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Investment in H2 is increasing. Type IV tank manufacturer NPROXX is now a 50/50 joint venture with Cummins, which has also acquired key suppliers of fuel cells and H2-producing electrolyzers. These 500-millimeter-diameter, 2,200-millimeter-long automotive/heavy-duty tanks by NPROXX store H2 at 350 bar. Photo Credit: NPROXX

High-pressure gas storage vessels represent one of the largest and fastest-growing markets for advanced composites, particularly for filament-wound carbon fiber composites. The primary end markets are for storage of liquid propane gas (LPG), compressed natural gas (CNG), renewable natural gas (RNG) and hydrogen gas (H2). While LPG tanks can be used in vehicles, there is also a growing market for cooking and heating in developing countries.

CNG, RNG and H2 fuel systems are increasingly used in passenger cars, buses, trucks and other vehicles or for bulk transportation/distribution — also called mobile pipeline — to supply refueling stations or industrial sites. In vehicles, these fuel storage tanks are a key component in reduced- or zero-emission powertrains for clean alternatives to gasoline, diesel and jet fuel. These powertrains also provide a chargeless alternative to battery-powered vehicles with refueling infrastructure and refill times similar to fossil fuels.

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Pressure vessel types and construction as classified by the American Society of Mechanical Engineers (ASME) and the International Organization for Standardization (ISO). Photo Credit: CW

Pressure vessels are organized into five types:

  • Type I: All-metal construction, generally steel.
  • Type II: Mostly metal with some fiber overwrap in the hoop direction, mostly steel or aluminum with a glass fiber composite; the metal vessel and composite materials share about equal structural loading.
  • Type III: Metal liner with full composite overwrap, generally aluminum, with a carbon fiber composite; the composite materials carry the structural loads.
  • Type IV: An all-composite construction, polymer — typically polyamide (PA) or high-density polyethylene (HDPE) liner with carbon fiber or hybrid carbon/glass fiber composite; the composite materials carry all the structural loads.
  • Type V: Linerless, all-composite construction.

Historically, Type I tanks have held more than 90% of the market. However, that is beginning to change, with increased sales of Type III and Type IV vessels that use composites to reduce weight and increase compressed gas storage efficiency. Type V is still nascent and mostly used in space applications, but is a sector to watch as the New Space industry develops.

 

Market drivers and growth

The overwhelming driver in this market is growing global commitment to reduce the impacts of climate change by switching away from fossil fuels to renewable, reduced-emission fuels (e.g., CNG, RNG and H2), aiming for zero emissions by 2050. According to the International Energy Agency:

“Climate pledges by governments to date — even if fully achieved — would fall well short of what is required to bring global energy-related carbon dioxide (CO2) emissions to net zero by 2050 and give the world an even chance of limiting the global temperature rise to 1.5°C, according to the new report, ‘Net Zero by 2050: a Roadmap for the Global Energy Sector.’

Internal combustion engine (ICE) global phase-out map

Governments with published targets for phasing out new sales of internal combustion engine (ICE) passenger cars, from November 2020 report. Photo Credit: International Council on Clean Transportation (ICCT)

Note, that in addition to the commitments shown above, the U.S. states of Connecticut, Maryland, Massachusetts, New Jersey, New York, Oregon, Rhode Island, Vermont and Washington have committed to no new fossil fuel passenger cars by 2050, and these states, plus California, Colorado, Hawaii, Maine, North Carolina, Oregon, Pennsylvania and the District of Columbia will prohibit new fossil fuel medium- and heavy-duty vehicle sales as of 2050.

 

Emerging hydrogen economy

The fastest-evolving segment of the pressure vessel market is hydrogen storage. Coming out of the pandemic there has been renewed and serious regulatory interest in North America, Europe and China in reducing carbon emissions in mobility applications. In the U.S., much of the decarbonization effort is being driven by the state of California, which has policies in place to ban sale of gas-powered cars by 2035. This and other efforts have led to very public efforts by car and truck manufacturers to launch new lines of battery-electric vehicles (BEVs).

However, BEVs come with challenges of their own — namely, difficulty accessing some of the rare Earth metals that batteries require, long battery recharge times and lack of refueling infrastructure. The latter will be addressed, in part, by the Biden Administration’s Infrastructure Investment and Jobs Act, which provides $1 trillion in public infrastructure investment over the next decade.

Battery recharge technology is evolving rapidly and will only get easier and faster, but the metals resource challenge is not easily solved. Because of this, some segments of the transportation industry have turned to hydrogen fuel cell (HFC) systems as a more sustainable alternative.

