Alkaline Electrolysers 101: Everything You Need to Know About the most reliable hydrogen production technology.  

Article main takeaways 

• Alkaline electrolysers are widely used in high-demand hydrogen applications, especially in chemicals, steel, and energy. 
• This technology has a rich history dating back to early 20th-century industrial systems. 
• They're ideal for large-scale hydrogen production and are known for reliability, scalability, and cost-effectiveness. 
• Cost considerations, maintenance, and efficiency are important factors for defining the right technology. 
• Alternatives include PEM and Solid Oxide electrolysers, each with distinct features. 
• FAQ section covers top questions around safety, usage, and costs. 

Introduction to Alkaline electrolysers 

Alkaline electrolysers are foundational to green hydrogen production and a preferred choice for industries requiring high volumes of hydrogen. In this guide, we explore their core function, history, and how they meet the specific needs of industries like chemical production, steelmaking, and energy storage. By the end, you will have a clear understanding of the technology, its benefits, alternatives, and cost considerations. 

What is an Alkaline Electrolyser? 

An alkaline electrolyser uses electrical energy to split water into hydrogen and oxygen gases through a process called electrolysis. Unlike other electrolysis methods, it relies on an alkaline electrolyte—usually potassium or sodium hydroxide. This alkaline medium enhances conductivity, making it suitable for stable and continuous hydrogen production. 

An alkaline electrolyser consists of multiple cells arranged in stacks, with each cell comprising an anode, cathode, and electrolyte separator. The cells are assembled into a unit to produce hydrogen on a large scale, offering a straightforward, efficient solution for industrial applications. 

Historical Evolution of Alkaline Electrolysis 

Alkaline electrolysers have an impressive legacy, beginning with early 20th-century innovators who pioneered electrochemical production. Heron Vrubel, Head of Electrode Development at Stargate Hydrogen is an historian of hydrogen technologies and highlights the early systems like the Schmidt system: “In the early 20th century, Schmidt systems were usually delivered with 26 or 44 bipolar electrodes to match the common 65 or 110 DC systems found in industry." These early designs laid the groundwork for industrial hydrogen production, especially before the advent of semiconductors that could actively control current. 

Norsk Hydro’s Pioneering Plant 

A landmark application was Norsk Hydro’s Rjukan facility, where electrolysis systems used DC generators to support high-volume hydrogen output for fertilizer production. Dr. Vrubel notes that early systems required a gradual start, allowing the electrolyte to adjust to initial bubbles forming in the cells. This slow start-up approach remains relevant for modern alkaline systems, which benefit from gradual heating for optimal function. 

Early Operational Improvements 

In 1931, Elworthy described how small installations used motor generators, while large systems used mercury arc rectifiers—a precursor to the stable power supplies available today. For instance, by coupling mercury rectifiers with variable transformers, industries achieved more control over electrolysis loads, improving efficiency. 

Key Applications of Alkaline Electrolysers in Industry 

Alkaline electrolysers play a critical role in sectors with consistent hydrogen needs. Here’s a breakdown of their applications: 

1. Chemical Production 

In chemical manufacturing, hydrogen is a primary feedstock for producing ammonia, methanol, and hydrogen peroxide. Alkaline electrolysers are especially valuable for their large-scale production capabilities, keeping up with steady demand while remaining cost-effective. 

2. Steel Manufacturing 

The steel industry increasingly favours hydrogen over traditional coke (carbon) for iron ore reduction, a process vital to steel production. Hydrogen can replace carbon in the blast furnace, drastically reducing carbon emissions while also yielding higher-purity steel with smaller carbon content and fewer impurities. Alkaline electrolysers are ideal here due to their consistent output and economic viability for bulk hydrogen. 

3. Energy Storage and Power-to-Gas Applications 

Renewable energy companies use hydrogen as a storage medium, converting excess electricity from wind or solar into hydrogen for later use. This stored hydrogen can be converted back to electricity or supplied directly to industries or fuel cells. Alkaline electrolysers fit well here, given their stability and compatibility with large-scale operations. 

