More than a decade ago, when geologist Peter Kelemen first saw bleached-white rock formations in Oman, he wasn't happy. The normally dark-hued rocks were peridotite whose composition he was trying to investigate. But every time Kelemen found an exposed surface, it had reacted with carbon dioxide in the air to form a carbonate similar to limestone. Goodbye, samples. "I ran in the other direction as fast as I could," he says. That outlook changed in 2004, when Kelemen had a eureka moment while talking with colleagues at Columbia University's Lamont-Doherty Earth Observatory about ways to sequester CO2 underground and slow the pace of global warming. Most sequestration plans risk creating a carbon-dioxide time bomb, with the greenhouse gas stored underground and always threatening to bubble out. Kelemen thought the peridotite might provide a longer-Âlasting solution. His idea is to drill into massive rock formations, heat them and then pump in CO2-enriched water. The rock would then turn to carbonate, trapping the gas in enduring, solid form. Kelemen stresses that the real-world practicality of his plan still needs to be proven. But field observations in Oman, which has more than 3000 cubic miles of peridotite, have been promising. Next up: investigating the idea in the United States.
The quest for controlled fusion power, that most future-topian of engineering feats, requires patience and enduring faith. Progress is being made, but workable reactors are decades off. While we wait, fusion may as well make itself useful. Researchers at the University of Texas recently unveiled a design for a hybrid fission-fusion reactor, a best-of-both-worlds device that would dispose of the deadliest waste from traditional nuclear power plants while generating power along the way. Most nuclear waste can be reprocessed for use as fuel in standard fission reactors, although that's not currently the practice in the United States. The hybrid reactor would be a next step. It would employ fusion reactions to flood the remaining, highly dangerous transuranic waste with neutrons, allowing it to be burned in a fission process. One-third of the resulting energy would be fed back into the fusion process and the remaining 700 megawatts would be fed into the grid. According to senior research scientist Swadesh Mahajan, at the end of the process, about 99 percent of all nuclear waste could be eliminated. "What we really want to do is to tell the world, Please allow the expansion of nuclear energy, through standard light-water reactors," Mahajan says. "It's the only thing that can be ramped up quickly enough to replace coal. Do not worry about the waste. Because we're going to give you the solution in 20 years. We will make it in time."
Heat exchanger (left): Airflow in and out of the house is carefully controlled. Fresh air is routed through a heat exchanger; it is warmed by air being vented outside.
Continuous insulation (top right): Loft insulation is used between studs. An unbroken layer of insulation on the outside wall ensures that the studs don't act as thermal bridges, conducting heat outside.
Triple-pane windows (bottom right): Window frames are surrounded by multiple layers of foam; gaskets have some flexibility, ensuring a tight, enduring fit.
The conventional American home bleeds heat from under doors and around window sashes—and right through underinsulated walls. While wind turbines and solar panels are impressive green technologies, the way to really slash one's bills and environmental impact is to live in a hyperefficient house—and it doesn't get more hyper than the "passive houses" now being developed. These are essentially maximum-security prisons for thermal energy, with thick insulation that leaves no unprotected studs to conduct heat to the outdoors, triple-pane windows and an overall approach to airtightness that lunar colonies could aspire to. In Europe, as many as 6000 homes have been passive-house-certified in the past decade, with thousands more approaching, though not quite meeting, the rigorous requirements. According to energy-efficiency consultant David White, a passive house in the northeastern United States could consume 90 percent less heat than equivalent homes. "Passive houses have been shown to be among the most reliable and cost-effective approaches to efficiency," White says. In Germany, off-the-shelf windows, gaskets and other passive-house-certified products have brought construction costs to within 5 percent of those for conventional homes. In the United States, that price premium can be 11 percent or more. White sees that number coming down. Since quitting his job at a green design firm to concentrate on passive housing projects, he's been working 18-hour days to keep up with an influx of new customers. The housing market may have crashed, but passive houses are on the rise.
After decades spent watching short-lived bursts of plasma sputter in research-oriented magnetic tokamak reactors, it would be easy to abandon the dream of fusion power. But the ultimate clean-energy technology may be getting closer. ITER (the letters don't stand for anything, but the word means "the way" in Latin) is expected to be the world's biggest tokamak when it's completed in southern France in 2018, and it could lead to efficient prototype power plants. Next year, the array of 192 lasers that form the heart of the National Ignition Facility (NIF) at California's Lawrence Livermore National Laboratory will begin firing at a tiny hydrogen target, testing a magnet-free fusion scheme. NIF director Ed Moses hopes that within a few years, the machine will release 20 times more energy than it consumes. "If this works, over the next couple of decades we can change the geopolitical story," he says.
The Green Energy Machine, or GEM, is an unlikely alt-fuel hero. Yet the dumpster-size cargo container jutting from a building in Waltham, Mass., can heat and power 200,000 square feet of space on a daily diet of 3 tons of garbage. The $850,000 system, which incorporates a Rube Goldberg-like array of devices, can pay for itself in three years, according to Michael Cushman, vice president of IST Energy, which makes GEMs. It can save some 540 tons of greenhouse gas emissions annually and—unlike much alt-energy tech—it's ready now. "We welcome revolutionary technology, but this is an evolutionary solution with substantial potential for high impact," Cushman says. "We don't need a 10-year-off solution, we need a today solution."
Nanotube arrays can increase the surface area of a catalyst, and thus are one of the many "next big things" in energy research, especially for batteries. But Craig Grimes, an electrical engineer at Penn State, has another use for them. In combination with sunlight, his nanotube membrane converts water and carbon dioxide into liquid fuel, such as butane and methane. If the technology were integrated into power plants, Grimes says, "it would basically be a closed loop—you have a fuel, you burn it, you collect the reactants, convert them back into fuel, and then feed that right back into the plant." He calculates that 4 square inches of the current version of the membrane could yield more than 130 gallons of fuel daily, squeezing a second act out of hydrocarbons before they enter the atmosphere.