• Life Cycle Assessment
• Power-to-X
• Hydrogen
• Electrolyzers
• Fuel Cells
• rSOC
• PEM
• Alkaline Cells

Power-to-Hydrogen-to-Power pathways offer a support for the transition to a low-carbon economy (LCE). The intermittent nature of the power supply using non programmable renewable energy sources (RES) highlights the need of storage strategies to achieve sustainability goals. This study aims to find out which of the proposed pathways is the best solution. Each system is based on a different technology among Alkaline cells (ACs), Polymer Electrolyte Membranes (PEMs) and Solid Oxide cells (SOCs). The function of these different pathways is the same: the conversion of electricity into hydrogen (H2), its compression and storage phases and subsequently its fuelling to a fuel cell to produce electricity. A key point of this study is that what appears to give important environmental benefits today may not be valid in a long-term perspective. Life Cycle Assessment (LCA) is a technique developed to provide insights into the realistic environmental footprint of a technology. This analysis includes every stage of the system’s lifetime from its manufacturing process to the waste treatment due to its disposal. This is also known as "cradle-to-grave" analysis and it helps to define the overall emissions throughout all the unit processes which are part of a product or service. The results indicate that the Solid Oxide technology has the best performance from a life-cycle point of view and long-term perspective. The rSOC (reverse solid oxide cell) product system has the best performance for each impact category. The recycling processes of materials and switching the energy source to wind power show to improve the life cycle impact assessment for each product system. For Italy, the electricity from all the product systems has lower climate change impact than the electricity from the grid: they are already viable solutions. In addition, the three pathways were applied one at a time to a reference building to see the evolution in one year of the CO2 emission profile of this building due to the different sources of electricity (grid, PV panels and fuel cell). The reference building for the CO2 emission profile is the EPFL’s building in Sion: it has a PV system on its flat roof. The over-production and under-production profiles for the PV panels system were provided. A Python code simulates the system wherein electricity surplus is converted to hydrogen, compressed, stored in a tank and subsequently used to generate electricity to balance building’s energy request, considering components’ efficiencies and storage capacity, too. Total CO2 emission values are influenced by two parameters: the round-trip efficiency and the climate change impact associated with each energy source. The reverse Solid Oxide technology shows promising potential for the global transition to a more sustainable economy.