IET - Institute for Energy and Transport Joint Research Centre, European Commission

1. International Conference on Hydrogen Safety - 4 September 12-14, 2011San Francisco, California, USA Hydrogen Tank Filling Experimentsat the JRC-IET GasTeF Facility IET - Institute for Energy and Transport Joint Research Centre, European Commission Petten - The Netherlands http://ie.jrc.ec.europa.eu/ http://www.jrc.ec.europa.eu/ B. Acosta, P. Moretto, N. Frischauf, F. Harskamp and C. Bonato

2. OUTLINE • Hydrogen storage at high pressures • Fast filling issues • GasTeF: Compressed hydrogen GasTesting Facility • JRC-IET GasTeF temperature evolution experiment • Experimental results • Next steps

3. hydrogen storage at high pressures A type 1 tank, or a standard compressed gas cylinder, is simply a stainless steel casing holding compressed gas. It has no extra covering or accessories, except for the coating of paint on the outside that identifies the contained gas. A type 2 tank is slightly more durable than a type 1. It has a base cylinder shell made of aluminium or stainless steel, and a partial wrapping around the outside of the cylinder. This wrapping is usually made of a polyester resin containing glass, aramid or carbon. A type 4 tank is a fully wrapped composite tank with a non- metallic liner. The mechanical loads are therefore only supported by the composite wrapping; the liner itself does not support the loads  “non-sharing-load” liner A type 3 tank is a fully wrappedcomposite tank with a metal linermade out of aluminium or stainlesssteel. The composite is wrappedaround the liner. Themechanical loads of the cylinderare supported by both liner and wrapping. Type 3 and 4 tanks may also have an additional glass fibre wrappingto protect the tank against external effects

4. fast filling : safety and convenience aspects • Tank (re)-fuelling Requirements: • Avoid exceeding high temperatures in tank Operating range -40 °C to 85 °C • Reasonable short filling duration Max. 3-5 minutes • … however… • The shorter the filling duration  The higher the temperatures inside the tank • Higher gas temperatures  Higher filling end pressures to assure a “complete tank filling” •  Three major risks to damage tank materials: • Over-pressurisation • Temperatures higher than the maximum allowed 85 °C (for example SAE J2579) • Over-filling if fuelling occurs at low ambient temperature The JRC-IET facility GasTeF is an EU reference laboratory designed to carry out performance verification tests of full-scale high pressure vehicle tanks for hydrogen or natural gas or of any other high-pressure components

5. GasTeF: safe testing of tanks and components GasTeF:Compressed Hydrogen Gas Testing Facility • Half-buried bunker with an attached gas storage area. • Designed to endure a sudden energy release equivalent to 50 kg TNT with a safety factor of 10. • Double walls of heavy-concrete, covered by a 3 meter thick sand layer armoured by geotextile every thirty centimetres • The bunker is closed by a gas-tight inner door and after that by a hydraulically operated 40 tons massive concrete door sliding on Teflon plates • The gas detectors form the heart of the safety monitoring system of the bunker • Operated under remote control – inertised during testing

6. GasTeF layout 1st Containment pressure vessel The cylinders are placed into a sleeve which contains an inert gas (He, N2...) and serves as chamber to detect permeation. The H2 level is measured using gas chromatography. H2 / He / CH4 300 bar package 55 kW two-stage pistoncompressor up to 880 bar GC and O2 free H2 detectors 2nd Containment Aluminium Sleeve

7. GasTeF : fast-filling, cycling and permeation tests on any type of hydrogen (and methane) tanks • Static permeation measurement as a function of time on tanks filled up to 70 MPa and up to temperatures to 100 °C. • Fast-filling cycling, in which storage tanks are fast filled and slowly emptied using hydrogen pressurized up to 70 MPa, for at least 1000 times to simulate their lifetime in a road vehicle. During the cycling process the tank is monitored for leaks and permeation rates using gas chromatography.

8. Local measurement of H2 temperature a boom with thermocouples is inserted into the tank • Temperature measurement at 3 axial (displaceable) and 5 radial positions • Measurement with He and with H2 Tank: Raufoss Type 4, 700 bar (29.8 l)

9. T Top 5 1 T Boss 2 T Line 6 7 8 H2 inflow 4 3 T Bottom • The temperature evolution experiment is also used to validate software models for tanks (see next presentation) • Experimental data presented hereafter are preliminary results of the on-going testing campaign to map local temperature evolution inside the tank as a function of filling rate under different starting conditions (Ti, pi) and final pressure pf

10. He versus H2 Preliminary Results Position T5: Axial: 500 – 525 mm from gas inlet Radial: 15 to 35 mm from liner • The graph summarises experiments with different filling rates for different pi, pf and Ti • In general H2 features a smaller temperature increase than He (evident only at high fill rates)

11. Measured temperatures at the inside and outside of the tank differ significantly Preliminary Results Top_inside ? H2 Max allowed T Top_outside • The graph summarises experiments with different filling rates and slightly different pi, pf and Ti • Temperature rise influenced by filling rate • Variation in temperature rise at a given filling rate is caused by pf, as well as (Ti, pi)

12. Long term static pressure tests 30 hours • After filling finishes, the temperature sharply decreases due to heat transfer from inside the tank to its outer surface • As temperature decreases, pressure does as well and hence it takes several hours to reach equilibrium values

13. Example of fill & emptying cycle Pressure holding Filling Emptying • non-linear filling induces a complex (non monotonic) gas temperature evolution • as soon as filling is finished, gas temperatures inside the tanks follow a stratification pattern

14. Next step: temperature control in GasTeF • a system to cool down the hydrogen when it is supplied to the tank • environmental control system to allow simulation of -40°Cambient temperature

15. With pre-cooling Example of tank temperature dependence on inlet temperature TC5, gas temperature top of the tank Without pre-cooling TC8, Gas inlet temperature • even without cooling, inlet temperature can increase • control of gas inlet temperature is not easy!

16. Is this maximum allowed temperature too limiting? Is this “historical” limit justified for the materials used? Is it important to consider the duration of the temperature overshoot? Next experimental step is to place the thermocouples touching or as close as possible to the tank internal surface to obtain accurate measurements of the liner temperature during filling and emptying Conclusions • measurements are in good agreement with those found in literature • results show that the maximum gas temperature during filling of a type 4 tank can locally exceed the limit established in current regulations and standards. • First results suggest that the low thermal conductivity of the plastic liner limits the effect of local temperature peaks on the liner itself as well as on the material of the external shell • The results serve to validate the computed fluid dynamic modelling of the fast filling process, also performed at JRC-IET – See next presentation!

17. Thank you for your attention beatriz.iborra-acosta@jrc.nl pietro.moretto@jrc.nl

18. control by PLCs and specific software tools In normal operation the facility runs fully automatically and the tests are operator controlled from a control room situated in an adjacent building