4. Electronics Manufacturing 

In electronics, high-purity hydrogen is used for processes like silicon wafer production. Silicon wafers are the feedstock for the production of processors which are the very heart of every computer and smartphone. Alkaline electrolysers, with their ability to produce significant volumes of hydrogen, are a suitable fit for manufacturing facilities that require steady hydrogen output. 

Why Are Alkaline Electrolysers Preferred? 

Among electrolysis technologies, alkaline electrolysers stand out for multiple reasons: 

• Cost Efficiency: With lower capital costs compared to other electrolyser types, they provide an economical solution, especially for high-demand scenarios. 
• Scalability: Their modular design enables scalability, from smaller units to industrial-sized stacks producing over 1,000 Nm³/h. 
• Proven Reliability: The technology’s long history in the industry translates into robust operation and established maintenance practices. 
• Longer Lifespan: Alkaline electrolysers typically last over 20 years, offering dependable performance with minimal disruptions. 

Pros and Cons of Alkaline Electrolysers 

Let’s explore the practical benefits and drawbacks of using alkaline electrolysers: 

Pros 

• Established Technology: Decades of use mean predictable performance and a wealth of operational knowledge. 
• Low Maintenance Costs: Alkaline electrolysers require basic maintenance, such as cleaning and electrolyte replacement, which is well-understood in the industry. 
• Resistant to Contaminants: Alkaline electrolysers are less sensitive to impurities in water than PEM electrolysers, which reduces operational complications. 

Cons 

• Lower Flexibility: Due to their gradual start-up, they need specific setup for applications needing rapid response or frequent on/off cycles such as wind and solar 
• Larger Footprint: Alkaline electrolysers require more space compared to other types, which may be a consideration for facilities with limited room. 
• Limited Pressure Range: These systems generally operate at atmospheric or low pressures, making them less ideal for high-pressure applications without additional compressors. 

Pricing of Alkaline Electrolysers 

Pricing varies based on capacity, custom features, and installation requirements. Broadly speaking, for smaller applications, procurement professionals expect prices in the range of $500–$1,500 per kW, with total project costs influenced by system size, auxiliary equipment (e.g., compressors, gas separators), and installation. For larger applications, the cost of an Alkaline electrolyser will be drastically reduced to under $500 per kW.  

While alkaline electrolysers are cost-effective at scale, it’s essential to consider the full lifecycle cost, including energy consumption, maintenance, and potential upgrades. 

Alternatives to Alkaline Electrolysers 

1. PEM Electrolysers 

Proton Exchange Membrane (PEM) electrolysers are a faster, more flexible alternative, and can be a better solution for applications with variable power sources, such as direct coupling with wind or solar. However, they come at a higher capital cost and require higher-purity water as input. They are also not as reliable as Alkaline and have not been around for long enough to guarantee desired results. 

2. Solid Oxide Electrolysers 

Emerging on the market, Solid Oxide Electrolysers (SOEs) operate at high temperatures, which offers superior efficiency. However, they are still in the developmental stages for most large-scale applications and require extensive heat management. Furthermore, their life spans are currently much shorter compared to alkaline and PEM electrolysers. 

3. AEM Electrolysers 

Anion Exchange Membrane (AEM) electrolysers combine features of both PEM and alkaline electrolysis, but they’re currently in an early stage of commercialisation and may not yet provide the reliability needed for high-scale, continuous operations.  

About Stargate’s Hydrogen Alkaline Electrolyser Stack 

The Stellar 100, our innovative next-generation pressurised alkaline electrolyser stacks are designed with engineering companies looking to become a Hydrogen Stack integrators in mind. They are supplied with clear documentation, full engineering support and performance guarantees. 

• From 20 to 100 Nm3/h 
• 48 KWh/Kg Hydrogen
• Full Engineering support 
• Operates at 32 bar 
• Patent-pending design 
   

Our pressurised alkaline electrolyser stacks are available with a 6-month lead time and come with performance guarantee. The stacks are build for long operational lifespans, which makes them a reliable choice for continuous hydrogen production. 

This durability aims to minimize downtime and maintenance costs, contributing to the economic feasibility of green hydrogen. The technology has been validated by Fraunhofer, and our stacks have been tested by  ZSW. 

The Stellar Series Stack is the product of choice for Rockfin. The integration was a success, the stack exhibited excellent compatibility and the Stargate team provided comprehensive support from the first meeting and throughout the integration process. 

