NATIONAL INSTITUTE OF AEROSPACE TECHNOLOGY Rosa Mª Rengel Gálvez Marina B. Gutiérrez García-Arias 11/09/2007 Rosa Mª Rengel Gálvez Marina B. Gutiérrez García-Arias 11/09/2007 OPTIMIZATION OF A SOLAR HYDROGEN STORAGE SYSTEM: SAFETY CONSIDERATIONS

NATIONAL INSTITUTE OF AEROSPACE TECHNOLOGY   Public organization for aerospace technology research and development.   Since the early seventies, renewable and alternative energies have been one of the R&D areas in which INTA has dedicated a continuous effort.   In 1989, INTA started a program focussed on the use of hydrogen as a storage medium for solar electricity.   Since 1990, interest in terrestrial use of fuel cells and hydrogen technologies.   Facilities in Torrejón de Ardoz (Madrid) and “El Arenosillo” (Huelva).   Public organization for aerospace technology research and development.   Since the early seventies, renewable and alternative energies have been one of the R&D areas in which INTA has dedicated a continuous effort.   In 1989, INTA started a program focussed on the use of hydrogen as a storage medium for solar electricity.   Since 1990, interest in terrestrial use of fuel cells and hydrogen technologies.   Facilities in Torrejón de Ardoz (Madrid) and “El Arenosillo” (Huelva).

- Hydrogen production from renewable energy, mainly solar and wind. - Development of new hydrogen storage systems. - PEMFC testing. - Integration of PEMFC in transport applications. - Development of hydrogen production systems from fossil or renewable fuels. - Simulation of hydrogen systems (energy and CFD aspects). - Safety. AREAS OF INTEREST Development of Metal Hydride H2 Storage Systems Fuel Cell vehicle 12 kW PEMFC Test Bench

INTA SOLAR HYDROGEN STORAGE FACILITY Built up in the period Original design: passive and active safety measures → legislation and good engineering practices, but not a specific risk assessment was done: ATEX Pressure vessel regulations. Operational period: additional safety recommendations from international standards → ISO/TR Basic consideration for the safety of hydrogen system Built up in the period Original design: passive and active safety measures → legislation and good engineering practices, but not a specific risk assessment was done: ATEX Pressure vessel regulations. Operational period: additional safety recommendations from international standards → ISO/TR Basic consideration for the safety of hydrogen system

STORAGE FACILITY CHARACTERISTICS Hydrogen production rate: 1.2 Nm 3 /h Hydrogen storage capacity: enough for an operation week (25-30 Nm 3 ) Operation during 48 weeks per year Charging cycles number higher than discharging cycles number Availability and reasonable cost for small facilities Other requirements: availability, auxiliary systems, etc. Hydrogen production rate: 1.2 Nm 3 /h Hydrogen storage capacity: enough for an operation week (25-30 Nm 3 ) Operation during 48 weeks per year Charging cycles number higher than discharging cycles number Availability and reasonable cost for small facilities Other requirements: availability, auxiliary systems, etc.

RISK ASSESSMENT H 2 production from renewable energy H 2 storage systems needs RISK ASSESSMENT Safety requirements A risk can be defined as “a measure of a significance of hazard involving simultaneous examination of its consequences and probability of occurrence for the scenario”.

QUANTITATIVE RISK ASSESSMENT (QRA) Hazard identification is the most important step in risk analysis

HAZARD IDENTIFICATION WHAT CAN GO WRONG? METHODS: FMEA HAZOP What-if analysis Check list analysis Fault tree analysis Event tree analysis BEFORE THE PROJECT IS FULLY IMPLEMENTED OR A REDESIGN OF A PLANT The objective is to determine a list of potential incidents might be occurred to the accidents.

FMEA Qualitative method. FMEA: systematic methodology to identify product and process problems, assessing their significance, and identifying potential solutions that reduce their significance. Each failure mode has a cause and a potential effect. Can be performed by two different approaches: bottoms-up / top down. Qualitative method. FMEA: systematic methodology to identify product and process problems, assessing their significance, and identifying potential solutions that reduce their significance. Each failure mode has a cause and a potential effect. Can be performed by two different approaches: bottoms-up / top down.

METHODOLOGY FMEA to the three different solar hydrogen storage systems => failure modes, causes and effects. FMEA is an ongoing process and must be updated every time design or process changes are made => Top-down approach. For a good quality hazard identification, complete information about the system must be compiled. The data was provided to a team with expertise on various aspects of hydrogen. FMEA to the three different solar hydrogen storage systems => failure modes, causes and effects. FMEA is an ongoing process and must be updated every time design or process changes are made => Top-down approach. For a good quality hazard identification, complete information about the system must be compiled. The data was provided to a team with expertise on various aspects of hydrogen.

