The Hydrogen Supply Chain Figure

9.4.1 Delivery Systems

One of the major challenges for the use of H2 as a vehicle fuel is to consider the hydrogen supply chain from production to the point of fuelling a car in a filling station. The first part of this process involves the production of hydrogen mainly from natural gas or hydrocarbons with CO2 capture and storage using one of the technologies described in Section 9.2. The distribution of hydrogen to the filling station can be in the form of gaseous or liquid hydrogen. Delivery of hydrogen as liquid or high pressure gas by road or rail is a very well-established procedure, which has been practised by the industrial gas companies for 50 years. The latest tube trailers, using lightweight high pressure cylinders, can deliver up to 600 kg of hydrogen. The largest liquid hydrogen tankers have a capacity of about 4 tonnes. The delivery of liquid hydrogen is, and always has been, a very safe operation.

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Fuel Station

Vehicle

Fuel Station

Vehicle

Fuel Cell or ICE

Fuel Cell or ICE

Fig. 13. Hydrogen supply modes for transportation

The container consists of an inner aluminium tank with an outer thick armoured steel jacket. The space between the tanks is insulated with wrapped super insulation and kept at a high vacuum to minimise heat leak and boil-off of the liquid hydrogen. The experience of one company, Air Products, is shown below.

• 75 trailers with armoured type construction

—inner aluminium tank with outer thick steel jacket

• 70 million gallons of liquid H2/year

• 8 million miles/year

• 160 million miles since inception without loss of liquid hydrogen onto the road

• 1996 NASA safety award winner

—200 million pounds of liquid H2 over 25 year period without a significant incident

In this entire period, although there have been a number of incidents, none has been the cause of a significant fire or explosion related to the release of hydrogen.

Other methods of hydrogen supply would be by pipeline or, in the immediate future for demonstration projects, from small hydrogen production units sited at a filling station or from mobile filling units supplied with compressed gaseous hydrogen.

The safe operation of a hydrogen production and delivery infrastructure has been developed by Air Products. In general, the important criteria which we apply are:

• Attention to detail;

• Multiple layers of protection for a given hazard;

• Inherent safety in the design;

• Quantified risk analysis;

• Training and periodic retraining of personnel; and

• Experimental verification of research and calculations where appropriate.

9.4.2 Comparative Economics for Hydrogen Supply

The comparative costs for hydrogen delivery to a vehicle in a filling station for different production and supply options is shown in Figure 14, based on the work presented by HYNET. Note the high cost of the electrolysis options for hydrogen production and the high cost of hydrogen liquefaction. There is an incentive to develop lower cost liquefaction technology for hydrogen. Currently, the power consumption for a hydrogen liquefier is in the range 9 to 11 kWhrs electrical energy per kg of H2. There

Hand Hygiene Compliance Graphs
Fig. 14. Comparative economic analysis of various liquid and compressed hydrogen supply

is a possibility to reduce this to the range of 2 to 4 kWhrs/kg. H2 by integration of the hydrogen liquefier with a liquid natural gas (LNG) terminal making use of the low temperature heat sink available when compressed LNG is heated to ambient temperature for delivery in a natural gas pipeline.

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