The electric boiler consists of an outer and inner container. High-voltage electrodes are suspended inside the inner container, which is electrically insulated from the outer vessel. Alternating current flows between three electrodes using the water as the current path. The electrical resistance of the water creates heat in the water itself such that steam is generated. As the water is boiled off to generate steam the insulated inner chamber is continuously replenished with water from the outer vessel via the circulation pump. The output of the boiler is proportional to the water level of the electrodes.
Unlike a conventional fired boiler, no hot surfaces are required as the heat is generated directly in the water itself. Electric boilers of this type operating at up to circa 30 bar g have been in operation since the 1950s. The electric boiler at Aughinish will be fed by renewable electricity at 22kV. It is a 25MW boiler producing 40 tonnes per hour of high-pressure steam at 52.5 bar g and 330degrees Centigrade. An electrical superheater is fitted on the boiler outlet to increase the temperature of the saturated steam.
The electric boiler to be installed at Aughinish is a first-of-its-kind high-pressure boiler: Low-pressure electric boilers operating at up to 30 bar g have been in operation since the 1950s, this first-of-its-kind boiler will produce steam at 52.5 bar g and is rated at up to 62 bar g.
This innovative high-pressure boiler has been developed between Parat and Equinor.