DME Fuel-Cell Hybrid System Combined with Diesel Engine for Commercial Vehicles with Electric Devices

Dimethyl ether (DME) has received a lot of attention recently as a possible alternative to diesel engines for little environmental effects and stable distribution. DME can be made from various resources in large quantities and easily transported. It has the same cetane number as that of diesel fuel and emits no smoke from diesel engines. Moreover it is also expected to be a fuel for fuel cells because much hydrogen can be obtained by steam reforming. This paper focuses on a hybrid power system for commercial vehicles with a diesel engine and a fuel cell fueled with DME as a single fuel. The system obtains a driving power by diesel engines with DME combustion and at the same time generates electricity by a fuel cell with hydrogen generated from DME reforming. The electric power can be supplied to a refrigerator or batteries. The total energy loss will be less in DME reforming by recovering the exhaust heat from the engine. It is possible to drive the system suitably on various load conditions, because the system can match a fuel cell power with an engine power for situations. Because the system is estimated to reduce emitted greenhouse gases and to have high efficiencies, the system in vehicles can be also used for an air-conditioner, an audio utility or a light for long idling stops even if the vehicles have a refrigerator.