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• The study investigates HRES sizes to achieve NZEB status for a hotel building. • An optimization analysis of a hotel's grid-connected HRES is presented. • The PV/wind grid-connected system has the lowest NPC and LCOE. • The electricity price of the proposed HRES, at 2.1 ¢/kWh. • The Egypt's retail electricity prices of 6.9 ¢/kWh. The tourism sector is a key source of national income, and the use of renewable energy resources promotes green and sustainable tourism. In addition, ensuring a reliable supply and efficient use of clean energy is a primary objective of Egypt's Vision 2030, as it has a significant impact on the sustainable development and growth of the tourism sector in Egypt. Net-zero energy buildings (NZEBs) are a promising decarbonization effort as they reduce energy consumption while increasing the share of renewable energy. Therefore, it is worth investigating the opportunities for NZEBs applications in tourism sector. This paper presents an optimization analysis of a hotel's grid-connected hybrid renewable energy system (HRES) based on its technical, economical, and environmental prospects. Seven scenarios are considered for on-site generation to match the energy requirements of the specific hotel building. The proposed hybrid systems incorporate photovoltaic (PV), wind turbine (WT), and biogas generators into a grid-connected system for supplying power to a tourist hotel. The size of the microgrid system is optimized to decrease the net present cost (NPC) and levelized cost of electricity (LCOE). The results reveal that the PV/wind grid-connected system, with renewable energy generators consisting of 143 kW of photovoltaic modules and one 20 kW wind turbine with a hub height of 18 m, has the lowest NPC and LCOE. This hybrid energy system has a net present cost of 388 k$, which is significantly lower compared to the electricity grid's cost of 873 k$. The electricity price of the proposed HRES, at 2.1 ¢/kWh, is highly competitive with Egypt's retail electricity prices of 6.9 ¢/kWh. Moreover, grid-connected HRES can lower the pressure on the electricity grid arising from the feed-in of electricity from HRES. Furthermore, the proposed HRES will help slow climate change by reducing GHG emissions and fossil fuel usage. Finally, this study will provide valuable guidance for the practical application of NZEBs in Egypt as well as similar global zones. [ABSTRACT FROM AUTHOR]

• Environmental life cycle impacts are assessed for current and future heating. • Electric air source heat pumps are the lowest-impact option to decarbonise heating. • Boilers using H 2 from natural gas with carbon capture cannot achieve Net Zero. • Boilers using hydrogen from electrolysis have the highest impacts in 17 categories. • The proposed 2050 Net Zero heating mixes reduce GHG emissions by 84–94% per kWh. Heating and hot water within buildings account for almost a quarter of global energy consumption. Approximately 90% of this heat is derived directly from the combustion of fossil fuels, primarily natural gas, leading to the unabated emission of carbon dioxide. This paper assesses the environmental sustainability of a range of heating technologies and scenarios on a life cycle basis. The major technologies considered are natural gas boilers, air source heat pumps, hydrogen boilers and direct electric heaters. The scenarios use the UK as an example due to its status as a major economy with a legally-binding net-zero carbon target for 2050; they consider plausible future electricity and natural gas mixes, including the potential growth of domestic shale gas. The environmental impacts are estimated using ReCiPe 2016. Current gas boilers have a climate change impact of 220 g CO 2 eq./kWh of heat, which could fall to 64 g CO 2 eq./kWh for boilers fuelled by hydrogen derived from natural gas with carbon capture. Heat from electric air source heat pumps or hydrogen from electrolysis can achieve net zero with a decarbonised electricity mix, but electrolysis has the highest energy demand of all options which leads to the highest impacts across 17 of the 19 categories. Despite their high carbon emissions, gas boilers remain the lowest impact option across 12 categories as they avoid the impacts related to electricity generation, including metal depletion, toxicities and eutrophication. By 2050, the best performing scenario sees the climate change impact of the heating mix fall by 95%; this is achieved by prioritising electric air source heat pumps without hydrofluorocarbon refrigerants, alongside demand reduction. The results show that, if infrastructure and financial challenges can be overcome, there are several viable decarbonisation strategies for heating, with heat pumps offering the most environmentally sustainable option of those considered here. However, increased renewable electricity demand may worsen some environmental impacts compared to natural gas boilers. [ABSTRACT FROM AUTHOR]