High Renewable Energy Sources (RES) share in energy systems entails environmental advantages in its use but drawbacks in its distribution, management and effectiveness. The interconnection between electricity, heat and transport sector seems to be a comprehensive answer. Its actual link is on-going and, currently, involves electricity and heat. Indeed, Power to Heat (P2H) is the strategy of meeting the heating demand by supplying electricity to feed Heat Pump (HP). Their higher efficiency compared to fossil fuel boilers requires a further check in the quality of the heating demand to meet, i.e. the temperature levels. Great part of current building stock calls for High Temperature (HT) Heat which is not affordable by HP maintaining their Coefficient of Performance. To face this issue, RES can be used to produce synthetic fuels for feeding existing energy systems, the so-called Power-to-Gas option. In this way, greening the fuel supply can be seen as the best option for meeting HT heating demand while, Medium and Low Temperature are met by HP. Therefore, two technological scenarios, P2H and its combination with P2G, are presented and assessed in three reference Urban Energy Systems. The authors investigated on the impact of RES share increase from 25% up to 50% in the electricity mix with the objective function of Primary Energy Consumption (PEC). The outcomes of twenty-four energy scenarios, eight for each Reference City were assessed also through the value of delivered Renewable Heat. Finally, the leverage effect of P2G on the system is evaluated in terms of renewable heat contribution.

This paper deals with the role of Hydrogen enriched Natural Gas (H2NG) in Hybrid Energy Systems for energy refurbishment purposes. In detail, three different plant layout options were investigated. A photovoltaics (PV) array and two-stage electric heat pump (EHP), a hybrid photovoltaic thermal solar collectors combined to gas heat pump (GHP) fuelled with H2NG, and a CHP fuelled with H2NG connected to a two-stage EHP were compared. The required receiving surfaces of PV array were estimated for three different direct normal irradiation (DNI) values in Italy in order to assess how the available roof surface affects the layout choice. A sensitivity analysis was carried out with varying the building power to heat ratio (PTHR) and the hydrogen volumetric fraction in the H2NG mixtures to assess the primary energy consumption (PEC) and renewable energy fraction. When feasible, the PV + EHP shows the best performance in terms of PEC with a solar energy share equal to 65%. In other cases, the PV/T + GHP fuelled with H2NG @30%vol. can be suitable for PTHR higher than 0.2 approximately. Furthermore, the third layout CHP + EHP is not competitive with the other solutions but, it is the best option where no roof surfaces are available for PV or PV/T installation.

Buildings with architectural constraints and recognized historical values entail careful design process, especially, when the aim is to improve the energy efficiency. Foreseeable interventions consist of preservation and improvement of building envelope energy performance as well as the adaptation of the built environment to modern use and its accessibility. The compatibility between the aforementioned constraints and its future more sustainable use represents the crucial challenge. In this paper, feasible interventions on the dwellings from the 40’s in Borgata Trullo, Rome were designed and analyzed. Public housing asset is an interesting environment to test a sustainable holistic approach due to its homogeneity in terms of building technology solutions and typologies. Furthermore, the absence of public funding made more difficult the ordinary and extra-ordinary maintenance processes. So, the approach accounts for the age of the building along with the subsequent reduced energy performance as well as the architectural values to preserve. The proposed energy retrofitting measures are related to the building envelope, in the installation of insulation layers, the substitution of windows and improvement of HVAC systems to enhance energy efficiency. Besides the case study, design guidelines were presented to help the stakeholders in compatible and sustainable interventions. New HVAC solutions showed high gains in energy saving even if building envelope modifications were limited by the willing to preserve the cultural heritage values. Therefore, a virtuous restoration can address effectively current energy efficiency targets.

This paper deals with the potential role of new hybrid CHP systems application providing both electricity and heat which are compatible with the building architectural and landscape limitations. In detail, three different plant layout options for high temperature heat production along with the electricity generation were investigated and compared each other. To do so, conventional natural gas CHPs and back up boiler, two-stage Electric Heat Pumps (EHPs) and trans-critical CO2 electric heat pump (CO2-HP) have been considered as reference technologies to build hybrid systems. In addition, hybrid solar collectors (PV/T) thermal output, along with the recovered low-grade heat from CHP exhaust gas, flowing to the stack, have been used as the CO2-HP low temperature driving source.