4. Proven Track Record%%

Hydrogen has been used commercially for many years [5]. Some of the current uses include:

• Ammonia produced from hydrogen for use in fertilisers and for reducing sulphur in crude oil.
• The manufacture of electronic components and chemicals.
• Food processing.
• In hydroelectric plants to cool large turbine generators. This shows that hydrogen is safe to use in the vicinity of large ignition sources.
• Approximately 2% of hydrogen is sold to outside customers. This means that rugged transport networks have been developed, consisting of large dedicated pipelines and liquid hydrogen transport in trucks.
• Extensive use by NASA, both as a liquid rocket fuel for the main engines, and as an onboard fuel in space craft for creating electricity and water to drink using fuel cells.

Commercially, it is found that the safety record for hydrogen is excellent; there is no evidence to suggest that hydrogen is any more dangerous than other fuels of similar energy content.

Composite Cylinders

The main fuel storage for compressed hydrogen will be in composite cylinders. These cylinders have been used extensively in the past and are engineered to high safety factors (2.25 minimum [5]) and tested exhaustively. According to a mechanical engineer at Quantum [13], a fuel storage systems company, some of the tests include:

“… placing the cylinder in a crash car, firing armor-piercing bullets at it, dropping the cylinder from six feet onto a concrete surface, placing it in a diesel fire, cycling it thousands of times, and subjecting the cylinder to extreme cold and to corrosive liquids encountered in automotive environments, such as battery acids, saltwater, brake oils, and methanols.”

There are also strict standards for the design and manufacture of hydrogen cylinders, one of which is a permeation standard which limits the allowable diffusion of hydrogen from the container. This standard is required as the hydrogen molecule is so small, meaning that minute quantities do pass through seemingly impermeable materials. Currently, the standard means that an explosive mixture of hydrogen and air would not be reached in a fully airtight garage for 3 to 5 years [14]. In reality, no garage is fully airtight meaning the minute quantities of hydrogen that do diffuse out of the cylinder will escape quickly posing no risk. In addition, Quantum is working to produce near zero permeation from their cylinders.

Composite cylinders have been used in road transport applications for some time now, both for hydrogen, liquid petroleum gas (LPG), and natural gas powered vehicles. Some interesting events are discussed below:

A bus with roof mounted hydrogen cylinders travelling at approximately 70 km/h collided with a low bridge [9]. The front cylinder was severely damaged but did not rupture. It was subsequently burst tested and was found to have a burst pressure of 597 bar. This is exceptional when compared to the legal requirement of 559 bar.

Another example is a rear impact with a vehicle with a type 4 CNG tank mounted in the trunk [9]. The collision was with a fully loaded gasoline transport. The tank did not rupture and the crash site investigator stated that the driver survived due to the strength of the CNG tank.

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