A proposed high voltage electrical cable running across the floor of the North Atlantic Ocean to tap Iceland's surplus volcanic geothermal energy would become the world's longest underwater electrical cable, if it goes ahead. The cable would be a significant step towards a pan-European super grid, which may one day tap renewable sources as far afield as Scandinavia, North Africa and the Middle East. It's argued that such a grid would be able to widely transmit energy surpluses from active renewable sources, thereby alleviating the need for countries to use (or build) back-up fossil fuel power stations to cater for peaks in demand when more local renewable sources aren't particularly productive.

If a European super grid comes to fruition, energy surpluses will be big business. So it's hardly surprising that both Germany and the United Kingdom are jostling for position at the other end of the Icelandic cable, with Norway and the Netherlands also having been mooted as potential connectees. That would necessitate a cable at least 745 miles (1198 km) in length, making it easily the longest electrical cable in the world.

The scheme, first proposed in March of last year by Iceland's largest energy producer Landsvirkjun, would aim to export five billion kilowatt-hours of energy per year for an estimated $350 to $448 million return. A feasibility study subsequently carried out has failed to find any terminal difficulties with the idea, and UK energy minister Charles Hendry is set to fly to Iceland in May to woo the relevant authorities.

An electrical link to Iceland is one of several international interconnectors either proposed or in progress in Europe, in addition to the fifteen or so routes that exist already (existing and planned connections can be seen on this map). Norway is a focal point for many of the confirmed forthcoming interconnectors which, unlike the proposed Iceland link, would see a two-way exchange of energy designed to further boost its energy security and that of its neighbors. The country is already linked via four North Sea interconnectors to Denmark, Germany, the UK, and the Netherlands—the latter being the current world record holder for longest submarine power link at 360 miles (580 km).

More ambitious are the proposed DESERTEC and Medgrid schemes to to interconnect countries and renewable energy sources on both the European and African sides of the Mediterranean Sea. German in origin, DESERTEC would involve the investment of more than $500 billion dollars by 2050, into 6500 square miles (nearly 17,000 sq km) of solar thermal collectors (plus a bit of wind) around the edge the Sahara Desert. The scheme could, it's suggested, supply 15 percent of mainland Europe's energy needs. Facts and figures for the French Medgrid scheme (conceptually very similar to DESERTEC) are rather more elusive, and interpretation varies as to whether the two schemes are complementary or in competition.

A problem inherent to all long-distance electrical transmission: energy loss due to the resistance of the cables. Thanks to Joule's first law, the problem is minimized by stepping up voltage, with a ten-fold increase resulting in a 100-fold loss reduction. The Norway-Netherlands link transmits AC at 300,000 and 400,000 volts.

Even the proposed Iceland interconnector, accounting for the worst case scenario of a 930-mile (1500-km) cable, falls well within the bounds of profitability according to the findings of a 1980s study which calculated the longest cost-effective distances for electrical transmission to be 2500 miles (4000 km) for AC and 4300 miles (7000 km) for DC. Official costs are yet to be tabled for the project.

The exportation of renewable energy is a logical next step for Iceland, which has done a grand job of getting its own house in order. The country currently meets 81 percent of its energy needs with domestic renewable sources—thanks in no small part to the country's tremendous geothermal assets, sitting as it does on the Mid-Atlantic Ridge (which can have occasional less welcome consequences). The country plans to be free of fossil fuels in the near future.