Reference Tables
Electrolyzer Technology Reference
Alkaline, PEM, AEM, and SOEC electrolyzer technologies compared on efficiency, load flexibility, lifetime, and capex.
README
Comparison
Electrolyzer Technology Comparison
| Parameter | Alkaline (AWE) | PEM | SOEC | AEM |
|---|---|---|---|---|
| Operating temperature | 60-90C | 50-80C | 650-900C | 40-60C |
| Operating pressure | 1-30 bar (typ 1-10) | 10-80 bar | 1-5 bar (some pressurized) | 1-35 bar |
| Electrolyte | 25-30 wt% KOH | Solid polymer (Nafion/PFSA) | YSZ ceramic | Anion exchange membrane |
| Nominal efficiency (LHV) | 62-72% | 65-78% | 80-95% (with heat integration) | 60-72% |
| Specific energy (kWh/kg H2) | 50-55 (LHV 33.3) | 48-55 | 38-45 (elec only); 34-40 w/ heat | 50-55 |
| Current density (A/cm2) | 0.2-0.8 | 1.0-3.0 | 0.3-1.0 | 0.5-2.0 |
| Stack lifetime (hrs) | 60,000-90,000 | 40,000-80,000 | 20,000-40,000 | 5,000-30,000 (commercial emerging) |
| Minimum load (% rated) | 20-40% | 0-10% | 30-100% (thermal inertia) | 5-20% |
| Cold start time | 30-60 min | <5 min | hours (thermal cycling) | <10 min |
| Dynamic response | seconds | <1 second | minutes-hours | seconds |
| H2 purity (pre-purify) | 99.5-99.9% | 99.99% | 99.9%+ | 99.9%+ |
| O2 crossover risk | moderate (H2 in O2) | low | not applicable | low-moderate |
| PGM catalyst | no (Ni, NiMo) | yes (Pt, Ir) | no (Ni-YSZ, LSM) | no (goal) |
| CAPEX 2024 (USD/kW) | 500-1100 | 700-1400 | 2000-4000 | 1000-1800 (pilot) |
| CAPEX target 2030 (USD/kW) | 300-500 | 400-700 | 700-1200 | 400-800 |
| Water consumption (L/kg H2) | 9-10 | 9-10 | 9-10 + make-up for steam | 9-10 |
| Stack size max (MW) | 1-17 (single) | 1-20 (single) | 0.1-1 (emerging) | <1 (pilot) |
| Commercial maturity | TRL 9 (100+ yrs) | TRL 9 (since 1960s) | TRL 7-8 (scaling) | TRL 6-7 |
| Best fit application | large-scale steady H2 | dynamic renewable-coupled | high-temp / eFuels w/ waste heat | small modular / cost-sensitive |
Vendors
Commercial Electrolyzer Offerings (representative, 2024)
| Vendor | Technology | Product | Stack (MW) | Efficiency (kWh/kgH2) | Notes |
|---|---|---|---|---|---|
| Thyssenkrupp nucera | Alkaline | scalum 20 MW | 20 | 50 | Modular 20 MW containers |
| Nel | Alkaline | A-485 | 2.4 | 52 | Atmospheric pressure, containerized |
| Nel | PEM | MC500 | 2.5 | 53 | Proton Energy heritage |
| Plug Power | PEM | 5 MW GEN2 | 5 | 53 | Skid-based |
| Siemens Energy | PEM | Silyzer 300 | 17.5 | 53 | Offshore-compatible |
| Cummins / Hydrogenics | PEM | HyLYZER-4000 | 20 | 54 | Modular |
| ITM Power | PEM | Neptune V | 5 | 53 | Deployed in refinery projects |
| Topsoe | SOEC | e-Methanol ready | 50 | 38 | Pressurized SOEC, heat integration |
| Sunfire | SOEC | SynLink | 1.1 | 40 | Coupled w/ industrial waste heat |
| Bloom Energy | SOEC | Bloom Electrolyzer | 0.1 | 37 | Reversible SOFC/SOEC |
| Enapter | AEM | EL 4.0 | 0.0024 | 53 | Small modular 2.4 kW stack |
| H2Pro | E-TAC (alkaline) | Pilot | 0.5 | 40 | Decoupled HER/OER cycle |
Energy BOP
Electrolyzer Plant Energy Balance (typical, 100 MW PEM)
| Component | Power fraction (%) | Notes |
|---|---|---|
| Electrolysis stack | 86 | DC power to cells |
| Power conversion (AC/DC) | 4 | Transformer + rectifier losses |
| Compression (30->100 bar) | 4 | Downstream compressor |
| Water purification (EDI) | 1 | Deionizer, UV, RO |
| Cooling (chillers / cooling towers) | 3 | 25-30C stack temp control |
| N2 / He purge, drying | 1 | PSA / TSA dryers |
| Controls, lighting, HVAC | 1 | Plant parasitic |
| Total |
SOEC Notes
SOEC Integration Notes for eFuels
| Topic | Value / Rule | Source |
|---|---|---|
| Steam requirement | ~1.0-1.1 kg H2O / Nm3 H2 (steam side feed) | Topsoe whitepaper |
| Thermal integration | Ideal w/ FT synthesis ~200C excess heat or methanol synthesis | Haldor Topsoe |
| Degradation rate | 0.5-2% voltage rise per 1000 hr, accelerated by thermal cycling | NREL SOEC review |
| Co-electrolysis (CO2+H2O) | Direct syngas production, ~42 kWh/kg syngas equiv | Sunfire demo |
| Pressure range | Atmospheric typical; pressurized SOEC (10-30 bar) in development | DLR, Topsoe |
| Reversibility | Some stacks operate as SOFC also; lifetime trade-off | Bloom Energy |
| Typical capacity today (MW) | 0.1-1 MW modules; 50 MW commercial by 2026 (Topsoe Herning) | Topsoe press 2023 |
| Fit for eMethanol | High - steam demand matches heat rejection of MeOH synth | Topsoe/Nel/Siemens studies |
| Fit for FT (Fischer-Tropsch) | High - waste heat from FT fits SOEC steam generation | INFINIUM, Nordic Electrofuel |
| NOT fit for | Intermittent operation (thermal cycling penalty); fast-start applications | IEA 2023 |
Source: Electrolyzer_Technology_Reference_v1.xlsx
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