Hydrogen Systems: Electrolysers, Fuel Cells, Pipelines

01

How efficient are electrolysers, from kWh to levelised cost?

Hydrogen systems only make sense when three things are examined together: how the gas is produced, what converts it back into useful work, and how it reaches the plants and vehicles that need it. Electrolyser efficiency sets the electricity bill, fuel cells set the duty cycle, and pipelines and contracts set whether either can scale. The operational detail behind those three links is set out topic by topic at WHEC hydrogen systems, which covers production, end use and infrastructure in one place.

An electrolyser is a load, not a generator, and its economics start with a single number: kilowatt hours per kilogram of hydrogen. Published ranges for commercial alkaline and PEM stacks sit between roughly 50 and 55 kWh per kilogram at stack level, with system-level figures higher once rectifiers, pumps, cooling and gas drying are counted. A plant quoting stack efficiency alone is quoting the best case.

Levelised cost of hydrogen follows from that number multiplied by the electricity price, plus capital recovery, maintenance and, where required, compression and storage. Because electricity dominates the running cost, a stack that is two or three kWh per kilogram more efficient than another changes the delivered cost by a margin that compounds over a twenty-year asset life. Operators therefore treat efficiency curves, not nameplate ratings, as the procurement document.

Efficiency also degrades. Membrane and catalyst ageing raise the voltage needed for the same current, so the kWh per kilogram figure drifts upward across the stack’s life. Maintenance schedules and stack replacement intervals belong in the cost model from the first year, not as an afterthought.

02

Can intermittent renewables run an electrolyser steadily?

This is the coupling problem, and it is a control problem before it is a technical one. Wind and solar output varies across minutes, hours and seasons, while electrolysers prefer steady current and stable temperature and pressure. A stack cycled hard and often wears faster; a stack held at low load for long periods runs at poor efficiency.

The usual answers are stacking and buffering. A plant built from several modules can switch modules on and off in steps rather than throttling one large unit across its whole range, which keeps the operating modules near their efficient band. Battery buffering smooths the fastest fluctuations, and grid import or export absorbs the rest. Curtailment, in this design, is a signal that the plant is undersized relative to the resource, not a fault.

The grid connection matters as much as the resource. A plant that can draw power when renewables are short and sell back when they are long behaves differently from one that is islanded, and the contractual arrangement with the network operator shapes the operating strategy more than the electrolyser model does.

03

Fuel cells for vehicles and backup power: what duty cycles demand

A fuel cell vehicle is judged on refuelling time, range and payload, and all three trace back to the tank and the stack. Compressed hydrogen at 350 or 700 bar gives refuelling times comparable to liquid fuels, but the tank mass and volume reduce payload in ways that battery-electric designs do not face in the same proportion. For buses, trucks and materials handling, where the vehicle returns to a depot on a known schedule, that trade is often acceptable.

Stationary fuel cells for backup power and microgrids follow a different logic. A data centre or hospital needs power that starts reliably after a grid event and runs for hours or days. Fuel cells offer long duration without the emissions of diesel generators, but they need stored hydrogen on site, and the storage is usually the larger part of the installation. Maintenance intervals, start-up time from cold and the purity of the feed gas all determine whether the system performs when it is called.

In both cases the stack is only one component. Air supply, thermal management, water management and power electronics determine real-world performance, and a specification that lists only stack power says little about the installed system.

04

Blending hydrogen into gas pipelines: what changes?

Blending is the cheapest way to move hydrogen at scale, because the pipeline already exists. The constraints are physical and regulatory rather than commercial. Hydrogen carries roughly a third of the volumetric energy of natural gas, so a blend of a few percent by volume delivers a smaller share of energy, and end users sized on energy input see the difference.

Materials are the second constraint. Hydrogen embrittles some steels, and compressors, valves and meters designed for methane may not be rated for a hydrogen mix. Leak detection and ventilation requirements change because hydrogen is buoyant, burns with a nearly invisible flame and ignites across a wide range. Safety cases for blended networks are therefore written around detection, ventilation and isolation rather than around the blend percentage alone.

Regulators in several markets cap blending percentages while evidence accumulates, so a project’s permitted blend is often lower than the technically achievable one. That gap, not the engineering, usually sets the timeline.

05

Industrial offtake and hydrogen markets: who signs first?

Hydrogen projects are built against contracts, and the contracts come from a small set of industries. Steel, fertiliser and refining are the three that dominate early offtake, because each already uses hydrogen at scale and each faces pressure to lower the emissions of that use.

Refining consumes hydrogen for desulphurisation and hydrocracking. Ammonia and fertiliser production uses it as a feedstock, where the hydrogen molecule itself matters and substitution is straightforward once supply is secure. Steel is the largest potential shift, with direct reduced iron using hydrogen instead of coke, but the investment is a plant-scale decision that depends on a decade of supply certainty.

Offtake agreements in these sectors are typically long, take-or-pay and tied to a specific industrial cluster, because the hydrogen is expensive to move and cheap to use next door. Clusters, where several plants share a pipeline, a storage cavern and a common supply, reduce the per-unit cost of infrastructure for everyone in them. The commercial structure, not the electrolyser, is what makes the first project bankable.

06

What determines whether a hydrogen project proceeds?

Four variables decide most projects: the price of electricity, the utilisation rate of the electrolyser, the distance to the offtaker, and the terms of the offtake contract. Efficiency improvements help at the margin, and fuel cell performance determines whether the end use is viable at all, but the project either has a customer with a long contract or it does not.

That is why the useful reading on hydrogen is operational rather than promotional. Efficiency figures, duty cycles, blend limits and contract structures are the material that lets a project developer or plant operator judge a proposal. The three subject areas, production, end use and infrastructure, are connected by the same arithmetic, and a project that is sound in one and weak in another does not proceed.