Michał Wróblewski, Rockfin CEO said – “The passion for electrolyser stack technology and the determination of the Stargate Team has been crucial to achieving this major milestone. We strongly believe in the long-term potential of hydrogen as a clean energy solution.” 

Download our Hydrogen Stack integration guide:  

If you are working in an engineering company looking to become a Hydrogen Stack integrator our latest guide will be a high-value asset. Download the guide here and ensure you will make informed decisions to achieve optimal efficiency.   

FAQs About Alkaline Electrolysers 

1. How does an alkaline electrolyser differ from a PEM electrolyser? 
   • While both split water into hydrogen and oxygen, alkaline electrolysers use a liquid alkaline solution and are more economical, especially at scale. 
      

2. How is hydrogen purity managed? 
   • Alkaline electrolysers typically achieve 99.5% purity, with further purification possible using auxiliary systems. 

3. Is an alkaline electrolyser safe to operate? 
   • Yes, with routine safety measures. It’s important to monitor for leaks and ensure proper grounding. 

4. What kind of maintenance is required? 
   • Basic tasks include cleaning electrodes, replacing electrolytes, and checking seals and safety equipment. 

5. Can they work in variable power settings? 
   • Yes, with the correct setup, Alkaline electrolysers can work in variable power settings. There is a misconception that they are only suited for continuous, stable power sources due to their slower response time.  

6. What type of power source is ideal? 
   • DC power from renewable energy or grid sources, is often coupled with rectifiers for control. 

7. What is the efficiency range? 
   • Efficiencies range between 60-80%, depending on the quality of materials and maintenance. 

8. How are alkaline electrolysers controlled? 
   • Voltage and current control systems regulate the operation, often with integrated monitoring systems. 

9. Are they adaptable to changing hydrogen demands? 
   • While less flexible than PEM electrolysers, alkaline electrolysers can still be adjusted for production needs with proper planning. 

10. Do they produce high-pressure hydrogen? 
    • Yes, Alkaline electrolysers can also produce hydrogen at high pressure. At Stargate, our Alkaline electrolysers produce hydrogen at 32 bar with no need for external compressors. 

Safety and Operational Insights 

Alkaline electrolysers are robust but should be operated with standard industrial safety precautions. Proper grounding, monitoring for leaks, and regular inspection of electrodes and seals are essential. The equipment should be placed in well-ventilated areas to prevent hydrogen build-up, and personnel should follow recommended safety protocols to mitigate risks associated with high voltage and pressurised gas. 

Looking to the Future: Alkaline Electrolysis Innovation 

Today, advancements in materials science are improving alkaline electrolysers. Researchers are developing durable, low-cost electrode materials and improved electrolytes that reduce degradation over time.  

Although alkaline electrolysis technology is often described as being free of precious metals, the fact is that a large fraction of alkaline electrolysers are still utilising electrodes made of ruthenium and iridium which are some of the rarest elements in Earth’s crust. 

While alkaline electrolysers boast high current densities and high efficiency, their wider adoption is hindered by raw material availability issues. Nickel-based alkaline electrolysers do not face raw material availability issues but suffer from lower current densities and lower efficiencies. 

At Stargate, we build upon the best aspects of proven alkaline electrolysis technology and complement it with breakthrough materials. This results in a completely new class of electrolysers: ceramics-based alkaline electrolysers, that have high current densities, and high efficiencies, yet contain no precious metals. This results in significantly lower hydrogen production costs and makes the electrolysers affordable for the end-users. 

Conclusion 

For industries that demand high volumes of hydrogen, the alkaline electrolyser offers a proven, cost-effective solution. Its reliability, scalability, and efficiency make it a viable choice for industries like chemicals, steel, and energy.  

As industries evaluate hydrogen production options, understanding the alkaline electrolyser’s benefits, limitations, and cost implications is crucial. For those needing a sustainable, long-term hydrogen source, an alkaline electrolyser remains an excellent choice. 

If you are curious to see if an alkaline electrolyser is right for your project? Contact Stargate Hydrogen to speak with our experts. We’re here to guide you through the options and find the best solution tailored to your hydrogen needs.