Design of a hydrogen-water nexus by integrating autothermal reforming, electrolysis, and desalination

A novel system for producing clean hydrogen and pure water is proposed, integrating an autothermal reforming (ATR), a proton exchange membrane electrolysis cell (PEMEC), and a multi-stage flash (MSF) desalination. This system maximizes energy and material utilization, leading to significant energy and cost savings. The ATR-PEMEC-MSF system can produce both blue and green hydrogen, as well as freshwater, using only natural gas, seawater, and renewable electricity. Waste heat from the ATR process satisfies the substantial thermal energy demand of MSF desalination, thereby enhancing overall energy efficiency. Furthermore, the ATR process utilizes oxygen generated as a by-product of the PEMEC process, eliminating the need for a separate energy-intensive air separation unit. Co-locating the desalination and hydrogen production facilities ensures that the PEMEC process is optimized for seawater as its primary water source. As a result, the components of this system are interdependent, with the production rates of green hydrogen and freshwater directly linked to the production capacity of blue hydrogen. Techno-economic analysis reveals that the system can produce 96.5 ton/d of blue hydrogen and 48.1 ton/d of green hydrogen, with competitive levelized costs of hydrogen at $0.825/kg and $6.467/kg, respectively. The net present value of $348.2 million and payback period of 4.12 years underscore the system's economic feasibility, presenting it as a superior alternative to existing systems. This novel integration offers a promising solution for the future hydrogen energy and water nexus.