Offshore wind turbines along Japan's coast could generate up to 40% of the country's energy needs, according to a new study by Hiroshi Nagai of Nihon University in Narashino. Nagai estimates that some 8200 kilometres of Japan's total coastline of 34,000 km are suitable for the construction of sea based wind turbines, up to three kilometres off the coast. Based on Nagai's calculations, which use 500 kW machines, wind turbines could supply between 13 and 39% of Japan's energy needs at 1993 levels -- or 93 billion to 270 billion kWh. Nagai also plans to make a similar simulation study using megawatt units. The public organisation promoting renewables, New Energy Development Organisation, is also engaged in a study of offshore wind turbines. Japanese energy developer Tomen Corp has shown interest in offshore wind too. One important point for Tomen, however, is price, says the company's Shigehito Nakamura. If there is no cost benefit from using sea based wind turbines, then one might as well put them on land, he adds.