Wind power is great — it's perfectly clean, it's relatively reliable and it can be scaled up quickly. But there are downsides. For one thing, to get to scale, wind farms have to grow and grow, and land is often at a premium. But put wind turbines just offshore, in the water, and you can take advantage of plentiful space and stronger winds. Increasingly, utilities are doing just that, especially in densely populated Europe, which lacks wide open plots of land like the American Great Plains. Offshore wind farms began in the North Sea in Denmark, and can now be found in the Baltic and off the coast of Britain. Though construction and maintenance costs tend to be higher for offshore turbines than land-based ones, offshore wind benefits from lower transmissions costs, since many major cities sit on the coast. There is no offshore wind farm yet in the U.S., but the controversial Cape Wind project near Nantucket Island is moving closer to approval.