4TH PERIODIC AACTIVITY REPORT - · PDF fileFourth Periodic Activity Report PES Date: ... a...

Project No.: 502667 Project acronym: STORHY

Project title: Hydrogen Storage Systems for Automotive Application

Instrument: Integrated Project

Thematic Priority 6: Sustainable development, global change and ecosystems

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PUBLISHABLE EXECUTIVE SUMMARY

Period covered: 01/03/2007 to 29/02/2008 Start date of project: 01/03/2004 Project coordinator: Dr. Volker Strubel MAGNA STEYR Fahrzeugtechnik AG & Co KG

Date of preparation: 04/07/2008 Revision: 1 Duration: 4,5 years

StorHy / Contract No. 502667 Revision: 1

Fourth Periodic Activity Report PES Date: 04/07/2008

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PUBLISHABLE EXECUTIVE SUMMARY

Main Project Goals Hydrogen storage is a key enabling technology for the extensive use of H2 as an energy carrier. None of the current technologies satisfies all of the H2 storage attributes sought by manufacturers and end users. Therefore, the Integrated Project StorHy aims to develop robust, safe and efficient on-board vehicle hydrogen storage systems suitable for use in hydrogen-fuelled fuel cell or internal combustion engine vehicles.

Concrete R&D work covering the whole spectrum of hydrogen storage technologies (compressed gas, cryogenic liquid and solid materials) is carried out with a focus on automotive applications (see Fig. 1). The aim is to develop economically and environmentally attractive solutions for all three storage technologies. These systems shall be producible at industrial scale and meet commercially viable goals for costs, energy density and durability. In addition, achieving sufficient hydrogen storage capacity for an adequate range is a major technology goal.

Pressure Vessel Cryogenic Storage Solid Storage

Source: Dynetek Source: StorHy SP Cryo Source: FZK

Fig. 1: Hydrogen storage technologies (compressed gas, cryogenic liquid and solids materials)

Technical Approach The overall approach of StorHy mainly involves two different types of activities (see Fig. 2). The vertical type includes the three technical subprojects (denoted SPs), SP Pressure Vessel, SP Cryogenic Storage and SP Solid Storage. These subprojects concentrate on relevant activities addressing the technological development of innovative H2 storage solutions. The horizontal SPs include the SP Users, SP Safety Aspects & Requirements (SAR) and SP Evaluation. In these subprojects, cross-cutting issues are addressed in order to link the vertical activities.



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Users: Requirements / DisseminationUsers:Users: Requirements / DisseminationRequirements / Dissemination

Safety Aspects and RequirementsSafety Safety AspectsAspects and and RequirementsRequirements

Multi-criteria EvaluationMultiMulti--criteriacriteria EvaluationEvaluation

PressurePressureVesselVessel

CryogenicCryogenicStorageStorage

SolidSolidStorageStorage

Users: Requirements / DisseminationUsers:Users: Requirements / DisseminationRequirements / Dissemination

Safety Aspects and RequirementsSafety Safety AspectsAspects and and RequirementsRequirements

Multi-criteria EvaluationMultiMulti--criteriacriteria EvaluationEvaluation

PressurePressureVesselVessel

CryogenicCryogenicStorageStorage

SolidSolidStorageStorage

Fig. 2: Structure of IP StorHy

Expected achievements / impact of IP StorHy The final outcome of the project is to identify the most promising storage solutions for different vehicle applications (car and bus with fuel cell or ICE). Such results should illuminate the future perspectives of hydrogen storage for transport and stationary applications and assist decision makers and stakeholders on the road to the hydrogen economy. Partnership In order to develop sustainable on-board storage solutions, a large-scale R&D effort is necessary with the strong participation of the European car industry, suppliers as well as research and testing organisations. Indeed, the consortium of this IP consists of:

• European automotive industrial companies; • Leading European hydrogen suppliers; • European S&T excellence (including research institutes and universities) • European standardisation and certification bodies.

The project is carried out by the StorHy partners: MAGNA STEYR Fahrzeugtechnik AG & Co KG (coordinator), Institut für Verbundwerkstoffe, Institute for Energy Technology, Daimler AG, CEA, Air Liquide S.A., AIR LIQUIDE Deutschland GmbH, BAM, BMW Forschung und Technik GmbH, Oerlikon Space AG, Forschungszentrum Karlsruhe, COMAT, Faber Industrie Spa, Wroclaw University of Technology, Weh, Ford Forschungszentrum Aachen, Volvo Technology Corporation, Dynetek Europe, University of Nottingham, MT Aerospace AG, Joint Research Centre, GKSS Forschungszentrum Geesthacht, National Centre for Scientific Research Demokritos, ADETE, PSA Peugeot Citroen Automobiles, Austrian Aerospace GmbH, Linde AG, Oeko-Institut e.V., CNRS, CIDAUT, ET-EnergieTechnologie, INTA, NV Material and Prochain e.V.



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Intermediate Results and Achievements

SP Users SP Users represents the major European vehicle manufacturers and contributes to StorHy by steering the different S&T approaches according to the needs and requirements of vehicle applications. Moreover, SP Users ensures effective dissemination, exploitation and training activities within the project.

