General Electric today said it would invest in eSolar, which specializes insolarthermal technology, and use the firm's technology to build solar thermal farms or hybrid power plants, which combine natural gas and solar thermal.

Think of a hybrid power plant as a form of risk mitigation. When the sun shines, steam for the plant can be made from the heat collected by the mirrors of a solar power plant. When it's night or raining, the gas plant can do the most work. The combination of the two technologies also allows power providers to provide fairly firm power and will potentially expand the geographic region for thermal technology. Most solar thermal plants are built, or are proposed, for incredibly arid regions like Arizona, California's Inland Empire, or North Africa. Increasing the gas component -- potentially -- lets power plant builders erect plants in areas where the sun doesn't have to be as strong or dependable. Florida Power & Light built one of the first such facilities in that state.

Solar thermal plants mostly provide baseline-quality power. The biggest problem that the solar thermal power plants in California's Mojave Desert have experienced in decades of operation came after volcanic explosions in the Philippines carried dust over the Pacific.

GE will integrate eSolar's technology with its FlexEfficiency 50 gas turbine, an extremely efficient (61 percent) turbine that can ramp up fairly quickly (more than 50 megawatts a minute). Adding on eSolar's thermal technology will boost the efficiency to over 70 percent.

The deal also marks something of a comeback for eSolar. The company, founded by IdeaLab's Bill Gross, has championed capturing heat from the sun with heliostats, which are freestanding mirrors, and then targeting those mirrors onto a tower filled with water. It's similar to the technology behind BrightSource Energy. However, although eSolar has nabbed funds from Google and others, it hasn't been as successful as BrightSource or SolarReserve at signing large-scale power purchase deals with utilities or landing loans from the Department of Energy. During the credit crisis, eSolar shifted toward licensing its technology to China and India. Some projects have been scuttled or downsized.

Factors such as required site size, land-use risks and multimillion-dollar costs have made it difficult for solar thermal developers to compete against wind and PV developers. Thus, hybrid power plants could become a substantial portion of the industry's future.

Terms of the deal were not disclosed.

This year, GE also announced that it would start to make high-efficiency cadmium telluride solar panels, putting GE in direct competition with First Solar. GE, however, said it won't open its main manufacturing facility, a 400-megawatt factory, until 2013.