Another pathway for converting gas to electricity is fuel cells, which produce electricity with no byproducts except distilled water and a little bit of waste heat. But their carbon footprint depends on where they get their own fuel, hydrogen.
One common source is natural gas, which is made up mostly of methane, a molecule with four hydrogen atoms and one carbon atom. Using steam, this can be converted to hydrogen and carbon dioxide. But natural gas is not usually considered a renewable fuel.
On Tuesday, a company in Hillsboro, Ore., ClearEdge Power, announced a deal with an Austrian company, Güssing Renewable Energy, to supply 8.5 megawatts of fuel cells that would run on methane made from renewable sources. The companies said the 8.5 megawatts would be in place within three years, and the longer-term goal is 50 megawatts by 2020.
Both numbers are enormous by the standards of fuel cells; the first phase of 8.5 megawatts is one of the largest deals ever signed involving stationary fuel cells, the companies say. (“Stationary” distinguishes this use of fuel cells from the other big potential market, buses and cars.)
The method to be used in Güssing, Austria, a town with a growing green reputation, is a bit roundabout. The company takes wood chips and crop wastes and gasifies them, which means that it zaps them into a fuel gas made of carbon monoxide and hydrogen. It then rearranges those molecules to make methane and carbon dioxide. The carbon dioxide is released to the atmosphere, yes; but if the original source of the carbon was trees or crops, then regrowing those would mean that the carbon dioxide would be reabsorbed from the atmosphere. The company’s goal is to build carbon-neutral communities.
ClearEdge builds a five-kilowatt module that takes in natural gas and converts it to hydrogen and carbon dioxide. It then runs the hydrogen through a fuel cell to make electric current. It is about the size of a kitchen refrigerator: “It takes up about that much space, and it makes about that much noise,’’ said Russell Ford, the company’s president and chief executive.
ClearEdge, established in 2003, began shipping commercial models in mid-2010 and has about 125 units operating, on the West Coast of the United States and in South Korea. It has orders in hand for another 250 in the United States and 800 in Korea.
But those are dwarfed by the Austrian project. The 8.5 megawatts will be met by 1,700 of the five-kilowatt units; some of them will stand alone while others will be grouped in office buildings, multifamily residential buildings and similar settings.
Some of the carbon dioxide byproduct might be captured to feed algae tanks that Güssing is building, Mr. Ford said. Algae can be converted to liquid fuel or used for a variety of other energy needs.
One of the attractions of the fuel cells is their reliability, which may be greater than that of the electric grid. “It’s riding on the natural gas infrastructure, not the electric infrastructure,” Mr. Ford said.
The fuel cell can use natural gas more efficiently than a utility-scale generator, if the waste heat, around 145 degrees, can be used for space heating or for heating domestic hot water. If not, a big utility generator can make more kilowatt-hours per unit of natural gas than a fuel cell.