As the automotive industry looks towards environmentally friendly, sustainable solutions, Hydrogen fuel cell electric vehicles (HFCEV) are becoming an increasingly common sight on the world’s roads.
Last month on the blog, AMS Composite Cylinders Director Steve Langron took a look at some of the pros and cons of hydrogen powered cars– examining how the technology works, and its potential as a mainstream alternative to the internal combustion engine.
In this follow up article, Steve looks at the technology a bit closer, examining how the hydrogen is stored, covering the technology, legislation and practicalities involved in delivering a safe, efficient fuel tank for HFCEVs.
How Hydrogen is Stored
There are two main methods of storing hydrogen for HFCEVs:
- As a compressed gas
- As a super-cooled liquid – also known as cryogenic hydrogen
In the late 90s, several hydrogen vehicles brought to market (including the Mini Hydrogen and BMW 7 Series Hydrogen) utilised liquid hydrogen as a combustion fuel source. Although manufacturers are still researching cryogenic hydrogen as a potential fuel source, the industry is now switching focus to the compressed gas route.
Today’s HFCEVs, like the Toyota Mirai and Honda Clarity use compressed gas systems, and major manufacturers are now investing significantly in compressed gas systems for the next generation of vehicles.
Storage Requirements – Practical Considerations and legislation
For any compressed gas system, having a safe, effective, and efficient way to store the hydrogen is essential.
When creating fuel tanks, manufacturers have to consider the following:
- Safety – hydrogen is extremely flammable, and tanks need to be able to stand up to potential damage.
- Range/capacity– the tank needs to contain enough hydrogen gas to power the vehicle over a similar distance to petrol/diesel vehicles.
- Ease of filling – the tanks needs to be quick, easy and safe to fill.
- Weight– weight impacts on fuel-efficiency, so systems need to be as light as possible.
- Filling pressures– tanks need to be able to handle pressures that are compatible with the existing and planned refuelling infrastructure. Currently, most fuel stations dispense hydrogen at either 5,000psi, 10,000psi or both.
- Lifespan – tanks need to last at least as long as the vehicle without requiring replacement.
As HFCEV technology matures, we’re also seeing the introduction of a series of quality standards and testing procedures covering hydrogen cars, such as EC 79/2009.
This regulation already sets out the quality and testing standards that tanks need to pass, in terms of burst testing, pressure testing, fire testing, stress testing, impact testing and penetration testing.
The Solution – Robust, Carbon Composite Cylinders
For current and next generation hydrogen vehicles, carbon composite cylinders make the ideal fuel tanks. Lightweight, durable, and with non-limited life, these specially designed cylinders provide an efficient, effective solution that will outlast the realistic working life of the vehicle.
When it comes to safety, these cylinders are literally bulletproof – when testing the hydrogen tanks for its HFCEVs, Toyota fired a selection of small and large calibre rounds at the cylinders. Bob Carter, Senior Vice President for Automotive Operations at Toyota is quoted as saying:
“They’re safe. In testing, we fired small-caliber bullets at the hydrogen tank and they just bounced off it. It took a 50-caliber armor-piercing bullet to penetrate the shell. And, even then, it just left a hole and the hydrogen simply leaked out. This is no Hindenburg.”
Another benefit to using carbon composite cylinders is that there are already robust quality standards in place – pressurised cylinders conform to ISO 11119-2 standards which ensures a high level of safety testing and re-testing every 5 years.
Lightweight Carbon Composite Cylinders from AMS
AMS Composite Cylinders is the exclusive continental European and UK distributor for an advanced range of lightweight gas cylinders from Advanced Material Systems (AMS).
Products include carbon composite cylinders for a wide variety of breathing air and oxygen therapy applications, including healthcare, respiratory, SCBA (Self-Contained Breathing Apparatus), laboratory, emergency and environmental uses.
Our light composite gas cylinders offer high pressure (300 Bar), NLL (Non-Limited Life) performance, and are accredited for use worldwide – holding a wide range of quality assurance accreditations, including: ISO 11119-2, UN-TPED Pi, DOT (USA) and TC (Canada).
Additional information about AMS Composite Cylinders and our products can be found at www.ams-composites.com.
Post written by Stephen Langron PhD, Director