Air Pollution Control Equipment Services, Coal

Molten-Carbonate fuel cell demonstrates its commercial readiness

Issue 3 and Volume 99.

GENERATING TECHNOLOGY

Steven E. Kuehn,

Senior Editor

Molten-Carbonate fuel cell demonstrates its commercial readiness

Fuel cells are fascinating devices?air goes in one side, fuel in the other and viola! Out comes heat and electricity. Although the process seems magical, the technology is really quite simple and the process is well understood by researchers and technocrats alike.

The difficult part, however, has been bringing the technology to market and producing a commercially-viable system at a price competitive with other sources. Nevertheless, there has been considerable effort made to do just that and recent events are proving that fuel cell commercialization has moved from the planning stage to reality.

It takes a team

Since 1987, a team of companies have been hard at work developing the commercial potential of the molten-carbonate fuel cell (MCFC). M-C Power Corp., Stewart & Stevenson Services Inc., Bechtel and the Institute of Gas Technology (IGT) have all provided well-fitting pieces to the puzzle of how to bring unproven but worthwhile technology to market.

According to M-C Power Corp., to develop and introduce a successful power generation product requires skills, experience, capabilities and resources beyond the manufacture of the product. Stewart & Stevenson Services Inc. provided the team with packaging and marketplace distribution expertise, along with global sales and service support. Bechtel contributed engineering experience that has helped to simplify the process, improve product reliability and reduce equipment capital costs, and IGT has provided research and development to improve performance and extend unit life.

IMHEX design

M-C Power?s MCFC technology is based on an internally-manifolded heat exchanger (IMHEX) stack design concept invented by the IGT. This design uses internal, as opposed to external, manifolding to distribute fuel and air to individual cells in the stack. In a MCFC, carbonate salts are heated to approximately 1,250 F, the salts melt and provide ionic conductivity.

At the anode, hydrogen reacts with the carbonate ions from the electrolyte to produce water, carbon dioxide and electrons. Similarly at the cathode, oxygen from process air and carbon dioxide from the anode react with electrons to form carbonate ions which replenish the electrolyte and transfer current through the cell.

Commercial demonstration

Right now, the commercialization team is proving the concept and is testing a 250-kW plant at Unocal Corp.?s research center in Brea, Calif. The demonstration is being underwritten by the Department of Energy, Electric Power Research Institute, Gas Research Institute, South Coast Air Quality Management District, Southern California Edison Co., Southern California Gas Co. and Unocal. The objective of the project is to demonstrate the operability and performance of a commercial-height IMHEX fuel cell stack in a complete power plant.

According to MC-Power, this is the largest MCFC ever built and tested. The unit includes a 250-cell stack, a fuel processing system known as a reformer (converts natural gas into hydrogen), process cooling equipment, heat recovery steam generator, CO2 recycle loop and dc to ac power conversion.

A second 250-kW unit will begin its demonstration testing very soon and will bring the team and the technology closer to the goal of a commercial product ready for market entry by 1999. Plans call for six 1-MW size modular units (Figure 1) to be demonstrated starting in 1997. Specifications include steam at 150 psi, 1,140 pounds/hour and an overall efficiency of 80 percent.

Sources say the concept is expandable to 3-MW-size units and that they are the first electric generation technology developed specifically to serve the distributed generation market. These units may also be especially well-suited to combined-cycle operation and other cogeneration applications. END