Process:Hydrogen Storage Section:Low pressure storage Design intent:Store up to 6 Nm3 of hydrogen at 6 bar NºFailure ModeCauseEffects 1Storage tank failureMechanical failure, corrosion, hydrogen embrittlementRelease of hydrogen. Potential risk of fire or explosion 2Piping/valves leakMechanical failureRelease of hydrogen. Potential risk of fire or explosion 3Charging process failMechanical failure in hydrogen inlet valve, human errorNo hydrogen stored. Negative influence on electrolyzer 4 Discharging process fail Mechanical failure in hydrogen outlet valve, human error No hydrogen supply to metal hydride, high pressure sections nor fuel cells 5Faulty PRD activationDefect/Fault in PRD, mechanical failureRelease of hydrogen. Potential risk of fire or explosion 6 Overpressure combined with failure of PRD to open Mechanical failure in PRD, purge line closedPotential risk of catastrophic rupture of the storage unit 7 Formation of hydrogen/ nitrogen mixtures in storage tank Mechanical failure in nitrogen inlet valve, human operation error Negative effects on metal hydrides kinetic Less efficiency in fuel cells 8Storage tank failureExternal fire Release of hydrogen. Potential risk of fire or explosion Potential risk of catastrophic rupture of the storage unit FMEA Results for each hydrogen storage section

Process:Hydrogen Storage Section:Metal hydride storage Design intent:Store up to 24 Nm3 of hydrogen in metal hydride NºFailure ModeCauseEffects 9Container failure Mechanical failure, corrosion, hydrogen embrittlement Release of hydrogen to atmosphere/cooling water. Potential risk of fire or explosion 10Piping/valves leakMechanical failure Release of hydrogen to atmosphere. Potential risk of fire or explosion 11 Overpressure in metal hydride containerFault in cooling water supplyPotential risk of catastrophic rupture of the storage unit 12Metal hydride failureHigh content of nitrogen in hydrogenDecrease of hydrogen charge rate. No safety hazard 13Metal hydride failureImpurities in hydrogen gas Decrease of hydrogen charge rate Poisoning of metal hydride and loss of storage capacity. No safety hazard 14 Discharging process failFault in heating water supply No hydrogen supply to high pressure section or fuel cells. No safety hazard 15Shell failure Mechanical failure, corrosion, hydrogen embrittlementLack of cooling/heating water. No safety hazard 16 Cooling circuit piping /valves leakMechanical failureLack of cooling/heating water. No safety hazard

Section:High pressure storage Design intent:Compress and store up to 36 Nm3 of hydrogen at 200 bar NºFailure ModeCauseEffects 17 Compressor suction line failureMechanical failure of line or fittingRelease of hydrogen and potential fire or explosion 18 Lubrication system failureLoss of fluid Compressor failure and hydrogen leak with potential fire or explosion 19Seal failureMechanical failureRelease of hydrogen and potential fire or explosion 20 Compressor suction or discharge valve failureMechanical failure No hydrogen supply to cylinders No safety hazard 21 Pressure relief device fails openMechanical failureRelease of hydrogen. Potential risk of fire or explosion 22Air driven supply fail Mechanical failure or human error and failure in compressed air line No hydrogen compression. No safety hazard 23 Valve on discharge of compressor fails closed Mechanical failure or human error and failure of pressure relief valve to open Overpressure compressor and rupture line. Release of hydrogen and potential fire or explosion 24 High pressure (200 bar) hydrogen supply line failureMechanical failureRelease of hydrogen and potential fire or explosion 25 Overpressure and fail storage tank Mechanical failure in hydrogen pressure regulator at compressor outlet Overpressure storage tank. PRV releases hydrogen with potential fire or explosion 26 Relief device failure (on cylinders) fails openMechanical failure Release of hydrogen to atmosphere and potential fire or explosion 27Storage tank failureMechanical failure, corrosion, hydrogen embrittlement Release of hydrogen to atmosphere and potential fire or explosion 28Piping/valves leakMechanical failure Release of hydrogen to atmosphere and potential fire or explosion 29High pressure fitting failureMechanical failure, human error Release of hydrogen and potential fire or explosion Potential hazard due to high pressure 30Storage tank failureExternal firePotential failure of tank due to overheating of metal

CONCLUSIONS Main potential failure modes: –container or cylinders failure, –piping leaks and valves fails, originated by mechanical or material failure, corrosion or hydrogen embrittlement, –human error. The results of the study have helped to identify a design inherent safety for the new facility, and identify potential prevention and/or mitigation corrective actions. Suitable choice of materials and the need of training of personnel are essential for safety purposes. Main potential failure modes: –container or cylinders failure, –piping leaks and valves fails, originated by mechanical or material failure, corrosion or hydrogen embrittlement, –human error. The results of the study have helped to identify a design inherent safety for the new facility, and identify potential prevention and/or mitigation corrective actions. Suitable choice of materials and the need of training of personnel are essential for safety purposes.

Thanks for your attention.