Alkaline Electrolysis for Green Hydrogen Explained: Exploring the Benefits
Picture a fuel that, when burned, gives off nothing more than pure water vapour. Swap today’s petrol cars, coal-fired kilns or gas-hungry chemical plants for equipment running on that fuel and you cut out a significant slice of global carbon emissions. That is the vision behind green hydrogen – hydrogen gas produced by splitting water with renewably generated electricity. Because the electricity comes from wind, solar or hydropower, the process adds virtually no greenhouse gases to the atmosphere, making green hydrogen clean [1].
Unlike “grey” hydrogen made from natural gas or “blue” hydrogen whose carbon is only partly captured, green hydrogen can feed the fertiliser industry, power long-haul lorries, store surplus renewable energy, and even replace coal in steel-making. No wonder governments are drafting hydrogen road maps and investors are pouring billions into electrolyser factories.
The Basics: From Water to Hydrogen
The electrolyser is at the heart of the green hydrogen revolution. When electricity is applied to water, it splits each H₂O molecule into hydrogen (H₂) and oxygen (O₂). Several designs exist, but the veteran is alkaline electrolysis, first commercialised over a century ago and still the dominant technology by installed capacity [2].
An alkaline electrolyser houses two metal electrodes – the cathode (negative) and the anode (positive) – immersed in a warm potassium or sodium hydroxide solution. A permeable separator keeps the product gases apart while allowing hydroxide ions to shuttle between the electrodes and complete the circuit. Hydrogen bubbles off the cathode whenever electricity flows, whatever its source, and oxygen rises from the anode. Engineers simply pipe the gases away, dry them and deliver the hydrogen to storage tanks or pipelines.
Think of the system as a modular stack of “water-splitting tiles”. One cell might only be the size of a dinner plate, yet hundreds can be stacked into a container-sized unit capable of producing tonnes of hydrogen daily. Because the underlying chemistry is so well understood, alkaline plants already achieve 60,000 operating hours or more lifetimes – two decades of near-continuous service [3].
Why Industry Still Loves Alkaline Electrolysers
Other electrolyser families, notably Proton Exchange Membrane (PEM) and AEM, grab headlines for high purity or headline efficiencies. Yet alkaline technology remains the workhorse for three solid reasons:
Lowest capital cost. Nickel-based catalysts and common industrial metals substitute for platinum or iridium, slashing hardware prices. Independent analyses routinely show alkaline plants cost 20–40 % less per installed kilowatt than equivalent PEM units [4].
Durability and ease of maintenance. Decades of incremental refinement have produced sealed-stack designs that need no internal cleaning—operators only monitor performance and top up electrolyte as required. Unplanned outages are rare, and replacement components are readily available.
Scalability. From a pilot plant feeding a hydrogen refuelling station to a multi-megawatt installation at an ammonia works, alkaline stacks scale by repetition. Megawatt-scale modules can be ganged together like Lego bricks until the required output – and, just as importantly, the lowest cost per kilogram – is reached [2].
How Does Alkaline Compare with PEM, SOEC and AEM?
When weighing up electrolyser options, engineers typically consider five headline metrics:
Typical efficiency (lower heating value). Alkaline and PEM systems convert about 60–70 % of the input electricity into usable hydrogen energy. In contrast, high-temperature SOEC units can exceed 80 % by harvesting process heat to do part of the work [5].
Capital cost as of 2024. Alkaline hardware is at the bottom of the cost ladder because it uses abundant nickel and steel. PEM equipment is noticeably dearer—precious metal catalysts and complex proton-exchange membranes drive up the price. At the same time, SOEC remains the priciest option, being at pilot-plant scale and relying on costly ceramic stacks.
Ramp-up speed. PEM stacks can jump from idle to full output in seconds, making them ideal for following erratic wind or solar generation. Alkaline units respond within minutes – perfectly adequate for most industrial processes – whereas SOEC systems must warm up and cool down slowly, so frequent cycling is discouraged.
Operating pressure. While traditional alkaline cells operate near atmospheric pressure, many modern designs are now supplied in pressurised configurations. The gas is compressed later if required. PEM designs can deliver hydrogen directly at 30 bar or higher, trimming downstream equipment. SOEC pressure varies with design but is generally kept modest to manage material stress.
Technology maturity. Alkaline electrolysers are a century-old commercial workhorse. PEM has been bankable since the early 2000s and continues to gain market share. SOEC is still in early demonstration territory, with a handful of field trials underway but no large-scale deployment.
These factors mean alkaline remains the default choice for large, steady hydrogen requirements, PEM excels in power-dense or highly variable applications, and SOEC occupies a promising but experimental niche where high-grade waste heat is abundant.
The Economics: Chasing the lower costs
Green hydrogen’s biggest hurdle is price. Depending on local electricity tariffs, producing a kilogram via alkaline electrolysis today costs anywhere from USD 2 to USD 7, still above fossil-derived hydrogen at roughly USD 1.50 [1]. Governments are therefore unleashing a raft of policies, from tax credits in the United States to Contracts-for-Difference in Europe, to bridge the gap while plants scale.
