In short, the ECAT produces the energy by fusing Nickel with Hydrogen to produce Copper. This reaction is exothermic, which means that it produces excess energy. The energy content of the Copper is less than the energy content in Nickel and Hydrogen alone – and the excess energy is in this case being released as heat energy.
The current design of the reactor is a small rectangular plate 20cm x 20cm with a thickness of about 4cm (external dimensions of reactor). The fuel, Nickel of very fine granularity + Hydrogen + catalyst, is placed in a thin layer at the center of the reactor core. The reactor is located at the bottom of a steel box (the outer hull of the E-Cat is currently at a size that can easily fit on a small table) and directly attached to the reactor is cooling elements in the form of wings. These wings are crucial as they transmit the heat generated in the reactor to the surrounding water.
There is a cold water inlet into the steel box and a warm water outlet. As the cold water flows past the reactor, the cooling elements will heat it up and the flux of the water (e.g. liters/h) dictates the difference between in and out temperature. In this way hot water or steam can be produced.
Watch the ECAT in action. Andrea Rossi explains how the measurements are made in Bologna October 6 for a public test of the E-Cat.