The hybrid, multi-megawatt DFC-ERGTM (Direct FuelCell Energy Recovery GenerationTM) system generates ultra-clean electricity and in addition, recovers energy normally lost during natural gas pipeline distribution operations. The DFC-ERG combines a Direct FuelCell® power plant with a gas expansion turbine. The pressure reduction process drives the gas turbine, generating additional electricity above and beyond that of the fuel cell power plant. This unique DFC-ERG configuration generates extremely high electrical efficiencies of 60% and higher with virtually zero smog emissions and quiet operation.
Natural gas transmission networks utilize long-distance pipelines operating at very high pressures. These pressures are required to maintain a high volume of flow in the system. Gas distribution to homes and businesses, however, uses a much lower pressure for safety and to accommodate end use equipment. Pressure is reduced at regional and local utility let-down stations to accommodate the distribution network. As pressure is reduced, the gas naturally cools because of the refrigerant effect of gas expansion. To prevent the gas systems and pipeline from freezing, the gas must be heated before it flows through the expansion process. Traditionally, the energy available in this letdown process is lost, and combustion-based boilers, which produce local emissions and CO2, provide the heat needed by the process.
The energy normally lost when natural gas expands is harnessed by the turboexpander to drive an electric generator. The DFC, operating on pipeline gas, produces additional electric power. High quality heat generated by the fuel cells provides the heat required by the expansion process, avoiding the need to use gas-fired boilers, saving fuel and eliminating a source of pollutants. The utility grade electric power produced by the turboexpander and DFC system can be used for on-site power requirements and the power grid.