So far, SP Users has defined the automotive requirements and goals, the StorHy Targets 2010, which are compared with selected state-of-the-art reference systems for each storage technology.

These StorHy Targets 2010 are based on the requirements elaborated in the preparation phase for the different storage systems and have been adapted to future internal and external developments. Tab. 1 shows the StorHy targets 2010.

Tab. 1: Automotive Requirements and StorHy Targets 2010

600kmDriving Range6 - 10kgHydrogen Storage Mass

1g/h per stored kg H2

Loss of usable H2(boil-off)

1H2 Ncm3/h per l internal volume

Permeation Rate6barMin. Pressure

2.0 FC, 5.5 ICEg H2/secDelivery Rate (max.)1.2kg H2/minRefuelling Rate

-40 to +85°COperating Temp.

1.54.5

kWh/lkg H2/100l

System Vol. Energy Density

2.06

kWh/kgwt%

System Gra. Energy Density

StorHy Target2010

UnitParameter

600kmDriving Range6 - 10kgHydrogen Storage Mass

1g/h per stored kg H2

Loss of usable H2(boil-off)

1H2 Ncm3/h per l internal volume

Permeation Rate6barMin. Pressure

2.0 FC, 5.5 ICEg H2/secDelivery Rate (max.)1.2kg H2/minRefuelling Rate

-40 to +85°COperating Temp.

1.54.5

kWh/lkg H2/100l

System Vol. Energy Density

2.06

kWh/kgwt%

System Gra. Energy Density

StorHy Target2010

UnitParameter

The results of the continuous S&T monitoring were summarized in the second technology watch report. SP Users has also maintained project-internal contact with and given support to SP SAR and SP Evaluation. SP Users has a liaison role with SP Evaluation to link automotive views and requirements to the evaluation work of different hydrogen storage systems, which is carried out by SP Evaluation.



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Moreover, SP Users carried out an acceptance study of vehicles with high pressure storage systems, which focused on interviews with the drivers of the Mercedes ‘F-Cell’ fleet operated in Berlin. The results of this study show that a vast majority of drivers have no or little concern about the safety aspects of hydrogen technology in vehicles. Their acceptance even increased strongly with the amount of information they were given.

The StorHy training course “TRAIN-IN” was also prepared within SP Users. A one-week full time training course covering the whole spectrum of hydrogen storage technologies (compressed gas, cryogenic liquid and solid materials) with a focus on automotive applications was organized from Sept. 25-29, 2006 at the University of Applied Sciences in Ingolstadt, Germany. The participants were given insight into the state-of-the-art and current research on H2 storage technologies.

SP Users started organising the StorHy Final Dissemination Event, which will take place in Paris on the premises of PSA on June 3-4, 2008. The main objectives for this event are to present results and achievements of the project and to get feedback from external experts regarding future perspectives and R&D needs. SP Pressure Vessel The StorHy Subproject Pressure Vessel aims to develop a light weight C-H2 vessel at a nominal pressure of 700 bar along with the necessary peripheral equipment. At 20°C, the pressure of 700 bar corresponds to a volumetric energy density greater than 1.4 kWh/l. At this pressure, a 125 litre reservoir (inner volume) can store ~5 kg of H2 so that ranges of 420-500 km driving autonomy per filling can be realised with a car equipped with a typical ~70 kWe fuel cell. A second objective is to achieve a gravimetric energy density larger than 2.2 kWh / kg. Since the calorific power of H2 is 33.33 kWh / kg, this corresponds to a targeted H2 storage capacity (system mass fraction) of 6 wt.%. Moreover, the tank has to withstand operating temperatures between -40°C and +85°C and the overall H2 permeation / leak rate of the tank should be maintained below 1 cm3/hr per tank-litre to meet the ISO TC 197 standard and the TRANS/WP29/GPRE/2004/3 regulations.

The desired pressure level requires the development of liners, which combine H2 chemical compatibility and low H2 permeation: these are the goals of Work Package P1. The work performed recently consisted in characterizing many liner materials regarding their barrier properties to H2 for polymeric materials and the embrittlement effect for steel materials. Materials compatible with H2 use were selected on this basis. The associated liner manufacturing technologies were also improved. A generation of seamless steel liners for 700 bar application was developed based on a deep-drawing process. This ‘conventional’ process was compared to a more exploratory hydroforming process with the potential of decreasing the equipment costs and increasing the liner quality. An innovative reactive rotational molding process (simultaneous polymerization and molding) with a specific PA6 formulation was developed and validated. A multilayer liner with a PA6 base also demonstrated good permeation properties. In addition, a manufacturing technology with a co-extrusion process was applied and validated. More than 50 liner prototypes were thus manufactured and used in Work Package P2 dedicated to composite wrapping technologies.



