WASHINGTON -- Solar power satellites beaming energy to Earth could present daunting technological challenges and offer questionable economic potential, a NASA-funded study has found.

But, the report also recommended that the federal government should continue to study the concept and put more emphasis on creating a power plant in space that might support Earth-orbiting spacecraft and deep-space missions.

Those are the key points from a study on 21^st-century power-beaming satellites released Friday by a Washington think tank called Resources for the Future.

Satellite solar power has been suggested as an alternative to terrestrial energy resources for electrical generation.

The nine-month-long study looked at the market for electricity from the present to the year 2020, roughly the year when many experts believe satellite solar power actually could be possible. Included were comments from the Electric Power Research Institute and Texaco.

Among the findings:

• Conventional electricity generation in both developed and developing countries may be more than adequate in terms of cost, supply and environmental factors.
• Satellite solar power is relatively immature technology. That makes it difficult to estimate costs and the likely competitiveness of such an idea measured against other energy systems.
• Lower launch costs could help make satellite solar power more promising. But until those costs go down, it is too early for the U.S. government to commit to related loan guarantees or tax incentives.
• Health risks associated with exposure to electric and magnetic fields generated by satellite solar power are likely to be of significant public concern.
• Such power may be useful for the International Space Station, moon bases or other space missions.

However, Molly Macauley, an economist who led the study, said the findings should not preclude NASA working on such a concept.

"But … it's going to be very difficult to make it competitive with terrestrial power," she told SPACE.com. "It's a very hard sell."

"My concern with satellite-solar-power advocates is that they aren't looking over their shoulders to realize that technological change and innovation in markets is happening within conventional approaches."

There have been dozens of approaches to building power-beaming satellites. "But fundamentally, so long as it costs as much to get to space, we've got a major problem," she said.

John Mankins, a NASA manager working with advanced concepts, said the study is consistent with the agency's own studies of beaming power from space.

"The technology to do very large scale solar-power systems that might deliver energy into terrestrial power markets is not at hand. It's going to take a fair amount of investment and a lot of success in research and development to mature these technologies to make them available," he said.

But Mankins believes it is smart to keep the idea of satellite power plants alive, since they may one day provide safe, economical power to an energy-hungry Earth.

"The real question that has to be tackled over the next 30 to 50 years," he said, "is what options are required if we get serious about global climate change and greenhouse gas emissions and accumulations?"

Systems like satellite solar power provide an opportunity to leapfrog the delivery of energy to the developing world. Electrifying Africa with a traditional power grid would cost at least $80 billion, according to a United Nations estimate.

"For space power, you don't necessarily have to do that," Mankins said. "You can beam the power into the market without electrifying the whole continent. That has the potential to have the same kind of transformational effect that wireless telecommunications is having in the developing world."