Green Hydrogen Distributed production

Nowadays, environmental concerns and climate change are priority and focal issues for both international institutions and the governments of single countries. These are closely linked to the supply and consumption of energy. The key point is to implement the 'energy transition', through which production and dependence on fossil fuels is increasingly reduced and, conversely, the use of renewables and related technologies is stepped up. Thus, realising the process of 'decarbonisation' with a consequent reduction in CO2 emissions. In this perspective, the widespread application of renewable energy source (RES) technologies is crucial, but not sufficient. Indeed, renewables have a weakness in that they do not guarantee continuity of supply as they depend on weather and climate conditions. This contrasts with the need, given the growing demand for energy, to be able to rely on a secure and affordable supply, both in production activities and in household consumption. Therefore, energy storage systems are indispensable to balance surpluses and shortages of supply. With respect to the latter, hydrogen is considered an outstanding storage system for renewable energies, a viable alternative to batteries, because it can be generated from water via electricity and returned to water after being used. At the moment, the main problem concerns green hydrogen, i.e. hydrogen produced by electrolysis using only renewable sources, as it entails a high production cost, two to three times more than hydrogen produced from fossil fuels (e.g. steam reforming of methane). Consequently, many efforts are being made worldwide to reduce the production costs of green hydrogen. Almost all projects are aimed at centralised large-scale production and/or cost reduction of electrolysers by acting on the development of materials, components and stacks. It should be noted that generally, when evaluating the production costs of green hydrogen, only the hydrogen as a product is considered, neglecting the by-products resulting from its production and application, which have a considerable impact on the final energy costs. In the present work the authors propose a different approach that stems from an analysis of the levelized cost of energy storage (presented at Hypothesis XI, Toledo 2015) followed by an analysis of the potential hydrogen impacts on energy and fuel markets. The focus was on the by-products of the green hydrogen cycle, oxygen and heat, were considered to reduce the cost of generating green hydrogen, i.e. increasing the economic efficiency of the production cycle. The analysis considered the technologies available today and the market costs for the calculation of the CAPEX and OPEX. In particular, the small and medium-scale distributed production of green hydrogen is proposed for the design of integrated energy systems according to the concept of polygeneration. This approach is supported by the results of case study simulation developed in recent years. The net present value (NPV) was used as a simple indicator of profitability. In particular, the valorisation of green oxygen, for small and medium-sized enterprises and hospitals, and the recovery of waste heat for residential applications were considered. The results indicate that oxygen valorisation could be really effective, while waste heat valorisation is not economically viable today but have potentialities for the future. This is without considering the monetization of socio-economic benefits such as the reduction of CO2 emissions and the resilience of services to energy problems. In this article we would like to present a summary of our previous results, already published, and some new insights that are in the publication phase, proposing a hydrogen-based polygeneration system adaptable to different types of applications. Acknowledgment The analyses reported here were carried out in the context of some projects of the VISTE research group (Evaluation of the socio-economic impacts of environmental and energy technologies) of the CNR-ITAE. The authors thank Prof. Massimo Santarelli and Mr. Giuseppe Baiardo (Polytechnic of Turin, Italy) for their collaboration.