Comparison of district heating CHP and distributed generation CHP with energy, environmental and economic criteria for Northern Italy

District heating CHP (combined heat and power) and distributed generation CHP have been compared in this paper on the basis of energy, environmental and economic criteria, and a deviation index has been proposed to establish, in aggregate form, what the improvement margins are for a given design choice. Three technologies that are suitable for both district heating and distributed generation have been chosen: a mature market technology, internal combustion engines, and recent entry market technologies, that is, microturbines, and fuel cells. The calculations have been based on the real heating load curve of a town in Northern Italy at the current market conditions: power and fuel prices, tax exemptions relative to cogeneration, white certificates, etc. Two scenarios have been considered: maximum energy saving and maximum present value saving. In the first scenario, district heating obtained better energy and CO2 savings than distributed generation, but critical values have been observed for local nitrogen oxides (NOx) and particulate matter emissions, when internal combustion engines are adopted. In the second scenario, all the options offer positive energy, environmental and economic savings, and the payback times are significantly reduced compared to the previous scenario. The district heating options show the best present value savings and payback times, while distributed generation is only economically viable when internal combustion engines are adopted. Microturbines leads to the best NOx savings. Finally, the comparison with an alternative separate production of heat and power has shown that there are scenarios where none of the analysed technologies leads to a significant improvement. All this information, analysed together, provides a sort of map for policy makers through which they can better orientate themselves among the different scenarios. (C) 2014 Elsevier Ltd. All rights reserved.