Green Hydrogen Plants: FRP Tanks, Pipes, Scrubbers and Grating by Zone

In short: In a green hydrogen plant, the electrolyzer package (stacks, separators, the hot lye loop and gas lines) comes from the electrolyzer maker. Around it sits a balance of plant that buys many standard FRP items: raw and treated water tanks, reject and brine tanks, chemical tanks for water treatment, ambient KOH storage, cooling towers and pipe, fume scrubbers, grating, handrail and cable tray. This guide lists them zone by zone, names what stays metal, and gives the information we need to quote.

How this guide fits with our others

This is the product and quotation guide for hydrogen plants. The reasons behind each material choice (KOH temperature limits, water purity, cooling water and why hydrogen vents stay conductive) are covered in this guide; the differences between alkaline and PEM plants have their own section. Other sectors are on our industries page and emerging industries page.

Start with the battery limits

HydrogenPro's technical data for its high-pressure alkaline electrolyzer is a useful example of a maker's scope. Its standard scope covers the electrolyzers, gas separator units with their lye circulation systems and gas scrubbers, and gas analyzers. It lists feed water tanks and pumps and lye mixing tanks and pumps as options. In other words, depending on the contract, those tanks are either inside the package or bought by the plant.

Before you build a tank and pipe list, get the electrolyzer maker's battery-limit drawing. Everything outside it is balance of plant, and that is where FRP is usually specified.

Zone 1: Water intake and treatment

What the zone does

The IRENA and Bluerisk report Water for hydrogen production (2023) gives pre-treatment permeate rates of about 66% for tap water, 58% for river or groundwater and 35% for seawater. Eurowater's leaflet shows treatment trains from raw water through softening, demineralization and EDI or mixed-bed polishing. One of its listed alkaline projects, a 20 MW plant, runs a water plant of 4,500 L/h.

FRP items

• Raw water and break tanks. FRP water tanks, either sectional panel tanks or filament-wound vertical tanks, sized from the withdrawal rate and storage time your process engineer sets.
• Permeate and demineralized water tanks. A resin manufacturer lists deionized and demineralized water at 80 °C for its main vinyl ester resins. For water after the final polisher, check the electrolyzer maker's material list first, because material leaching is one of the factors Eurowater lists for sizing the refinement loop.
• Reject and brine tanks. With seawater, roughly two thirds of the intake leaves as reject. Brine is a chloride duty where FRP avoids the stress corrosion cracking that SSINA describes for austenitic stainless steels above about 60 °C.
• Pipe. FRP pipe for intake, reject and drain lines. See FRP pipe vs HDPE and steel.
• Regeneration chemicals. Where ion exchange is regenerated on site, cation resin uses acid (for example hydrochloric acid) and anion resin uses sodium hydroxide. That brings acid and caustic tanks, dosing tanks and a neutralization tank.

Zone 2: Electrolyte handling (alkaline plants)

Alkaline stacks run on about 25–30 wt% KOH, and HydrogenPro lists about 20 metric tons of electrolyte per stack. The KOH is delivered, stored and mixed before it enters the system. The resin manufacturer's chemical resistance guide rates KOH 0–45% at 65 °C for its standard bisphenol-A epoxy vinyl ester, with a double synthetic veil and a post cure. That covers ambient storage and mixing tanks. It does not cover the hot loop, which runs at 70–90 °C according to IRENA's 2020 cost report.

For each KOH tank, tell us the delivered concentration, the mixing method and the highest temperature the tank can see. Dilution of concentrated caustic gives off heat, so the design temperature may be above ambient. If the KOH arrives as solid flake rather than solution, say so, because dissolving the solid in the tank releases heat as well and changes the mixing design. PEM plants have no KOH electrolyte, so this zone drops out.

Zone 3: Cooling

The IRENA water report states that hydrogen plants use evaporative cooling at 4–6 cycles of concentration, and that no existing plant has yet used air cooling, based on industry interviews. That means a cooling tower, circulating water pipe, basin and blowdown line.

• FRP cooling towers with fill media and fans, sized from heat load, flow, range and design wet-bulb temperature. See cooling tower sizing basics.
• FRP pipe for circulating and blowdown water, which carries salts concentrated four to six times.
• Drift eliminators to limit droplet carry-over from the tower.

The electrolyzer's own heat exchangers come with the package.

