I haven't seen the print version of the entire issue September 2006 Scientific American, "Energy's Future: Beyond Carbon", but judging from its table of contents http://www.scientificamerican.com/­issue.cfm, readers of this list will want to buy the issue.

One article is "The Rise of Renewable Energy", by the versatile Daniel Kammen. He reviews progress and potential of solar, wind, biofuels and other solutions, suggests R&D and other government actions to promote a market for green fuels. Below is the overview summary and the full text of his half-page box on plug-in hybrids. (That's a good follow-up to Prof. Andy Frank and Dr. Joseph Romm's April 2006 article on PHEVs http://www.calcars.org/­calcars-news/­329.html

You can also find an online-only story, US Stabilization Wedges, building on the high-regarded work of Princeton scientists Pacala and Socolow (who also have an article in the issue), at http://www.scientificamerican.com/­article.cfm?articleID=000E196C-AD52-14E9-AD0683414B7F4945, that, unfortunately, does not include PHEVs as a factor.

The Rise of Renewable Energy
Solar cells, wind turbines and biofuels are poised to become major
energy sources.
New policies could dramatically accelerate that evolution

OVERVIEW:

• Thanks to advances in technology, renewable sources could soon become large contributors to global energy.
• To hasten the transition, the U.S. must significantly boost its R&D spending on energy.
• The U.S. should also levy a fee on carbon to reward clean energy sources over those that harm the environment.

DANIEL M. KAMMEN is Class of 1935 Distinguished Professor of Energy at the University of California, Berkeley, where he holds appointments in the Energy and Resources Group, the Goldman School of Public Policy and the department of nuclear engineering. He is founding director of the Renewable and Appropriate Energy Laboratory and co-director of the Berkeley Institute of the Environment.

Plugging Hybrids

The environmental benefits of renewable biofuels would be even greater if they were used to fuel plug-in hybrid electric vehicles (PHEVs). Like more conventional gasoline-electric hybrids, these cars and trucks combine internal-combustion engines with electric motors to maximize fuel efficiency, but PHEVs have larger batteries that can be recharged by plugging them into an electrical outlet. These vehicles can run on electricity alone for relatively short trips; on longer trips, the combustion engine kicks in when the batteries no longer have sufficient juice. The combination can drastically reduce gasoline consumption: whereas conventional sedans today have a fuel economy of about 30 miles per gallon (mpg) and nonplug-in hybrids such as the Toyota Prius average about 50 mpg, PHEVs could get an equivalent of 80 to 160 mpg. Oil use drops still further if the combustion engines in PHEVs run on biofuel blends such as E85, which is a mixture of 15 percent gasoline and 85 percent ethanol.

If the entire U.S. vehicle fleet were replaced overnight with PHEVs, the nation's oil consumption would decrease by 70 percent or more, completely eliminating the need for petroleum imports. The switch would have equally profound implications for protecting the earth's fragile climate, not to mention the elimination of smog. Because most of the energy for cars would come from the electric grid instead of from fuel tanks, the environmental impacts would be concentrated in a few thousand power plants instead of in hundreds of millions of vehicles. This shift would focus the challenge of climate protection squarely on the task of reducing the greenhouse gas emissions from electricity generation.

PHEVs could also be the salvation of the ailing American auto industry. Instead of continuing to lose market share to foreign companies, U.S. automakers could become competitive again by retooling their factories to produce PHEVs that are significantly more fuel-efficient than the nonplug-in hybrids now sold by Japanese companies. Utilities would also benefit from the transition because most owners of PHEVs would recharge their cars at night, when power is cheapest, thus helping to smooth the sharp peaks and valleys in demand for electricity. In California, for example, the replacement of 20 million conventional cars with PHEVs would increase nighttime electricity demand to nearly the same level as daytime demand, making far better use of the grid and the many power plants that remain idle at night. In addition, electric vehicles not in use during the day could supply electricity to local distribution networks at times when the grid was under strain. The potential benefits to the electricity industry are so compelling that utilities may wish to encourage PHEV sales by offering lower electricity rates for recharging vehicle batteries.

Most important, PHEVs are not exotic vehicles of the distant future. DaimlerChrysler has already introduced a PHEV prototype, a plug-in hybrid version of the Mercedes- Benz Sprinter Van that has 40 percent lower gasoline consumption than the conventionally powered model. And PHEVs promise to become even more efficient as new technologies improve the energy density of batteries, allowing the vehicles to travel farther on electricity alone. D.M.K.