Fire safety of EVs and FCEVs in buildings

Our commitment to renewable energy is to ensure its safe integration within the built environment. Therefore, our expert guidance on the use of electric vehicles (EVs), charging infrastructure, and hydrogen-powered fuel cell electric vehicles (FCEVs) will support you in shaping future-proof buildings.

We provide renewable energy solutions to help clients reduce their carbon footprint and lower energy costs. Hexa Fire has extensive fire safety experience in the design and provision of expert advice on integrating EV charging infrastructure, electric vehicles (EVs), hydrogen-powered fuel cell electric vehicles (FCEVs), batteries, and photovoltaic (PV) systems across a wide range of building types. We use the latest reliable studies to provide the safest fire safety possible for our projects. Our research background helps us keep up with this fast-evolving field and implement a reliable solution. 

If your building incorporates EVs and/or FCEVs, our team can deliver high-level expert guidance in terms of fire safety.

Hydrogen Jet Fire from a Thermally Activated Pressure Relief Device (TPRD) from Onboard Storage in a Naturally Ventilated Covered Car Park

MDPI - Hydrogen- 2021 · Aug 16, 2021

Hydrogen jet fires from a thermally activated pressure relief device (TPRD) on onboard storage are considered for a vehicle in a naturally ventilated covered car park. Computational Fluid Dynamics was used to predict behaviour of ignited releases from a 70 MPa tank into a naturally ventilated covered car park. Releases through TPRD diameters 3.34, 2 and 0.5 mm were studied to understand effect on hazard distances from the vehicle. A vertical release, and downward releases at 0°, 30° and 45° for TPRD diameters 2 and 0.5 mm were considered, accounting for tank blowdown. direction of a downward release was found to significantly contribute to decrease of temperature in a hot cloud under the ceiling. Whilst the ceiling is reached by a jet exceeding 300 °C for a release through a TPRD of 2 mm for inclinations of either 0°, 30° or 45°, an ignited release through a TPRD of 0.5 mm and angle of 45° did not produce a cloud with a temperature above 300 °C at the ceiling during blowdown. The research findings, specifically regarding the extent of the cloud of hot gasses, have implications for the design of mechanical ventilation systems.

Dispersion of hydrogen release in a naturally ventilated covered car park

International Journal of Hydrogen Energy  · Jul 31, 2020
By necessity hydrogen-powered vehicles will be parked in covered and underground car parks. This has implications for the safety of life and property, and the development of regulations, codes and standards governing passenger vehicles and car parks. This study utilises Computational Fluid Dynamics (CFD) to investigate unignited hydrogen release and dispersion from 700 bar onboard storage in a naturally ventilated covered car park. The impact of leak diameter and angle of leak direction on the formation of the flammable cloud and the implications for vehicle passengers, first responders and car park ventilation are discussed. A typical car park with dimensions LxWxH = 30 × 28.6 × 2.6 m with two opposing vents based on the British Standard (BS 7346–7:2013) was considered. Releases through three different Thermally Activated Pressure Relief Devices (TPRD) with diameters of 3.34, 2.00 and 0.50 mm were compared, to understand the gas dispersion, specifically the dynamics of envelope formation for 1%, 2% and 4% vol of hydrogen. Concentrations in the vicinity of the vehicle and of the vents were of particular interest. It was shown how blowdown through a TPRD diameter of 3.34 mm leads to the formation of a flammable cloud throughout the majority of the car park space in less than 20 s. However, such a flammable envelope was not observed to the same extent for a TPRD diameter of 2 mm and the flammable envelope is negligible for a 0.5 mm diameter TPRD. A release through a 2 mm TPRD diameter resulted in concentrations of 1% hydrogen along the length of the car park ceiling within 20 s, which should activate hydrogen sensors, in contrast an upward release through a 0.5 mm diameter led to concentrations of 1% reaching a very limited area of the ceiling......

