Transport of PEM and alkaline electrolysers: equipment, dimensions and logistics for green hydrogen plants in Spain

For the special-transport operator, this is the logistics picture. Each industrial-scale green hydrogen project needs between 10 and 700 MW of electrolysis capacity, which translates into tens or hundreds of PEM containers or alkaline skid-format modules moving from European or Asian factories to the Spanish site, across an operational window that runs from the developer's final investment decision to the plant's commercial entry into operation. This article sets out which type of electrolyser needs which type of special-transport equipment, which rules have applied since the Spanish framework tightened in 2025–2026, and how an end-to-end operation is planned, from departure at the European factory to unloading at the Spanish plant.

Why the electrolyser is special cargo: three factors

Unlike the photovoltaic flow, where most cargo travels in conventional trucks, and unlike the wind flow, where every component activates special transport but with very different equipment profiles, the electrolyser's logistics profile is shaped by three factors:

First, weight per unit. An industrial alkaline stack frequently weighs 40-60 tonnes per unit; the higher-capacity integrated modules can reach 150 tonnes. A 40' HC PEM container with a 2.5 MW electrolyser generally sits between 25 and 40 tonnes, depending on the manufacturer. Both profiles activate the special-transport regime by mass under Anexo IX del Reglamento General de Vehículos, especially after Orden PJC/780/2025 raised the standard administrative maximum mass to 44 tonnes for articulated combinations of five or more axles.

Second, dimensions. Containerised PEM electrolysers usually keep to the standard ISO format (20', 40' or 40' High Cube at 2.90 m height) and travel on a conventional extendable platform. Alkaline skid-format electrolysers vary far more: some modules can exceed 4 metres in height and 3 metres in loaded width, which activates an ACC in the exceptional category for width under Anexo III del Reglamento General de Circulación and Instrucción 16/TV-90 de la DGT.

Third, the equipment's operational sensitivity. PEM membranes travel hydrated and are sensitive to dehydration; alkaline electrodes are dry but structurally fragile; solid-oxide (SOEC) stacks operate at high temperature, and their ceramic components do not tolerate the vibration of poorly damped transport. The special-transport operator works with air-suspension platforms, manufacturer-validated lashing and, in some cases, acceleration monitoring along the route.

PEM, alkaline, AEM and SOEC: four technologies, four transport profiles

The commercial electrolysis market splits across four technologies, and each defines a distinct transport profile:

In logistics terms, the key distinction is PEM versus alkaline, which together cover more than 95% of the current industrial market. AEM is an emerging technology with a residual presence in small or pilot projects. SOEC still has low commercial penetration and clusters in demonstration projects, with a logistics profile close to alkaline. PEM containers travel on a standard extendable platform and are indivisible loads by construction: they are not disassembled for transport. Alkaline skids range from the conventional low-bed band (modules <44 tonnes) to the hydraulic modular band (large configurations above 60 tonnes).

One Spanish data point captures the pattern. The Onuba phase of the Andalusian Green Hydrogen Valley, developed by Moeve in Palos de la Frontera with a final investment decision approved in February 2026, builds its initial 300 MW by combining 15 scalum® alkaline units from Thyssenkrupp nucera, 20 MW each, with PEM technology from Siemens Energy for technology-risk management. That is fifteen alkaline skid-format movements plus a non-public volume of PEM movements, in a single project.

The PEM container and the alkaline skid are two distinct loads with two distinct equipment profiles. The logistics file begins with that distinction.

Weights and dimensions by capacity: from 1 MW to 100 MW

A project's capacity sizing determines how many shipments it needs, and of what type. Three market references:

Typical 1 MW PEM: small skid or 20' container, weight 15-20 tonnes. Fits a conventional low bed, with no overhang and no exceptional width. Market example: the Petronor pilot plant in Muskiz (Bizkaia), 2.5 MW PEM, operational since 2023.

Typical 5 MW PEM: 40' HC container, weight 25-40 tonnes. Extendable platform. The Cummins HyLYZER 1000, the benchmark in this segment, is advertised in its datasheet as "only two trucks per module", a clear design choice to keep logistics movements per unit to a minimum. Market example: the Iberdrola–bp plant in Castellón, 25 MW PEM, with operation planned for the second half of 2026.

20 MW PEM or alkaline: for PEM, 4 to 8 containerised modules, depending on the manufacturer; for alkaline, 1 to 2 large skids, or the single standardised scalum®-type module. Market example: the Iberdrola Puertollano plant (Castilla-La Mancha) has run since 2022 on a Nel Hydrogen PEM electrolyser made up of 16 stacks of 1.25 MW, the distributed modular PEM format.