Zone 4: Chemical stores and fume control

Hydrochloric acid storage is a classic FRP duty; our guide to FRP tanks for hydrochloric acid covers resin, veil and venting. Where the plant permit or the designer asks for treatment of acid tank breathing and filling vents, an FRP acid fume scrubber can be added. Sizing is covered in packed bed scrubber sizing.

A scrubber here treats acid fumes from chemical tanks. It is not part of the hydrogen gas train. The gas scrubbers inside the electrolyzer package belong to the maker's scope, as HydrogenPro's scope list shows.

Zone 5: Access, walkways and cable routes

Water plants, cooling towers and chemical stores need platforms, stairs and walkways. Typical FRP items are:

• Molded grating and stair treads around tanks and pumps.
• Handrail systems on tank tops and cooling tower decks.
• Cable trays and cable supports on pipe racks and in wet areas.
• Trench and tank covers for neutralization pits and drains.

Hydrogen safety guidance on H2Tools says hydrogen piping should be conductive and bonded or grounded. FRP is an insulator, so where grating or tray sits in a classified hazardous area, your electrical engineer should confirm the bonding and static approach for that area before order. Our data center cable tray guide explains how non-conductive tray is used in electrical spaces.

Zone 6: Drains, neutralization and wastewater

Water treatment and cooling both produce waste streams. Ion exchange regeneration releases spent acid and caustic, cooling towers bleed off blowdown, and reverse osmosis sends reject to drain or to a brine line. Most plants collect these in a neutralization tank or pit before discharge, under the limits in the site permit.

FRP items for this zone include:

• Neutralization tanks with mixers and pH dosing nozzles, built for the acid and caustic that reach them.
• Covers for pits and sumps, flat or domed, with access hatches. See our odor control covers guide for cover shapes and spans.
• Drain and effluent pipe in FRP, which handles changing pH without lining repairs.

Tell us the worst-case chemistry the tank will see during a regeneration, not only the average after mixing.

Coastal and desert sites

Many green hydrogen projects are planned where wind and solar power are strong, which often means coastal or desert land. Both are hard on outdoor equipment.

• UV. Outdoor tanks, pipe, grating and tray need a UV-resistant surface. Our guide to UV degradation of FRP explains surface veils, gel coats and coatings.
• Salt and chlorides. Salt spray and seawater intake favor non-metallic tanks and pipe; see the SSINA note above on stainless steel.
• Heat and sand. Give us the maximum metal-surface and ambient temperatures, and wind and sand loads, so wall thickness and supports can be set.

When to bring us in

The best time to send an inquiry is when the battery limits are fixed and the process engineer has a first tank and pipe list. Early data lets us propose standard sizes where they fit, which shortens fabrication, and flag custom items early. If your schedule has long-lead tanks or cooling towers, send those first.

What stays out of FRP

We do not supply FRP for:

• Hydrogen gas lines and vent stacks. H2Tools states that hydrogen piping should be conductive and bonded or grounded, and quotes CGA G-5.5 that all vent stacks shall be grounded.
• The hot KOH loop, separators and lye filters. These run above the resin rating and belong to the electrolyzer package.
• Oxygen lines, compressors and pressure vessels in gas service. These are specified by the plant designer under the applicable pressure and gas codes.

Alkaline vs PEM: what changes for materials

Most of this guide applies to both main electrolyzer types, but the differences matter for the tank and pipe list.

• Electrolyte. Eurowater explains that PEM electrolyzers do not add an electrolyte such as KOH; the membrane is the electrolyte and the stack runs on ultrapure water. A PEM plant therefore has no caustic make-up or storage tanks for the electrolyte, though the water plant may still store regeneration chemicals.
• Water purity. PEM asks for cleaner water: below 0.1 µS/cm as a starting point in Eurowater's paper, against below 1 µS/cm for standard alkaline units.
• Fluoride. In PEM, fluoride released from the stack forms hydrofluoric acid in the water loop, according to Eurowater. That loop is part of the electrolyzer package and is outside our scope.
• Water use. IRENA's 2023 report finds that PEM on average needs about 20.3% less water withdrawal than alkaline electrolysis, which changes the size of raw water and reject tanks.

Ask your electrolyzer supplier for the battery-limit list early. It tells you which tanks, pipes and cooling items are yours to buy and which come inside the package.

