Compact automatic controlled internal combustion engine cogeneration system based on natural gas with waste heat recovery from the combustion process

This paper is related to cogeneration, or combined heat and power systems (CHP) and its development, which is based on an already used and low-cost internal combustion engine ICE with a fuel system redesigned for the injection of natural gas. The main role of this system is heating and electricity production and is mainly designed for small or medium-sized households or family houses. Heat is recovered from the engine's cooling circuit and its exhaust system using a special exhaust heat exchanger. The entire process is automatically controlled to keep the output heat transfer fluid at the required temperature and to keep the engine temperature within the operating range. This fluid is then used for heating the building or domestic hot water DHW. As a power generation unit - PGU, a three-phase asynchronous motor with the power of 12.5 kW was used. The theoretical charging current can be around 400 A. Part of the development is the design of control loops, which are implemented in the main control system. This control system can be connected to a smart home energy management system SHEMS and is designed for fully automatic operation. The functionality of all operating states and conditions was supported by testing and measurements. The paper includes an analysis of the energy balance from testing and measurements. The maximum overall efficiency of the CHP can reach up to 87% in operation mode, with a heating power output of 15 kW and an electrical power output of 4 kW.