Power to the people

The US Department of Energy is working to generate power closer to consumers by expanding its research into distributed power generation.

Fuel cells and micro turbines already provide distributed generation, but the DoE believe that an even better approach may be a ‘hybrid’ of both technologies.

The DoE’s Office of Fossil Energy is currently testing one type of fuel cell-turbine hybrid, and this spring will begin running a second type of test unit. Now, the DoE, through its National Energy Technology Laboratory, plans to add a third hybrid system to its fossil energy research program.

The Laboratory has selected Honeywell to begin the first stages of development for a new type of ‘planar solid oxide fuel cell’ hybrid system.

Honeywell’s planar solid oxide fuel cell will be made up of stacked sheets of flat ceramic material consisting of anodes, electrolytes and cathodes.

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 may provide a way to tap the significant energy remaining in the high-temperature exhaust gases exiting the fuel cell. The gases could then spin the blades of the microturbine to produce a second source of electricity.

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, whereas approximately 30 to 35 per cent are extracted from conventional power plants.

Boosting efficiencies is said to be one of the best ways to reduce the amount of greenhouse gas emissions 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.