Feasibility Study of an Organic Rankine Cycle System Coupled to a Diesel Engine

A feasibility study has been conducted for an organic Rankine cycle (ORC) system coupled to the exhaust of a Diesel engine generator. The objective of this study was to determine the possible electrical generation of the ORC using the exhaust gas of a 78 kW diesel engine as its energy input. A thermodynamic model was developed to predict the possible electricity generation of the ORC. Using this model it was determined that the preferred working fluid for the ORC was R245ca. The calculated maximum ORC thermal efficiency was 14.3%. The net electrical power generated from the ORC was 5.36 kWe. The ORC would require no additional fuel and would not generate any additional emissions. The most cost-effective and simple means to develop a small packaged ORC system is to high volume production HVAC system components. An ORC system consisting of air conditioning system components, including a scroll expander, yielded a projected ORC efficiency of 10.7%, and a net electrical power of 4.02 kWe. The total capital cost of the ORC system was $2,140 CAD. Three engine usage scenarios were developed, with the time to payback of the initial capital cost of the ORC ranging from 12.8 to 0.58 years, depending on low or high usage.