Efficiency of a cogeneration plant based on a diesel engine under uneven electrical load conditions

Abstract

A feature of electrical energy is that it must be produced at a given moment as much as the consumer needs. However, the graphs of energy consumption are very uneven over the time of day. In order to cover peak loads, the highly mobile equipment, which is often less economical, is used. This equipment is operated at partial power modes, where its efficiency is markedly reduced. One of the real ways to get out of this situation can be the use of heat pumps (HP) in circuits with cogeneration units (CU) based on heat engines. In this case, it becomes possible to use the heat engine in an economical mode throughout the day, and direct excess electricity at night to the heat pump drive. The paper considers two options for the operation of a cogeneration plant based on a diesel engine in power supply schemes for an individual consumer under conditions of an uneven electrical load schedule. Wartsila 12V32 is taken as an example of a CU. Such plants are operated in different regions of the Russian Federation. The main data of the CU in the design mode are given. Diesel generator: electric power - 6000 kW, hourly fuel consumption - 1080 kg/h, thermal power - 5240 kW, exhaust gas temperature - 485 °C, effective efficiency - 0,46, fuel heat utilization factor 0,89. In the first version, the CU operates in a standard mode. This ensures the generation of electrical power in accordance with the schedule. In the second version, the CU is used in conjunction with the HP to obtain additional thermal power. Calculations have shown that by including a heat pump in a cogeneration unit operating in an uneven electrical load schedule mode, it is possible to ensure that the diesel engine operates at maximum efficiency during the whole day and to increase the fuel heat utilization rate by 17-20 %.