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Photographer: Jacob Kepler/Bloomberg Photographer: Jacob Kepler/Bloomberg

For more than a generation, solar power was a environmentalist fantasy, an expensive and impractical artifact from the Jimmy Carter era. That was true right up until the moment it wasn't. Solar silicon prices dropped 94 percent from early 2008 to the end of 2011. Crystalline silicon has since fallen an additional 47 percent, to $15.20 a kilogram.

Many were caught off guard by the emergence of solar as a competitive power source. The scientist who led Exxon's research arm back in the 1980s wasn't one of them.

Peter Eisenberger, now an environmental science professor at Columbia's Earth Institute, co-authored an internal report for Exxon projecting that solar wouldn't become viable until 2012 or 2013. The report, written before he left the company in 1989, suggested that Exxon would do best to sell its solar assets; not surprisingly, the company did just that. What is surprising is that Exxon's 25-year-old solar projections nailed the timing for the arrival of affordable solar power.

Why the oil giant now known as ExxonMobil was in the solar photovoltaic business in the 1980s is a longer story. The late 1970s traumatized the energy industry. The year 1979 alone brought the Iranian revolution, a consequent oil shock, and the Three Mile Island nuclear accident. Energy woe was the centerpiece of President Carter's "crisis of confidence" speech that July. Two weeks later, in a development remarked upon by virtually no one at the time, a committee of scientists met to produce the U.S.'s first major assessment of climate change science.

Energy-sector tumult led Exxon to boost research and development efforts. Eisenberger recalled that the internal thinking went like this: If oil ever runs out, Exxon would have to become an energy company, not just an oil company. Today, a spokesman said, the oil giant thinks of itself as just that—an energy company.

Probing the basic science of energy and materials drove Eisenberger's research in the 1980s. Initiatives included research into climate change, which both the journalism nonprofit InsideClimateNews and the Los Angeles Times recently chronicled at length. Democratic politicians are piling on to their conclusions. ExxonMobil rejects the notion that it "knew" about climate change, stopped funding research, and started denying the whole thing. The news media have started refereeing the disputed history.

Eisenberger said he helped hire many scientists to investigate energy options and conduct basic research at the company. After oil prices crashed in the mid-1980s, Exxon started looking hard at its assets. That's around the time Eisenberger co-wrote, along with a physicist in strategic planning, Exxon's internal assessment regarding the cost of solar power. The duo concluded that solar wouldn't become worth the investment until about 2012.

"Technology really evolves in a very regular way, in a surprisingly regular way," Eisenberger told us recently. With enough data on how investment and effort lead to progress, "you can use it pretty accurately to forecast what might happen in the future." In part, however, Exxon came up with the right answer for the wrong reason. The report predicted that utilities would embrace solar-thermal power plants, huge mirror arrays that concentrate and store heat. The economics of that technology have turned to be less favorable than those of solar panels installed on homes and businesses—or even, it turns out, in utility-scale facilities.

Eisenberger left for academia and in 2010 co-founded a alternative-energy company, Global Thermostat, at which he now serves as chief technology officer. The company works to reduce the cost of capturing atmospheric carbon dioxide and rendering it useful for synthetic fuels and materials. "Almost all the people that are involved in founding this company—and in helping me get going—were from Exxon," Eisenberger said. "Every one of them. They're the only people who didn't think I was nuts."

Today, while the nascent solar power industry becomes increasingly competitive, Exxon is keeping an eye on developments. The oil giant continues to support research into photovoltaics, as well as biofuels and CO2 capture technologies. But as Exxon CEO Rex Tillerson told investors in May, the company isn't investing in renewable businesses. "We choose not to lose money on purpose," he said.

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