Yet research on solar power and methods for storing intermittent energy has long received less spending, both in the United States and in other industrialized countries, than energy options with more political support.

Indeed, there are few major programs looking for ways to drastically reduce the cost of converting sunlight to energy and — of equal if not more importance — of efficiently storing it for when the sun is not shining.

Scientists are hoping to expand the range of sunlight’s wavelengths that can be absorbed, and to cut the amount of energy the cells lose to heat. One goal is to make materials to force photons to ricochet around inside the silicon to give up more of their energy.

For decades, conventional nuclear power and nuclear fusion received dominant shares of government energy-research money. While venture capitalists often support the commercialization of new technologies, basic research money comes almost entirely from the federal government.

These days, a growing amount of government money is headed to the farm-state favorite, biofuels, and to research on burning coal while capturing the resulting carbon dioxide, the main heat-trapping smokestack gas.

In the current fiscal year, the Energy Department plans to spend $159 million on solar research and development. It will spend nearly double, $303 million, on nuclear energy research and development, and nearly triple, $427 million, on coal, as well as $167 million on other fossil fuel research and development.

Raymond L. Orbach, the under secretary of energy for science, said the administration’s challenge was to spread a finite pot of money to all the technologies that will help supply energy without adding to global warming. “No one source of energy that we know of is going to solve it,” Dr. Orbach said. “This is about a portfolio.”