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Fig. 3: Prototypes of plastic liners Fig. 4: Finished 700 bar Type IV Pressure Vessel

In Work Package P2, two different hydrogen high pressure composite systems are investigated:

- The first system is a thermoset resin wet winding process on thermoplastic liners or metallic liners (manufactured in WP P1), with a special goal on tank manufacturing and development of a processing technology for high volume production. Both 6l and 34l 700 bar tank prototypes were manufactured and characterized for design validation and cycling behaviour. A new fast wrapping process with a Ring Winding Head was developed and successfully tested; the lay-up of the laminate was defined and implemented in the path generation tool. Moreover, a new impregnation unit was manufactured.

- The second system is a thermoplastic-based modular multi-cylinder storage system (see Fig. 5), with a special goal on continuous cylinder production, dome production and joining (see Fig. 6). The feasibility of manufacturing composite tubes with thermoplastic matrix material in combination with reinforcement fibres and a thermoplastic liner was successfully demonstrated. The device for thermoforming the cylindrical section to the metallic end-caps was set up. The first tanks were manufactured and tested; the results obtained now contribute to the optimization of the process.

12

4

78

3

5

6

9

124

78

3

5

6

9

Fig. 5: Design of a thermoplastic-based modular multi-cylinder

vessel

Fig. 6: Continuous composite tube and winding manufacturing process

The qualification of 700 bar composite tanks is also part of this work package. A full test equipment has been designed, manufactured and is now available for the qualification of StorHy 700 bar tanks. The following tests can be performed:



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• Cyclic test under room temperature (max. 1.200 bar) • Cyclic test under low temperature • Cyclic test under higher temperature with controlled humidity • Static test including burst (max. 2.800 bar) • Leak test & changes of volume

In Work Package P2, permeation tests at cylinder level have been performed on the developed Type IV tank. No leakage has been detected during the test and results are currently analyzed to calculate the permeation rate of the cylinder and validate the technology for H2 use. SP Pressure also develops sensors for monitoring the structural integrity of C-H2 pressure vessels on vehicles within WP P3. The work package scope and objectives were revised to focus on the comparison of different sensors technologies at material and cylinder level and definition of a concept for on-board monitoring based on both experiments and simulations. In the 4th year, tests with defined flaws of large pressure vessels equipped with the selected sensor types were performed. The main goal of investigation was to compare two different types of optical fibers sensors: fiber Bragg gratings and SOFO from Smartec. The main target of these tests was to assess their response to vessel pressurization and select the best method for vessel monitoring. Based on the tests results, it was concluded that both optical fiber based methods enable the strain field measurements of the high pressure vessels. The flaws can be detected by means of these techniques due to a change in symmetry of the deformation in the cross sections containing defects. These results can be used as a basis for designing an on-board monitoring system.

To demonstrate the operational suitability of the tank system in a vehicle, it is necessary to have test runs of the filling process up to 875 bar and to optimise the gas filling procedure from the fuelling station. The challenge is to achieve the maximum filling speed of the vehicle tank while avoiding overheating of the composite vessel structure due to quasi-adiabatic compression. The target of WP P4 is to fill a ~150 litre tank in less than 4 min. Moreover, specific high pressure components are needed. In WP P4, the fuelling components, the prototypes for 700 bar break-away and linear valve were designed, manufactured and validated for 700 bar use. Two filling processes are studied: a cold fuelling process, in which hydrogen is pre-cooled at liquid nitrogen temperature, and a warm fuelling process, in which hydrogen is compressed at a liquid state and then vaporized at high pressure into the tank. Cold filling tests have already been performed and demonstrated down to a filling temperature of -100°C. Warm filling tests have been performed in 4th year period on both Type III and Type IV 700 bar tanks manufactured by StorHy partners. The objective was to test and compare three different storage vessels (2 Type III cylinder and 1 Type IV cylinder). Filling tests have already been finalized on the two Type III cylinders and fast filling (< 4 min). To achieve a high filling rate (> 97%) within 3 to 4 minutes, a reduced cooling (filling temperature around 0°C) is required to avoid vessel temperature above the accepted limit of +85°C.



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Fig. 7: Prototype of 700 bar coupling Fig. 8: Test bench for cold fuelling process

To demonstrate the viability of the high pressure technology, the whole life cycle of the tank has to be considered and the tank recycling issue should be addressed in particular. The aim is to demonstrate viable recycling processes to recover high quality carbon fibre from these vessels (with the potential to replace virgin material, which consumes significant resources, in different manufacturing processes), identify the issues in meeting the End-of-Life Vehicle Directive and demonstrate a positive environmental balance of H2 fuelled cars. These are the goals of work package P5.

Before entering the recycling process, a first step consists in preparing the pressure vessel by removing the liner from the vessel and shredding the composite into small pieces. Two different recycling processes were investigated and developed (Fig. 9):

• A fluidized bed recycling process was investigated to treat composite material supplied by two different tank manufacturers. The recycled carbon fibre demonstrated very good properties like a clean surface free of polymer, a tensile modulus of the recycled carbon fibre almost comparable to virgin fibre and a reduction of 50% of the tensile strength compared to virgin fibre. This recycled fibre can therefore be used as replacement material for virgin fibre in many applications, like electromagnetic shielding or reinforcement fibres in polymer composites.

