Combined heat and power (CHP) systems which are able to produce heating and power simultaneously, are getting more attention since they have many economical and environmental benefits. CHP systems for buildings are an important application of CHP on various systems designs. In this study, we have investigated a CHP system applicable for the building of Azad University of Shahrood. The prime mover utilised here is an internal combustion engine (ICE) with natural gas fuel, and the CHP system is evaluated under different sizes of engine, between 200 kW to 1,800 kW. Based on the cost analysis, fuel consumption and emission deducting, an evaluation factor indicator (EFI) is defined which can be applied to select an ideal engine for the proposed CHP system. The lower the EFI, the better option for the engine sizes can be achieved. The result shows that a gas engine with the size of 1,200 kW has the lowest EFI factor. Regarding this size of engine, a CHP system is designed and it found that the CHP system is economically viable for the operation period, and the return on investment will be higher than the interest rate.
Keywords: CHP systems, internal combustion engines, ICE, fuel consumption, emissions reduction, economic analysis, engine size, combined heat and power, environmental impact, university buildings, natural gas, cost analysis