Oxygen from electrolysis for medical use: an economically feasible route

Today, worldwide hydrogen production (around 70 Mt/year, in 2018) is almost exclusively (96%) derived from fossil fuels, with water electrolysis accounting for a residual share (4%) [1]. But, the conventional processes used for hydrogen generation - mainly, steam methane reforming (SMR) - are responsible for about 5% of the global carbon dioxide emissions [2]. By contrast, water electrolysis powered by renewable energy sources (solar, wind, etc.) is a mature and environmentally friendly technology for large-scale hydrogen production, whose main bottleneck for a widespread diffusion is still related to economic concerns [3]. In fact, according to the literature [4, 5], the production cost of hydrogen from electrolysis is at least 5-6 EUR/kg, which is not competitive compared with hydrogen production by SMR (ca. 1.5-2.3 EUR/kg [6]). In our previous investigations [7, 8], we performed some evaluations of a system based on alkaline water electrolysis (180 kW) coupled with a photovoltaic plant (200 kW), looking at the oxygen valorisation for reducing hydrogen production costs. These studies allowed us to demonstrate the economic profitability of the system when the extra revenues generated from the selling of the co-produced oxygen (usually vented into the atmosphere) are considered. Recently [9], we completely reversed the usual concept, and considered a photovoltaic-powered electrolysis plant whose main purpose was to satisfy the oxygen requirements of a hypothetical enterprise, while the obtained hydrogen could be sold to external users to achieve additional revenues. The obtained results evidenced that the proposed plant was economically attractive if compared to the case when the same enterprise buys the compressed oxygen from local gas distributors/resellers. In particular, by assuming a hydrogen selling price of 10 EUR/kg (a reference price for hydrogen as a fuel, at the pump), the economical sustainability (recovery of the investment within 20 years) is achieved if the market price of oxygen is at least 3 EUR/kg, whatever the size of the electrolyser (in the range from 100 kW to 10 MW). Nowadays, the energy-health nexus is a key theme whose importance and priority cannot be neglected or postponed anymore. The availability and quality of energy supply affect the quality of primary healthcare, and some studies [10] evidenced that sustainable decentralized renewable energy technologies could bridge the gap for access to healthcare in medical centres located in remote areas. In addition, due to the current COVID-19 pandemic, the demand for oxygen increased - e.g., in parts of Italy, oxygen consumption has tripled [11] - and this has exacerbated the shortage of medical oxygen in many developing countries [12]. Based on these considerations, in this work we consider an electrolysis plant devoted to gaseous oxygen generation for a typical medium-size hospital (200-250 beds capacity) and, assuming that the hydrogen produced from the plant is sold at 3 EUR/kg (a price competitive with hydrogen from fossil fuels), we perform some calculations to estimate what should be the (market) price of oxygen to achieve economic profitability within 15 years through the oxygen self-production from the proposed system.