• A microwave pyrolysis process was also investigated to further improve the recycling rate and the product quality of the recyclate. In this case, the recycled carbon fibre demonstrated a substantially clean surface with less than 0.5 % of the polymer remaining, a tensile modulus similar to virgin fibre and a reduction in tensile strength of only about 10%. In addition, 74% of the polymer material was recovered (with a potential of 90% recovery in a scaled-up process), which corresponds to a total material recovery from the carbon fibre composite of 87%.



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(a) (b)

Fluidised Bed

Preheated Nitrogen

Microwave waveguide

Fig. 9: Composite recycling process by (a) fluidised bed process and (b) microwave pyrolysis

Finally, the Work package P6 studies the innovative integration of a removable hydrogen storage system, which does not require a complete refuelling station infrastructure. WP P6 has aimed to design and realise a complete 700 bar hydrogen storage system based on the concept of a removable rack (called hereafter swap-rack). The swap-rack made with FABER cylinders developed within StorHy is being set up. FABER cylinders were tested based on the EIHP draft. The long delay observed in the swap-rack delivery is mainly due to the late delivery of manifolds to PSA only in January 2008.

This swap-rack will be validated on a bench in March 2008 and on the vehicle in April 2008.

A feasibility study was performed as well: it shows that there is a real economic potential for the swap-rack concept at the very beginning of hydrogen vehicle development. However, considering compressed storage volumetric efficiency and handling issues plus current deployment of hydrogen stations in the main developed countries, this concept does not seem to be relevant for automotive application. PSA has started working on a fixed on-board storage system based on its swap-rack experience. In parallel, Air Liquide is still working on swap-racks for smaller transportation applications, like motorbikes, for which the swap-rack concept characteristics are more suitable.

SP Cryogenic Storage

SP Cryogenic Storage develops free-form light weight tanks manufactured from composite materials as well as adequate production technologies. Thanks to its low required working pressure (compared to high pressure systems), cryogenic storage of liquid hydrogen allows for new concepts with conformable geometries more adaptable to vehicle design. Moreover, the use of new composite materials entails a great potential for weight reduction - with these materials a specific energy storage mass similar to that of conventional fuel tanks can be achieved.

The cryogenic storage system mainly consists of an outer jacket and an inner tank. A vacuum between the outer jacket and the inner tank and a multi-layer insulation are used to ensure that the cryogenic temperature in the inner tank is maintained. Free-form light weight tank materials and processes have to be developed and evaluated. The current status of the research activities is demonstrated by four prototype tanks:

Cyclone

Air

Electric Pre-heaters

Fibre

Scrap CFRP

Recovered Bed

300 mmAfterburner

Clean flue gas To energy recovery

Fan

Fluidised

Air distributor plate



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• Cylindrical Tank 1 – light weight outer jacket with structural inner liner, • Cylindrical Tank 2 – light weight inner tank with an outside coated liner, • Cylindrical Tank 3.1 – light weight inner tank with structural inner liner and a coated outer

liner, • Cylindrical Tank 3.2 – light weight inner tank with an inside and outside coated liner.

Furthermore, design work for the free-form outer jacket and inner tank have been developed and finished. First parts of the inner tank and outer jacket of the free-form tank system have been manufactured to be able to build up an exhibition demonstrator (mock-up tank). To improve the auxiliary system box as well, the development of a cryogenic multi-way valve has started. These experiences and research activities result in the development of a virtual model for a working free-form light weight tank system.

Cylindrical Tank 1 – Cylindrical outer jacket

Based on the specifications defined during the first reporting period, the cylindrical Tank 1 was developed and manufactured. It consists mainly of a cylindrical outer jacket. Cylindrical Tank 1 consists of a CFRP lay-up around a structural liner. This structural aluminium liner is manufactured by spin forming. The evaluated and preferred manufacturing process for the CFRP application is the so-called VARI (Vacuum Assisted Resin Infusion) process. In order to manufacture the outer composite shell by means of the VARI process, it is necessary to inject the matrix resin into the already positioned fibre structure around the (thin) structural aluminium liner. To insert the liner in this manufacturing process, a specific tooling was developed and manufactured. The liner is applied onto the tooling.

Cylindrical Tank 2 – Cylindrical inner tank

Cylindrical Tank 2 consists of a light weight inner tank and a steel outer jacket. The light weight components of the structure include two dome sections as well as two tension sheet half-shells bonded together and an overwrapping layer. The finished tank was coated with copper by means of a combination of electro less plating and electroplating.

In contrast to the outer jacket, which has an operating pressure and temperature based on surrounding conditions, the inner tank must withstand the gas pressure and the temperature of the cryogenic liquid. The main load cases are shown below:

• Temperature range: +85 °C to -253 °C, • Test pressure: 10,4 bar at -253 °C, • Burst pressure: 32 bar.

Pressure tests with the coated inner tank of cylindrical Tank 2 revealed that a sole galvanic coating on the outside of the CFRP tank wall is not sufficient to prevent loss of gas from the tank. It was recognized that an additional leak barrier (inside and outside) was necessary. From extensive development tests, a leak barrier made of glass fibre reinforced plastic (GFRP) applied on the existing shell seemed most promising. Identical processes were applied on the outer surface of cylindrical tank 3.2 after assembling the tank shell components to complete the inner tank, i.e. application of GFRP layer as leak barrier, metallic coating as permeation barrier.



