Sweden is expected shortly to embark on an immense construction project to build more than 50 windfarms to produce electricity along coastal areas and far out at sea.

The project envisages the construction of some 4,000 big wind power plants. This is probably the most ambitious current proposal in the world for investment in environmentally acceptable energy generation, although many other countries are also turning to wind power in a big way.Low oil prices in recent years have produced a great deal of complacency over developing new forms of power, according to a reports by Worldwatch Institute, a Washington-based think tank. But the Chernobyl nuclear accident coupled with increased concern over the role of fossil fuel in creating the "greenhouse effect" is prompting energy planners once again to look at the alternatives.

Sweden is especially receptive to new ideas in energy management because of its national commitment, based on long-term public health considerations, to end nuclear power generation by the year 2010. One of the country's 12 existing nuclear reactors may well be dismantled and its radioactive parts buried beneath the seabed, while another could be taken out of service by 1996.

The Swedish construction project, outlined in a specialist report commissioned by the government, will be watched very closely in countries which have recently accepted the principle of large-scale commercial exploitation of wind turbines.

Despite the unsatisfactory initial operating record of some big units, Britain, Canada, Denmark, Holland, and West Germany as well as Sweden are building multimegawatt machines. California is the world leader in the field with 16,600 turbines.

"The annual gross electricity sales there per acre from windfarms typically reach $6,000," calculates the Worldwatch Institute, "some 15 times more than the $400 gross financial return per acre of farmland arned by an Iowa corn grower and easily 100 times that of a Texas rancher."

Wind power is expected to become substantially cheaper than electricity generated by coal and nuclear power plants in the coming decade. It is a clean, renewable and domestic source of energy, says the study placed before the Swedish Departments of Environment, Energy and Housing.

But the analysis concedes drawbacks: the generators' great impact on the landscape and the competition for land and sea space in the coastal areas.

The report recommends 17 areas at sea and 35 on land for wind-power generation. They are located in the coastal regions of southern Sweden along the Baltic Sea, the Sound and the Kattegat where conditions are favorable.

Each windfarm location would comprise groups of plants yielding a combined energy output of 20 Twh/year at sea and half that much on land.

These turbines - totalling 2,500 units at sea and 1,500 on land - would be about the same size as the two test plants currently in operation. It would take 750 to replace each existing nuclear power plant.

Planting windfarms at sea is more convenient than on the land, and it alo avoids the competition for land from business and the community. The large-scale exploitation of wind power is also easier at sea because physical conditions there enable generators to yield a higher energy output than on the land.

Britain's Central Electricity Generating Board is building three coastal demonstration wind parks comprising 25 turbines each in a program intended to save a million tons of coal a year by the turn of the century. This is despite the fact that the Thatcher government is strongly in favor of increasing Britain's use of nuclear power.