The district heating system of the municipality of Ferrara: reduction of pumping energy consumption

District heating is an effective way to increase the share of renewables in the thermal energy sector. In this context, low enthalpy geothermal resources are particularly suitable to supply energy for space and domestic water heating. The district heating of the municipality of Ferrara in northern Italy uses a geothermal reservoir at a depth of 1 km supplying hot water at 100\ub0C. Besides geothermal energy, the overall thermal demand is covered by a CHP plant fed by municipal solid waste, and by auxiliary natural gas boilers. A control system has been recently implemented to supply a high level service to the customers connected to the district heating, searching for the maximum energy saving by reducing the supply pressure of the pumping station. The paper describes the main design and operational features of the district heating system, and shows how an improved operating strategy can reduce the power consumption. The improved pressure management consists in monitoring the differential pressure in many substations, especially those located at the periphery of the network, and adjusting the water supply pressure in order to fulfil the minimum differential pressure at the most critical substation. Experimental data measured in the first months of operation show an energy saving in the order of 30%