Moving Toward a Hydrogen Economy

For an automobile-addicted, fossil fuel-dependent economy, hydrogen could be an eco-dream come true: cars that purr about on electric motors with only water droplets emerging from their tailpipes. But before the dream can be realized, some humbling realities must be overcome. SAIC is at work with the Florida Solar Energy Center (FSEC) of the University of Central Florida, one of the leading hydrogen research centers in the world, to deal with one of them — the difficulty of economically producing hydrogen without using fossil fuels.

Hydrogen is one of the most abundant elements on Earth but it is not found alone; it has to be separated from other elements. In water, hydrogen is combined with oxygen. In fossil fuels, it is combined with carbon as in petroleum, natural gas or coal. About 95 percent of industrial hydrogen is presently produced from fossil fuels. And it takes energy to separate it. If that energy comes from fossil fuels, that's hardly a help. And it is no economic bargain, either. It is currently three to four times as expensive to produce as gasoline, according to the U.S. Department of Energy (DOE).

So, in order for the United States to move towards a non-carbon hydrogen fuel infrastructure, a reliable, cost-effective and renewable hydrogen production process must be developed, said SAIC Senior Program Manager Rob Taylor.

To help address these challenges, SAIC researchers are working on an innovative production technology that "splits" hydrogen from water by using the ultimate renewable energy resource — sunlight.

"This is one of the most promising technologies to efficiently and economically produce hydrogen," said Taylor, who has 30 years of experience in renewable energy research.

The research and development project is part of a U.S. initiative to reverse America's growing dependence on foreign oil by encouraging the development of hydrogen production technology and fuel cell vehicles, which are powered through a chemical reaction between hydrogen and oxygen and emit only water and heat as exhaust.

While a transition to hydrogen vehicles will not be easy and will require substantial investments, hydrogen could become a competitive fuel within 15 years, according to a July 2008 congressionally mandated report from the National Research Council.

To accomplish this goal, a number of research efforts are under way to develop better ways of producing, storing and delivering hydrogen. The DOE target for hydrogen production cost is $2 to $3 per gallon of gasoline equivalent, which would permit hydrogen fuel cell vehicles to compete with gasoline vehicles on a cost per mile basis. (One kilogram of hydrogen is approximately equivalent to 1 gallon of gasoline.)

SAIC's Solution

The SAIC team's goal is to generate hydrogen more efficiently by developing an "advanced solar thermo chemical water-splitting cycle" for hydrogen production that utilizes the "quantum boost" effect of sunlight. Preliminary estimates are that the SAIC-FSEC system can produce hydrogen at about $2.25 per kilogram.

To produce the temperatures needed to drive chemical reactions that produce the hydrogen, SAIC is developing a solar concentrator system that uses a field of heliostats to track and focus sunlight onto a tower-mounted central receiver. Heliostats are two axis flat mirrors that accurately follow the sun and reflect the sun's rays onto a centrally located receiver. Since all of the heliostats are focused on the same receiver, high concentrations of the sun's intensity can be achieved.

According to Taylor, it is important not to degrade the solar energy but to use the high-value photonic energy of the solar spectrum as well as the thermal energy.

The SAIC receiver approach converts the full spectrum of sunlight — photonic plus thermal — into hydrogen, and therefore achieves efficiencies of 35-45%. By contrast, systems employing photovoltaics for electrolysis of water to produce hydrogen at ambient temperature operate at approximately 10% efficiency. Systems based solely on thermal energy would have to operate at extreme temperatures — often well above 1000ºC — to achieve similar efficiencies. This significantly limits the choice of materials and solar concentrating systems available for such an approach.

SAIC has been investigating solar field configurations appropriate to supply solar energy to this cycle, including the heliostat/central receiver approach, parabolic dishes, and other geometries.

Solar Energy Expertise

Since 1984, SAIC has designed and constructed mirrors, tracking systems and controls for a variety of solar energy systems as a contractor to the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories. For example, SAIC has developed and operated five 22-kW solar systems located at the Pentagon; in Phoenix, working with the Arizona Public Service Commission and Salt River Project; in Las Vegas in connection with the University of Nevada, Las Vegas; and at NREL in Golden, Colo.

Taylor and SAIC Project Manager Roger Davenport presented a paper on their latest research at the 17th World Hydrogen Energy Conference in Brisbane, Australia, in June 2008.

Going forward, the SAIC-FSEC team plans to develop a thermo chemical reactor/solar receiver system for use with the selected cycle, test a bench-scale system, and develop a pilot-scale unit using a SAIC solar concentrator. The final phase of the work calls for installing and demonstrating a 50-kW solar-powered hydrogen production unit in Tempe, Ariz.