Among the several typologies of storage technologies, mainly on different physical principles (mechanical, electrical and chemical), hydrogen produced by power to gas (P2G) from renewable energy sources complies with chemical storage principle and is based on the conversion of electrical energy into chemical energy by means of the electrolysis of water which does not produce any toxic or climate-relevant emission. This paper aims to pinpoint the potential uses of renewable hydrogen storage systems in Europe, analysing current and potential locations, regulatory framework, governments’ outlooks, economic issues, and available renewable energy amounts. The expert opinion survey, already used in many research articles on different topics including energy, has been selected as an effective method to produce realistic results. The obtained results highlight strategies and actions to optimize the storage of hydrogen produced by renewables to face varying electricity demand and generation-driven fluctuations reducing the negative effects of the increasing share of renewables in the energy mix of European Countries.@en

This paper focused on the hydrogen-methane mixtures (H2NG) implications on end-user devices such as boilers, so as to provide a useful tool for maintenance operators. In detail, according to current standards, H2NG blends characteristics parameters for boilers combustion efficiency measurement are calculated. Then, the Ostwald chart for each blend is built by the analytical procedure and is plotted. Additionally, the chemical equations as well as the blended gas characteristic values are computed in order to implement them within software library of commercial gas analysers. Indeed, they are commonly based on Ostwald combustion equation for correlating CO, CO2 and O2 concentrations. The results can be applied to analyze conventional and widespread domestic boilers fueled with H2NG addressing all of the technical implications for their performance certification when they are operating also in condensing mode. Air excess and relative humidity are chosen as variables to evaluate their effects on boilers performance. The oxygen concentration ranges from 0% vol. up to 15% vol. The specific heat values drop non-linearly down for each mixture, showing a maximum reduction equal to 9.825%, for H2NG@30%. A maximum Energy Fraction of Condensation (EFC) enhancement of 0.9% points is noticed for H2NG@30% vol. While, the highest EFC gain, 4.8% points, occurred at relative humidity of 90% compared to the assumed reference values for calculations.@en

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.@en

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.@en

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.@en

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.@en

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.@en