The forthcoming implementation of national policies towards hydrogen blending into the natural gas grid will affect the technical and economic parameters that must be taken into account in the design of building heating systems. This study evaluates the implications of using hydrogen-enriched natural gas (H₂NG) blends in condensing boilers and Gas Adsorption Heat Pumps (GAHPs) in a residential building in Rome, Italy. The analysis considers several parameters, including non-renewable primary energy consumption, CO₂ emissions, Levelized Cost of Heat (LCOH), and Carbon Abatement Cost (CAC). The results show that a 30% hydrogen blend achieves a primary energy consumption reduction of 12.05% and 11.19% in boilers and GAHPs, respectively. The presence of hydrogen in the mixture exerts a more pronounced influence on the reduction in fossil primary energy and CO₂ emissions in condensing boilers, as it enhances combustion efficiency. The GAHP system turns out to be more cost-effective due to its higher efficiency. At current hydrogen costs, the LCOH of both technologies increases as the volume fraction of hydrogen increases. The forthcoming cost reduction in hydrogen will reduce the LCOH and the decarbonization cost for both technologies. At low hydrogen prices, the CAC for boilers is lower than for GAHPs; therefore, replacing boilers with other gas technologies rather than electric heat pumps increases the risk of creating stranded assets. In conclusion, blending hydrogen into the gas grid can be a useful policy to reduce emissions from the overall natural gas consumption during the process of end-use electrification, while stimulating the development of a hydrogen economy.

Offshore wind energy is a strategic pillar for achieving European climate neutrality targets, yet its deployment faces geographical and technological constraints. Fixed-bottom offshore wind (FBOW) has reached industrial maturity in shallow waters but is limited by depth. Floating offshore wind (FOW) emerges as a solution for deep-water contexts, unlocking vast resources and enabling integration with advanced energy systems such as power-to-X. This analysis conducts a systematic comparative analysis of FBOW and FOW technologies through a techno-economic framework based on six key parameters: installation depth, turbine power, capacity factor (CF), CAPEX, OPEX, and levelized cost of energy (LCOE). A review of 313 sources, reduced to 61 after applying selection criteria, reveals that FOW operates at depths up to 1550 m, with higher average turbine capacities (16 MW vs. 11 MW for FBOW) and superior CF (38% vs. 22%). Economic results show combined averages CAPEX of 2.43 M$/MW, OPEX of 22.7 k$/MW/year, and LCOE around 120 $/MWh, with significant variability. While FOW currently exhibits higher initial costs, its scalability and operational advantages, such as tow-to-shore maintenance, suggest strong potential for cost reduction. These findings highlight FOW as essential for exploiting deep-water wind resources and achieving long-term decarbonization goals in regions like the Mediterranean.

The revised Energy Performance of Buildings Directive (EPBD) has introduced ambitious targets aimed at accelerating the decarbonization of the building sector. In parallel, the forthcoming implementation of the Emission Trading System for buildings and road transport (ETS2) in January 2027 adds a further dimension to the policy landscape. This study investigates three renewable energy retrofit strategies (Scenarios A, B, and C) for a hotel building in northern Italy, assessing their effectiveness in meeting the decarbonization objectives set by the EPBD and ETS2. Scenario A couples photovoltaic generation with an existing gas boiler, Scenario B integrates PV with an electric heat pump for space heating, and Scenario C implements the full electrification of both heating and domestic hot water. The results of the three scenarios are evaluated using selected metrics, such as renewable primary energy consumption (EPren), non-renewable primary energy consumption (EPnren), CO₂ emission (CO₂), carbon avoidance cost (CAC), levelized cost of energy (LCOE), net present value (NPV), and Emission Trading System (ETS)2. The results show that PV deployment alone provides economic benefits but yields limited reductions in CO₂ emissions and non-renewable primary energy consumption due to continued reliance on natural gas. The introduction of a heat pump significantly enhances environmental performance, with reduced fossil fuel consumption, increased renewable energy use, and improved cost-effectiveness of carbon avoidance. The ETS2 has no impact in the case of full electrification, as fossil fuel consumption is completely eliminated. Full electrification achieves the greatest emission reductions and the lowest non-renewable primary energy demand while offering the strongest long-term economic performance. Overall, the analysis demonstrates that combining PV systems with building electrification is essential to achieving deep decarbonization, and that fully electrified configurations present the most robust pathway for compliance with emerging ETS2 policies.