Assessing Fuel Consumption Reduction of Revercycle a Reversible Mobile Air Conditioning/ Organic Rankine Cycle System

Abstract : Regulators are imposing a reduction of fleet fuel consumption to car manufacturers due to the global warming. Among the different technologies able to improve vehicle efficiency Organic Rankine Cycle (ORC) is a promising solution. ORC systems are studied from more than 40 years, but their commercial success is hindered by the compactness and cost requirements of the automotive sector. In the attempt to overcome these limits a reversible Mobile Air Conditioning (MAC)/ORC, called hereafter ReverCycle, is developed by the CES in collaboration with PSA Group. ReverCycle is a compact system able to operate in two different modes: a standard mobile air conditioning system, when a cabin cooling need is required, or an ORC recovering mechanical energy from the waste heat of an engine cooling system. This paper presents a simulation methodology to assess ReverCycle fuel consumption gain. A system approach is developed with a global light duty vehicle model. The global model allows estimating the yearly working hours for each of the ReverCycle operating modes and to quantify the recovered mechanical energy in ORC mode. By coupling the two results it is possible to provide the fuel consumption reduction for a given climatic region. In order to be as close as possible to real driving conditions the calculation of the waste heat recovery potential is based on a WLTP cycle at different ambient temperatures. In a temperate zone the MAC activation is limited to 21% of trip occurrences. ReverCycle average fuel consumption reduction is 1.3% with cold start conditions and 2 % with hot start conditions. The reversible MAC/ORC system loses 25% of the ORC waste heat recovery potential due to MAC activation time, but there is an advantage of a significant cost and compactness reduction.