Using some type of renewable fuel to generate electricity instead of nuclear reactors would take considerable land under today's technology, according to experts.

Policymakers concerned about the danger of an accidental release of radiation or the challenge of safely storing the waste for millions of years are considering alternatives to nuclear power. But fossil fuels such as coal and natural gas have their own drawbacks, including emissions that can cause climate change.

Nuclear energy and fossil fuels are compact and reliable. That makes replacing them as power sources difficult.

Author William Tucker calculated how much land would be required for each energy source to generate the 24-hours/seven-days-a-week power equal to one of the 1,225-megawatt reactors scheduled for Plant Vogtle in Burke County. What he found:

- 250 square miles of dammed-up water for hydropower, more than twice the size of Lake Thurmond

- 125 square miles for wind power, though it would have to be three times bigger to offset the fact that the wind doesn't blow a third of the time

- 25 square miles for solar, though there is currently no way to store solar energy for when the sun isn't shining

- 1,000 square miles of forest for a biomass plant

Mr. Tucker writes for many mainstream science magazines, but his views on energy are clear from the title of his 2008 book, Terrestrial Energy: How Nuclear Power Will Lead the Green Revolution and End America's Energy Odyssey.

As wind farms spread in the West and mountain ridges in the Midwest, where wind is more constant than in the Southeast, the Nature Conservancy has begun to talk about "energy sprawl." The private foundation estimates that compliance with all current federal energy mandates for renewable fuels would require land the size of Minnesota by 2030.

"It is not a paradox, just a trade-off: Renewable energy takes more space to produce than fossil-fuel energy, and society needs to think carefully about how best to meet that challenge," writes Rob McDonald, a Nature Conservancy scientist.

Reach Walter Jones at walter.jones@morris.com.