100 MW alkaline or PEM: between 5 and 15 large skids in alkaline (scalum® 20 MW × 5 units), or between 20 and 40 40' HC PEM containers, depending on manufacturer and plant design. Examples under construction: Repsol Petronor 100 MW PEM (announced in January 2026, €292 million investment, operation planned for 2029); Repsol Cartagena 100 MW (approved in September 2025, Repsol's first infrastructure of this size). The split is clear: alkaline concentrates the weight in fewer, higher-tonnage modules; PEM spreads it across more standard units.

For a 300 MW plant, the Onuba format of the Andalusian Valley, the critical flow sits at 15-25 special shipments on the alkaline line + dozens more on the PEM line, spread across an installation window that usually runs between 12 and 24 months from the first shipment to commercial entry into operation.

Balance of Plant: what usually goes uncounted

The electrolyser stack is only a fraction of the plant's logistics flow. The Balance of Plant (the auxiliary equipment the stack needs in order to run) often generates more special trips than the stacks themselves. A typical list for an industrial-scale plant:

• Power rectifiers with integrated HV/MV transformer: up to 50 tonnes per unit for large configurations; logistics profile identical to that of the evacuation substation transformer of a photovoltaic plant or wind substation. Exceptional category by mass when it exceeds 40 tonnes.
• Hydrogen purification and drying systems: gas separators, PSA adsorption columns, molecular-sieve dryers. Generally skid-mounted, weight 10-30 tonnes, with lengths that can exceed 12 metres.
• Cooling systems: chillers, heat exchangers, cooling towers for the largest projects. Some can travel pre-assembled; others are assembled on-site.
• Intermediate compressors for storage at 30 bar or above.
• Intermediate hydrogen storage tanks: variable weight, depending on material and capacity.

Each of these items has its own manufacturing window, its own delivery schedule and its own transport profile. Sound logistics planning builds them in from the first commercial phase, rather than treating them as a separate flow discovered mid-execution.

Applicable Spanish and European regulation

The regulatory framework for electrolyser transport in Spain has tightened sharply between 2025 and 2026. The key reference points:

Maximum weights and dimensions (Orden PJC/780/2025). Published in the BOE on 23 July 2025, it amends annexes II, IX, X and XVIII of the Reglamento General de Vehículos. The main change relevant to the electrolyser flow: an administrative maximum mass of 44 tonnes for articulated combinations of five or more axles (in force since 23 October 2025), and a length of up to 32 metres for euromodular combinations (in force since 24 July 2025). The height increase to 4.5 metres applies only to specified cases (closed containers approved for combined/intermodal transport, live livestock, straw and fodder, and industrial supplies on set routes under 50 km), so it is marginal in the standard electrolyser flow, where the 40' HC PEM container stays at 2.90 metres. The consequence that matters for the electrolyser: the standard alkaline skid band (30-44 tonnes) can travel under the general regime without an exceptional ACC by mass, provided the vehicle configuration allows it and the ITV reflects the new limit.

Complementary Circulation Authorisation (ACC). Electrolysers that exceed the standard limits of Anexo IX RGV require an ACC. Jurisdiction follows territorial traffic competence, not road ownership or the origin and destination of the operation. Traffic is a transferred competence in Catalonia (since LO 6/1997), the Basque Country and Navarre; across the rest of the common territory, the DGT manages it. In practice: the Servei Català de Trànsit (SCT) authorises all circulation that touches Catalan roads, including the AP-7 and AP-2 state motorways within Catalonia; the DGT authorises the rest of the common territory, on state and regional networks alike (Aragón, Comunidad Valenciana, Castilla-La Mancha and others). Since 1 May 2024, all special-transport circulation running wholly or partly on the Catalan road network must hold SCT authorisation, and a DGT ACC is not valid for Catalan stretches. A shipment France → Catalonia → Aragón therefore needs an SCT ACC for the whole Catalan stretch (including the AP-7 from La Jonquera) and a DGT ACC for the Aragonese stretch of the Ebro Corridor. Aragón issues no ACC of its own; its traffic is managed by the DGT.

Administrative control document in electronic format. Ley 9/2025 de Movilidad Sostenible (BOE no. 291 of 4 December 2025, in force 5 December 2025), in its Eighth Transitional Provision, makes the administrative control document compulsory in exclusively electronic format from 5 October 2026, ten months after the law took effect. It replaces the paper administrative control document regulated by Orden FOM/2861/2012, which in practice usually coincides with the consignment note under Ley 15/2009 LCTTM when it carries the data required by article 6 of that order. The term taking hold in the market for the Spanish domestic electronic document is "documento de control electrónico" (electronic control document), alongside the e-CMR already established for international transport. The special-transport operator must have its platform integrated with the shipper's system before 5 October 2026; paper shipments after that date are administratively invalid.

