(310a) Green Hydrogen from Solar Power for Decarbonization: What Will It Cost? | AIChE

(310a) Green Hydrogen from Solar Power for Decarbonization: What Will It Cost?

Authors 

Tsang, F., NUS
Karimi, I., National University of Singapore
Shamsuzzaman, F., National University of Singapore
Nations and regions across the globe are converging to the urgent need for carbon management and eventual need for deep decarbonization. This growing impetus coupled with the geopolitical dynamics surrounding the conventional energy resources (coal, oil, natural gas, etc.) are compelling researchers, industries, and nations all over the world to explore sustainable, low/no carbon energy options. A highly sought-after option is to transition from the current oil and gas-based economy to a hydrogen-based economy. While steam methane reforming can be augmented with carbon capture and sequestration (CCS) to produce (low carbon) blue hydrogen, economic production of green hydrogen (GH2) is the long-term objective for deep decarbonization in a hydrogen-based economy. The pace of GH2 adoption will depend heavily on the economic competitiveness of its robust large-scale production. Currently, water electrolysis (WE) accounts for only 5% of global hydrogen production due to the cheaper black/grey/blue hydrogen from fossil fuels. Hence, cost economics or LCOH (Landed Cost of H2) is the key challenge facing GH2 production.

The literature on GH2 production is replete with studies on the cost of production via different types of electrolyzers. Almost all of them restrict their analysis boundary around the water electrolysis plant (WEP). Additionally, these studies do not consider the impact of the intermittent nature of renewable electricity generation. Rather, they assume fixed availability and cost of renewable electricity, which can only be achieved through active energy management (e.g. energy storage devices) that comes at an additional cost. Basically, the literature has not considered an all-inclusive scope for the design and analysis of a GH2 production facility.

Besides electrolysis technologies, the availability, intermittency, and dynamics of renewable solar energy influence LCOH. The works in the literature do not consider intermittency and dynamics while doing technoeconomic analysis and design of GH2 facilities. Let us understand how the intermittent nature of renewables can be managed and its impact on the facility design. One can size WE plant to fully utilize solar power instantaneously. In this route, the WE plant (WEP) must be sized for the highest irradiance level. It will operate mostly in part-load conditions during the day and shut down during the night, resulting in a low utilization i.e. a low operational capacity factor. The produced hydrogen must be stored to supply during the non-operational period; hence the additional cost of physical hydrogen storage is incurred. Alternatively, one can install a battery storage system (BSS). This would enable the storage of the electrical energy produced during the day in excess of the WEP capacity and the stored energy would be used during the night. The utilization of WEP will increase and its size/capacity/cost will decrease, but additional cost of BSS will be incurred, and physical hydrogen storage may still be required. Clearly, balancing these multiple factors is not straightforward, as the truly optimal design may lie between the two extreme options. The problem becomes even more complex when the dynamic variation in solar irradiance at a fine granularity in time is considered.

To this end, we developed and solved a rigorous, comprehensive, and versatile optimization model for designing a GH2 production facility (see attached Figure) based on solar PV to achieve the least LCOH (Landed Cost of H2) or TAC (Total Annualized Cost). The aim of this work is to equip industry personnel and research community with a comprehensive and versatile model that can be employed to evaluate a variety of options for each of the technologies involved in the GH2 production value chain and yield an optimal GH2 production facility design. The GH2 production facility model considers the local intensity profile of solar irradiance, physical hydrogen storage, land footprint, carbon intensity of the local grid, and various other factors (types, sizes, capital and operating costs, efficiencies, characteristics, lifespans) related to WE, battery storage, and solar PV (photovoltaic) technologies. Furthermore, our mixed-integer nonlinear programming model accommodates several technoeconomically competitive options for solar PV panels, battery storage units, and WE stacks. It also allows electricity import from and export to the local grid. More importantly, it accounts for both intra-day and day-to-day variations in solar irradiance essential for an optimal facility design at any geographical site.

The model is employed to study green hydrogen production in Saudi Arabia, Australia, Singapore, and Germany and highlight the impact of geospatial solar irradiance on the facility design. The least LCOH of $10.68 /kg-H2 occurs in Saudi Arabia which is 10% cheaper than the current estimated cost in Australia, another prominent candidate for GH2 production. Germany suffers from harsh seasonal conditions resulting in large variations in solar intensity and availability, thereby yielding the highest LCOH. A stand-alone GH2 facility needs to store electrons in batteries or hydrogen molecule in storage tanks to ensure that the given GH2 demand is met irrespective of sunshine availability. At present, hydrogen molecule storage in tanks appears to be cheaper than electron storage in batteries. Interestingly, the installed hydrogen storage capacity is dictated by the worst sunshine period experienced by the GH2 facility. The stabler and more uniform the solar irradiance, the lower the hydrogen storage capacity.

Grid-connected green hydrogen production facilities may yield lower hydrogen production cost but cannot guarantee carbon-free hydrogen. The sensitivity analyses with respect to key technoeconomic factors highlight that massive reductions in solar panel and battery costs combined with low-interest loan incentives can make GH2 cost competitive. Even though GH2 has the potential to be a carbon-free energy source, rapid advances in various technologies as well as investment policies are needed before it can economically compete with other low carbon options Indeed, GH2 seems like a potential yet costly silver bullet for deep decarbonization at this time.