Electrolytic hydrogen production infrastructure options evaluation. Final subcontract report

This study investigates the centralized production of hydrogen gas (H2) by electrolysis of water using photovoltaic (PV) electricity. H2 can be used to power all modes of transportation. The logical first large-scale application of H2 is as a replacement fuel for light-duty vehicles, light commercial trucks, and buses. Since H2 is an expensive fuel compared to gasoline, consumer acceptance of H2 is contingent on its use in advanced fuel economy vehicles such as fuel cell vehicles (FCVs), which lowers the cost of H2 relative to the cost of gasoline used by conventional fuel economy vehicles. The purpose of the study is to provide baseline projections of capital investments, levelized H2 prices, and fuel cycle greenhouse gas (GHG) emissions of a centralized PV electrolytic H2 production and distribution system. This is important in order to evaluate the economic and environmental impacts of utilizing PV electrolytic H2 as a fuel source. The use of PV electricity for electrolytic H2 production is a means of storing solar energy and overcoming its limitations as an intermittent power source. However, the intermittency of solar energy reduces the utilization capacity factor of electrolysis plants, which increases H2 production cost. The relevant question is whether the

The Department of Energy (DOE) has identified hydrogen production by electrolysis of water at forecourt stations as a critical technology for transition to the hydrogen economy; however, the cost of hydrogen produced by present commercially available electrolysis systems is considerably higher than the DOE 2015 and 2020 cost targets. Analyses of proton-exchange membrane (PEM) electrolyzer systems indicate that reductions in electricity consumption and electrolyzer stack and system capital cost are required to meet the DOE cost targets. The primary objective is to develop and demonstrate a cost-effective energy-based system for electrolytic generation of hydrogen. The goal is to increase PEM electrolyzer efficiency and to reduce electrolyzer stack and system capital cost to meet the DOE cost targets for distributed electrolysis. To accomplish this objective, work was conducted by a team consisting of Giner, Inc. (Giner), Virginia Polytechnic Institute & University (VT), and domnick hunter group, a subsidiary of Parker Hannifin (Parker). The project focused on four (4) key areas: (1) development of a high-efficiency, high-strength membrane; (2) development of a long-life cell-separator; (3) scale-up of cell active area to 290 cm2 (from 160 cm²); and (4) development of a prototype commercial electrolyzer system. In each of the key stack development areas Giner and our team members conducted focused development in laboratory-scale hardware, with analytical support as necessary, followed by life-testing of the most promising candidate materials. Selected components were then scaled up and incorporated into low-cost scaled-up stack hardware. The project culminated in the fabrication and testing of a highly efficient electrolyzer system for production of 0.5 kg/hr hydrogen and validation of the stack and system in testing at the National Renewable Energy Laboratory (NREL).

The implementation of electrolysis systems for hydrogen production has continued to grow as the paradigm shift towards renewable energy and fuels progresses. However, when intermittent renewable energy sources power conventional polymer electrolyte membrane (PEM) electrolysis systems, the performance and safety of PEM electrolyzers degrade due to gas crossover. In order to make electrochemical hydrogen production safer when using intermittent renewable energy, decoupled electrolysis systems have been introduced to temporally and spatially separate the evolution of hydrogen and oxygen. This makes the electrolysis system safer, but it sacrifices efficiency compared to conventional electrolysis systems. In this presentation, I will discuss a cerium-mediated decoupled electrolysis system that can both produce hydrogen and store energy in the redox couple. Cerium was chosen due to its large redox potential of 1.6V, which is higher than water oxidation. This means that in one cell (charging cell), an energy input allows cerium to be oxidized while hydrogen is reduced, and in the other cell (discharging cell), energy can be generated by reducing cerium and oxidizing water. By combining experimental results and grid modeling, we identify optimal grid-integration strategies for the decoupled electrolysis system and provide guidelines for its dynamic operation with variable renewable electricity sources. Furthermore, since the oxidation of cerium and water are competing in the charging cell, Faradaic efficiency (FE) for the cerium reaction is less than 100%, which limits total efficiency of the system. To improve the FE of cerium oxidation, dynamic potential pulsing was employed to maintain a high concentration of cerium at the electrode surface improving the FE. The four variables that affect the behavior of the pulses include the oxidation pulse voltage, the rest voltage, the oxidation pulse duration, and the rest duration. Since the effect of these four factors on the FE and cerium conversion rate were unknown, we employed a Bayesian optimization (BO) to approach to identify the optimum combination of the four variables. The BO method was combined with electrochemical models of the reaction to accelerate the search. Finally, the optimal results will be put into context in terms of their effect on the performance and feasibility of the proposed cerium-mediated decoupled water electrolysis and energy storage system. Figure 1