Safety Considerations of an Unignited Hydrogen Release from Onboard Storage in a Naturally Ventilated Covered Car Park

The Ninth International Seminar on Fire and Explosion Hazards - Saint Petersburg, Russian Federation · Apr 19, 2019

Unignited hydrogen release from 700 bar onboard storage in a naturally ventilated covered car park has been simulated and analysed. A typical car park with dimensions LxWxH=30x28.6x2.6 m was considered. The car park had two vents of equal area on opposing walls: front and back to facilitate crossflow ventilation based on the British standard (BS 7346-7:2013). Each vent had an area equal to 2.5% of the car park floor area, in line with BS 7346-7:2013 and similar international standards. Releases through three different Thermally Activated Pressure Relief Devices (TPRD) diameters of 3.34, 2.00 and 0.50 mm were compared, to understand the gas dispersion, specifically the dynamics of the flammable envelope (4% vol H2 ), and envelopes of 1% and 2% H2 as these are relevant to sensor and ventilation system activation as required by NFPA 2 standard for enclosures. Concentrations in the vicinity of the vehicle and of the vents are of particular interest. A blowdown model developed in Ulster University was applied to simulate realistic scenarios, and a comparison between an idealistic constant flow rate release and blowdown through a 3.34 mm TPRD diameter highlighted the conservative nature of a constant flow rate release. However, even accounting for the blowdown demonstrated that a release through a TPRD diameter of 3.34 mm leads to the formation of a flammable cloud throughout the majority of the carpark space in less than 20 s. Such a flammable envelope is not observed to the same extent for a TPRD diameter of 2 mm and the flammable envelope is negligible for a 0.5 mm diameter TPRD. Based on ISO/DIS 19880-1, NFPA 2 and IEC (60079-10) standards for equipment with gaseous hydrogen, the ventilation system must work to maintain hydrogen concentration under 1% of hydrogen mole fraction in the air, above this there should be ventilation sensor activation....................

Pressure effects of an ignited release from onboard storage in a garage with a single vent

International Journal of Hydrogen Energy  · Apr 2, 2019

A numerical study has been performed comparing the hazards, in particular overpressures, arising from the sustained unignited and ignited release from an onboard hydrogen storage tank at 700 bar through a 3.34 mm diameter orifice, representing a thermally activated pressure relief device (TPRD) in a small garage with a single vent equivalent in area to small window. It has been demonstrated how the overpressure predicted in the case of an unignited release using both CFD and an analytical model is in the region of 0.55 kPa and thus unlikely to cause structural damage. However, the overpressure predicted for the ignited release is two orders of magnitude greater, reaching over 55 kPA in less than 1 s and thus potentially causing destruction of the structure.  It has been shown that whilst the overpressures resulting from the unignited release are unlikely to cause harm, the garage is engulfed by a flammable atmosphere in less than 1 s and the oxygen is depleted to levels dangerous to people within this time. In the case of the ignited release, whilst the resultant overpressures are the primary safety concern, it has been shown how the thermal effects resulting from the release extend almost 9 m from the jet in 1.5 s.

Numerical validation of pressure peaking from an ignited hydrogen release in a laboratory-scale enclosure and application to a garage scenario

International Journal of Hydrogen Energy  · Sep 13, 2018

This work focuses on the overpressures arising from the rapid ignited release of hydrogen in an enclosure, specifically the peak in overpressure that may result in the initial period of the release, dependent on the level of ventilation. Two volumes are considered: a 1 m3 laboratory scale enclosure for which experimental data exists, and a real scale residential garage. Various vent configurations are considered for each scenario for leak rates typical of those from a fuel cell (laboratory scale enclosure) and from onboard hydrogen storage tanks through a thermally activated pressure relief device (TPRD) in the garage-like enclosure. A validation study has been performed for the laboratory scale enclosure and the modelling approach which gives optimum results has been identified. The influence of heat transfer on the pressure peak has been highlighted, particularly, the importance of radiation in predicting the pressure peak. The validated modelling approach has been applied to a range of experiments and garage scenarios. Both the laboratory and real scale simulations demonstrate the complex relationship between vent size and release rate and indicate the significant overpressures that can result through pressure peaking following an ignited release in an enclosure. The magnitude of the pressure peak as a result of an ignited release has been found to be two orders of magnitude greater than that for the corresponding unignited release. The work indicates that TPRDs currently available for hydrogen-powered vehicles may result in a dangerous situation for the specific scenario considered which should be accounted for in regulations, codes and standards. The application of this work extends beyond TPRDs and is relevant where there is a rapid, ignited release of hydrogen in an enclosure with ventilation.