After Gutenberg

Oxygen flows through the cathode and methane flows past the anode. “Negatively charged oxygen ions migrate through the electrolyte membrane and react with the hydrogen to form water, which reacts with the methane fuel to form carbon dioxide and hydrogen. This electrochemical reaction generates electrons, which flow from the anode to an external load and back to the cathode, a final step that both completes the circuit and supplies electric power. To increase voltage output, several fuel cells are stacked together, a configuration called a fuel cell stack that forms the heart of a clean power generator.”

The Biopact team gets down DFC-like. In this case, DFC is an acronym for Direct Fuel Cell. A company called FuelCell Energy announced that they had sold three DFCs to the EMWD (Eastern Municipal Water District) in California.

This blog recently “gave you the straight poop” on bio-gas, yet missed an opportunity to submit for your approval the very best in fine ceramics. As Jim Fraser knows, it is possible to run Direct FuelCell units with methane. In fact, the residual waste heat from operating three, 300-kilowatt fuel cells goes to warm the digesters to stimulate further methane production.

Since EMWD currently uses anaerobic digesters for biosolids treatment and to generate methane gas, addition of the fuel cells will increase facility efficiency. The DFC300 power plants, which will supply 750 kilowatts (kW) of the electricity to run the EMWD wastewater processing facility, will make use of waste heat in a similar fashion.

FuelCell Energy’s cells operate with an electrical efficiency of 47 %, much higher than traditional fossil fuel power plants that average 30 to 35 percent. When the DFC power plant’s heat is also used, system efficiency can be as high as 80%. This added efficiency results in less fuel being consumed to generate a kilowatt of power or a BTU of heat, saving money and substantially reducing greenhouse gases.

FuelCell Energy, Inc., a manufacturer of high efficiency, ultra-clean power plants for commercial, industrial and utility customers, stated in their announcement that annual operation of the three Direct Fuel Cell power plants by EMWD would reduce greenhouse gas emissions by 10,400 tons.

Because no combustion is involved and because the units are more efficient than traditional power plants, DFC fuel cells emit near-zero pollutants and much less CO2 than other power generators in their size class. DFC fuel cells’ low emissions will also help the District meet California’s CARB 07 requirements – some of the most stringent in the U.S.

The DFC power plants require that the bio-gas is upgraded before the methane in the stream of gases can be used for fuel. DFC units do not burn fuel, rather, as biopact previously informed, the direct fuel cells transform it electrochemically into hydrogen, water and electricity. Although there is no combustion, the DFC power plants have high operating temperatures, reports the Biopact team.

The heated humid fuel stream is sent to the fuel cell stacks where the fuel is converted to hydrogen, most of which is used in the electrochemical reaction.

Unlike other fuel cell products, DFCs internally reform readily available fuels such as natural gas and biogas into the hydrogen gas required to power the fuel cell system. This internal reformation process is a key ingredient to the DFC’s ability to operate at high electrical power generation efficiency. Internal reforming is possible due to the relatively high operating temperature (650-750°F) of the DFCs. This operating temperature has other advantages: non-precious metals can be used for the anode and cathode instead of platinum, resulting in significant cost savings. Also, the exhaust from the system is high-grade heat, capable of supporting a variety of heat recovery options, including steam generation.

Actually, there is combustion involved in the overall process: “Residual fuel — i.e., fuel not consumed in the electrochemical reaction — is supplied to a catalytic reactor to heat incoming air.

The heated air flows to the cathode to provide the cathode reactants (oxygen from the air and carbon dioxide from the anode reaction). Cathode exhaust gas exits the system through the heat exchanger used to preheat the fuel and water supplied to the HRU.

“Fuel and water are heated to the required fuel cell temperature in a HRU (Heat Recovery Unit), which transfers heat from system exhaust gases.”

Because there is waste heat involved in production, the DFC power plants are made more efficient by co-generation, or as in one case when a Germany IT firm used the heat from a similar biogas operation fuel cell cool its servers, tri-generation. (The servers were powered by electricity generated by the fuel cells.) The exhaust temperature from the DFC power plants ranges from 650°C to 750°F. This heat energy can be captured to provide heat for buildings, swimming pools, and other facility needs.

Our ability to reduce air emissions and operating and maintenance costs were key factors in our decision to install FuelCell Energy fuel cells. In looking at the alternatives, including availability of grant funding through Southern California Edison’s Self-Generation Incentive Program, our engineering team determined that DFC fuel cells were a cost-effective and environmentally friendly co-generation technology that meets the needs of our critical wastewater operations.

– Charlie Bachmann, Assistant General Manager of Engineering, EMWD

Fuel cells running on digester gas, if they utilize waste heat recovery meeting Public Utilities Code 218.5, qualify for Southern California Edison’s Self-Generation Incentive Program of $2.50 per watt. There is no minimum system size; there is a maximum limit of 5.0 MW. Fuel cells (non-renewable fuel) are categorized as renewable in California, qualifying them for the same treatment as either solar or wind power. As previously noted, the City of San Diego, California become a model in the use of renewable energy resources and energy conservation in part because the Point Loma Waste Water Treatment is a cogeneration facility powered by methane gas.

Unlike solar and wind power, however, DFC fuel cells operating on biogas deliver ultra-clean power 24/7, meaning less dependence on costly and polluting grid electricity. FuelCell Energy’s products are gaining market share in California and currently California orders and installations represent 43 percent of its worldwide business. Wastewater treatment customers in California are 40 percent of FuelCell Energy’s California backlog and installed base.