Sustainable Energy

The Year in Energy

Biowaste to fuels, cars that plug in, lithium-ion batteries that don’t explode, and cheap energy from the sun.

Biowaste to ethanol could soon power cars.
Converting a vehicle to run primarily on ethanol costs just a couple of hundred dollars. But ethanol won’t make much of a dent in gas use as long as the source of ethanol in the United States remains corn grain, which requires a lot of energy and land in order to grow. A much better alternative is cellulosic materials such as wood chips and switchgrass, which are both cheap to grow and require fewer natural resources. (See “Biomass: Hope and Hype.”) In an effort to reduce the processing costs of these materials, researchers are genetically engineering organisms that can devour grasses and waste biomass, digest the complex sugars, and then transform the resulting simple sugars into alcohol. (See “Better Biofuels” and “Redesigning Life to Make Ethanol.”) Already, advances in parts of this process have led to planned cellulosic-ethanol plants. (See “Making Ethanol from Wood Chips.”)

Colonies of recombinant Streptomyces bacteria are designed to produce enzymes called cellulases. With these enzymes, the bacteria can break down cellulose on the way to producing ethanol.

The plug-in hybrid-vehicle era begins.
For years, hobbyists and a few companies have been adding bigger battery packs to hybrid vehicles, which have both battery power and an internal combustion engine, and plugging them into electrical outlets. This allows the cars, which typically rely on the electric power only for short bursts or to assist the onboard gasoline engine, to run on electricity alone for short trips. The idea of the “plug-in hybrid” has now caught the attention of government officials and researchers, who note that gas consumption would plummet if drivers could rely almost exclusively on electricity for average daily driving of about 33 miles. The gasoline engine would be available to boost performance and make it possible to use the car for long trips. Now the major car companies are taking notice and are finally developing plug-in hybrids. (See “GM’s Plug-In Hybrid.”) Meanwhile, researchers are beginning to anticipate benefits from plug-ins beyond gasoline conservation: millions of plug-in vehicles could serve as massive energy storage to stabilize the electric grid and make renewable energy sources more feasible. (See “How Plug-In Hybrids Will Save the Grid.”) Battery costs still need to drop before such cars will approach the price of conventional hybrids or gas-only vehicles. But better batteries are already becoming available.

Massive recalls spark interest in better batteries.
The safety-related recall of millions of lithium-ion laptop and cell-phone batteries made by Sony and Sharp put batteries in the spotlight this year. Just in time, a new type of lithium-ion battery that uses materials inherently much safer than those involved in the battery recall started appearing in professional power tools. In addition to being safer, the new batteries are more powerful, have longer useful lifetimes, and are potentially less expensive than those utilized in laptops and cell phones today. All of this could make them attractive for use in mass-produced plug-in hybrids. (See “More Powerful Hybrid Batteries.”) Meanwhile, a number of materials-science advances promise to as much as double the storage capacity of batteries and make them more long-lived. (See “3M’s Higher-Capacity Lithium-Ion Batteries” and “Making Electric Vehicles Practical.”)

Cheaper solar power is on the horizon.
Solar cells have a well-deserved reputation for being too expensive. But a steady drop in costs, along with high electricity prices and government subsidies around the world, have led to a boom in the solar market. And while advances in conventional silicon cells will continue to play a major role in continuing this boom, emerging technologies will also play an important role. A number of companies are developing efficient solar cells based on microscopically thin layers of semiconductor material; they’re also developing fast, high-volume manufacturing methods that could cut costs. (See “Large-Scale, Cheap Solar Electricity.”) Meanwhile, others are developing similarly inexpensive manufacturing for mirrors and lenses to concentrate sunlight, which reduces the amount of expensive photovoltaic material needed. The concentrators make it feasible to use ultra-high-efficiency (and expensive) solar cells originally developed for use in space. (See “Cheap, Superefficient Solar.”) This month one manufacturer of such cells set a new record by producing cells that convert 40.7 percent of the energy in sunlight falling on them into electricity. At the same time, others are developing advanced solar cells that mimic photosynthesis or harness nanocrystals to make better cells. (See “New Solar Technologies Fueled by Hot Markets.”)

Clean coal technologies get mixed up in politics.
Coal will be a major source of electricity for a long time, especially in places such as China and the United States. That’s because it’s cheap. The problem is that burning coal emits huge amounts of carbon dioxide. While President Bush supports research into new technology that can reduce such emissions, the fact is that good technology, such as gasification, burning coal in pure oxygen, and methods for sequestering carbon dioxide, exists now that could make a big difference. (See “Simpler and Cheaper Clean Coal Technology” and “The Dirty Secret.”) At this point, cleaning up coal is more in the hands of policymakers than in the hands of researchers.

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