to help balance large contributions from variable renewables effectively there is also a need to link to national and international grids.

Some look to very large scale integration. For example there have been proposal for links between the grid systems of Europe and Asia, and even for a cross-Atlantic undersea grid link. The Nature article suggests that piecemeal, incremental, development is more likely, and given the technical complexity and political difficulty of making cross country links, that may well be how it plays out. But it does seem clear that we will be seeing supergrids stretching out around the world soon. Although organisations like GENI (http:geni.org) have been promoting world-wide links using HVDC, so far no one is proposing anything like the vast round- the-planet global power transfer system once famously outlined by Nicola Tesla, using the upper atmosphere and the earth itself as the paths. Round-the-planet links, of whatever sort, would of course mean that solar energy from the sunlit side could be fed to meet demand from those on the dark side, but so far ideas like this remain the province of science fiction.

For more on renewable energy-related developments and policies see www.natta-renew.org

Posted by Dave Elliott on December 18, 2010 4:07 PM | Permalink