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Explainer: Eight obstacles to a green energy future

  • Image: Hurdles
    Rusty Kennedy  /  AP

    The green energy future envisions a technological road that leads to an infinite supply of power, independence from potentially hostile nations and an atmosphere cleared of the excess heat-trapping gases that are blamed for warming the planet. The track to this future, however, is full of technological and policy hurdles. Click ahead to learn how eight of the biggest hurdles might be cleared.

  • Clean up the existing supply with a price on carbon

    Image: Sleipner
    ?yvind Hagen  /  Statoil
    Statoil's Sleipner natural gas facility off the coast of Norway strips excess carbon dioxide from the recovered gas and injects it underground.

    Statistics show that the vast majority of the energy used today, about 90 percent, comes from fossil fuels: coal, oil and natural gas. When burned, these fuels emit carbon dioxide into the atmosphere that scientists believe is forcing the global climate to change. But these fuels are also cheap, energy-dense and abundant — reasons why they won't go away anytime soon, according to Jim Dooley, a senior research scientist with the Department of Energy's Pacific Northwest National Laboratory and the Joint Global Change Research Institute at the University of Maryland.

    One way to keep using these fuels, but cleanly, is to capture the carbon dioxide and store it in the ground. Critics say the technology is unproven and prohibitively expensive. Dooley disagrees. "This class of technologies exists, full stop. No caveats needed," he says. For example, Statoil's Sleipner natural gas facility off the coast of Norway, shown here, strips excess carbon dioxide from the recovered gas and injects it underground.

    What's needed to clear the hurdle to widespread implementation of this type of technology is a public policy that puts a price on carbon emissions, says Dooley. "We as a species, by and large, have assigned a price of zero dollars to CO2 that is vented to the atmosphere. The class of technologies, carbon dioxide capture and storage, has no other use than large-scale greenhouse-gas mitigation."

  • Store wind and solar energy for later use

    Image: Wind energy
    Justin Sullivan  /  Getty Images

    Widespread use of energy generated from the wind and sun would help humans shift away from reliance on fossil fuels, but the scale-up of wind and solar technologies is hobbled by the fact that the sun doesn't always shine and the wind doesn't always blow when people want power the most.

    One way to resolve this unreliability is to store solar- and wind-generated energy for use when it's needed. Advanced technologies such as giant sodium-sulfur batteries are currently being tested by a few electric utilities, but they will require years of research and development to prove their effectiveness and drive down costs, according to Bob Hawsey, an associate director at the Department of Energy's National Renewable Energy Laboratory in Golden, Colo. Other technologies are viable today — such as using electricity when it's cheap to pump pressurized air or water into holding tanks, and then releasing that stored energy to drive generators when prices are higher.

    What's more, Hawsey says, time is on our side to make the necessary improvements to storage technologies. For example, the electricity grid can handle having up to 20 percent of its energy generated by renewable sources such as wind and solar, just by shuttling power around the grid more efficiently to where it's needed. Up to that point, power storage really isn't necessary. "Why that number is important is we are at less than 2 percent today," Hawsey says, "so we have a long way to go."

  • Limit impact of transmission lines

    Image: Transmission lines
    Warren Gertz  /  NREL

    New transmission lines will be required to shuttle the existing energy around the electricity grid, as well as bring wind and solar energy generated in the prairies and deserts to urban centers where it is needed. Community groups often see the lines as a visual blight that they feel compelled to resist.

    "There is no silver bullet" to the problem, says NREL's Hawsey, but the use of technology options such as high-voltage direct-current transmission lines (instead of alternating current) and low-sag conductors that can handle more heat, thus higher loads, will allow utilities to transmit more energy without expanding transmission corridors.

  • Drive down costs of electric cars

    Image: Nissan Leaf
    Itsuo Inouye  /  AP file

    Next-generation electric vehicles such as the Nissan Leaf, shown here, are beginning to roll onto showroom floors, but they'll set consumers back a relatively hefty $33,000 (at least that's the cost before tax breaks are applied). Dale Gardner, an associate director at NREL, says the high cost of electric vehicles can be summed up in a word: batteries.

    "In general, we are talking 10 to 15 to 20 thousand dollars just for the battery pack, and that's as much as some whole vehicles, so we need to get that cost down," he says.

