The Technology That Unlocks Green Hydrogen
Water electrolysis — the electrochemical process that uses electrical energy to split water into hydrogen and oxygen — is the foundational technology of the green hydrogen economy, converting renewable electricity into a storable, transportable energy carrier and industrial feedstock whose carbon intensity is determined by the carbon intensity of the electricity used for electrolysis rather than by the chemistry of hydrogen production itself. The electrolyser — the device that performs this electrochemical conversion — has consequently become one of the most commercially and strategically significant pieces of equipment in the global energy transition, attracting investment capital, government policy support, and manufacturing scale-up ambitions from a broad range of electrochemical engineering companies, industrial conglomerates, and energy companies whose strategic positioning in the green hydrogen supply chain depends on access to competitive electrolyser technology and cost structures.
The electrolyser market's transition from pilot and demonstration scale — where installations of 1 to 10 megawatts have been the standard commercial offering — toward the 100-megawatt to gigawatt scale that the industrial green hydrogen production projects in pipeline require is the commercial development that is defining the current market phase. The technical challenges of scaling electrolyser systems — maintaining stack performance, managing the thermal and mechanical stresses of large-scale operation, and building the balance of plant systems whose engineering at large scale differs substantially from the smaller-scale systems whose performance data underlies commercial guarantees — are being addressed through the parallel routes of manufacturing larger individual stacks and combining multiple stacks in modular installations whose engineering replicates proven smaller-scale designs rather than requiring new engineering validation for each step-change in scale.
Technology Competition: PEM, Alkaline, and SOEC
Three electrolyser technology platforms are competing for market share in the green hydrogen production market, each with distinct performance characteristics, cost structures, and operational advantages that create differentiated competitive positions across the range of green hydrogen production applications. Proton exchange membrane electrolysers — using a solid polymer membrane as the electrolyte and operating at relatively high current densities — provide the fast response time and operational flexibility that makes them well-suited to coupling with variable renewable electricity sources, accepting the intermittent and variable power supply from wind and solar generation without the operational constraints that alkaline systems impose. The PEM electrolyser market is dominated by a small number of companies — Nel Hydrogen, ITM Power, Plug Power, and Siemens Energy's electrolyser business — whose technology development and manufacturing scale-up investment is establishing the cost and performance benchmarks against which alkaline and solid oxide technologies are measured.
Alkaline electrolysers — the more established technology using liquid potassium hydroxide electrolyte — have the advantage of lower capital cost per megawatt than PEM and the track record of industrial-scale deployment in the chlor-alkali and fertiliser industries that provides operational experience at scales that PEM commercial deployment has not yet matched. The alkaline electrolyser's main competitive limitation is its less flexible operation — alkaline stacks require minimum load operation, respond more slowly to power input changes, and require more complex management of the liquid electrolyte — that makes them less well-suited to the intermittent renewable electricity supply profiles that characterise the most cost-competitive green hydrogen production scenarios. The solid oxide electrolyser — operating at high temperatures above 700 degrees Celsius and achieving higher electrical efficiency than either PEM or alkaline at the cost of thermal management complexity and the degradation challenges of high-temperature ceramic components — is at an earlier commercial stage but is attracting increasing investment for applications including industrial heat integration and the reversible fuel cell systems that could provide both electrolysis and power generation from a single electrochemical system.
Cost Reduction: The Race to Competitiveness
The commercial viability of green hydrogen as an industrial feedstock and energy carrier depends critically on the cost reduction trajectory of electrolysers and the renewable electricity whose cost constitutes the largest single component of green hydrogen production economics. Electrolyser system costs have declined substantially over the past five years as manufacturing scale has increased, component supply chains have developed, and engineering optimisation has reduced the material content per unit of installed capacity. The industry's cost reduction trajectory — targeting electrolyser system costs below 500 euros per kilowatt from current levels of 700 to 1,000 euros per kilowatt for leading PEM systems — is supported by the manufacturing scale-up that the growing project pipeline is enabling and by the learning rate that the electrolyser industry is achieving as cumulative installed capacity grows. The electrolyser manufacturing investments being made by Thyssenkrupp Nucera, Nel Hydrogen, McPhy, and a range of Asian electrolyser producers whose government support has enabled rapid capacity expansion are creating the manufacturing scale whose unit cost implications will determine how quickly green hydrogen production economics become competitive with the grey hydrogen that industrial consumers currently purchase at prices that reflect the marginal cost of natural gas reforming without a carbon cost.
The green hydrogen production economics are most favourable in locations combining very low-cost renewable electricity — the utility-scale solar generation in Chile, Saudi Arabia, Morocco, and Australia whose levelised cost of electricity is approaching 20 to 25 euros per megawatt-hour in the most favourable locations — with proximity to industrial hydrogen consumption or liquid hydrogen export infrastructure. The large green hydrogen projects in development in these locations — including projects in NEOM, the Moroccan Atlantic coast, and Western Australia — represent the demand pipeline whose financial close decisions will determine how rapidly the electrolyser manufacturing scale required to supply them is brought forward. The timeline for these large projects to reach financial close and construction start has consistently been extended beyond initial projections as the project economics, offtake arrangements, and financing structures required have proven more complex to finalise than the scale of government and corporate commitment to green hydrogen would have suggested.
Grid Integration and the Flexibility Value
The role of electrolysers as demand-side flexibility assets — consuming renewable electricity when generation exceeds grid demand, producing hydrogen that can be stored and used when electricity generation is insufficient — is creating a commercial value proposition for electrolyser deployment that complements the primary green hydrogen production rationale with a grid services revenue stream whose value is growing in the high-renewables European and North American electricity market contexts described elsewhere in this series. An electrolyser that can modulate its power consumption from zero to full rated load in response to grid frequency, wholesale electricity price signals, or transmission system operator balancing requests provides a flexibility service that has commercial value in ancillary service markets whose revenue supplements the hydrogen production economics. The design of electrolysers for operational flexibility — optimising the minimum load, ramp rate, and cycling capability of electrolyser systems that will operate in intermittent modes driven by electricity price optimisation rather than continuously at full load — is an engineering priority whose commercial importance grows with the frequency of extreme wholesale price events in the markets where electrolysers are deployed.