# [TECH-Idea] Green Hydrogen Economy
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**Green hydrogen** — produced by electrolysis of water using renewable electricity — is a carbon-free energy carrier enabling decarbonisation of sectors that cannot be easily electrified directly: steel, cement, shipping, aviation, and long-duration energy storage.
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## Overview
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Hydrogen is energy-dense (120 MJ/kg vs. 44 MJ/kg for petrol) and produces only water when combusted or used in a fuel cell. Today, 96% of hydrogen is "grey" (from natural gas reforming, producing CO₂). Green hydrogen uses renewable electricity to split water (electrolysis): 2H₂O → 2H₂ + O₂.
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**Applications**:
- **Steel** (8% of global CO₂): replacing coal in blast furnaces with hydrogen direct reduction. HYBRIT (SSAB/LKAB/Vattenfall) produced first commercial hydrogen-reduced steel (2023, delivered to Volvo). ThyssenKrupp, ArcelorMittal, Salzgitter all scaling.
- **Ammonia/fertilisers** (1–2% of global CO₂): green ammonia by combining green H₂ with air-separated N₂ via modified Haber-Bosch. Yara, CF Industries, Fortescue.
- **Aviation**: Airbus ZEROe (hydrogen turbofan and fuel-cell aircraft, 2035 target). ZeroAvia (hydrogen fuel cell commuter aircraft, 2024 trials).
- **Shipping**: ammonia-fuelled ships (MAN Energy, Wärtsilä engines). Hydrogen fuel cell ferries in Norway since 2021.
- **Long-duration storage**: hydrogen stored in salt caverns or tanks provides seasonal energy storage complementing solar and wind.
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**Cost trajectory**: Green H₂ currently USD 4–8/kg; target USD 1/kg by 2030 (IEA). US IRA provides USD 3/kg production tax credit. EU Hydrogen Bank provides up to EUR 4.5/kg in auctions.
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## Key Actors
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Nel Electrolyser (Norway, largest electrolyser manufacturer), ITM Power (UK), Plug Power (US, largest US fuel cell company), Thyssenkrupp Nucera, Cummins, Air Products, Linde, Shell (Holland), HYBRIT consortium, Airbus, ZeroAvia.
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## Economic Value
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Green hydrogen market: USD 200B/year by 2030, USD 1T+/year by 2050 (IEA, IRENA). Decarbonising steel globally (1.9 GtCO₂/year): USD 2T+ in industry transformation. Aviation hydrogen (Airbus ZEROe by 2035): USD 900B aviation market addressable. Long-duration storage enabling higher renewable penetration: USD 500B+/year in grid value.
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## Notes
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IEA *Global Hydrogen Review* 2023: green hydrogen production must grow 100× to meet 2050 net-zero scenarios. Electrolyser costs declined 60% between 2010 and 2023 and are on a solar-panel-like learning curve. The Hydrogen Council (industry group) estimates USD 320B in committed investment through 2030.
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## Discovery Character
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**Surprise level**: Moderate — electrolysis has been known since 1800 (Nicholson & Carlisle). The surprise is economic: renewable cost reductions have made green hydrogen economically viable for the first time, at a pace faster than projected.
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**Mode**: Systematic-engineering (electrolyser scale-up, infrastructure development). The creative element is the policy and market design (IRA, EU Hydrogen Bank) that is driving cost reductions via scale — a deliberate policy innovation rather than a technical one.
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## What This Enables
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This node is a current frontier — downstream effects (green steel at global scale, hydrogen aviation, decarbonised fertilisers) are themselves at the leading edge.
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# Parents
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* [SCI] Electrochemistry⏎