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Technology: Electrolysers – part 3

Electrolyser technology

The last part of the electrolyser series is a comparison between Alkaline (ALK), Polymer Electrolyte Membrane (PEM) and Solid Oxide electrolysers (SOEL),  explaining the advantages and disadvantages with the different technologies.

Did you miss the previous parts in the electrolyser series? Read them here: part 1 and part 2.

Maturity and costs

The alkaline electrolysis stacks have been available on a MW-scale for a long time, and a scale-up of PEM has been realized the last few years, largely driven by the drive to run electrolysis from Variable Renewable Energy (VRE) and to reduce plant footprint. Alkaline stacks are available up to 6 MW and PEM stacks up to 2MW. The SOEL is still in laboratory scale with up to 10kW. 

Alkaline electrolysers have the lowest cost per kW. In commercial scale plants (2 MW +), Alkaline electrolyser plants have a capital cost of $ 800 – 1 000 /kW. PEM electrolysers come in at an overall higher capital cost at 1 400 – 1 700/kW. The price difference between Alkaline and PEM electrolysers is largely explained by the maturity of the technology and the use of precious metals in PEM electrolysers. There is an uncertainty regarding the investments cost due to the pre-commercial status for SOEL.

Renewable energy applications

Usage of intermittent power sources requires flexibility. A State-of-the-art PEM electrolyser can operate more flexibly than current Alkaline technology, and these characteristics are suited for variable renewable energy. Historically, the alkaline electrolyser was designed for stationary applications with grid connections and must be adapted to the new flexibility requirements.

Advancements in Alkaline technology, specifically ‘Pressurized’ Alkaline electroysers have made them once again suitable for variable renewable energy if the system components are engineered to operate with an intermittent power supply. 

While PEM electrolyers offer best in class use of intermittent power sources, both PEM and (pressurized) alkaline electrolysers can offer fast load dynamics when they are in operating temperature and is suited for grid stabilizing.

Figure 1 compares parameters regarding the different electrolyser technologies:

Start-ups

The development of PEM has been driven by energy storage application. PEM has short startups, especially from cold. Alkaline electrolysers have a slower start-up taking up to an hour. The SOEL has a cold start-up time up to several hours and needs a high energy consumption (in the form of heat) to maintain a temperature that allows a short start-up time. 

One of the most significant issues with start-ups is when shut downs extend for a extended period of time resulting in the need to purge the equipment using nitrogen. This can increase the start-up time signficantly beyond normal start-up periods. Nitrogen purge requirements however largely differ from manufacturer to manufacturer.

Flexibility

The production rate for PEM can be varied over the full load at 0-100%, but the alkaline electrolyser typically has a load limit of 20% meaning it cannot operationally drop below 20% of the nominal load. It is worth noting that some alkaline electrolysers can offer higher flexibility such as pressurized alkaline. The SOEL has the ability of co-electrolysis of CO2 and steam to produce syngas containing H2 and CO2 for synthesis of fuels. It is also possible to have the reversible operation. This allows operating range from -100 to 100%. However, SOEL is still at the research stage based on single-cell or short-stack tests and any capabilities such as this may not be realized on a commercial stage.

A lower operating limit and the number of stops permitted by the manufacturers are limitations for the commercial Alkaline electrolysers. Reducing the electrolysers’ lower operation limit and improving the response times are key aspects in development.

Pressure

The outlet pressure of each of an electrolyser can influence the overall production facility and maintenance requirements. While the alkaline typically offers low outlet pressure of only 2 – 3 bar, SOEL has a slightly higher output pressure around 5 bar, and the PEM offers the highest outlet pressure in the range of 20 – 30 bar.

Lifetime

Alkaline electrolysers offer the longest lifetime, some have been in regular operation for 30+ years. Typically, cell stacks need replacement after 80 000 operational hours. PEM electrolysers also offer long times, however, degrade faster than their Alkaline counterparts requiring stack replacement after 40 – 50 000 hours. Finally, SOEL offers little to no lifetime with a ~8 000 hours lifetime – this is due to very high temperature used in the process causing material breakdown.

Efficiency

Solid Oxide Electrolysis is the most electrical efficient with electricity consumption around 42 kWh/kg, however this comes with the requirement that very high excess heat is available and therefore the true efficiency is significantly higher. Alkaline electrolysers have the highest overall efficiency with energy consumption around 52 kWh/kg produced. Meanwhile, PEM electrolysers have the lowest overall efficiency at 59 kWh/kg produced.

