Caltech Chemist Assesses Global Clean Energy Options

Nathan Lewis, professor of chemistry at the California Institute of Technology and editor-in-chief of the Royal Society of Chemistry journal, Energy & Environmental Science, delivers Presidential Lecture on Energy and Sustainability.
Nathan Lewis, professor of chemistry at the California Institute of Technology and editor-in-chief of the Royal Society of Chemistry journal, Energy & Environmental Science, delivers Presidential Lecture on Energy and Sustainability.

Dubbed “the moon shot of our generation” by New York Times columnist Thomas L. Friedman, the quest for energy independence and a low-carbon future raises many difficult technical, economic and political questions. In a Presidential Lecture on Energy and Sustainability on Oct. 28 at the Boston University Photonics Center, Nathan Lewis, George L. Argyros professor of chemistry at the California Institute of Technology and editor-in-chief of the Royal Society of Chemistry journal, Energy & Environmental Science, addressed these questions directly.

“It is not true that we have all the technology we need, and we only need the political will,” said Lewis. “We do need political will, but we also need to understand that this is a challenge for science and engineering to bring affordable clean energy to global scale in the time that we have left to do it.”

Based on estimates of the world’s available fossil fuel reserves and projected energy consumption rates (now about 15 trillion watts, or terawatts per year), he predicted that the world will not run out of oil, coal and natural gas anytime soon. But he cautioned that projected “business as usual” consumption rates of these fuels—and their attendant carbon dioxide and other greenhouse gas emissions—could boost average global temperatures beyond a point where human technology can mitigate them.

“This is absolutely not about waiting for sound science; this is absolutely all about risk management in an experiment with our planet that we get to do (or not do) exactly once,” he warned. “We need to find a way to bring online as much clean energy, starting today, as all the oil, gas, coal and nuclear power on our planet combined.”

To that end, Lewis explored the potential of nuclear power, carbon sequestration and various renewable energy technologies ((hydroelectric, geothermal, wind, ocean, biomass, solar) to produce sufficient carbon-free power to meet the world’s projected energy needs—an estimated 10 to 30 terawatts annually—by 2050.

Three Promising Solutions
Based on his analysis of available resources and technical, economic and political challenges, Lewis identified nuclear power, carbon sequestration and “cheap solar fuel” as the most promising options to scale to the production levels that the world will need. But he cautioned that all three have their drawbacks.

Nuclear power could produce 10 terawatts (TW) per year, he said, but only if the world built 10,000 nuclear power plants, or about one reactor every day for the next 40 years. Sequestering carbon emitted from coal-burning power plants underground in aquifers would permit the ongoing use of coal without adding carbon dioxide to the atmosphere, he added, but even small leaks could counteract the technology’s environmental benefits.

According to Lewis, solar panels with a 10 percent conversion efficiency could yield 60 TW of electricity per year, but would require vast territory (a Kansas-sized land mass could produce 3 TW) and dramatic cost reductions to satisfy global needs. To produce sufficient amounts of solar electric power, he maintained, will require that scientists and engineers find a way to store massive amounts of energy received from the sun the way plants and fossil fuels do now: in the form of chemical bonds. And that entails devising a process to directly produce chemical fuel from the sun with far greater efficiency than plants, explained Lewis, who studies artificial photosynthesis.

“I’m sure we can develop [all] this technology and make it cost effective and affordable and globally scalable,” he said. “We just have to decide that this is really important and we can’t afford to wait.”
 
Lewis’s presentation was sponsored by the BU Clean Energy and Environmental Sustainability Initiative (CEESI), a collaboration of six Colleges and Schools at BU, including the College of Engineering, which hosted the event. CEESI faculty members, many based at the Cdollege of Engineering, are leading cross-disciplinary and world-class research efforts on problems such as the smart grid, the hydrogen economy, green manufacturing and smart lighting.