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Cylindrical Tank 3 – Cylindrical outer jacket and inner tank

Instead of one tank system with one inner tank and one outer jacket, two different light weight inner tank concepts were realised. Thus it was possible to generate more knowledge regarding the behaviour of light weight tank system structures in cryogenic tests.

The manufacturing of cylindrical Tank 3.1 and cylindrical Tank 3.2 have already been finished. Similar to the manufacturing technology of cylindrical Tank 1 and cylindrical Tank 2, all half shells of cylindrical Tank 3.1 and cylindrical Tank 3.2 were produced by using the same materials and the same production process.

Cylindrical Tank 3.1 – inner tank with structural inner liner and a coated outer liner

Cylindrical Tank 3.1 is almost identical in construction to cylindrical Tank 1. It consists of a structural aluminium liner and CFRP half shells. Cylindrical Tank 3.1 was assembled, welded and leak tested. Afterwards, cryogenic fluids were filled into cylindrical Tank 3.1 to get results about the behaviour of the interaction of such a construction of a cryogenic light weight tank system. Fig. 10 shows cylindrical Tank 3.1 after welding.

Due to a leak at a welding seam in one of the dome sections of the aluminium liner, repair activities have started in February 2008. Apart from this one very local leak spot, the tank proved to be completely tight, though. The cryogenic tests will continue in March and April 2008.

Fig. 10: Cylindrical Tank 3.1 after welding

Cylindrical Tank 3.2 – inner tank with coated inner and outer liner

Based on the results of cylindrical Tank 2, the SP Cryogenic Storage team decided that cylindrical Tank 3.2 would be equipped with a galvanised liner inside and outside of the tank wall structure.



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The best suited glass fibre material combination and application technique selected on the basis of the experience with cylindrical Tank 2 was applied on cylindrical Tank 3.2. This material was placed onto the inner surface as well as on the outer surface of the tank wall structure. Afterwards the inner surface of the tank wall of each part of the inner tank was galvanised separately (see Fig. 11, left). A super conducting level sensor was built into one half shell of the inner tank. Temperature sensors verify the data of the level sensor during the test runs. Furthermore, a complex piping system was placed in the inner tank. All parts were joined, sealed and finished by applying the over-wrapping.

In February 2008 the galvanic layer was applied on the outer surface of cylindrical Tank 3.2 (see Fig. 11, right) using an improved galvanisation rack.

Fig. 11: Cylindrical Tank 3.2 after galvanisation process at inner surface (left) and

outer surface (right)

Free-form light weight tank

As planned the manufacturing concepts and material selections for the free-form tank system are all based on experience gathered with the cylindrical tank systems. The selection of the liner and of the light weight material as well as the design and calculation of inner tank and outer jacket were finalised. During all development steps, the manufacturing process was considered. In particular, the second cylindrical tank was used to prove the feasibility of manufacturing as well as the functionality of the free-from design. Due to the assembly process and the structural loads in operation of the tank, a multi-chamber tank solution has emerged as the most promising design option to decrease manufacturing efforts, weight and costs. From a number of concepts, tension sheets were selected. By using these intermediate walls, extremely unrealistic deformations and stress will be avoided

Thus the light weight free-form tank has been developed to an advanced level. Fig. 12 shows the status of the free-form tank system.



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Safety workshops

The first phase of the SP Cryo safety activities involved a simplified failure mode and effects analysis (FMEA), which was completed in early 2006. The second phase of the safety activities was undertaken during 2007 after the issues identified by the FMEA had been taken into account in the project. The second phase activities will be completed early in the 5th period. The second phase safety activities focussed on the liquid hydrogen tank and included:

• Fault tree analysis, • Event tree analysis, • Gap analysis, • FMEA Update.

SP Solid Storage

Regarding solid hydrogen storage technologies, StorHy focused on light weight complex alanates, since these have been considered to be among the most promising materials for solid hydrogen storage. The investigations concentrated on improving H2 storage density as well as hydrogenation / dehydrogenation kinetics. Initially, efforts were devoted to the further improvement of Na-alanate as well as the development of Mg-alanate as a potential and attractive candidate with more than 6 wt.% hydrogen capacity. However, during the first 24 months of the project, it was found that Mg(AlH4)2 is not suitable as reversible hydrogen storage material due to its unfavourable thermodynamic properties (a small transition enthalpy of ca. 2 kJ / mol points to an easy hydrogen release at low temperature and the requirement of equilibrium pressures in the kbar range for rehydrogenation at ambient temperature). In this respect, it was decided to orient activities towards the investigation of new alanate systems based only on aluminum, alanates and/or hydrides from alkaline and alkaline earth metal elements.