A caveat to the ‘efficiency’ discussion: PEM electrolysers are better suited than ALK electrolysers for operation under pressure due to smaller cell surfaces. It is more efficient to have a higher pressure inside the stack. The PEM electrolysers have a higher power consumption but the result is a higher output pressure. Given that the hydrogen is to be compressed later for distribution  or storage then the additional energy consumption from the PEM electrolyser is not entirely wasted.


 

 

Do you have a project you want to realise and need more information? Please contact us at greensight@greensight.no. This is the last part in the electrolyser series. Read the previous parts here: part 1 and part 2. 

Technology: Electrolysers – part 2

Electrolyser technology

Alkaline, PEM and Solid Oxide electrolysers produce hydrogen using different technologies. In this part of the technology series, we will present application areas for electrolysers and hydrogen. We will also present the suitability of the technologies to each application.

Did you miss «Technology: Electrolysers – part 1»? Read it here. You can read part 3 here.

Hydrogen is a potential key factor to address the energy transition, and water electrolysis is the cleanest and most sustainable way to produce hydrogen. If hydrogen is produced from renewable energy sources, e.g. solar or wind power, it is a zero-emission energy carrier. Hydrogen can be used in sectors that are difficult to decarbonize through electrification.

Electrolysers can produce Hydrogen that can be used in:

  • Transport
  • Off Grid
  • Grid Balancing
  • Industry 

In the following paragraphs we will discuss some of the application areas for electrolysers in general.

Transport

This is the rather obvious application electrolysers can be used for. Hydrogen can be used not only for light-duty vehicles such as the Toyota Mirai, but also heavy-duty vehicles such as the Nikola Tre. Hydrogen can be used beyond these areas of transport in applications such as trains & maritime. Airbus is even looking to fuel a plane with hydrogen!

How an electrolyser can help electrify & decarbonize the transport sector is by producing hydrogen from water & electricity which when used in transport is a zero emission fuel. Hydrogen for transport can be produced locally at the dispenser or centralized and then distributed & dispensed in compressed or liquid form.

Illustration of Electrolysis/Hydrogen use in transport:

Off-grid

Off-grid production and use of Hydrogen as a solution is possible with electrolysers. Here, we must consider fluctuations in the electrolyser operating conditions when using Variable Renewable Energy (VRE) such as wind or solar power.

Another configuration is an off-grid solution combining electrolysers, storage and fuel cells. This solution can be used to supply energy to remote areas with no connection to the electricity grid. Normally in these situations you want to have a short-term storage based on batteries, and a long-term storage based on hydrogen. However, the round trip efficiency is low, and the investment cost is high compared to alternatives like pumped hydro and battery storage.

Illustration of Electrolysis/Hydrogen direct use in an off-grid Scenario:

Illustration of Electrolysis/Hydrogen in a micro electricity grid:

Grid Balancing*

Electrolysers are systems that can typically be turned on and off and ramped up and down in unilization levels which can increase or decrease it’s electricity consumption and thereby providing grid balancing services. Grid balancing has been given an asterix(*) because it is a service that can be provided but it unlikely justifies the case on its own. Here it is possible to have multiple benefits at the same time. Electrolysis can be used to balance the grid by only taking the surplus electricity from the grid when it is available. This way the system is always in balance and no excess electricity production from VRE is wasted.

The hydrogen that is produced from the electrolyser for grid balancing can be added back into the grid as electricity through use in turbines or fuel cells as described in the Off-Grid application or used in transport or industrial applications.

Illustration of Electrolysis/Hydrogen use in grid balancing:

Industry

Within industrial applications hydrogen is mostly used as an «ingredient» in a chemical process, rather than an energy carrier (or “source”). For instant when making ammonia (which in the next step can be used to make fertilizers) hydrogen is added to a chemical process that combines hydrogen with nitrogen into ammonia, NH3. In smelters hydrogen can replace carbon (typically from coal) as a reductant in the chemical process of removing the Oxygen from the oxidised metal-ore (the reduction process). In that case the resulting product of the reduction process is the pure metal and clean water (vapor) instead of CO2.

Hydrogen can also be made into other energy carriers, based on hydrocarbons, like methanol, jet fuel, diesel etc. This is called “Power-to-X” meaning that electricity (the “power”) can be turned into different fuels (the “X”) by first making hydrogen in an electrolyser and then adding carbon (for instance from CO2 in the air) into the preferred hydrocarbon fuel. This process will “re-use” carbon/CO2, but not eliminate it.

