Abstract

Internal combustion Rankine cycle (ICRC) power plants use conventional fossil fuels, but oxygen rather than air as the oxidant. They use recycled water and its vapor in place of nitrogen to control combustion temperatures and to act as the dominant component in the working fluid for the cycle thermodynamics. High efficiency and specific power output can be achieved with this cycle, but importantly, the exhaust products are only CO2 and water vapor: the CO2 can be captured cheaply on condensation of the water vapor. Capture and geo-sequestration of CO2 from the combustion of fossil fuels is seen as being one of the most promising routes for the sustainable mitigation of greenhouse gas (GHG) emissions. Here we investigate the feasibility of using a reciprocating engine version of the ICRC cycle for automotive applications. The vehicle will carry its own supply of oxygen and store the captured CO2 . On refueling with conventional gasoline, the CO2 will be off-loaded and the oxygen supply replenished. Cycle performance is investigated on the basis of fuel-oxygen-water (FOW) cycle calculations. Estimates are made for the system mass, volume and cost and compared to other power plants for vehicles. Market opportunities in the forthcoming carbon controlled economy are assessed. It is found that high thermal efficiencies can be obtained and that huge increases in specific power output are achievable. The overall power-plant system mass and volume will be dominated by the requirements for oxygen and CO2 storage. Even so, the performance of vehicles with ICRC power plants will be superior to those based on fuel cells and they will have much lower production costs. Operating costs arising from supply of oxygen and disposal of the CO2 are expected to be around 20c/l of gasoline consumed and hence likely to be a much less expensive option than bio-fuels. On a carbon-control basis the operating costs are estimated to be about $25/tonne of carbon controlled and this is much less than the projected price of $80/tonne that is forecast for carbon trading. This could make ICRC vehicles much less expensive to operate than conventionally powered vehicles that pay for carbon credits. Market entry for this new system will be eased by the fact that it uses existing technology in its development and mass production. Over all, ICRC engines are seen to be a potentially competitive option for the powering of motor vehicles in the forthcoming carbon-controlled energy market.”