Engineering question
How can electrical power and specific energy consumption be converted into preliminary hydrogen production without implying a complete electrolyser design?
A first-pass electrolyser calculation divides electrical input by a user-entered specific energy consumption (SEC) in kWh per kilogram of hydrogen. It is a transparent energy balance, not a universal efficiency claim. SEC depends on technology, load, stack condition, power boundary, auxiliaries, temperature and the OEM guarantee definition.
The boundary matters more than an extra decimal place. Stack DC consumption, rectifier input, electrolyser package input and complete plant import can all yield different kWh/kg values. Water treatment, cooling, drying, compression, storage and export pressure must be stated separately when they are not included.
Calculation basis
Formulas and units
Hydrogen from power
H2(kg/h) = electrical power(kW) / SEC(kWh/kg)
Power and SEC must use the same defined system boundary.
Required power
Power(kW) = target H2(kg/h) × SEC(kWh/kg)
Add separately defined balance-of-plant loads when the SEC excludes them.
Annual output
H2(t/y) = kg/h × operating hours/y / 1000
Operating hours are not automatically equivalent to full-load hours.
Normal volume
Nm³ = mass / density at stated normal reference
This guide's calculator displays dry H2 at 0°C and 101.325 kPa absolute by default.
Worked example
Apply the formula
5 MW boundary input, user-entered SEC 52 kWh/kg and 8000 full-load-equivalent hours per year.
- 1Production = 5000/52 = 96.15 kg/h.
- 2Annual output = 96.15 × 8000 / 1000 ≈ 769.2 t/y.
- 3If auxiliaries are outside the 5 MW or 52 kWh/kg boundary, total plant import will be higher.
Result: The screened production is about 96.2 kg/h and 769 t/y at the stated boundary. Only OEM/project data can establish guaranteed performance.
Open Hydrogen Electrolyser Sizing CalculatorInputs needed beyond the simple screen
- Technology and OEM performance curves across load and life
- AC/DC and package/plant energy boundary
- Turndown, ramp, start/stop and degradation assumptions
- Feedwater quality, consumption and treatment recovery
- Cooling duty, ambient conditions and heat rejection
- Hydrogen purity, drying, delivery pressure and compression
- Availability, planned maintenance and renewable-power profile
Automation and electrical interfaces
A project may require utility and package PLC integration, rectifier/power-conversion interfaces, sequence coordination, alarm and trip philosophy, historian data, energy KPIs and remote monitoring. Functional safety, hazardous-area classification, gas detection, ventilation, pressure systems, fire protection and statutory approval require competent project-specific engineering and authorities.
- Define package/EPC/owner interface signals and control authority.
- Separate normal control, protective trips and emergency shutdown.
- Use approved cause-and-effect and permissive matrices.
- Protect remote access and commands within the cybersecurity architecture.
Elexorn capability boundary
Elexorn presents transferable automation, electrical, water, energy-monitoring and software integration capability. This guide does not claim that Elexorn manufactures electrolysers, supplies a complete hydrogen EPC, licenses a process, certifies hazardous areas or acts as an independent HAZOP, LOPA or SIL authority.
Common mistakes
- Using a universal SEC without defining boundary
- Treating calendar availability as full-load operation
- Mixing Nm³ reference conditions
- Presenting calculated output as an OEM guarantee
Troubleshooting checks
- Calculated and quoted output differ: align AC/DC, auxiliary, purity and pressure boundaries.
- Annual total looks high: distinguish operating hours from full-load-equivalent hours.
- Nm³ conversion differs: compare temperature, pressure, dryness and density basis.
- Plant import exceeds model: identify rectifier, cooling, water, compression and standby loads.
Assumptions
- SEC is a user-entered project/OEM value
- Power and SEC boundaries are aligned
- Operating hours represent an explicitly defined load basis
Limitations
- Preliminary energy and mass conversion only
- Does not size stacks, rectifiers, water treatment, compression or storage
- Does not perform process-safety or regulatory engineering
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