A Benign, Small-scale Power Unit for the Arctic: The Carnot Cycle Concept

Small amounts of useful power may be generated in polar or subpolar regions during the winter period by placing a heat engine between a large body of water (near PC), acting as a heat source, and the atmosphere (near -25OC), acting as a heat sink. The scheme consists of a fuelless modular system operating on the Carnot cycle. Power is extracted by a reciprocating vapour engine drawing saturated vapour from a water-heated evaporator and exhausting to an air-cooled condenser from which nearly saturated liquid is returned to the evaporator using a reciprocating feed pump. The thermal performance model incorporates both the engine cycle power and the parasitic losses, the latter being incurred as a result of circulating the working fluid (ammonia), pumping water through the evaporator and blowing air through the condenser. Curves indicate power levels in excess of 1 kW, with thermal efficiencies around 5%. The power curves show a maximum with respect to speed. The principal difficulties with this scheme are in heat exchanger design in near-freezing water. The principal advantages are small power levels, flexibility through modular construction and reduction of the capital and operating costs associated with the supply of energy to northern