Experimental fusion power reactor ohmic heating energy storage

The Ohmic Heating (OH) Systems for all the Experimental Power Reactor (EPR) designs to date have used temporary energy storage to assist in providing the OH current charge required to build up the plasma current. The energies involved (0.8 x 10 to the 9th J) are so large as to make capacitor storage impractical. Two alternative approaches are homopolar dc generators and ac generators. Either of these can be designed for pulse duty and can be made to function in a manner similar to a capacitor in the OH circuit and are therefore potential temporary energy storage devices for OH systems for large tokamaks. The study has compared total OH system costs using homopolar and ac generators to determine their relative merits. The total system costs were not significantly different for either type of machine. The added flexibility and the lower maintenance of the ac machine system make it the more attractive approach.