More specifically, SP Solid partners joined forces towards systematic screening experiments under different conditions, aiming at the identification of new mixed alanates. By using reactive ball milling of combinations of alkaline, earth-alkaline elements and aluminium under high pressure, it was possible to generate and characterise selected cation-substituted (Li, Na, K, Ca)

Fig. 12: CAD model of the light weight free-form tank system



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Mg alanate derivatives based on tetra- and hexahydrides. More specifically, (Mg, Al, Li, H), (Mg, Al, Ca, H), (Mg, Al, Na, H), (Mg, Al, K, H), (Ca, Al, Li, H), (Ca, Al, Na, H) and (Ca, Al, K, H) systems have been intensively investigated up to now. This work was concluded in the fourth year and the pertinent results pointed to (NaAlH4+LiH) and AlH3 (alane) as the most promising systems. (NaAlH4+LiH) revealed a maximum storage capacity of 2.8 wt.%, leads to formation of reversible Na2LiAlH6, exhibits a dissociation enthalpy of 56.4 kJ / mol H2 (calculated from pressure composition isotherms -PCI - at 3-40 bar and 170-250 oC), and can be rehydrogenated in 1-2 h at 200 oC. On the other hand, AlH3 contains 10.1 wt. % hydrogen and has a theoretical H density of 148 g / L. Within SP Solid a simpler alane synthesis method based on cryomilling was developed, while it was found that decomposition of two specific alane phases (alpha-prime and alpha alane) starts at 80 oC and 95 oC, respectively. Moreover the possibility to modify the composition of alane through the addition of several compounds (e.g., FeF3, MgD2) was investigated thoroughly. In this way different routes towards changing the stability of alane and improving the respective reaction synthesis were explored. In parallel, upscaling issues (with regard to both material production processes as well as the design, construction and testing of appropriate operational tanks) have been addressed. More specifically, focus has been placed on the (a) evaluation of the concept for upscaling of production of alanates, (b) design and development of a laboratory scale tank (at least 0.5 kg alanate material) and (c) design and development of a large scale tank. The evaluation of different production routes for alanate-based hydrogen storage material, led to a very simple process enabling the synthesis of a high product quality (fuelling times less than 10 min.). This production route was upscaled to kg level and the target currently is to produce 8 kg of alanate to meet the needs of the large scale tank. The kg-amounts of material produced so far were thoroughly characterised in order to obtain data for the design of large scale tanks. Finally, the laboratory scale alanate tank was completed and preliminary tests were carried out, while a first design for the large scale tank was presented.

Fig. 13: Lab scale solid storage tank, semi-assembled

Towards an integrated approach for the optimal design and control of hydrogen storage beds, a detailed mathematical model for metal hydride beds was also developed and validated in the framework of SP Solid. The model was used to find the optimal tank and storage process design and operating strategy in order to minimize the fuelling time, while satisfying a number of operating constraints (such as pressure drop limitations, cooling fluid availability and maximum tank temperature). Systematic simulation and optimization studies were performed at two different length scales (tank and adsorbent pore level) for physisorbing materials to demonstrate the optimization concept. The macroscopic approach (at tank level) determines the optimal values of the sorption parameters while, based on these results, molecular simulation



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techniques were employed to determine the nanopore size distribution of the physisorbing material.

Finally, a series of chemical safety tests were performed in order to obtain valuable information about the potential hazards in case of malfunction of a component of a solid storage system. Such risks could occur from the chemical interaction of e.g. the alanate powder with surrounding media (air, water and oil). In this respect, a systematic series of ejection tests (in dry and wet air, with and without spark ignition) with ca. 100 ml Ti-doped NaAlH4 were conducted. The safety related activities were concluded in the 4th year with tests on the response of hot alanate powders when they get in sudden and intimate contact with heat exchanger fluids such as water and thermo-oil. The respective results strongly recommend water-free mineral oil as heat exchanger fluid in a tank system.

SP Safety Aspects and Requirements

The technical developments are accompanied by safety studies and pre-normative research in the SP SAR. The general safety level of onboard storage systems is currently validated by a deterministic system of defined test procedures described, e.g., in the draft paper UN WP 29 GRPE rev. 12b or the comparable draft for an EC regulation concerning hydrogen. These tests aim to demonstrate isolated target values only, which merely provide the information for a decision of ‘Passed’ or ‘Not passed’. Some of these target values are based on single fixed safety factors, as e.g. the burst ratio or an excessive number of cycles. The uncertainties of this concept increase with the complexity of composite containers. Based on this, the objective of SP SAR has been to collect experimental data as basis for the future development of an alternative probabilistic approval concept. Economic efficiency of the design is directly related to the degree of light weight optimization. In order to assure a high level of safety, a better understanding of the structural behaviour of the storage structures, which are usually hybrid designs, is necessary. In order to address the issues concerning light weight design, safety, economical high-quantity production and reliability under static and dynamic loads a database is necessary, which has to be based on tests. Therefore, first long term tests under sustained load have been performed. Moreover, a sophisticated analytical stress analysing model was presented and first simulations of the structural behaviour of hybrid cylinders were done. This model makes it possible to conduct a sensitivity analysis for production parameters. Fig. 14 shows results of the autofrettage simulation. The left graph shows the impact of temperature deviation and the right one the impact of pressure deviation at the final stage of residual stress after the autofrettage process.