Illustration of Electrolysis/Hydrogen use in industry:


 

Suitability of Different Electrolyser Technologies

While many hydrogen users do not care what the source of Hydrogen is, it is important to note that there are certain attributes to each electrolyser technology that make it more suitable within certain applications.

In the case of Transport for instance there is no noticeable difference between the suitability of the technology however economic conditions or electricity sources may dictate that one is better than the other.

In the case of Off Grid and Grid Balancing, there are clear differences in the suitability of different electrolysers due to technological limitations.

In the case of Industry, we have the same scenario as with Transport where there is no noticable difference in the suitability however specific conditions may dictate one is more suitable than another.

The suitability of the different electrolyser technologies: Alkaline (ALK), Proton Exchange Membrane (PEM) and Solid Oxide Electrolyser (SOEL) to the applications is summarised in the illustration below:


In part 3, we will compare between the different electrolyser technologies and highlight the trade-offs between each other, their perfect applications and actual economic implications.

Do you want more details regarding the applications for the different electrolyser technologies?  Contact us at greensight@greensight.no. Did you miss «Technology: electrolysers – part 1»? Read it here.

 
 

Technology: Electrolysers – part 1

Electrolyser technology

Hydrogen has many colours and can be produced with a broad range of technologies. Green hydrogen is produced by water electrolysis with renewable electricity. Water electrolysis is the cleanest and most sustainable way to produce hydrogen. The next weeks we will discuss the different electrolyser technologies.

We will discuss the technologies in three parts:

Electrolysis is the electrochemical process splitting water into hydrogen and oxygen by supplying electrical (or thermal) energy given by the equation:There are currently three main technologies for electrolysis:

  • Alkaline Electrolyser
  • Proton Exchange Membrane Electrolyser
  • Solid Oxide Electrolyser
 

Electrolyser

The alkaline electrolyser (ALK) is a mature technology. In an alkaline electrolyser, the electrolyte is usually a 25-30% aqueous KOH-solution and is operated at 60-90˚C. The electrodes are immersed in the liquid electrolyte, separated by a separator that only allows transport of ionic charges. Historically, the separator was made of asbestos, but is currently made of Zirfon PERL.

When a direct current is applied to the water, the water molecule is split into oxygen and hydrogen. The electrolyte let the ions be transported between the electrodes. The purity is 99,5-99,9% for the hydrogen.

The electrolysis reactions: 

Alk redoks reaksjon

 

Alkaline cell

Conceptual set-up of an alkaline cell. Source: The International Journal of Energy

Electrolyser

Proton exchange membrane (PEM) systems are based on the solid polymer electrolyte concept for water electrolysis introduced in the 1960s.  The PEM electrolysers that are commercially available today, are more flexible and tend to have smaller footprint than the alkaline electrolysers. 

A proton exchange membrane separates the two half-cells, and the electrodes are usually directly mounted on the membrane. The membrane only allows transportation of hydrogen ions. It is necessary to use noble metal catalysts like iridium for the anode and platinum for the cathode. Water is supplied at the anode. The cell temperature of a PEM cell is 50-80˚C. 

The electrolysis reactions are as follow:

PEM redoks-reaksjon

The resulting purity is higher than for alkaline and is typically greater than 99,99% H2. PEM has a compact module design because of the solid electrolyte and has a high current density operation compared to alkaline.

pem electrolyser technology
Source: Wood Mackenzie, U.S. Department of Energy

Electrolyser

Electrolysis of water can be performed at high temperature using steam. A Solide Oxide Electrolyser (SOEL) is a high-temperature electrolyser that perform a solid oxide electrolysis and operates at temperatures of 700-900˚C. The technology is currently immature and has only been tested at laboratory scale. High temperature operation results in higher electrical efficiencies than alkaline and PEM, but it has challenges in material stability and also depend on waste heat. The high temperature steam is either supplied by an external heat source or by an electrical heater, therefore the applicability of SOEL is limited to specific instances (more in part 2)

SOEL use a solid ion-conducting ceramic as the electrolyte and comprise of three layers. Yttria-stabilized zirconia is often used as electrolyte.

The half reduction equations:

Solid oxide cell

Conceptual set-up of a solid oxide electrolyser cell. Source: International Journal of Hydrogen Energy

 

Part 2 will discuss the applications for the different technologies. Part 3 compares the different electrolyser technologies.


