Waste heat utilization from internal combustion engines for power augmentation and refrigeration

Abstract

More than half of the input fuel energy to marine engines, tractive diesel engine, and electricity generators is wasted as exhaust and cooling water heat, at temperatures sufficient to generate power, refrigeration, and heating. This motivates waste heat recovery (WHR) from diesel engine for generating power by using organic Rankine cycle (ORC) systems and by providing refrigeration using absorption refrigeration systems (ARS) and adsorption cooling system (ACS). Recovery of engine waste heat by ORC was evaluated to result in a 5–11.3% reduction of its specific fuel consumption and in an increase of about 5% of the engines' thermal efficiency. Use of adsorption systems energized by WHR attains a coefficient of performance and specific cooling power of 0.125–0.6 and 0.016–0.6 kW/kgad, respectively. Use of WHR for ORC-ARS systems has improved heat recovery by 3% and exergy efficiency by 13%, over those of ORC by itself. The influence of integration of these heat recovery systems on the engine emissions was found to be negligible, and the associated increase of the engine backpressure was found to be below the manufacturers’ permissible value. The payback period of using WHR with diesel engines was found to be 2–6 years. It is recommended to conduct comprehensive economic feasibility analyses that consider the ongoing efforts for lowering carbon emissions, future carbon taxes on emissions, and potential changes in the cost of fuel, as well as studies for ensuring long-term high performance and robustness of the required WHR heat exchangers.