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Energy's Best Bets

November 3, 2008 | APPEARED IN VOLUME 86, ISSUE 44

RUDY BAUM is rightly concerned about the lack of consensus on where we go next in tackling the problems of energy (C&EN, Oct. 6, page 2). Forming a consensus may be helped by reviewing the options for achieving self-sufficiency and, at the same time, reducing greenhouse gas emissions.

The U.S. electrical utilities have about 1,600 plants, 70% of which are fired by fossil fuels, each with a power of about 1,000–1,500 MW. Two highly publicized renewable power sources are wind and solar photovoltaics, which generate electricity only when the wind blows or the sun shines. Their inherent limitation is the lack of a method to bank electricity on a multi-thousand-megawatt scale. For the passive periods, these methods require conventional generators for back-up.

Clean coal by carbon capture and storage is also highly publicized but hasn't yet been tried. Its limitation is that there is no practical method to store CO2 at the required volumes, which are huge. Geothermal and hydroelectric energy work well but only at specific locations.

Two promising green technologies for electricity generation are solar heat and nuclear power. In modern solar heat technology, the sun's rays are concentrated by mirrors and provide heat-exchange fluid at about 1,000 oF. This fluid is a continuous source of steam for power generation even after sundown. More engineering development is needed, but nuclear technology is mature. For more extended use, the treatment of nuclear waste as practiced in France should be transferred to the U.S.

Three highly publicized but questionable green technologies for cars are hydrogen, natural gas, and ethanol. Their common shortcoming is the difficulty of creating an infrastructure for distribution. Gases must be stored under pressure, and natural gas supplies are limited. Hydrogen can now be generated only by involving CO2 emissions, and ethanol is a relatively inefficient source of energy.

The electric car is the technology of the future. Even with electricity based 70% on fossil fuels, the plug-in motor causes less CO2 emissions than the gasoline engine and provides much lower operating cost per mile. Although a gasoline engine is necessary to charge batteries for long-range driving, extensive use of plug-in/hybrid cars will allow spectacular reduction of oil consumption.

The new Administration will have limited financial resources. It should support with ample developmental funds and tax subsidies only those few green technologies that will provide the greatest beneficial impact during the next one to two decades.

John L. Gardon
Bloomfield Hills, Mich.



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