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Thread: Solar power to produce liquid fuels

  1. #1

    Solar power to produce liquid fuels

    These soalr cells ar in prototype stages but this seems like a potential way of overcoming some of the limitations in using solar power for vehicles and storable energy:

    http://www.guardian.co.uk/environmen...-fuel-sunlight
    Haile estimates that a rooftop reactor could produce about three gallons of fuel a day. She thinks transport fuels would be the first application of the reactor, if it goes on to commercial use. But she said an equally important use for the renewable fuels would be to store solar energy so it is available at times of peak demand, and overnight. She says the first improvements that will be made to the existing reactor will be to improve the insulation to help stop heat loss, a simple move that she expects to treble the current efficiency.
    The key component is made from the metal cerium, which is almost as abundant as copper, unlike other rare and expensive metals frequently used as catalysts, such as platinum. Therefore, said Haile, availability would not limit the use of the device. "There is nothing cost prohibitive in our set-up," she said. "And there is plenty of cerium for this technology to make a major contribution to global gasoline supplies."
    There is a way to go yet to develop this so that the benefits outweigh the costs but is is an exciting development in alternative energy sources and as the cost of fossil fuel extraction continues to rise that will surely give more than just environmental impetus to this line of research:

    The prototype is grossly inefficient, the fuel created harnessing only between 0.7% and 0.8% of the solar energy taken into the vessel.
    Most of the energy is lost through heat loss through the reactor's wall or through the re-radiation of sunlight back through the device's aperture.
    But the researchers are confident that efficiency rates of up to 19% can be achieved through better insulation and smaller apertures. Such efficiency rates, they say, could make for a viable commercial device.
    http://www.bbc.co.uk/news/science-environment-12051167

  2. #2
    This recent article (19th January 2011) fills in more information about the process that Sossina Haile is working on to use solar enrgy to produce liquid fuels.
    http://media.caltech.edu/press_releases/13398

    "What is special about the material is that it doesn't release all of the oxygen. That helps to leave the framework of the material intact as oxygen leaves," Haile explains. "When we cool it back down, the material's thermodynamically preferred state is to pull oxygen back into the structure."
    Specifically, the inhaled oxygen is stripped off of carbon dioxide (CO2) and/or water (H2O) gas molecules that are pumped into the reactor, producing carbon monoxide (CO) and/or hydrogen gas (H2). H2 can be used to fuel hydrogen fuel cells; CO, combined with H2, can be used to create synthetic gas, or "syngas," which is the precursor to liquid hydrocarbon fuels. Adding other catalysts to the gas mixture, meanwhile, produces methane. And once the ceria is oxygenated to full capacity, it can be heated back up again, and the cycle can begin anew.
    For all of this to work, the temperatures in the reactor have to be very high—nearly 3,000 degrees Fahrenheit. At Caltech, Haile and her students achieved such temperatures using electrical furnaces. But for a real-world test, she says, "we needed to use photons, so we went to Switzerland." At the Paul Scherrer Institute's High-Flux Solar Simulator, the researchers and their collaborators—led by Aldo Steinfeld of the institute's Solar Technology Laboratory—installed the reactor on a large solar simulator capable of delivering the heat of 1,500 suns.
    If the technology becomes viable it could not only use solar energy to produce liquid fuels but another possibility is to link the solar plant to an existing fossil fuel power station and use the carbon dioxide from the power station to produce methane to fuel another power plant:
    Ultimately, Haile says, the process could be adopted in large-scale energy plants, allowing solar-derived power to be reliably available during the day and night. The CO2 emitted by vehicles could be collected and converted to fuel, "but that is difficult," she says. A more realistic scenario might be to take the CO2 emissions from coal-powered electric plants and convert them to transportation fuels. "You'd effectively be using the carbon twice," Haile explains. Alternatively, she says, the reactor could be used in a "zero CO2 emissions" cycle: H2O and CO2 would be converted to methane, would fuel electricity-producing power plants that generate more CO2 and H2O, to keep the process going.

  3. #3
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    Using the CO2 to grow algae is being done here experimentally which I think is a better use for the CO2 than some of the carbon sinks they are considering. The algae is then used to create biodiesel.

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