Joseph Wyatt Jr., age 17, of Nashua$ N.H., for his question:

HOW DOES A FUEL CELL WORK?

A fuel cell is an electrochemical device 1n which the energy of a chemical reaction is converted directly into electricity. Unlike an electric cell or battery, a fuel cell does not run down or require recharging. It operates as long as the fuel and an oxidizer are supplied continuously from outside the cell.

A fuel cell consists of a platinum coated cathode and anode, which are separated by a thin porous membrane that contains an acid or alkaline electrolyte. The membrane is permeable to ions, but not to atoms or molecules.

The most commonly used fuel is hydrogen gas, but hydrazine, ammonia and alkali metals also have been used successfully. Oxygen (in pure form or from air) serves as the oxidizer.

Theoretically, fuel cells are capable of converting chemical energy into electrical energy with nearly 100 percent efficiency, superseding by far the efficiency of heat engines (steam turbines or internal combustion engines) used in conventional electrical generation. Consequently, intensive research is being conducted to achieve large scale electricity production by fuel cells.