Overview of Direct Carbonate Fuel Cell Technology and Products Development

Abstract

Significant progress has been made in development of power generation products based on carbonate fuel cells. Carbonate fuel cell systems provide high efficiency and ultra-clean power generation from a variety of gaseous, liquid, and solid carbonaceous fuels. The high operating temperature of 650 °C in carbonate fuel cell allows significant system simplification by integrating the internal reforming feature into the fuel cell stack as well as use of the byproduct heat in an efficient bottoming cycle. Direct FuelCell® (DFC®) is a unique version of the carbonate fuel cell, which generates electricity directly from a hydrocarbon fuel by reforming the fuel inside the fuel cell and producing hydrogen. The direct reforming concept eliminates the need for an external reformer resulting in power plants with reduced capital cost. This feature also allows the DFC power plants to utilize the existing fuel distribution infrastructure. The first generation of products offered by FuelCell Energy (FCE) range from 250kW to 2MW and is suitable to operate on natural gas, digester gas and other fuels. Presently, a fleet of natural gas fueled units is operating in the US and Europe at customers’ sites. Additionally, there are subsequent power plants planned to operate on a variety of fuels, including coal-bed methane, digester gas, and coal-derived gas. A 2 MW fuel cell power plant (DFC3000) will soon be operating with coal gas in Wabash River, Indiana’s coal gasification plant. The field tests of a 1 MW unit (DFC1500) at King County (Seattle, WA) waste treatment will be demonstrating the unique features of the DFC technology with digester gas as a fuel. There are plans to operate a 250 kW (DFC300) unit on coal-bed methane fields in Cadiz, Ohio. FCE is also developing a 500 kW unit for the US NAVY, operating on marine distillate fuels. FCE is also developing fuel cell/turbine ultra-high efficiency hybrid power plants with efficiencies approaching 75%. In the Direct FuelCell/Turbine® (DFC/T®) power cycle, the fuel cell is integrated with an indirectly heated gas turbine. FCE has recently completed the operation of a ‘proof-of-concept’ system that combined a sub-megawatt DFC with a 30-kilowatt microturbine. The proof-of-concept tests demonstrated that the DFC/T hybrid concept, indeed, has the potential for achieving higher efficiencies than the single cycle fuel cell. The demonstration of two, packaged sub-megawatt DFC/T units, one in Danbury and one at a customer site in Montana, is planned. In addition to pioneering the Direct FuelCell technology, FCE has established a strong manufacturing base. Currently the manufacturing facility at Torrington, CT, has the equipment in place to produce 50 MW per year of fuel cells. FCE has also established commercial distribution alliances with electric power equipment sales and service companies, energy service and solution providers, and specialty application developers for marketing DFC products. The operation of FCE’s power plants at customer sites, continuing efforts in technology improvement, and the favorable reception of the customers for DFC-based units, combined with a network of partners for sales and services, are the key factors for market penetration of DFC products.