Scale is indeed coming. New gigafactories in Germany, China, and North America will ship more than 20 GW of alkaline stacks annually by 2026 [6]. Mass manufacturing, cheaper renewable electricity, and more intelligent control software are forecast to push green hydrogen prices even lower within this decade. [7].
Grid Balancer and Energy Store
Hydrogen is not merely a fuel; it is chemical energy on tap. Electrolysers can soak up surplus wind at night, convert it into hydrogen, and release that stored energy later through turbines or fuel cells when demand peaks. Engineers call this power-to-gas-to-power, and while today it is less efficient than utility-scale batteries, it offers week- or month-long storage that batteries cannot economically provide [5].
Several pilot projects already use alkaline stacks for seasonal storage, particularly in Nordic regions where hydroelectricity peaks in summer meltwater. The gas is stored in underground salt caverns, piped to industry or re-electrified in winter when hydro reservoirs run low. Analysts forecast that by 2040, long-duration hydrogen storage could balance up to 15 % of Europe’s electricity demand [5].
Decarbonising Heavy Industry
If the grid is the first frontier, heavy industry is the second, arguably the more critical. A tonne of conventional steel emits almost two tonnes of CO₂, chiefly from the coke that strips oxygen from iron ore. Replace that coke with green hydrogen, and most of the carbon disappears. Trials in Sweden and Germany already produce “direct-reduced iron” at pilot scale, with full commercial roll-out for 2030. Each plant will require roughly 600 MW of electrolyser capacity, a scale tailor-made for modular alkaline stacks [2].
Fertilisers tell a similar story. Ammonia synthesis currently consumes roughly 200 million tonnes of fossil-derived hydrogen annually. Convert just a quarter to green hydrogen; the climate savings would equal Spain's annual emissions. Again, significant, steady hydrogen demand and generous site footprints favour alkaline equipment.
Technical Challenges Still to Crack
The engineering community is not complacent. Key challenges include:
Dynamic operation. Traditional alkaline cells prefer a steady current. New power electronics and advanced controls are being developed to let stacks safely ramp between 10 % and 110 % of rated load, opening the door to deeper renewable integration [2].
Electrolyte management. Potassium hydroxide is corrosive, so researchers are focusing on new electrode coatings and alkaline-stable membranes that curb corrosion and lower electrical resistance while retaining the proven KOH electrolyte.
Materials efficiency. Nickel is cheaper than platinum, but not free. Replacing nickel with coated steel or earth-abundant catalysts could reduce capital expenditures by another 10 %.
Balance-of-plant costs. Compressors, dryers and power rectifiers constitute more than half the bill of materials. Integrating stacks directly with renewable DC sources or coupled electrolyser-compression systems promises significant savings.
Policy Momentum and Market Signals
Policy support is accelerating. The European Union’s REPowerEU package targets ten million tonnes of domestic renewable hydrogen production by 2030. The United States’ Inflation Reduction Act offers up to USD 3 per kilogram in production tax credits, making some projects profitable from day one. India, Australia and the Gulf states have all announced multi-gigawatt green-hydrogen hubs, often co-located with solar mega-parks.
Off-takers are stepping up, too. Automotive OEMs have signed offtake agreements for fuel-cell-grade hydrogen, while steelmakers are underwriting long-term supply contracts. These commitments de-risk investment in electrolyser plants, accelerating the virtuous circle of scale and cost reduction.
Looking Ahead: The Alkaline Renaissance
In the 1920s, alkaline electrolysers supplied hydrogen for fertilisers; in the 1960s, they filled balloons and airships; today, they are gearing up to decarbonise heavy industry and transport. Far from being eclipsed by flashier newcomers, the technology is experiencing a renaissance. Expect to see containerised alkaline skids parked next to offshore wind farms, desert solar arrays and nuclear reactors, quietly pumping out zero-carbon fuel.
Continued R&D could raise electrical efficiency to 80 % while extending stack life to 100,000 hours. Digital twins will predictively schedule maintenance, and recyclable components will close material loops. Coupled with plummeting renewable-power prices, these advances mean that green hydrogen should be cheaper within a decade than grey hydrogen everywhere, where sun, wind, or water are plentiful.
Conclusion
Green hydrogen is no silver bullet; it supplements rather than replaces direct electrification. Yet it is the most realistic route to deep decarbonisation for sectors where electrons cannot easily go – shipping, aviation, fertilisers, and high-temperature metallurgy. Alkaline electrolysis, with its rock-bottom cost, proven longevity and straightforward scalability, will provide the lion’s share of that hydrogen for years to come.
Are You Ready to Ride the Green Hydrogen Wave?
Hydrogenera’s engineering teams design, build and maintain turnkey alkaline-electrolysis solutions, from compact 1 MW stacks to 100 MW industrial clusters. If your organisation wants to slash its carbon footprint or secure a hedge against volatile fossil-fuel prices, contact Hydrogenera today to discuss how affordable green hydrogen can power your next growth stage.