Do you have a project you want to realise and need more information? Please contact us at greensight@greensight.no. You can sign up for our  newsletter here. Read more blogposts here

Week 42: Hydrogen projects

Hydrogen production project

It is finally Friday and we present the highlights from the past week. The EU Horizon 2020 project Haelous will demonstrate hydrogen production in Berlevåg, Norway, while Enapter plans to build a mass-production facility for its AEMs. You can also read about a solar and hydrogen energy solution for a preschool in Sweden and a Power-to-X project in the Netherlands. 

Future plans for hydrogen production in Berlevåg

Haelous, an EU Horizon 2020 project, will demonstrate hydrogen production form windpower in Berlevåg.  The wind park at Raggovidda has a concession for 200 MW, where only 45 MW have been built because of the export limitations. 2nd October Haelous partner Varanger Kraft informed that they plan to produce one ton hydrogen/day by electrolysis in the demonstration period. The wind park’s owner, Varanger Kraft, released on Wednesday their long-term plan for the exploitation of the hydrogen that will be produced in Berlevåg.

 The ammonia production plant will have a capacity of 110 000 tons a year, and could be ready by 2025. This would imply a hydrogen production capacity of about 50 tons a day, or 50 times the Haeolus project and about 125 MW of electrolysers. The main application is to supply ammonia to Svalbard as compensation for coal power. The demand at Svalbard alone is too low for cost-efficient ammonia production. ZEEDS is looking into the possibility of using the ammonia produced at Berlevåg as green fuel for ships.  


 

Mass-production facility for AEMs in Germany

Enapter, a company that designs and manufacture highly efficient hydrogen generators, has this week revealed plans to build its first mass-production facility for AEMs (Anion exchange membrane) in North Rhine-Westphalia, Germany. The «Enapter Campus» will include both production centre and research and development facilities. The new production site will be capable of production of more than 100 000 AEM electrolyser modules per year.

The construction is planned to begin in early 2021, and the Campus is expected to be operational in 2022. The Enapter Campus will be using renewable energy provided by Saebeck’s solar, wind and biomass plants, and from the Campus’ own solar arrays and hydrogen storage systems.

The AEM technology is patent-protected by Enapter. The AEM electrolyser use a semipermeable membrane to allow anions to pass, in contrary to a PEM electrolyser that let protons pass the membrane. This results flexbility, fast response time high current density and high purity hydrogen. This type of electrolyser does not require expensive noble metal catalysts materials or large amount if titanium. The electrolysers has a hydrogen production rate at 1,1 kg/hour, resulting in a capacity of about 26 kg/day.

Enapter electrolyser AEM hydrogen production

Enapter’s electrolyser has a capacity of 1kg per hour. Source: Enapter


 

Preschool with a solar and hydrogen energy solution

Construction company Serneke is, in collaboration with Mariestad municipality, building a preschool with a solar and hydrogen solution. The total costs of the project is SEK 65 million, and the preschool will be the first of its kind in Sweden. Construction will start this month in Mariestad, and the preschool will be built on the same property as the old Kronoparksskolan was located. The project is expected to be completed by January 2022.

Nilsson Energy is the supplier for the energy solution where solar cells will be installed at the roof. Hydrogen will be produced by surplus electricity, and the production and storage will take place outside the school building. Hydrogen gas will be converted to electrical and thermal energy during the dark periods of the year. 

preschool hydrogen energy solution

Illustration of the preschool with a solar and hydrogen energy solution . Source: Serneke


 

Power-to-X pilot project in the Netherlands

The Dutch energy company Alliander has contracted Green Hydrogen Systems (GHS) to supply electrolysers for for their large-scale Power-to-X pilot project in the Netherlands. The pilot is under construction at the Ecomunitypark in Oosterwolde. The contract covers the supply of three alkaline electrolysers with a combined capacity of 1,4 MW.

Solar-farm developer GroenLeven is also involved in this project. The electrolysers will be used to convert excess solar or wind energy into hydrogen, and the hydrogen will be stored and sold for use in transportation, industry, heating and other areas.


 

Hydrogen podcasts

Listening to podcasts is a good way to learn something new or to get an update on something you are interested in. We want to introduce you to three podcasts that has  energy and hydrogen on the agenda:

Greenpod (Norwegian)

Greenstats’s brand new Greenpod. New episodes are just around the corner. You can find the podcast here.

AksjeSladder (Norwegian)

The episode is about hydrogen and the development of hydrogen in the maritime sector, transport sector and the industry. Listen here

H2Podcast: Everything About Hydrogen (English)

Everything About Hydrogen is a podcast that converts the technical to the relatable and explores how hydrogen and its derivative technologies may change the energy world as we know it. Listen here.