    Driving down battery cost has proven an elusive goal, compelling engineers to rethink how the cars are designed. One idea is to use smaller batteries but put charging stations in more places, such as the parking garage at work. That would allow smaller batteries that require a range of only about 20 miles to meet the commuting needs for 75 percent of the workforce. "If the battery needs to be half the size, then back of the envelope [calculation] says it can be half the cost," Gardner says.

  • Build a portfolio of transportation options

    Image: Provoq
    General Motors via AP

    If the cost of electric vehicles is driven down by the widespread use of smaller batteries that have a range suited to the needs of commuters, that will pose another challenge: Working parents hoping to haul the family across the river and through the woods to grandma's house on the weekend are going to need a new transportation option.

    NREL's Gardner envisions that need being met by a second car in the garage, perhaps one powered by a hydrogen fuel cell that doesn't have recharge issues. One such concept vehicle, the Provoq from General Motors, is shown here. Production models from several manufacturers may hit showroom floors by 2015.

    "When you go into your garage, if you are like most Americans, you are going to have two vehicles, but they are going to be two kinds of vehicles that you use for different purposes," Gardner says. "The bottom line is we have to start thinking in terms of a portfolio of different transportation options and really aim the technologies at what you are doing with the vehicle to get the efficiency out of the entire system."

  • Mine the earth for rare minerals

    Image: Prius
    Toyota

    Many auto buffs and electric utilities aren't waiting for the green energy future. For them, it is already here. Toyota has sold 1.8 million Priuses, the popular gas-electric hybrid vehicle shown in this image, and wind energy continues its heroic rise, reaching an installed capacity of 159,213 megawatts in 2009, according to the World Wind Energy Association. To continue this growth, however, requires a ready supply of so-called rare earth elements such as neodymium, which is used to make the battery magnets at the heart of Prius batteries and large wind turbines.

    About 97 percent of these elements are currently produced in China, according to David Menzie, an analyst with the U.S. Geological Survey's National Minerals Information Center in Reston, Va. China sent a wave of fear through the green and high-tech sectors when it warned that it might need to stop exporting the elements within five to 10 years in order to keep up with domestic demand.

    Menzie says the fears are overblown: the Chinese hold only about 35 percent of the world's reserves of rare earths. To overcome the production roadblock, the reserves outside of China need to be mined and processed. Molycorp Minerals has a deposit of rare earths from its mine at Mountain Pass, Calif., and the company is seeking loan guarantees from the federal government to acquire the capital required to build out the processing infrastructure in the U.S.

  • Grow energy crops; save the food

    Image: Energy crops
    Stephen Ausmus  /  USDA-ARS

    Technology is progressing along a path that should make producing fuel from biomass such as wheat stalks, tree limbs and switchgrass (shown here) cost-competitive with gasoline by the year 2012, according to NREL's Gardner. A shift to this type of fuel, called cellulosic ethanol, would reduce the strains that corn-brewed ethanol has put on the global food and feed supply. However, scaling up the technology sufficiently to make a statistically significant dent in the nation's fuel needs would still require massive amounts of land, again raising concerns about competition with food.

    "We need to find pathways that don't displace acres that are used for food, feed or fiber today," says Gardner. Promising approaches include increasing use of agricultural residues such as cornstalks, planting grasses such as the tall and dense miscanthus that can take root on lands unsuitable for food cultivation, and growing new varieties of trees that reach maturity in a single decade instead of three or four.

  • Bury hang-ups on nuclear waste

    Image: Yucca Mountain in Nevada,
    Joe Cavaretta  /  AP file

    Nuclear energy is viewed by many experts as a key technology for a low-carbon future, but the industry has been dogged for decades by concerns about the ever-growing stockpiles of high-level nuclear waste. Some 60,000 tons of the stuff are currently in limbo at the plants where it was generated, awaiting transfer to permanent storage in a stable geological area. Yucca Mountain in Nevada, shown here, is no longer in the running, thanks to concern about the site's geology and strong political and public opposition.

    "We literally have no designated location to put hazardous waste," says Eugene Rosa, a sociologist at Washington State University who has proposed proactively addressing public mistrust in the energy department as a way to overcome this roadblock.

    According to Rosa, research shows that the Department of Energy is one of the most mistrusted institutions in the country. To improve that relationship will require greater transparency on behalf of the agency as well as public engagement in the site selection process. Though such actions are no guarantee of success, he says, sticking with the status quo "is pretty much predetermined to failure."

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