Consignment note and contract (Ley 15/2009 LCTTM). The Inland Freight Transport Contract Act governs the inland transport contract and the national consignment note (arts. 10–14). It applies to every shipment with an origin, destination or transit point in Spain, and remains the central contractual document of the electrolyser flow.

A critical clarification on ADR. During its transport from factory to plant, the electrolyser itself is not ADR dangerous goods. The equipment travels dry, with no hydrogen content and no working electrolyte. The hydrogen produced later is indeed ADR Class 2 (UN1049 for compressed hydrogen, UN1966 for refrigerated liquefied hydrogen), but transporting that hydrogen is a separate operation, after the plant is commissioned, governed by its own ADR regime. That second operation belongs to operators specialised in gas transport; it is not part of delivering the electrolyser.

Regulation (EU) 2024/1789 on the internal hydrogen market and decarbonisation. The European reference framework for plant operation; it applies to the logistics file only indirectly, through the documentation the developer completes.

The electrolyser in transit is not ADR. The hydrogen it later produces is. Confusing the two operations is the first mistake in the file.

Operational window: from the European factory to the Spanish plant

A typical schedule for an industrial-scale electrolyser project:

• Final investment decision (FID) and factory order: the developer closes the OEM contract. From here the clock runs.
• Factory production: 6 to 12 months for standard configurations (containerised PEM, modular alkaline skid); 12 to 18 months for large or custom configurations. Manufacturers at scale (Nel, Cummins-Accelera, Thyssenkrupp nucera, Siemens Energy, ITM Power) run plants with capacities on the order of several GW/year, which shortens the lead time when the production slot is booked in advance. The Cummins-Accelera gigafactory in Guadalajara (Castilla-La Mancha), with 500 MW/year of PEM scalable to 1 GW/year, is Spain's first case of large-scale domestic manufacturing, and it cuts dependence on the imported flow for PEM technology.
• Dispatch from the European factory: overland through France for German, Belgian or British factories (Thyssenkrupp nucera, John Cockerill, ITM Power); overland through France plus a ferry from Norway for Nel Hydrogen; by national road for Cummins-Accelera Guadalajara orders. 8 to 20 days in transit, depending on origin and the customs-clearance window.
• Arrival at the logistics centre: the Port of Barcelona as the maritime entry point for the imported flow from Asia, or as a transfer point for the overland flow with a stop in the free-trade zone. Direct delivery to the plant when the itinerary allows it with no stop.
• Distribution to the plant site: 2 to 7 days more, depending on the corridor (Mediterranean, Ebro, A-2, A-66) and the final rural stretch.
• Coordination with the installation window: the developer's plant confirms the unloading and lifting slot (where applicable); the special-transport operator delivers in a window that matches the availability of the lifting crane and the OEM's assembly team.
• Typical total time from order to operation: 12 to 18 months for standard configurations; 24 to 36 months for the largest plants with FID subject to IPCEI or Recovery Plan financing.

Operational cases: two typical routes

Two composite examples, both built on real market profiles, show how the flow works:

Case 1: PEM Nel Hydrogen, Norway to Catalonia. 40' HC PEM container with an MC500 electrolyser of 2.5 MW, gross weight around 35 tonnes. Origin: Nel Hydrogen plant in Heroya (Norway). Destination: a site in the province of Tarragona, Catalonia. Itinerary: ferry from Larvik or Oslo to Hamburg or Rotterdam, then overland through Germany, Belgium and France (Languedoc corridor), entry into Spain at La Jonquera, logistics centre in the Port of Barcelona free-trade zone, and a final stretch on the AP-7 to the plant. Permits: an ACC for the French stretch, subject to French national authorisations; an SCT ACC for the Catalan itinerary (including the AP-7, by transferred traffic competence). Vehicle configuration: conventional extendable platform, with no pilot vehicle required on size grounds (the container does not exceed 3 metres in width). Total door-to-door time: 9 to 14 working days, with the documentation prepared in advance.

