Green hydrogen based poly-generation systems, potentialities and case study financial analysis

Poly-generation is meaning as the generation of different forms of energy by the same machine/system. This concept is applied in distributed generation from renewable energy sources (RES) for increasing the conversion efficiency, in particular looking at near-zero energy buildings. In this case, usually, batteries are used for storing excess RES energy production and using it during lack of energy periods. Looking at hydrogen, nowadays, it is worldwide accepted that storing RES power as hydrogen is the best way to fulfil the expectation of a greener future and addressing the ambitious targets of greenhouse gas emission reduction. In the present work, we propose a new concept of poly-generation based on hydrogen technologies. In this new vision both energy and goods are produced from RES. In particular, we propose a poly-generation system able to supply electric energy, thermal energy (heat and cooling), and H2/O2 co-production. So that the proposed system is able to produce different forms of energy and also goods (hydrogen and oxygen) giving a new sense to the concept of RES-polygeneration. Water electrolysis powered by renewable energy sources (solar, wind, etc.) is a mature and environmentally friendly technology for large-scale hydrogen production (green hydrogen), whose main bottleneck for widespread diffusion is still related to economic concerns. In fact, based on the literature, the production cost of hydrogen from electrolysis is at least 5-6 EUR/kg, which is not competitive compared with hydrogen production by SMR (ranging from about 1.0 to 2.3 EUR/kg, according to the literature). As highlighted in our previous publications, one of the main lack in the usual calculations of green hydrogen costs is that oxygen is typically considered a not useful good and it is released in the atmosphere. In the same studies, we performed financial evaluations demonstrating that by valorising the produced oxygen it is possible to strongly reduce the production cost of hydrogen. Here, we propose a system able to produce energy (in different forms), hydrogen and oxygen. Moreover, a case study was selected for demonstrating the financial viability of this system. In the case study, a simplified system is applied to an Italian hospital and it is addressed to supplying only medical oxygen and hydrogen, opening also a new vision on the RES-health nexus. The results show that the simplified system is economically viable, moreover by this approach the production cost of green hydrogen is strongly reduced, up to less than 1 EUR/kg, becoming largely competitive with steam reforming production. Economic studies on the full system are running.