Various forms of energy, such as mechanical, electrical, and/or heat energy are produced by an energy conversion mechanism which includes a spool, the spool including a shaft on which a compressor and turbine are mounted. A generator is operably connected to the energy conversion mechanism for converting mechanical energy thereof into electrical energy. Fuel and air are supplied separately to the compressor. A regenerator type heat exchanger has a cold side for conducting compressed air traveling from an outlet of a compressor to an inlet of the microturbine, a hot side for conducting hot waste gas from the energy conversion mechanism, and a rotary core movable sequentially through the cold and hot sides for absorbing heat in the hot side and giving up heat in the cold side. A catalytic combustor combusts the fuel at a location upstream of the turbine. During start-up, the catalytic combustor is preheated independently of the heat exchanger by an electric heater.