Do you want to be updated on the development in the hydrogen market? Sign up for our news letter here. Contact us for an overview of existing and planned projects in Norway and the world: greensight@greensight.no

Week 39: Hydrogen-powered aircrafts and MW electrolysers

AirbusZeroe blending wing body hydrogen-powered

Several companies have unveiled plans within hydrogen-powered aircraft this week. Green hydrogen is also presented as one of five priority technologies in Australia. We can also read about hydrogen filling solutions for trains and hydrogen production in Taiwan and Nottinghamshire.

 

Hydrogen-powered passenger jet

European aerospace giant Airbus has unveiled a concept called ZEROe for three possible aircraft types that run on a combination of hydrogen combustion and hydrogen-powered fuel cells. The goal is to have at least one zero-emission commercial airplane on the market by 2035. A fully scale prototype is estimated to arrive by late 2020. According to its plan, Airbus needs to launch the ZEROe aircraft programme by 2025.

The ZEROe concepts are named Turbofan, Turboprop and Blended-Wing-Body. They will be powered by modified gas-turbine engines that burn liquid hydrogen as fuel, while they at the same time will use hydrogen fuel cells to create electrical power that complements the gas turbine. Each of the different concepts have a slightly different approach to integrate the liquid hydrogen storage and distribution system.

Air travel is responsible for two percent of the worldwide carbon emissions, but aviation is a sector that is challenging to decarbonise. Batteries for larger electronic planes would be too heavy, and hydrogen can be a better solution. Airbus estimates that hydrogen has the potensial to reduce CO2 emission in aviation by up to 50 percent.


 

Partnership on hydrogen-powered aviation

Power Plug and Universal Hydrogen are partnering up to develop a hydrogen fuel cell-based propulsion system designed to power commercial regional aircraft. The partnership aims to certify and fly the world’s first two megawatt hydrogen-electric aircraft powertrain.

The technology will enable a converted mid-sized regional turboprop aircraft to fly up to 1000km. The propulsion system will include a lightweight Plug Power ProGen-based hydrogen fuel cell stack and Universal Hydrogen’s modular hydorgen distrobution and fuell cell delivery system. The partnership is the first step toward establishing a complete ecosystem for the aviation market.


 

Australia: Green hydrogen one of five priority technologies

Morrison Government’s first Low Emissions Technology Statement was presented this week and green hydrogen was presented as one of five priority technologies. The statement is the first milestone in Australia’s Technology Investment Roadmap, a framework to accelerate technologies that will deliver lower emissions, lower cost and create jobs.

Hydrogen produced under two australian dollars per kilogram is named as a priority technology stretch goal. The Australian Government expects to invest more than 18 billion dollars on low emission technologies over the decade by 2030. Read the full statement here.

 


 

 Filling stations for passenger trains

Hydrogen trains were one of the topics in last week’s news update. This week, Fuel Cell Systems, Vanguard Sustainable Transport Solutions and TP Group have joined forces to deliver hydrogen fuelling solutions to the rail industry. The initial focus will be to deploy a portable, modular refuelling solution.

The UK-based companies will explore opportunities for on-site hydrogen generation, storage, dispensing and fuel cell integration into rail rolling stock. Hydrogen infrastructure will be critical to decarbonise the energy sector.


 

25 MW of electrolysers to Taiwan

John Cockerill, a major player in the production of hydrogen by electrolyser of water, will supply 25 MW of electrolysers for the Taiwanese market. The company reinforces its position among the world leaders of green hydrogen.

The order includes five stacks of five megawatts, for a total capacity of 25 megawatt. The electrolysers will be installed in Taiwan and will serve the semi-conductor’s industry. Hydrogen will be produced at a pace of 5000 Nm3/hour. The electrolysers will be partly fed from renewable energy, preventing an estimated 20 000 tonns of carbon dioxide annual emission.


 

Green light for Nottinghamshire’s hydrogen energy project

C. A. Strawson Farming has secured planning permission for an electrolyser in Nottinghamshire. An 1,25 MW electrolyser will be located at Featherstone House Farm in Bilsthorpe as a part of the project. The electrolyser will use solar and wind energy produced at the farm, and turn water into green hydrogen. The fuel can be used off-site or by the landowner to power hydrogen farm vehicles.


Do you want to be updated on the development in the hydrogen market? Sign up for our news letter here. Contact us for an overview of existing and planned projects in Norway and the world: greensight@greensight.no