Wooden Biomass Cogeneration Coupled with Groundwater Heat Pumps and Photovoltaic Systems: the Case Study of a New Low Carbon District in Northern Italy

In the framework of the de-carbonization of the building sector, which can be achieved also by new generation district thermal plants and renewable sources integration, the case of a new nearly zero energy district is presented. After the evaluation of the energy needs, an innovative district thermal plant was designed to be integrated with groundwater heat pumps (GWHP) and solar photovoltaic (PV) systems. The core is a biomass boiler coupled with a small combined heat and power (CHP) unit with a twin-screw steam expander (TSSE). Heat produced by the CHP satisfies a consistent fraction of space heating and domestic hot water (DHW) needs during winter season. GWHPs coupled with PV satisfy remaining thermal needs in winter and the entire thermal needs in mid-seasons and in summer period. The outcomes demonstrate the benefits of the combination of a biomass CHP with GWHPs and PV with a significant increase of renewable energy share with respect to conventional applications in nearly zero energy districts.