Proponents of renewables are using the disaster at Fukushima to push alternative-energy development, but even wind, geothermal and solar-energy supporters say they cannot replace the massive base-load power provided by nuclear, natural gas and coal.

You can't really talk about one replacing the other, Harris says. To build enough wind or solar to replace a nuclear plant, it's a very large number. Gabriel says each megawatt of solar photovoltaic takes about five acres.

Jeff Bencik, an energy analyst for New York-based Kaufman Bros., says it would be possible to begin construction of a solar photovoltaic farm almost immediately. About one megawatt a day could be installed on a site, he says, meaning it would take more than three years and 5,000 acres to build a solar PV plant that is roughly equivalent to a nuclear plant.

Even when complete, that solar farm could not produce electricity 24 hours a day, as coal, gas or nuclear can. Bencik says solar power can provide additional electricity during peak demand periods.

Gabriel and others say solar, wind and geothermal can be efficientfor example, smart-grid technology could better match load to generation.

That model of distributed generation, which relies on smaller modules of power spread over a greater geographic area, is a very long, long road, Gabriel says. The challenge is how all these pieces are going to interact together. [This solution] doesn't make utility engineers happy, he admits. It isn't as easy as flipping a switch on a 650-MW coal plant, but utilities have to face the new generation in which we are living.