Why FuelCell Energy?

How do Fuel Cells Work?

Fuel cells produce energy electrochemically — without combusting the fuel

DFC-schematic_smFuel cells cleanly and efficiently convert chemical energy from hydrogen-rich fuels into electrical power and usable high quality heat in an electrochemical process that is virtually absent of pollutants.

Similar to a battery, a fuel cell is comprised of many individual cells that are grouped together to form a fuel cell stack. Each individual cell contains an anode, a cathode and an electrolyte layer. When a hydrogen-rich fuel such as clean natural gas or renewable biogas enters the fuel cell stack, it reacts electrochemically with oxygen (i.e. ambient air) to produce electric current, heat and water. While a typical battery has a fixed supply of energy, fuel cells continuously generate electricity as long as fuel is supplied.

FuelCell Energy’s Direct FuelCell® (DFC®) power plants are based on carbonate fuel cell technology. The carbonate fuel cell derives its name from its electrolyte, which consists of potassium and lithium carbonates. To produce electricity, carbonate fuel cells generate hydrogen directly from a fuel source, such as natural gas or renewable biogas, in a process referred to as internal reforming. This internal reforming process, which has been patented by FuelCell Energy, is a distinct competitive advantage of carbonate fuel cells because it allows readily available fuels to be used.


Typical multi-megawatt DFC® power plant comprised of two fuel cell modules (green). One of four fuel cell stacks within each of the modules is visible in the cutaway. The incoming fuel is processed by the mechanical balance of plant (gray). The electrical output is processed by the electrical balance of plant (blue).

As illustrated in the diagram on this page, fuel is supplied to the fuel cell stack where methane (CH4) from the fuel is internally reformed to create hydrogen (H2) and carbon dioxide (CO2). Spent fuel exits the anode and is consumed to supply oxygen (O2) and CO2to the cathode. Heat and water vapor (H2O) exit the cathode. The resulting electrochemical reactions in the fuel cell anode and cathode produce direct current (DC) power, which is then converted to alternating current (AC) power by the electrical balance of plant. The cathode exhaust supplies heat to warm the incoming fuel and externally to the customer for facility heating and cooling or for making steam.

Because there is no combusting of fuel, virtually no harmful emissions are generated by the fuel cells. This results in power production that is almost entirely absent of nitrogen oxide (NOx), sulfur dioxide (SOx) or particulate matter (PM).

The fuel cell power plant is composed of the fuel cell stack or, for multi-megawatt power plants, a fuel cell module that contains multiple stacks as illustrated in this graphic that shows one of four fuel cell stacks in the module [modules are green]. The incoming fuel is processed by the mechanical balance of plant [MBOP is grey]. The electrical output is processed by the electrical balance of plant [EBOP is blue].