Hydrogen is often transported via a multiple element gas container (MEGC), which is comprised of multiple carbon fiber composite pressure vessels ganged in a metallic cage and loaded onto a truck. The largest MEGCs have as many as 81 tanks. Photo Credit: Hexagon Purus

There are several advantages of HFCs. First, they can be refueled at hydrogen refueling stations (HFS) with pump and nozzle technology very similar to that used at gasoline stations. Second, the only emissions from the HFC process is water. Third, hydrogen can, ultimately, be produced using methods that minimize carbonization — called “green” hydrogen.

Although green hydrogen technology is still being developed, its viability is helping spawn rapid expansion of the HFC economy, particularly in light-, medium- and heavy-duty trucks; fleet vehicles; buses; trains; ships; and some passenger vehicles. Aerospace is also expected to adopt hydrogen as a fuel source for combustion.

This market expansion is increasing demand for storage and distribution of hydrogen. Storage of hydrogen, like gasoline, is primarily done onboard the vehicle and is achieved with a series of carbon fiber/epoxy-overwrapped pressure vessels. The larger the vehicle, the more pressure vessels are required. Distribution is achieved primarily via transport of hydrogen in multiple composite pressure vessels on tractor trailers.

Hydrogen’s energy density, on a mass basis, is nearly three times that of gasoline. On a volume basis, however, the situation is reversed — gasoline’s energy density is four times that of hydrogen. Hydrogen, therefore, would best be stored in liquid form to maximize its energy density. But storing hydrogen as a liquid requires cryogenic temperatures, which is not easily or cheaply achieved. So, for now, hydrogen is most efficiently stored as a gas, typically compressed in a range of 350-700 bar. 

Schematic of elements comprising a hydrogen refueling station (HRS). Type IV composite pressure vessels may be used in tube trailers to deliver H2 to the station and/or in the cascade of tanks for buffer storage on site. Photo Credit: CW

The range of a hydrogen fuel cell vehicle (HFCV) depends on the total mass of hydrogen it can store, and the mass capacity depends on the size of the pressure vessel and the pressure of the gas. For example, the 2022 Toyota Mirai HFCV has three 142-liter, Type IV tanks, each with a max pressure rating of 700 bar and a hydrogen mass capacity of 5.6 kilograms. Total hydrogen capacity per car is 16.8 kilograms and the range is 360 miles. Hydrogen storage tanks on trucks, buses and other large vehicles are larger, and tank quantities are greater. 

 

Pressure vessel economics

Carbon fiber/epoxy pressure vessels are manufactured using either wet wind or towpreg filament winding. The good news here is that filament winding can be automated relatively easily, so increasing manufacturing capacity will be very manageable. The bad news is that the type of carbon fiber required for hydrogen pressure vessels is relatively expensive and not currently produced at volumes suitable for the demand.

The carbon fiber of choice for hydrogen pressure vessels is Toray Composite Materials America’s (Tacoma, Wash., U.S.) T700S, a standard modulus (SM) fiber that offers particularly high translational properties. Similar carbon fibers are offered by all of the major carbon fiber manufacturers, including Hexcel (Stamford, Conn., U.S.), Mitsubishi Group (Tokyo, Japan), Teijin (Tokyo, Japan), SGL Carbon (Wiesbaden, Germany) and others.

Carbon fiber use per tank depends on the capacity of the tank and its pressure rating, but a good rule of thumb is that 10 kilograms of carbon fiber is required for every 1 kilogram of hydrogen stored at 700 bar. So, a tank that holds 5 kilograms of hydrogen at 700 bar will require 50 kilograms of carbon fiber.

The eventual challenge for this market may be one of reliable carbon fiber supply. There are nine major manufacturers of carbon fiber pressure vessels for hydrogen storage: Faurecia, Hanwha Cimmaron, Hexagon Composites, Hexagon Purus, Iljin Hysolus, NPROXX, Plastic Omnium, Toyota and Toyoda Gosei. All project varying levels of tank production expansion over the next five years. By some estimations, total market for the hydrogen storage market could, by 2025, approach half a million carbon fiber composite tanks. Meeting this market’s needs could be a challenge.

Carbon fiber manufacturing is capital-intensive and expensive, with a carbon fiber line requiring investment of about $100 million and two years to construct (click here for more about how carbon fiber is made). Because of this, carbon fiber producers are loathe to invest in new capacity without a compelling business case to do so. And in some cases, where demand is high, a contractural commitment is required by the carbon fiber customer to justify the cost to the carbon fiber producer.

The hydrogen market is in the early stages of what appears to be rapid maturation, so it remains to be seen how carbon fiber manufacturers will respond to the demand signals being sent by tank producers. And, of course, carbon fiber manufacturers have other markets to monitor as well, including wind energy, aerospace and automotive, all of which are exerting their own demand pressures.

For more on composite pressure vessels in the hydrogen storage market, visit the CW #hydrogen hashtag, or read Ginger Gardiner’s two-part series in CW:

Landscape Photo Credit: CST Composites

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