An off-grid single utility micro-cogenerator fed with biogas

In the paper is discusses the project, the design and overall performance of a micro-cogenerator prototype of 2.0 kW of electric power and about 5.0 kW of thermal power, suitable for single off-grid applications and fuelled by gas produced from biomass anaerobic digestion. This unit is based on a previous prototype designed and developed at Istituto Motori CNR of Italy and it has been conceived specifically as a local individual off-grid energy platform, born to be mated with small biomass reactor, which need part of the heat produced by the internal combustion engine to have a stable and efficient behaviour. The adopted internal combustion engine maintains many technical solutions and constructive elements already experimented in previous prototypes, the unit has been modified in order to be fuelled by natural gas with partial methane content, or with LPG when necessary. The generation system is a permanent magnet generator fed by a low cost inverter which can offer very high efficiency and a reasonable bulk and weight and gives to possibility to include an electric energy storage to compensate service discontinuity. The proposed cogeneration unit has in cost reduction, durability, low noise/vibration and a good electric efficiency the most important achieved objectives. It is very flexible in terms of gas supply and in respect of the electric needs of a generic utility, representing a very smart way for energy conversion in many situations when electricity couldn´t be easily produced because of fuel availability and a cheap way to reach the full utilization of fuel energy together with a significant CO₂ reduction.