Distributed hydrogen generation

It is a common opinion that the renewable sources play a primary role to reduce the greenhouse gas (GHG) emissions and that, according to the IEA, solar may become the largest source of low-carbon capacity by 2040 by which time the share of all renewables in total power generation reaches 40%, led by China and India. In the European Union, soon after 2030, renewables will account for 80% of new capacity and wind power becomes the leading source of electricity, due to strong growth both onshore and offshore [1]. A key issue is that electricity generation from renewables is heavily weatherdependent and this entails fluctuations causing instability of the power systems. Consequently, systems for storing energy are becoming increasingly significant. Among the evaluated solutions, hydrogen is currently considered to be one of the key enabling technologies allowing future large scale and long term green storage of renewable power to be combined, for instance, with the well-established pumped hydro storage. Another issue, today not completely addressed, is that with the aim of reaching 100% electric power from RES, will be necessary to install much more power and to distribute these installations on as large as possible geographic area. This will allows to have low cost electricity also locally, creating the opportunity for "distributed hydrogen generation". At present, hydrogen is mainly produced from fossil fuels: about 96% of the world's hydrogen production [2]. Steam methane reforming (SMR) is the most widely used route for producing hydrogen from natural gas. Other thermochemical conversion technologies starting from coal, oil, biomass-derived fuels, biomass and wastes [3]. However all these approaches are not GHG-free. The Power-to-Gas concept, based on water electrolysis utilizing electricity derived from renewable energies (wind, solar, geothermal, hydro) is the most environmentally friendly approach. This attractive method for hydrogen generation, based on a mature technology, currently accounts for only 4% of the hydrogen production but its large expansion is expected in the next few years: a share of 22% is predicted for 2050 [4]. Centralised methane steam reforming allow very low production prices, but the costs of transportation of hydrogen are very impressive. On the market, hydrogen can be sold as a fuel, as a means to produce electricity through fuel cells and as a feedstock in several industrial processes. Just the feedstock could be in the short term the main market of RES hydrogen. The hydrogen feedstock market has a total estimated value of USD 115 billion and is expected to grow significantly in the coming years, reaching USD 155 billion by 2022 [5]. In 2015, total global hydrogen demand was estimated to be 8 Exajoules (EJ) [6]. The largest share of hydrogen demand is from the chemicals and refining sectors. Other industry sectors also use hydrogen, but their combined share of total global demand is small [5]. But if the hydrogen will continue to be produced mainly from fossil sources, an increase of CO2 emissions, estimated in around 500 Mt, is expected. For this reason, the international community purpose is decarbonisation of the hydrogen production through carbon capture, electrolysis or the increased use of by-product. However hydrogen produced from renewable electricity could replace carbon (from natural gas or coal) as a reducing agent in the ironmaking process, and it could be used together with captured CO2 to replace fossil feedstock in the production of hydrocarbon-based chemicals such as methanol and derived products. Therefore, the large industrial sectors, as refineries and chemicals, are expected to be key early markets for power-tohydrogen. Al-Subaie et al. [7] have claimed that the hydrogen can be consumed instantaneously by the oil refining and chemical industries without the necessity for increasing FCEV (Fuel Cells Electric Vehicle) market penetration. In this work, we present the results of our techno-economic studies about the selling of renewable hydrogen production, in particular from a small plant, as a feedstock to industries. From the analysis carried out, we found out that the production of renewable hydrogen for the technical gas market is, in the short term, an achievable opportunity. One of the effects, deriving from this condition, could be the starting of distributed generation of hydrogen.