Exergetic life cycle assessment of hydrogen production from renewables

The development of a new electrolytic water hydrogen production coupling system is the key to realize efficient and low-cost hydrogen production and promote its practical application. Herein, a green and efficient electrocatalytic biomass to formic acid (FA) coupled hydrogen production system has been developed. In such a system, carbohydrates such as glucose are oxidized to FA using polyoxometalates (POMs) as the redox anolyte, while H2 is evolved continuously at the cathode. Among them, the yield of glucose to FA is as high as 62.5 %, and FA is the only liquid product. Furthermore, the system requires only 1.22 V to drive a current density of 50 mA cm-2 , and the Faraday efficiency of hydrogen production is close to 100 %. Its electrical consumption is only 2.9 kWh Nm-3 (H2 ), which is only 69 % of that of traditional electrolytic water. This work opens up a promising direction for low-cost hydrogen production coupled with efficient biomass conversion.

Combining the framework of digital twin and the working mechanism of electrolytic water hydrogen production, a digital twin model of alkaline electrolytic water hydrogen production is constructed, and the influence of electrolyzer cell voltage by temperature and pressure is analyzed according to the mathematical model of electrolytic water hydrogen production. In order to improve the adaptability of the electrolyzer of the hydrogen production system to the power fluctuation of renewable energy input, a wide power adaptation model with multiple electrolyzers sharing one set of gas-liquid handling device is proposed. The case study shows that by reasonably selecting the electrolyzer model of the hydrogen production system, the use of the wide power adaptation model can effectively adapt to the fluctuation of wind power and improve the adaptation capability of the electrolyzer to wide power fluctuations.

The year 2018 saw the emergence of a broad social movement demanding stringent policies for climate change mitigation in Europe and other world regions. Widespread meteorological extreme events consistent with rapid global warming are stoking this movement. Especially in Europe, it has already changed the political landscape in a number of countries as green parties have scored record votes. Therefore, policymakers in many countries are sharpening their emission reduction targets for 2030 and 2050. At the same time, strong interest in an integrated hydrogen economy is emerging, where hydrogen would become a key fuel for transportation, industrial uses and even electricity generation. Countries as diverse as Australia, China, European Union (EU) member states and Japan are embarking on far-reaching strategies for a hydrogen economy, starting with the support of fuel- cell electric vehicles (FCEVs) but reaching beyond the transport sector. Hydrogen production technologies are manifold: feedstocks include fossil fuels and renewable electricity. At present, the costs of ‘green’ hydrogen, which is produced with renewable electricity, are still about five times higher than those of gas or coal-based hydrogen. An expansion of green hydrogen production, however, is likely to close the gap within less than a decade. Especially promising are emerging technologies that allow to use hydrogen as a fuel in existing thermal power plants without major refurbishment. The Gulf region faces a significant risk of oil exports becoming squeezed by a successful hydrogen revolution in the next decades. At the same time, Gulf countries are blessed with abundant solar energy resources that can easily be used for green and low-cost hydrogen production at large scale. Therefore, it is recommended that they proactively participate in this revolution, also given the region’s long experience with pipeline and ship transport of other flammable materials. Early movers are likely to benefit from scale effects and become leaders in the market, especially if there are lock-in effects for hydrogen supply chains – i.e. hydrogen importing countries wanting to continue to procure from suppliers with which they have long-term experience. The UAE is already a leader in the Middle East with the first solar hydrogen electrolysis plant under construction in Dubai and a fledgling FCEV fleet. Given its success in bringing down the cost of solar, the UAE would be in an excellent position to achieve the lowest global cost of green hydrogen production. With both the World Expo hosted by Dubai and the G20 presided by Saudi Arabia in 2020, the UAE could leverage either of these platforms to establish, and host, a high-profile International Hydrogen Economy Initiative (IHEI). This initiative could serve as a policy coordination tool between hydrogen importers and exporters, initially focusing on accelerating interactions between the Gulf region – a potential supplier – and Japan and the EU who both are likely to become key hydrogen importers in the next decade based on their self-defined energy policy targets.