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Dev

iatio

n of

resi

dual

stre

sses

to re

fere

nce

leve

l [%

]

Autofrettage temperature [°C] Deviation from reference autofrettage pressure level [%]

13 20 27

110

105

100

95

90

110

105

100

95

9095 100 105

Fig. 14: Influence of temperature and pressure level during the autofrettage process on the resulting residual stress level.

To assess the applicability of hydrogen detecting sensors for automotive application, a second test round on sensors has been performed. One result is that variations in ambient pressure, temperature and humidity within the limit values given by the manufacturers (90 -110 kPa, -20, +80ºC and 10-90% respectively) have no significant effects on sensors measurements. Special attention must be paid to avoid condensation in the detector head, which can distort the measurement. The most significant variables to be focused on when selecting an appropriate sensor could be response time and minimum sensitivity (i.e. the lower detected hydrogen concentration value), when the sensor is located in open areas.

Fig. 15: Decrease of the pressure due to relaxation

To evaluate the current safety level of cylinders, basic static fatigue tests with commercial design Type IV cylinders were performed. In these tests, the pressure was kept at the maximum



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working pressure (≈ 50% of burst pressure). The temperature was kept at a level of 80°C in order to accelerate the test. It was recognized that due to volume expansion the rising temperature also raised the pressure. It was also recognized that the pressure drops due to relaxation of the composite, that the limiting failure mechanism for this pressure container can be leakage at the boss instead of bursting and that the leakage is time and temperature dependent. The Fig. 15 describes these effects.

To demonstrate the toughness and safety level of the new design pressure containers, further hydraulic cycling tests up to leakage were performed at low temperature (-45°C ± 5 °C) for 200 bar pressure containers. It was recognized that the number of cycles up to leakage differs (Fig. 16). It is assumed that this can be caused by a reduction of the residual stress in the liner. Here further research is inevitable to understand these complex effects.

Overview of StorHy Life Cycle Tests at BAM (pmax=MAWP)

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] CGH2-cylinder with p = 20....875 bar

tested 2008 tested 2007

tested 2007

Fig. 16: Test results of life cycle tests

For the assessment of permeation and tightness issues, different regulations and standards were investigated and compared. Furthermore, a study of literature was performed to identify parameters, which influence permeation. Moreover, the results of permeation tests investigated by Air Liquide were discussed. BAM also did some permeation tests on material samples. First results are given in Fig. 17.

The inter-laboratory tests entered their final stage, in which all measured data collected during the cycling tests at four different test facilities in Europe are assessed. A first overview of the average temperatures during the different load steps is given in Fig. 18.



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Permeation rate and flux

1,00E-16

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1,00E+00Teflon tape Rubber seal Plastic-Fermit* Coupon Liner

Material

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eatio

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te [m

ol/(P

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/s]

PermeationrateFlux

Fig. 17: Permeation rate and flux for different sealing materials

Fig. 18: Results of the inter-laboratory tests for all involved facilities (Air Liquide, BAM, WUT, Faber). The average temperatures for different loading rates over a certain period of time are

shown.



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SP Evaluation SP Evaluation aims to present an overall evaluation of all the hydrogen storage technologies developed within StorHy, applying a common evaluation approach. Technical performance, costs, risks, environmental impact and social acceptance of the hydrogen storage technologies are assessed. Each one of these 5 “points of view” is detailed by defining and quantifying appropriate evaluation criteria.

The evaluation system boundaries and final applications to be considered were defined in WP E1 by a collective and individual approach in cooperation with representatives of the other subprojects. “Upstream” boundaries correspond to the hydrogen chains from hydrogen production to dispensing at the refuelling station (C-H2, L-H2…), while “downstream” boundaries are related to the hydrogen storage systems (including dispensing devices towards FC or ICE vehicle). Nevertheless, before any global evaluation, SP Evaluation primarily focuses on the detailed study of the performance of the hydrogen storage systems themselves.

SP Users provided the requirements for 5 different automotive applications that have to be considered for the assessment of the hydrogen storage systems (fuel cell private car, hybrid car with FC as range extender, hydrogen internal combustion engine sedan car, fuel cell bus, hybrid fuel cell bus).

Finally, a set of appropriate evaluation criteria for the assessment of hydrogen storage systems regarding technical performance, costs, risks, environmental impact and social acceptance was defined in interaction with the partners. Social criteria were obtained from the results of a social acceptance study performed by CEA.

The implementation of the overall evaluation methodology was clarified during WP E2. The notion of performance tables was defined. Such performance tables aim to establish the performance achieved by each hydrogen storage technology regarding the whole set of evaluation criteria and final automotive applications previously defined. Drafting such performance tables was identified as the central step of the evaluation process. Moreover, a review of the existing mathematical models for multi-criteria evaluation (ELECTRE methods, MACBETH software…) was conducted in order to prepare for the final step of evaluation synthesis in WP E4.

