Application summary: Emerging-energy QRA uses the same frequency–consequence–risk framework as conventional process QRA, but the scenario set and models must reflect the technology. Hydrogen, ammonia, LNG, battery energy storage and dense-phase carbon dioxide each require different release physics, harm endpoints, safeguards, data and emergency-response assumptions. A generic hydrocarbon template is not sufficient.
Energy-transition projects can introduce unfamiliar inventories, operating modes and interfaces. QRA should begin early enough to influence siting, separation, layout, isolation, ventilation, detection, drainage, fire protection and emergency access—not after those choices are fixed.
How QRA changes by emerging-energy application
| Application | Priority scenarios | Modelling focus | Critical inputs |
|---|---|---|---|
| Hydrogen production, storage and refuelling | High-pressure leaks, jet fires, delayed ignition, confined or congested explosion, cryogenic releases where applicable | Buoyant dispersion, small-leak detectability, ignition, flame radiation, overpressure and enclosure ventilation | Pressure, inventory, orifice range, ventilation, congestion, detector response, isolation and compatible materials |
| Ammonia storage, refrigeration or energy carrier | Toxic liquid/vapour releases, flashing jets, pool evaporation, indoor accumulation, loading-transfer failures and fire exposure | Source term, aerosol/rainout, toxic dispersion, sheltering, exposure duration and emergency isolation | Concentration, storage state, temperature, bunding, water interaction, meteorology, population and toxic endpoint |
| LNG facilities | Transfer-arm or hose release, pool spread, vapour dispersion, flash fire, pool fire, rollover/overfill and escalation | Cryogenic release, pool spreading and evaporation, dense-gas dispersion, ignition and thermal radiation | Composition, inventory, impoundment, surface, weather, shutdown time, transfer frequency and ignition assumptions |
| Battery energy storage systems (BESS) | Cell failure, thermal runaway propagation, off-gas accumulation, fire, explosion, toxic products and re-ignition | Propagation evidence, enclosure ventilation, gas generation, deflagration potential, heat release, firefighting and exposure | Chemistry, cell/module/rack configuration, test data, state of charge, BMS/EMS logic, spacing and enclosure design |
| CO₂ capture, transport and storage | Pipeline or equipment rupture, dense-phase decompression, dry-ice formation, low-point accumulation and asphyxiation | Real-fluid source term, phase change, terrain-sensitive dense dispersion and oxygen displacement | Composition/impurities, pressure-temperature envelope, isolation spacing, terrain, weather and occupied low areas |
| Electric-vehicle charging or hydrogen fleets | Vehicle fire, charger fault, cascading exposure, indoor gas accumulation, collision and emergency isolation | Occupancy, enclosure, detection, vehicle spacing, thermal escalation and responder access | Fleet pattern, charging state, ventilation, fire barrier, equipment layout and emergency procedures |
Hydrogen QRA: what must be different?
Hydrogen is non-toxic, but the US Department of Energy notes its wide flammable range, relatively low ignition energy, nearly invisible flame and potential material-compatibility issues. QRA should therefore test small and large leaks, immediate and delayed ignition, ventilation effectiveness, detector coverage, isolation time, congested regions and occupied enclosures. Dispersion assumptions suitable for a heavier hydrocarbon should not be transferred without validation.
Ammonia QRA: toxicity usually drives the study
Ammonia can threaten workers and the public through inhalation and corrosive exposure, while fire and explosion may also matter in defined conditions. The analysis should preserve release thermodynamics through flashing, aerosol formation, rainout and pool evaporation. Toxic endpoints must match the regulator and decision; an occupational exposure limit is not automatically an emergency or fatality endpoint.
BESS risk assessment: combine QRA with test evidence
A BESS study should not infer propagation or gas generation from nameplate energy alone. Use representative cell, module, rack or installation evidence; identify initiators; model escalation; and test ventilation, detection, isolation, spacing and emergency-response assumptions. NFPA 855 addresses stationary energy-storage installation and includes BESS hazards and firefighting considerations. The applicable edition and authority having jurisdiction must be confirmed.
Minimum emerging-energy scenario register
| Register field | Required detail |
|---|---|
| Initiating event | Equipment, failure mode, operating state and credible cause |
| Release or energy state | Inventory, pressure, temperature, phase, composition and duration |
| Safeguard timing | Detection, alarm, operator action, automatic trip, isolation and blowdown |
| Outcome branches | Ignition timing, ventilation state, propagation, escalation and emergency intervention |
| Consequences | Thermal, overpressure, toxic, asphyxiation, cryogenic and environmental endpoints |
| Exposure | Workers, public, responders, traffic, transient occupancy and vulnerable receptors |
| Frequency basis | Generic data, technology-specific evidence, operating demand and uncertainty |
| Risk result | Scenario risk, individual risk, societal risk and dominant contributors as applicable |
When is CFD or specialist modelling justified?
Consider higher-fidelity modelling when three-dimensional geometry, confinement, congestion, terrain, phase behaviour or ventilation materially affects the decision. Examples include hydrogen inside an enclosure, explosion loads in congested modules, ammonia or CO₂ around complex terrain, and BESS off-gas accumulation. The QRA should state why the model is suitable, how boundaries and mesh were selected, what evidence supports it and how uncertainty affects the recommendation.
Emerging-energy QRA data checklist
- Process description, heat and material balance, PFDs, P&IDs and cause-and-effect
- Technology-specific composition and thermodynamic property basis
- Equipment, piping, transfer and mobile-interface inventories
- Layout, elevations, congestion, enclosures, ventilation and terrain
- Detection, shutdown, isolation, blowdown, drainage and fire-protection performance
- Technology and configuration-specific test or failure evidence
- Local meteorology and time-varying worker/public population
- Adjacent assets, domino pathways, emergency routes and responder strategy
- Applicable codes, authority criteria and model acceptance requirements
When should the QRA be updated?
- Technology, chemistry, storage state or inventory changes
- Layout, enclosure, ventilation or separation changes
- New test data, incident evidence or model validation becomes available
- Control logic, detection, isolation or firefighting strategy changes
- Population, neighbouring development or emergency access changes
- Applicable legislation, code edition or regulator guidance changes
- A major incident, near miss or unexpected model result challenges assumptions
Official and primary sources
- US Department of Energy: safe use of hydrogen
- US Department of Energy: hydrogen safety, codes and standards
- H2Tools: hydrogen safety best practices and lessons learned
- US OSHA: ammonia hazard recognition
- NFPA 855: stationary energy storage systems
- US Department of Energy: energy-storage safety plan
- US PHMSA: pipeline safety authority and CO₂ rulemaking resources