Natural gas heating technologies: energetic, environmental and economic analysis of modern local technologies in comparison with district heating

Generally, a CHP plant coupled with district heating is considered more efficient than traditional local heating systems from an economic and environmental point of view.This is certainly true for municipal waste CHP plants but for plants fuelled by natural gas the important developments intervened in these last years regarding both boilers (premixed and modulating burners, condensing boilers, etc.), mechanical vapour compression and absorption heat pumps can change the traditional view. At the same time also district heating plants improved. Therefore it is worth to analyse the whole matter comparing advantages and disadvantages of the different alternatives with their wide differentiation among them.The paper reports on the analysis of major district heating natural gas based technologies (vapour and gas turbines, internal combustion engine, combined cycles); the cost of the heat power produced in these plants is compared to the cost of producing the same quantity of electrical energy by a reference GTCC- Gas Turbine Combined Cycle (actually the most efficient technology for pure electrical production) and the cost of heat production by modern local heating technologies using natural gas as fuel (condensing boilers, electrical, gas engine and absorption heat pumps). Regarding energy efficiency and polluting emissions, modern local heating turns out to be more efficient than district heating for most CHP technologies. However, it is not the same from the economic point of view, because in Italy natural gas used by cogeneration plants is subjected to a taxation much lower than local heating technologies.