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Posted: Mar 21, 2013

Green super power grid for the world

(Nanowerk News) If we want to obtain power on a large scale from renewable energy sources such as the sun or wind, there are certain natural constraints. Where most people live and need electricity, the potential for wind or solar power is not always as great. On the other hand, in desert regions such as the Sahara, where the sun always shines, enough energy could be produced in a relatively small area to supply the entire world population with power. Similar is the situation with wind power. Zones where a constant strong wind blows mostly lie in inhospitable corners of the globe, such as Patagonia or the Arctic. The problem in both cases is how to transport the power to where it is effectively needed.
Göran Andersson, professor of electric power systems at ETH Zurich, his doctoral student Spyros Chatzivasileiadis and Damien Ernst, professor at the Université de Ličge see a “global grid” as a solution and have developed a concept that has just been published in the journal Renewable Energy ("The Global Grid"). This provides an idea of where the greatest potential for wind and solar energy is and how a global transmission network would have to be organised to get the power to the consumers.
global power grid that transports renewable energy from remote regions to the consumer centres of the world
How the ETH-Zurich researchers envisage a possible global power grid that transports renewable energy from remote regions to the consumer centres of the world. (Diagram: S. Chatzivasileiadis / ETH Zurich)
Wind power from Greenland
The researchers identified the areas of the globe where solar radiation is particularly high or constantly high winds prevail, for instance. They placed solar power plants and wind farms in their model and connected them to existing power grids, which provided a rough idea of how the global grid might supply the world with clean power from wind farms and solar power plants in future.
The three authors placed an offshore wind farm off the coast of Greenland as the first piece in the overall puzzle of the global power grid. The conditions there are ideal for a large wind power station: on average, the wind blows at over thirty kilometres an hour and the sea is not very deep. The three energy researchers assume an output of three gigawatts from an offshore wind farm. The power would be transmitted via Iceland and the Faroe Islands to the UK and from there to the mainland. The Icelandic and British governments are already discussing the realisation of such a power line to transport geothermal power from Iceland to the British Isles.
Better a long line than a reservoir
The Greenlandic wind farm could possibly be connected via a line also to North-Eastern Canada and the USA. Such a line would have a length of over 3,200 kilometres, a third of which being submarine cables. While this would increase the costs per kilowatt hour supplied by up to 25 per cent, it would have a major advantage: the peak consumption times in the USA and Europe would be shifted by several hours, making it possible to cover both peak times without having to store the wind power temporarily in the reservoir of a pump storage station. While the day begins in the USA and the peak consumption period is just getting underway, the consumption in Europe plummets due to the time difference. This would enable the wind power from Greenland to be always sold at higher prices – half of the day to Europe and half of the day to North America. According to the initial estimates, the total production and transmission costs for the wind power from the far north should not be more than for power from conventional stations which are closer to the consumption centres. The authors estimate that except for the most expensive renewable generators, it would be more economical for the USA to import renewable power from Europe than operate its own fossil fuel power plants.
Technically feasible thanks to high-voltage direct current transmission
Technically, says Spyros Chatzivasileiadis, the global power grid and the corresponding power stations are feasible. For instance, there are already technologies that transport power over several thousand kilometres with minimal losses. The laying of submarine cables is established and floating offshore oil platforms form the technical basis for the construction of offshore wind turbines.
High-voltage direct current technology (HVDC) was developed to transfer power over large distances and is already used on a large scale in China, but also Brazil, the USA and partly in Europe. Especially in China, very high amounts of power are transferred with this technology, thanks to which transmission losses – around three per cent per 1,000 kilometres – can be minimised.
Big money well invested
Professor Andersson refuses to accept the argument that it would be far too expensive to realise the global power grid. Even if millions of dollars were necessary to produce only one single section of the network, the investments would be comparable to those currently being made for the development and expansion of the power network. Estimates expect the construction of the submarine cable network for the transfer of power from numerous wind farms in the North Sea to cost between EUR 70 and 90 billion.
However, Andersson expects that possible investments in the “Global Grid” could soon be recovered. The submarine power line between Norway and the Netherlands that has been in operation since 2008, recorded a return of EUR 50 million in the first two months in service – equivalent to one eighth of the capital invested.
Let’s not miss the boat
The ETH-Zurich researchers are also confident that certain technical gaps which would complicate the realisation of a global grid can be eliminated in the next few years. For instance, an 800-kilovolt submarine cable and a breaker to interrupt the high-power direct current are still needed. However, the researchers expect solutions from industry in the near future.
What is still required most of all are bold investors and a large international organisation such as the OECD or World Bank, for instance, to back a global grid. Consequently, in their paper, the researchers propose the formation of working groups to pursue the plans for the global grid further. Both the advantages of a global grid with renewable energies and the risks need to be weighed up. A solar power station in the Sahara, for instance, is currently unfeasible from a political standpoint as the region is at war.
“It is worth discussing the topic in depth,” Andersson believes. “If we want clean energy in fifty years, we need to do something about it today.” The European power grid is currently undergoing large changes and we must not miss the opportunity to integrate the alternative energies, he explains. Andersson and his colleagues hope that they will be able to start the discussion on a global network fed from renewable energy sources with their project.
Source: By Peter Rüegg, ETH Zurich
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