fuelcell

Fuel cells are electrochemical devices that convert the chemical energy of a fuel and an oxidant directly into electrical energy, with heat and water as byproducts. They consist of an anode, a cathode, and an electrolyte that conducts ions. Fuel oxidizes at the anode, releasing electrons that flow through an external circuit to the cathode while ions move through the electrolyte to complete the reaction.

There are several chemistries, including polymer electrolyte membrane (PEMFC), solid oxide (SOFC), phosphoric acid (PAFC), molten carbonate (MCFC), and direct methanol (DMFC) fuel cells. PEMFCs operate at 60-80°C and primarily use hydrogen. SOFCs function at 700-1,000°C and can reform hydrocarbons internally. PAFCs and MCFCs target stationary power, with MCFCs tolerant of natural gas. DMFCs feed methanol directly to the cell. The choice depends on efficiency, cost, fuels, and duty cycle.

Electrical efficiencies typically range from 40-60%, with higher total energy efficiency in cogeneration setups. Fuel cells produce minimal pollutants at the point of use, especially when hydrogen is produced from low-carbon sources. They are used in stationary power plants and backup power, portable devices, and transportation, including fuel cell electric vehicles and buses.

Major challenges include cost and durability of catalysts, hydrogen production and distribution, fuel purity requirements, and cold-start performance for some types. Ongoing research aims to reduce precious metal loading, improve membranes and electrolytes, and better integrate with renewable energy. The concept dates to the 19th century, with modern development accelerating in the late 20th century for space and civilian power.