Category Archives: Hydrogen

National Grid in JV to build New York green hydrogen storage, delivery project

Atlantic U.S. utility National Grid is partnering to demonstrate a multi-use renewable hydrogen-based energy storage and delivery system in New York.

The venture with Standard Hydrogen Corp. will focus around developing what National Grid called the first such hydrogen storage and delivery system in New York’s Capital Region. The project is expected to be completed late next year.

The planned system will produce hydrogen from purchased renewable power exclusively. Once stored, it then can be offered for market-based zero-carbon energy services that support electric services, heating, zero emissions vehicles and commercial gas services.

“Green, renewable hydrogen is a key piece of the puzzle to reach net-zero by 2050,” said Badar Khan, president of National US, in a statement. “The new hydrogen-based system is doing to reduce emissions in New York across power, transportation and heating—the three most difficult sectors to decarbonize.”

Green, or carbon-free, hydrogen can be produced from an electrolysis fueled by other zero-carbon energy resources such as utility-scale wind or solar.

Read more of our coverage of hydrogen’s potential role in future power generation

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Standard Hydrogen Corp. will operate the hydrogen production and storage site to reduce potential financial impact on National Grid’s utility customers.

National Grid said the move to hydrogen helps achieve its goal such as reducing greenhouse gas emissions from direct operations 80 percent by 2030, and reduce GHG emissions from the electricity and gas businesses 20 percent by 2030.

The utility provides electric and gas service to customers in New York, Massachusetts and Rhode Island.

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POWERGEN International will return live next January in Dallas. Hydrogen: What’s New, What’s Next? is one of the tracks and seeking presentations to explain the future of H2 in the generation mix. Our call for speakers is now open until May 17. Submit your idea here.

The post National Grid in JV to build New York green hydrogen storage, delivery project appeared first on Renewable Energy World.

Introduction to Electrolyzer Technologies

by Ishaan Goel

Hydrogen has become increasingly prominent as a potential carbon-free fuel, for both automobiles and providing electricity to buildings. It has direct applications in decarbonizing important industries like steel, and can serve as a storage medium for extra renewable energy over seasonal durations too.  

Since hydrogen gas does not occur naturally in our atmosphere, its method of production is an essential component of the hydrogen economy. There are several such methods (discussed in detail here), but the one with least emissions involves using renewable power to run electrolyzers – devices that use electricity to convert water into hydrogen and oxygen gas.

This article introduces a series on electrolyzers which will explore the various technologies, the efforts and challenges to improving them, and their prospects for wide-spread adoption.

While there exist several types of electrolyzers, the two primary kinds today are alkaline electrolyzers (ALKE) and polymer electrolyte membrane electrolyzers (PEME). 

ALKALINE ELECTROLYZERS

ALKEs comprise two solid electrodes containing catalysts, immersed in a liquid, alkaline electrolyte. An electric current passes through these electrodes, which splits water at the negative electrode into hydrogen gas and hydroxide (OH) ions.  The positive electrode attracts the hydroxide ions, which travel to it within the electrolyte. They combine there to form oxygen gas and electrons, which keeps the reaction going. During this process, they pass through a porous membrane (diaphragm) designed to internally segregate the gases. 

The mechanism of an alkaline electrolyzer (diaphragm has not been shown in this figure). Source: Shell Hydrogen Study

PEM ELECTROLYZERS

Instead of liquid electrolytes, PEMEs utilize solid polymer compounds present within a porous, central layer. This layer is surrounded on either side by electrodes with catalysts, followed by meshy gas diffusion layers, and then by bipolar plates. Water (as steam) is introduced through the bipolar plate, and passes through the diffusion layers towards the positive electrode. Here, it splits into oxygen gas and hydrogen (H+) ions. The ions permeate through the central electrolyte towards the negative electrode, where they combine with free electrons to form hydrogen gas that is collected through the other bipolar plate. In both electrolyzer variants, the catalysts hasten the reaction.

Diagrammatic outline of a PEM electrolyzer. Orange – bipolar plate, purple – gas diffusion layers, green – electrodes and blue – polymer membrane. Source: Tijani et al., 2019

ADVANTAGES OF PEMEs 

Each technology comes with its own tradeoffs. PEMEs are advantageous because their production level responds faster to changes in power supply and they can tolerate higher current densities, making them ideal for fluctuating power sources like solar/wind energy. The layered structure and lack of liquid electrolyte allows for compact designs, so they are effective within space constraints. The solid electrolyte enhances ion conductivity, which boosts the overall efficiency. Any electrical energy lost as heat can be redirected into the conversion of water into steam, which reduces wastage and further increases efficiency. 

WEIGHING UP ALKEs

However, PEMEs have higher capital costs than ALKEs. Their conductivity is highly dependent on factors like hydration of the membrane and temperature, and maintaining optimal operational conditions requires extra components. They also need platinum and iridium-based catalysts, which are not only very expensive, but also limit the scalability of PEMEs based on their availability. 

ALKEs usually use cheaper nickel or stainless steel-based catalysts. Further, their durability will also be higher because of less corrosive environments and the replaceability of the electrolyte after extensive usage. ALKEs also tend to exhibit lower internal mixing of gases, so the produced hydrogen has greater purity. However, nickel-based membranes and separators are being developed for PEMEs too, which may possibly bring down the cost differential in the future. 

OTHER ELECTROLYZER TYPES

To blend the best of both technologies, certain firms have come up with anion exchange membrane electrolyzers (AEMEs). These utilize solid membranes similar to PEMEs, but involve the transfer of hydroxide ions instead of hydrogen ions like ALKEs. As a result, the catalyst can be cheaper nickel or stainless steel instead of platinum/iridium while still preserving efficiency and responsiveness benefits. Companies actively engaged in the area include Enapter and Evonik Industries (EVK.DE, EVKIF, EVKIY). Another alternative is ThyssenKrup’s (TKA.DE, TYEKF, TKAMY) “advanced alkaline electrolysis”, that aims to deliver modules with lower maintenance and capital costs. 

DESIGN INNOVATIONS

Electrolyzers are usually sold as modular “stacks”, which consist of multiple units conjoined together to scale up their joint output. For instance, NEL Hydrogen (D7G.F, NLLSF, NLLSY) produces electrolyzer stacks ranging in production capacity from 1.05-3880 nm3/hour, suitable for large-scale centralized production or household/office-level distributed applications. Some firms also design for the produced hydrogen to have pressures suitable for direct use – for example, Giner ELX (a subsidiary of Plug Power (PLUG)) systems yield hydrogen directly in an ideal range of about 435-580 psi. 

A typical electrolyzer stack. Source: Giner ELX

CONCLUSION

With growing interest in the adoption of hydrogen, active research continues into improving existing electrolyzer technologies across various parameters. The next articles in this series will focus on the current status of such parameters, including capital costs, for both ALKEs and PEMEs.  

Disclosure: The author has no interests in any firms mentioned. 

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