What is a natural gas fuel cell?
A natural gas fuel cell (NGFC) energy system is a simple, reliable way to improve natural gas utilization and efficiency. This technology converts natural gas into electricity to provide a quiet, clean, and highly efficient on-site electric generating system and thermal energy source that can reduce facility energy service costs by 20 percent to 40 percent over conventional energy services.
The NGFC utilizes an alternative co-generation technology for improving natural gas utilization and efficiency. It is an environmentally friendly fossil-fueled energy generator with cleaner emissions than the ambient air in some cities. NGFCs can serve effectively as an on-site energy supply to meet needs for base-load electricity, heat, and hot water, while local electric and natural gas utilities provide for energy demand beyond the NGFC capacity.
A natural gas fuel cell (NGFC) is a direct-energy conversion system with no moving parts. Like batteries, fuel cells are based on the principles of electrochemistry, except that they consume fuel to maintain the chemical reaction. The most common electrochemical reaction in a fuel cell is that of hydrogen with oxygen. The oxygen is usually derived from the air, and the hydrogen is usually obtained by steam-reforming fossil fuel.
Natural gas is the most commonly used fuel; however, other fuels can be used: peak-shaved gas, air-stabilized gas from local production such as landfills, propane, or other fuels with high methane content.
Typical fuel cell fuel-to-electricity conversion efficiencies range from 40 percent to 60 percent.
NGFC technology can be a net-energy-saving technology when viewed from a source energy perspective. The high conversion efficiency of a fuel cell reduces total fuel consumption when the prime energy source for electric generation is taken into account.
NGFC technology is an energy-cost-reduction technology. For sites with low natural gas costs and high electricity or electrical demand costs, NGFC can be a cost-effective energy technology alternative. The cost savings comes from fuel switching. By reducing electricity consumption and increasing natural gas consumption, operational energy costs can be reduced by 25 percent to 40percent over conventional energy service.
The fuel cell is very much like a battery; it contains electrodes (anodes and cathodes) separated by an electrolyte. But unlike a battery, a fuel cell consumes fuel and does not require recharging. Also, fuel cells are exothermic, producing heat as a byproduct of the chemical reaction, and this heat is available for cogeneration applications.
A NGFC system is composed of three primary subsystems: a fuel processor or reformer, a fuel cell stack, and a power converter. A secondary subsystem for thermal management (a cooling module) is required if recoverable thermal energy is not fully utilized in some form of cogeneration application.
The fuel processor combines natural gas with steam (recovered from the power section) to reform the fuel into a hydrogen-rich mixture for use by the fuel cell stack in the power section. In the power section, the fuel mixture, rich in hydrogen, is combined with oxygen from the air to produce electricity. The process generates heat and produces carbon dioxide and water as exhaust gases.
Besides the possible cost savings available with NGFC, there are environmental benefits associated with installing this technology. Because NGFCs convert the fuel to electricity through an electrochemical process rather than a combustion process, the emissions from the NGFC are much cleaner and are primarily carbon dioxide and water.