Commonly referred to as tube trailers, they are built to accommodate a stack of long steel or carbon fibre cylinders which hold gaseous hydrogen under compression, typically at from 180bar upwards. The cylinders are carried in a protective frame. Demand for these trailers is rising worldwide, with Fairfield Market Research estimating that the global market for them will be worth almost $500m (£411m) by 2026.
Key players in the sector include Spain’s Calvera Hydrogen, which has developed a 45ft tandem-axle semi-trailer which carries carbon fibre cylinders full of hydrogen at 517bar. That means it has the highest working pressure of any tube trailer currently available, the Zaragoza-based company contends.
Able to carry more than 1.3 tonnes of gas, it was developed in conjunction with Shell and will be used to replenish its hydrogen filling stations. Complying with both European and US regulations, it will be initially deployed in Germany and the USA. Not to be outdone, Costa Mesa, California, USA-based Hexagon Agility has come up with the Titan 450, a 40ft tandem-axle trailer it describes as a mobile pipeline. With a likely price tag of around £650,000, such trailers do not come cheap. That of course presupposes you can obtain them at all, thanks to a regulatory obstacle that is hampering the supply of tube trailers and related equipment in a post-Brexit world.
The Department for Transport (DfT) points out in a guidance note that since 1 January 2023 it has only been possible to put transportable pressure equipment on to the Great British market if it has had its conformity assessed and approved by a GB-appointed body.
It has to bear a ‘Rho’ mark, named after the Greek letter (P) to show that this is the case. The European Union’s ‘Pi’ (Π) conformity mark is no longer acceptable. Pi-marked equipment placed on the market prior to 1 January can still be used if it complies with the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2009 (as amended). Different arrangements apply in Northern Ireland.
However, in practical terms, it does not matter whether items are ‘Rho’ or ‘Pi’ says Robin Futcher, managing director of Southampton-based Commercial Fuel Solutions (CFS). The requirements are exactly the same, as is the equipment concerned.
The rule change means, however, that many overseas suppliers will not be interested in obtaining the extra verification needed to sell their products on this side of the Channel given the size of the market outside Great Britain and the opportunities it presents, he contends. British customers will enjoy less choice as a consequence.
For the moment, the UK market for big-capacity tube trailers is likely to be limited, at least so far as servicing the needs of the transport industry is concerned, given the comparatively modest number of vehicles with hydrogen fuel cells in service.
Their current needs may be more readily served by the compact tandem-axle fuel bowser CFS has developed. “It could benefit major fleets that are currently trialling a small number of hydrogen fuel cell vehicles,” Futcher observes.
A drawbar trailer, CFS’s bowser can transport up to 74.5kg of gaseous hydrogen at a pressure of up to 500bar from a production side to a transport depot. “In energy terms that’s the equivalent of 220 litres of diesel,” he says. It does so in seven composite-and-metal tubes weighing an average 145kg apiece housed inside a steel shell.
The trailer grosses at no more than 3.5 tonnes, he says, and can be towed by most 4x4 double-cab pick-up trucks. Still, the driver has to be licensed in line with the requirements of ADR and his or her employer must employ someone qualified as a DGSA (Dangerous Goods Safety Adviser; see also pp24-25), says Futcher; obligations which would also apply to the operation of full-size tube trailers.
SAFETY FEATURES
CFS’s trailer has been constructed with safety as a priority. “Should the hydrogen leak, then none of the electrical equipment on it is an ignition source,” Futcher says. This should hopefully go some way to reassuring nervous insurers. “If you mention hydrogen they become absolutely petrified, despite the stringent control measures that are in place,” he remarks.
At a likely £175,000 to £225,000, the bowser will not come cheap – the cylinders alone cost over £9,000 apiece – but should last 15 to 20 years and cope with up to 20,000 refuelling cycles, says Futcher. “Bear in mind that at present a hydrogen refuelling nozzle can cost £6,000 to £7,000 compared with just £200 for a petrol refuelling nozzle.”
The trailer’s maintenance requirements are modest, and include periodic inspection of the cylinders and dispensing system by a competent person.
CFS’s bowser should be available to deliver fuel to transport depots by road and dispense it by next October at the latest, Futcher says. One for use solely off-road on construction sites is scheduled to appear in mid-2024.
Liquefy hydrogen by cooling it to -253°C and deliver it in an insulated cryogenic tanker and you can transport approximately three-and-a-half times more than if it stays in its gaseous form. Liquefaction is an expensive process, however, and some of the hydrogen will be lost through evaporation.
Handling such a cold fluid has safety implications, especially if there is a spillage. “If that happens, then you need to evacuate the area, but you may find it difficult to see where you are going because of the fog that will be created,” comments Futcher.
Different derivatives of hydrogen are under development which should overcome some of the drawbacks of transporting it purely as either a liquid or a gas, he says. “They include cryo-compressed hydrogen, which is best described as a sludgy gaseous hydrogen,” he observes.
If you are already storing hydrogen on site but have neither the room nor the budget for a permanent filling station, then it is worth noting that Logan Energy has developed a horsebox-sized trailer that functions as a mobile refueller. Connect it to a hydrogen cylinder at one end, and a vehicle at the other, and it will fill the latter at pressures of up to 450bar, says the Wallyford, East Lothian, company. “Its automated compressor ensures a vehicle can be filled in one go,” it adds, “with no attendant required.”