by Michael Fraase • Rapson Hall on the University of Minnesota’s East Bank has been equipped for about 20 years with 72 solar photovoltaic panels on its roof. In addition to electricity, those solar panels can also provide the power for a device that splits water molecules into hydrogen and oxygen. Hydrogen, the most abundant element on the planet, is clean and holds tremendous promise as a green substitute for fossil fuels in many applications, including generating electricity and powering vehicles.
The solar-generated hydrogen is presently being used to provide electrical power to Rapson Hall during those times when the solar array is not producing power. Louise Goldberg (Building Physics and Foundations Research Programs), the project’s principal investigator, has proposed using the hydrogen to fuel a passenger vehicle, initially a hydrogen/gasoline or hydrogen/ethanol hybrid automobile, and eventually, a vehicle that uses solely hydrogen as its fuel.
Hydrogen by volume is very large compared with gasoline. “One gallon of gasoline is roughly equivalent to 10 gallons of hydrogen under average automotive operating conditions,” said Goldberg. “So a Honda FCX Clarity hydrogen fuel cell car gets a combined 72-mile-per-gallon (of gasoline) EPA estimate and a 280-mile driving range with a 144-liter [38 gallon] storage tank.”
Tom Fisher, dean of the College of Design, stressed the larger importance of Goldberg’s solar hydrogen fuel cell demonstration project. “In the future, we will be powering our houses and fueling our cars with hydrogen generated from solar power collected on our roofs,” said Fisher. “The greatest challenge we have in transitioning to a hydrogen-fueled economy lies not in the fuel-cell technology itself, but in the lack of infrastructure needed to create and deliver hydrogen. This project shows how one building, with rooftop solar equipment, can produce enough hydrogen fuel to meet a diversity of needs.”
As of mid-September 2008, the system had produced about 4,205 cubic feet of hydrogen at an average generation rate of 26.2 cubic feet per hour. The maximum generation rate is 44 cubic feet per hour.
Even though the solar panels are operating at less than their optimal output, because of their age, they generate about four times as much power—about 12.6 kilowatts—as the approximately three kilowatts an average urban home consumes.
About a third of the electricity generated by the Rapson solar panels (4.2 kilowatts) is used to power an electrolyzer, a device that uses an electro-chemical reaction to split water into its component elements: hydrogen and oxygen. The hydrogen is stored under pressure and the oxygen is currently vented. If sufficient new wiring were put in place, six additional solar panels could be added to the electrolyser array increasing its yield to about six kilowatts.
Recently, the electrolyzer and hydrogen storage system was recommissioned in a new, permanent facility adjacent to Rapson Hall. Additional components will be placed in service on an ongoing basis. A safety control system and fuel cell were also put in place and a real-time monitoring and instrumentation system should be operational by the end of November 2008.
Surprisingly, none of this is new. Actor Jack Nicholson drove around in a hydrogen-powered automobile in 1978. The hydrogen was generated by a solar-powered electrolyzer. The byproduct of hydrogen combustion is water vapor. Nicholson vamped for a Canadian news broadcast by deeply breathing his car’s exhaust.
What is new is the potential decentralization of hydrogen production. One of the keys to making hydrogen generation practical is lowering the cost. Two years ago, General Electric introduced a new industrial electrolyzer that replaced expensive tooled metal parts with plastic ones. Solar photovoltaic tubes, while currently more expensive than traditional solar panels, have the advantage of taking up less space, being lighter, being capable of collecting solar energy from virtually any angle (including underneath if the roof is white), and can be installed in a flat configuration, reducing problems and installation costs associated with wind resistance.
The Solar Hydrogen Fuel Cell Demonstration Project was cosponsored by Xcel Energy, the Minnesota Office of Environmental Assistance, and the University’s Initiative for Renewable Energy and the Environment (IREE).