Quotation checklist

Send the following with your inquiry. A full data sheet saves a round of questions:

1. Battery-limit drawing and plot plan with the zones above marked.
2. Tank list: medium, concentration, volume, normal and upset temperature, pressure or vacuum, nozzles.
3. Pipe list: medium, size, pressure, temperature, route length, above or below ground.
4. Cooling duty: flow, range, design wet-bulb, water quality and cycles.
5. Scrubber duty: source vents, gas flow, contaminant and outlet limit.
6. Access items: grating loads and spans, handrail layout, stair heights, cable tray sizes and spans.
7. Site: coastal or desert, UV, wind and seismic data, and any classified areas.
8. Standards and documents your client asks for, plus marking and packing needs.

For grating-only packages, our FRP grating RFQ checklist goes into more detail, and the tank data sheet checklist covers tanks.

How FIBROVX builds for hydrogen projects

Every item above is made to your drawings and data sheets. Resin, corrosion barrier, wall build-up, color and fittings are set per item. Where a client asks for it, a tank can be built to a specification based on ASME RTP-1; this is not an ASME stamp or certification. Sizes, nozzle layouts and special parts outside our standard range are custom / available on request. Read custom FRP manufacturing for how an order runs, and our chemical plants guide for a similar package in a related sector.

We do not claim hydrogen-specific certification. Tell us your client's requirements and we will state which tests and records we can supply for that order.

Watch: FRP in a Green Hydrogen Plant in 27 Seconds

Large water storage and pumping

Electrolysis needs large volumes of treated water and wastewater handling: field-wound FRP tanks up to 5,000 m³ and prefabricated FRP pumping stations.

FAQ

Which FRP items does a green hydrogen plant buy?

Water and chemical tanks, pipe, cooling towers, fume scrubbers for chemical stores, grating, handrail, stairs, cable tray and covers in the balance of plant.

Are feed water and lye tanks part of the electrolyzer package?

It depends on the contract. HydrogenPro lists feed water tanks and lye mixing tanks as options outside its standard scope.

Can you supply FRP hydrogen vent stacks?

No. Hydrogen safety guidance says hydrogen piping should be conductive and grounded, and CGA G-5.5 requires vent stacks to be grounded. FRP is an insulator.

Do PEM plants need KOH tanks?

No. PEM stacks use ultrapure water without a liquid electrolyte, so the KOH zone drops out.

Can FRP grating be used in hydrogen plant process areas?

It is used on water treatment, cooling and chemical store platforms. In classified hazardous areas, your electrical engineer should confirm the bonding and static approach before you order.

What is the most useful document for a quote?

The electrolyzer maker's battery-limit drawing, together with tank and pipe lists giving medium, temperature and pressure.

Sources

• HydrogenPro, High-pressure alkaline electrolyzers technical data (standard scope, options, 30 wt% KOH, about 20 metric tons of electrolyte per stack): https://hydrogenpro.com/wp-content/uploads/2025/06/Technical-details_1.3.pdf
• IRENA and Bluerisk (2023), Water for hydrogen production (permeate rates, cooling cycles, air cooling): https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2023/Dec/IRENA_Bluerisk_Water_for_hydrogen_production_2023.pdf
• IRENA (2020), Green hydrogen cost reduction (alkaline 70–90 °C): https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2020/Dec/IRENA_Green_hydrogen_cost_2020.pdf
• Eurowater, Water treatment for green hydrogen leaflet (treatment train, 20 MW alkaline plant at 4,500 L/h): https://www.eurowater.com/Files/Files/eurowater/Country/International/Leaflets/Basics_water-treatment-for-hydrogen_mini-leaflet_EUROWATER.pdf
• Eurowater, Keeping the water inside electrolyzers ultrapure (KOH 25–30 wt%, leaching potential): https://www.eurowater.com/Files/Files/eurowater/Country/International/Leaflets/WhitePaper-RefinementLoop-UPW-Hydrogen-EUROWATER.pdf
• A resin manufacturer, resin selection guide (KOH and deionized water ratings)
• H2Tools, Static charge in hydrogen piping: https://h2tools.org/faq/static-charge-piping
• H2Tools, H2 vent stack grounding and lightning protection requirements: https://h2tools.org/faq/h2-vent-stack-grounding-and-lightning-protection-requirements
• Wikipedia, Ion-exchange resin (regeneration with hydrochloric acid and sodium hydroxide): https://en.wikipedia.org/wiki/Ion-exchange_resin
• SSINA, Chloride stress corrosion cracking: https://www.ssina.com/education/corrosion/chloride-stress-corrosion-cracking/
• Eurowater, Water treatment for green hydrogen (conductivity starting points, treatment train): https://www.eurowater.com/Files/Files/eurowater/Country/International/Leaflets/White-paper_water-treatment-for-hydrogen_EUROWATER.pdf