Case 2: Alkaline Thyssenkrupp nucera, Germany to Aragón. scalum® alkaline skid of 20 MW, gross weight around 120 tonnes, approximate dimensions 12 × 3.5 × 4 metres. Origin: Thyssenkrupp nucera plant in Dortmund (Germany). Destination: a green hydrogen plant in the province of Zaragoza. Itinerary: by road from Dortmund, through Belgium and France, entry at La Jonquera, across the Catalan network and on along the Ebro Corridor to the Aragonese site. Permits: an exceptional ACC by mass (>44 t) and by loaded width (>3 m), with SCT authorisation for the whole Catalan stretch (entry at La Jonquera and passage across the Catalan network towards the Ebro) and DGT authorisation for the Aragonese stretch of the Ebro Corridor. Vehicle configuration: large-format hydraulic modular, a setup outside the conventional fleet range, coordinated by Pastor together with a specialised operator. A private pilot vehicle is mandatory along the whole itinerary, with escort handover between administrations when the convoy crosses two or more jurisdictions in a single day. Total door-to-door time: 8 to 12 working days, sensitive to permit windows.

The difference between the two cases sums up the sector pattern: the containerised PEM fits the conventional special fleet and moves on a tight schedule; the large-format alkaline needs a specific equipment setup and denser permit coordination.

How we approach this at PASTOR

Sixty years of family tradition in special transport from Catalonia, with an established operational presence on the Mediterranean Corridor (the Port of Barcelona as the main entry point for the imported flow), links through the Ebro Corridor to Aragón, La Rioja, Navarre and eastern Castilla y León, and a cross-border connection with France via La Jonquera, Le Boulou and Le Perthus. Specific accreditation from the Centro de Servicios al Transporte at the Port of Barcelona lets us handle imported equipment from the point of maritime entry.

PASTOR's natural operating area takes in four relevant green hydrogen projects: the Iberdrola–bp plant in Castellón (25 MW PEM, operational in the second half of 2026); the Repsol Cartagena project (100 MW, approved in September 2025); the Iberdrola Zona Franca Barcelona plant (2.5 MW PEM, operational since January 2022, for TMB buses); and the Iberdrola Puertollano plant (Castilla-La Mancha, 20 MW PEM Nel since 2022, with a phase II of a further 200 MW on order for delivery in 2028 and commercial operation in 2029). For projects whose flows do not touch the Mediterranean–Ebro axis (Moeve Onuba in Palos de la Frontera, Repsol Petronor in Muskiz, other developments in the Andalusian Valley or the Basque Hydrogen Corridor), special-transport operators with a closer geographic base are the shipper's natural choice, and we say so to the developer in the first conversation. Knowing where we fit is the mark of a mature operator, not a diminished one.

In the electrolyser flow, PASTOR concentrates on components whose logistics fit our own fleet: PEM containers in ISO 20' / 40' / 40' HC format (conventional extendable platform), alkaline skids up to 44 tonnes (conventional or extendable low bed), and skid-mounted Balance of Plant (rectifiers, PSA systems, chillers, compressors). These components make up the bulk of the logistics flow on most medium-sized PEM and alkaline projects. For large-format alkaline skids that exceed the conventional fleet range (scalum® 20 MW-type configurations with a gross weight around 120 tonnes, or heavier stacks from >100 MW projects), PASTOR coordinates the operation end to end. We bring the large-format hydraulic modular into the plan from the first project-planning phase, alongside the conventional flow, under a single point of contact for both commercial and documentation matters.

The ADR regime does not apply to transporting the electrolyser itself. Once in operation, the plant will generate hydrogen under ADR Class 2 (UN1049 / UN1966), but transporting that hydrogen is a separate operation that needs an operator specialised in gases; it is not part of delivering the electrolyser in the installation phase. We put this clarification in the commercial file from the first conversation with the shipper.

For each green hydrogen project, from a 2.5 MW PEM pilot to a 100 MW phase with fifteen coordinated alkaline movements, the PASTOR operations engineering team prepares: an analysis of physical parameters by component (stack, skid, BOP); ACC categorisation under the DGT or SCT regime, according to the territory the itinerary crosses; a configuration proposal by component (conventional extendable, low bed, or large-format hydraulic modular, as applicable); the administrative control document in electronic format under Ley 9/2025 de Movilidad Sostenible, ahead of its 5 October 2026 deadline; coordination with the competent traffic authorities on the critical points of the final stretch; coordination with the port authority when components enter via Barcelona; and synchronisation with the OEM's on-site lifting and assembly schedule.

When the unloading window arrives, the PEM containers are positioned in installation order, the alkaline skids on their day, the rectifiers and BOP equipment in their synchronised slot, and the electronic documentation closed before departure from origin. The shipper holds a single point of contact: ours.