Environmental emissions and decreasing costs of renewable energy sources (i.e., photovoltaic (PV), wind, hydrogen (H2), etc.) are prompting a sharp increase in renewable energy penetration into the grid. Among various energy sources, H2 energy with its promising technical, economic, and environmental merits has demonstrated great potential for large deployment in distribution systems. This article proposes a multiobjective network-constrained framework for the day-ahead scheduling of hydrogen systems (HS), including hydrogen production from water electrolysis by electrolyzers, hydrogen storage, stationary fuel cells, and fueling of fuel cell electric vehicles (FCEVs). This framework includes various physical constraints to ensure reliable operation and considers integrated demand response and conservation voltage reduction, and reactive power support from HSs for realistic day-ahead scheduling. It also incorporates the cooperative operation of PV units and HSs to supply power for water electrolysis from stationary HSs equipped with onsite PVs. Moreover, conditional value-at-risk is applied to address the risk of PV output, FCEVs’ H2 demand, loads, and market price. The proposed model is formulated as a mixed-integer linear programming problem and validated by testing on a 33-node distribution test feeder.

On-board hydrogen storage and production: An application of ammonia electrolysis

Solar‐driven water electrolysis has been considered to be a promising route to produce green hydrogen, because the conventional water electrolysis system is not completely renewable as it requires power from nonrenewable fossil fuel sources. This review emphasizes the strategies for solar‐driven water electrolysis, including the construction of photovoltaic (PV)‐water electrolyzer systems, PV‐rechargeable energy storage device‐water electrolyzer systems with solar energy as the sole input energy, and photoelectrochemical water splitting systems. The basic discussions of the above strategies for solar‐driven water electrolysis are first presented. Meanwhile, replacing the oxygen evolution reaction with the electrooxidation of organic compounds can effectively improve the efficiency of water splitting. Also, solar‐driven seawater electrolysis greatly broadens the practical applications due to the abundant reserves of seawater. Recent years have witnessed great development in the field of solar‐driven water electrolysis. The recent research development in the area is subsequently reviewed. Finally, perspectives on the existing challenges along with some opportunities for the further development of solar‐driven water electrolysis are provided.

Hydrogen is seen as a potential energy intermediary between renewable energy sources and end-use applications including transportation, power, and industrial feedstocks. Central to this approach is low-cost generation of hydrogen via water electrolysis. Significant research has been undertaken to improve the electrolysis stack technology, including enhancements in electrical efficiency, lowering performance degradation, and lowering total stack cost. Strategic Analysis Inc. (SA) has developed a process-based Design for Manufacturing and Assembly (DFMA) cost model for Alkaline, Proton Exchange Membrane (PEM), and Anion Exchange Membrane (AEM) electrolysis cell stacks. We assess the impact of technology improvement and manufacturing scale-up on the projected selling price of electrolyzer stacks for near-term and future deployments.Relative to the total cost of installing an electrolysis plant, the stacks contribute less than 50% of the initial capital investment. Therefore, from an electrolysis project perspective, the mechanical balance of plant and electrical systems required to operate the plant are equally important to understand. To explore the near-term and future cost projection for levelized cost of hydrogen via electrolysis, SA has developed a bottom-up project cost model for Alkaline, PEM and AEM hydrogen production plants. This project cost model incorporates: 1) Stack cost, 2) Mechanical Balance of Plant Cost, including process equipment, piping, valves, and instrumentation, derived from equipment quotes, scaling, database values, and Aspen estimates; 3) Electrical Balance of Plant Cost, including wiring, rectification, and electrical infrastructure upgrades, derived from time and material cost correlations; 4) Site Preparation Cost, focused on green field installation; and 5) Construction Overhead Cost, including engineering, procurement, and construction (EPC) costs and project contingency. Through a project level perspective, potential stack cost improvements through catalyst optimization and cell refinement can be contextualized against cost reductions from scaling up hydrogen plant deployment. The SA project cost model results are fed into a Levelized Cost of Hydrogen (LCOH) model that accounts for the full CapEx and OpEx involved in plant operation, including electricity and water consumption, labor, maintenance, and stack replacements.The SA project cost model and the LCOH model are used to conceptualize electrolysis system sizes from 10 MW to 1 GW for Alkaline, PEM, and AEM electrolysis systems. From a project perspective, electricity costs contribute 50-80% to the LCOH while capital and maintenance costs contribute the remaining 20-50% to the LCOH. Although improvements in stack performance and cost can provide incremental LCOH reductions, significant cost decreases will require optimization of the stack cell voltage and operating current density, as well as reductions in net electricity prices through integration with low-cost electricity. SA will explore potential opportunities to reduce hydrogen production costs through stack operating point optimization and scenarios where hydrogen production plants can selectively use low-cost renewable electricity to reduce net hydrogen costs.

