On 17 July, former US vice-president Al Gore proposed that the United States should commit to producing 100% of its electricity from renewable energy and truly clean carbon-free sources within ten years. That is an ambitious and optimistic plan, to put it mildly. But whether or not the United States achieves Gore's goal, the country is already expanding its generation portfolio to include renewable sources of electricity, such as solar, wind and geothermal, and could do so much faster with a better regulatory and incentive system. Successful examples of the latter can be found in Germany, where 'feed-in tariffs' offer end-users a guaranteed price for selling renewable electricity back to the grid (see page 558).

True, these shifts towards greener sources of electricity can have side effects that are not so green. A case in point is Texas, whose famous winds are now producing more than 5,300 megawatts, by far the largest installed wind-turbine capacity in the United States. Another 2,000 megawatts of capacity are under construction — and the pace may well pick up. Billionaire oilman T. Boone Pickens, who has invested heavily in wind, has recently released a series of television adverts and appeared on news programmes touting 'the Pickens Plan', in which the country would shift towards wind for electricity and natural gas for transportation.

Unfortunately, the strongest and most reliable wind is often found far from customers. That is why the Texas wind farms cluster in the gusty Panhandle region, hundreds of kilometres from the centres of population farther east. So earlier this month, Texas approved a nearly $5-billion plan to build new transmission lines linking wind farms to customers. Wind-energy proponents say this will greatly ease the bottleneck limiting the development of wind resources in the state, and might even allow Texas's installed wind-power capacity to overtake Germany's — currently the world leader at more than 22,300 megawatts. Yet this triumph for renewable energy will be a bitter pill for many environmentalists, as it will mean large transmission lines cutting through once-natural landscapes.

Wind, like the sun, is also fickle. In February, for example, a sudden lull idled the Panhandle's wind farms and forced managers of the Texas grid to cut power to some large customers for an hour and a half. So another sour note for environmentalists is that renewable power sources may have to be backed up by generators that are more reliable, such as natural gas and cogeneration plants.

Yet these not-so-green side effects are not the end of the story. Giant wind farms are something of an exception in the renewable-energy picture, as they resemble the traditional model of big, centralized coal, gas or nuclear power plants feeding bulk-distribution networks. Looked at more broadly, renewables point to a future in which the power grid could be far less centralized than it is today, with a much greater reliance on local power sources such as rooftop solar panels. This could make the electricity grid more efficient, as less power would be lost in long-distance transmission.

Renewables point to a future in which the power grid could be far less centralized than it is today.

Such a grid would benefit from better electricity storage — in the form of large-scale batteries, say — to smooth out drops in wind or cloudy days. And it would certainly have to be smarter than it is today. To manage this decentralized proliferation of sources and users, the grid would have to be liberally studded with microprocessors that can take actions on their own, without humans pressing any buttons or picking up any phones (see page 570).

Public and private programmes to achieve these goals will probably generate many new, highly skilled 'clean-tech' and 'green collar' jobs. Both candidates for the US presidency have talked about investing in the grid, and Democrat Barack Obama has specifically promised to spend $150 billion to create 5 million green jobs if elected. Meanwhile, countries such as Germany, Denmark, Britain and Australia are already showing that green jobs can buoy their economies.

Serious attention to the newer, greener grid should be a continuing priority for governments and private investors around the world. With effective investment, regulations and incentives, the enormous task of remodelling the grid for renewables will be a boon to both the environment and the global economy.