Pittsburgh, PA, Feb. 15, 2001 Generating power close to the consumer – a concept called distributed generation – may be one way to take the future strain off the nation’s electric grid. Two of the best technologies for distributed generation are the fuel cell and the micro-turbine – but an even better approach may be a “hybrid” of both technologies.
The Department of Energy’s Office of Fossil Energy is already testing one type of fuel cell-turbine hybrid, and this spring will begin running a second type of test unit. Now, the Department, through its National Energy Technology Laboratory, plans to add a third hybrid system to its fossil energy research program.
The Laboratory has selected Honeywell International of Torrance, Calif., to begin the first stages of development for a new type of “planar solid oxide fuel cell” hybrid system. The development effort is planned as a three-and-a-half year effort valued at approximately $5 million. The Energy Department will fund about $3.48 million.
Honeywell’s planar solid oxide fuel cell will be made up of stacked sheets of flat ceramic material – anodes, electrolytes and cathodes – that resemble a stack of record albums sealed at both ends. Natural gas and air will be fed into the fuel cell, and an electrochemical process – much like the process a battery uses to generate electric current – will produce one source of electricity.
For the initial development effort, Honeywell will test three 5-kilowatt planar fuel cells connected to a turbocharger. The turbocharger is a key component of the company’s advanced turbogenerator technology and is also used as a compressor to boost the operating pressure of the fuel cell.
In the mature version of the technology, linking the fuel cell with a microturbine will provide a way to tap the significant energy remaining in the high-temperature exhaust gases exiting the fuel cell. The gases can spin the blades of the microturbine to produce a second source of electricity.
This dual source of power generation boosts efficiency (the amount of electricity generated from a given amount of fuel). Fuel cell-turbine hybrids may be able to extract from 65 to 80 percent of the energy value from a fuel and convert it to useful electricity. A conventional power plant operates at much lower efficiencies, typically in the range of only 30 to 35 percent. Boosting efficiencies is one of the best ways to reduce the amount of greenhouse gas emissions, such as carbon dioxide, released per unit of electricity generated.
The Department is already testing a tubular version of the solid oxide fuel cell technology in a hybrid unit. In this system, the ceramic materials are arranged in concentric tubes. Later this year, another type of fuel cell configuration – one that uses a molten carbonate as the electrolyte, rather than ceramics – will be tested in a hybrid configuration.
Each of the systems has its advantages, but the Honeywell flat planar design may offer greater power density that is, more kilowatts of power per cubic inch of material. Power density is an important factor in reducing costs.
The system envisioned by Honeywell would be a low cost, small size, highly efficient power unit that would have such low emissions that it could be sited virtually anywhere. Future applications could include hospitals, military installations, or computer centers all of which need a reliable, uninterruptible source of power.