Authors

<div class="section abstract"><div class="htmlview paragraph">One of the most critical elements in engineering a hydrogen fuel cell vehicle is the design of the on-board hydrogen storage system. Because the current compressed-gas hydrogen storage technology has several key challenges, including cost, volume and capacity, materials-based storage technologies are being evaluated as an alternative approach. These materials-based hydrogen storage technologies include metal hydrides, chemical hydrides, and adsorbent materials, all of which have drawbacks of their own. To optimize the engineering of storage systems based on these materials, it is critical to understand the impacts these systems will have on the overall vehicle system performance and what trade-offs between the hydrogen storage systems and the vehicle systems might exist that allow these alternative storage approaches to be viable.</div><div class="htmlview paragraph">To gain a better understanding of the interactions that exist between various materials-based hydrogen storage systems and the vehicle system as well as the engineering challenges that exist when integrating one of these systems with a vehicle, the National Renewable Energy Laboratory (NREL) developed a vehicle-level model designed to be sensitive to these issues. The Hydrogen Storage Simulation Model (HSSIM) was developed under the Hydrogen Storage Engineering Center of Excellence (HSECoE) as a specialized tool that could be used to assist in the design and engineering of materials-based hydrogen storage systems being considered by the HSECoE. This tool is designed to not only allow for understanding key trade-offs, but also to have a seamless integration with the HSECoE fuel cell and detailed hydrogen storage system models and to evaluate progress towards the U.S. Department of Energy's hydrogen storage technical targets. This model has been integrated with a fuel cell model developed by Ford Motor Company in a HSECoE common modeling framework developed by United Technologies Research Center and other HSECoE partners.</div><div class="htmlview paragraph">This paper focuses on the development, structure, and validation of the vehicle model HSSIM and summarizes its integration within the framework. HSSIM and the framework are then used to obtain trade-offs for various specific materials-based storage system designs. This includes hydrogen storage sizing analyses, mass compounding analyses, range versus volume studies, and vehicle and component performance analyses, such as acceleration rates and fuel cell and energy storage interactions.</div></div>