During the 4th year, the provision of industrial data has been the main activity of SP Evaluation. This activity allowed collecting both state-of-the-art data and StorHy internal information on C-H2, L-H2 and solid storage technologies. Concerning C-H2 storage technology, a synthesis of state-of-the-art and StorHy C-H2 vessels and system data on gravimetric and volumetric energy densities has been worked out. The analysis shows that the highest gravimetric capacities are achieved by 700 bar high pressure vessels designed for the storage of larger hydrogen amounts corresponding to high internal volumes (160l). From an economic point of view, preliminary results were obtained from a dedicated cost calculation model. The calculations for large scale production lead to C-H2 tank costs of about 400 € per kilogram of hydrogen stored. A sensitivity analysis confirmed that the carbon fibre is the main cost driver of C-H2 tanks. Indeed, the safety factor of 2.35 leads to about 10 kg of T700S carbon fibre per kg of hydrogen stored. For a carbon fibre cost of 30 € / kg, this material already represents about 300 € per kg of hydrogen stored. A system level analysis of the literature also shows that regulators and valves represent about 25% of the overall cost of C-H2 storage systems. This analysis points out the fact that the use of multiple vessels increases costs, primarily driven by the need for multiple regulators and valves. From an environmental point of view, Oeko Institut provided a preliminary life cycle analysis of C-H2 vessels. It has been highlighted that high pressure vessels are made of materials with a



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high environmental impact. A life cycle inventory shows that standard automobile materials have an average Cumulative Energy Demand (CED) of approx. 80-100 MJ / kg. The pressure vessels under investigation showed a CED of approx. 300 MJ / kg. So this CED is remarkable higher than for average automotive parts. Taking into account that a gasoline tank is lighter, the new storage systems add a significant weight to the vehicle and additionally have a higher specific environmental impact. The highest environmental impact of the pressure vessels results from carbon fibre, due to its complex and energy-intensive production process. Because carbon fibres are not widely applied and still to be considered as high tech material, the environmental data have a high uncertainty. But even if the “best options” are taken into account, the contribution of carbon fibres to the total environmental impact of pressure vessels is very high. With the introduction of carbon fibre in broader application, the plant sizes will grow and thus process designs will be energy-optimized, which may result in a lower environmental impact in the future. The recovery of carbon fibre may play an important role for the overall assessment. A switch from simple energy recovery to a high quality recycling scheme would fundamentally impact the environmental assessments. Concerning L-H2 storage technology, technical data on both state-of-the-art and StorHy storage systems have been collected from literature, from SP Cryo deliverables and from direct exchanges of information between SP Evaluation and SP Cryo. Concerning gravimetric energy density, conventional steel cylindrical storage systems reach 1.33 to 2.66 kWh / kg (4 wt.% to 8 wt.%), depending on the hydrogen mass stored. For the moment the main improvement concerning gravimetric energy density has been achieved by Air Liquide using an aluminium technology. This system reaches more than 5 kWh / kg (15 wt.%). StorHy projections show that liquid hydrogen storage systems with more than 6 kWh / kg (18 wt.%) are achievable by using composite material. Concerning volumetric energy density, it appears that the real external volumetric energy density of conventional storage systems ranges between 0.8 and 1.5 kWh / l (2.4 to 4.5 kgH2 / 100l), while the StorHy cylindrical Tank 3 system is projected to reach 1.28 kWh / l (3.85 kgH2 / 100l). According to SP Cryo, with innovative packaging and valve concepts, the volumetric energy density of the StorHy system can be increased to 1.33 kWh / l (4 kg H2 / 100 l). The economic evaluation of L-H2 storage systems could not be provided within StorHy for confidentiality reasons. However, information on the cost distribution of these storage systems could be found in the literature. It is shown that for this technology, costs are mainly driven by components and assembly (hand made technology, numerous non automated steps in the manufacturing process). Concerning solid storage technology, it has to be stated first that this technology is not at the same level of maturity than C-H2 and L-H2 storage technologies. The technical data collected by SP Evaluation come from existing state-of-the-art prototypes, developed either by industrial companies (Toyota, Honda, Ovonics) or by research institutes such as UTRC. In addition, technical data on the StorHy 8 kg alanate breadboard tank developed by GKSS and TUHH have been collected. It is shown that the mass of the breadboard tank is mainly influenced by the mass of the oil shell and the reactor element tubes which represent 29% and 37%, respectively, of the overall mass of the tank. The main cost driver of the breadboard tank are the sintered metal tubes, which represent about 43% of the tank costs (without taking into account the costs of the alanate itself, nor the cost of the oil).

Based on the results of WP E2 concerning the relevant mathematical models for multi-criteria evaluation, the commercial MACBETH software (Measuring Attractiveness by a Categorical Based Evaluation TecHnique) has been identified as an appropriate tool for evaluating currently



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developed hydrogen storage technologies. For obtaining a commonly approved analysis of the comparison between the performances of hydrogen storage technologies, the proposal of SP Evaluation was to work out a participative implementation approach in close cooperation with SP Users. Until now, 2 car manufacturers have participated in the MACBETH implementation, focusing especially on the technical performance of the hydrogen storage technologies and considering the specific case of a fuel cell vehicle application (6 kg of hydrogen onboard storage).

The results of the implementation procedure were summarized in an evaluation synthesis, which explains how to use the MACBETH software for the evaluation and the comparison of hydrogen storage technologies, describes the inputs and outputs, and gives software downloading information.

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