Introduction Water electrolysis is expected a key energy conversion system to introduce large-scale renewable electricity under power grid management. Here, less expensive large system is needed. Alkaline water electrolysis (AWE) systems are well-developed large system to combine hydropower generation, but fluctuated operation with start and stop operation is not considered for conventional systems. Therefore, improvement of durability to combine photovoltaic and/or wind turbine generation is significant issue. In this study, we have been investigated reverse current behavior of bipolar alkaline water electrolyzers and proposes accelerated durability test (ADT) protocol. Theoretical and Experimental Figure 1 shows configuration of bipolar alkaline water electrolyzer, principle of reverse current. An equivalent circuit to analyze reverse current is also shown in the figure. During electrolysis, surface Ni of anode oxidizes to Ni(III) and that of cathode reduces to Ni(0). They electronically connect on a bipolar plate and ionically connect through manifold to distribute electrolyte. In the equivalent circuit, electrochemical potential difference between anode and cathode on a bipolar plate correspond to electromotive force of Uk(t). The R 1 and R 2 correspond ionic resistances of branch and communicating tubes, respectively. Relationship among these parameters can describe as eq. 1 in Fig. 1 based on the Kirchhoff's laws, so reverse current would be estimated. In this study, we measured electrode potential and reverse current after 1 h water electrolysis at 0.6 Acm-2 for 2 to 4 cells stack bipolar electrolyzer using commercially available industrial anode and cathode (De Nora Permelec Ltd). The reverse current was measured ionic current through communicating tube with D. C. clamp meter.As bipolar electrolyzer evaluation, we measured electrode potential and reverse current after 1 h water electrolysis at 0.6 Acm-2 for 2 to 4 cells stack bipolar electrolyzer using the commercially available anode and cathode. Effective electrode size was 27 cm2. The reverse current was measured ionic current through communicating tube with D. C. clamp meter (KEW2510, Kyoritsu).As start & stop operation simulated ADT protocol, we propose the combination of constant current electrolysis, potential sweep, and chronoamperometry as the inset of illustration in Fig. 4, because constant current measurement is easier to get reproductivity in high current that need accurate iR correction for constant potential measurement and current control measurement never simulate stop operation. Results and discussion Figure 2 shows the setup of lab-scale electrolyzer and cell performances in the stacks. All cells showed almost the same performance. Figure 3 shows reverse currents and electrode potentials as a function of time for 2 to 4 cells stack electrolyzer. The longer cell stack had lager reverse current at initial period of stop operation. As the potential difference between anode and cathode decreased, the reverse current decreased. The anode potential significantly decreased certain time, and that for longer cell stack was shorter. For the 4 cells stack, the time for the BP2 was shorter than that for the BP1 and BP3. Simultaneously, the I 2 was larger than the I 1 and I 3. These behaviors could be explained with eq. 1 in the Fig. 1 with the same electromotive force of the U(t=0)s for initial period and time function of U(t)s with same surface condition for all cells at the end of electrolysis. Remarkable point is that the cathode potential of BP2 was higher than the anode, which is impossible with discharge of BP2 itself. This opposite potential of the BP2 would be forced by electromotive force of the BP1 and BP3.Figure 4 shows the anode potential at 10 mAcm-2 (E @10mAcm-2) of oxygen evolution reaction (OER) current during the ADT protocol with various minimum potential: E min. The all anodes significantly degraded for around 3-days test protocol, although DN851 was developed as an active and durable anode for conventional OER electrode. The degradation increased with decreases of the E min. Above 0 V vs. RHE of the E min, The E @10mAcm-2 increased after ca. 800 cycles of introduction period and reached around 1.69 V vs. RHE after 1900 cycles, although it increased from initial period and the increase continued around 2000 cycles for -0.3 V vs. RHE of the E min. From these experimental results, the E min of between 0 to 0.3 V vs. RHE might be suitable for the ADT protocol because of rapid degradation with robustness to the E min. Acknowledgements This study was based on results obtained from the Development of Fundamental Technology for Advancement of Water Electrolysis Hydrogen Production in Advancement of Hydrogen Technologies and Utilization Project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Figure 1

The recent expansion of unconventional natural gas production in the United States has enabled a steady increase of its use in all consumption sectors, including transportation. In this study, the environmental footprints of three natural gas-based personal mobility options are examined from a life cycle perspective: battery electric vehicles (BEVs), compressed natural gas vehicles (CNGVs), and fuel cell vehicles (FCVs). The results suggest that natural gas-powered vehicles have the potential to considerably reduce the overall environmental impact associated with driven miles in comparison to conventional petroleum-powered internal combustion engine vehicles (PICVs). BEVs and FCVs in particular offer significant reductions in greenhouse gas emissions, especially if carbon capture and sequestration (CCS) technologies are implemented at the fuel conversion facilities. It was furthermore determined that the use phase dominates the life cycle impacts of all of the vehicles considered, although the manufacture of power sources for BEVs and FCVs significantly contributes to their respective environmental burdens. Efforts presently being exerted for the greener manufacture and more efficient powertrain design of BEVs and FCVs are likely to further extend their environmental advantages over CNGVs for the utilization of natural gas as a transportation energy resource.