This lecture explores silicon as a renewable metal energy carrier, comparing it with aluminium and iron in terms of efficiency, availability, and environmental impact.

It examines production pathways, from carbothermal reduction to emerging electrochemical molten salt reduction.

Silicon’s potential discharging reactions with water and steam to produce hydrogen are discussed, together with the challenge of its natural passivation.

The lecture concludes with a comparison of ReMEC cycles and an overview of the REVEAL project, highlighting industrial applications and the role of metals in a circular, low-carbon energy system.  

CONTENT

1. Silicon  

  • Production and Market 

  • Power-to-Si: Charging  

  • Si-to-Energy: Discharging 

  • Global warming potential

2. ReMEC Cycles Comparison

3. Project REVEAL and Activities  

Main Findings

  • Silicon is the most abundant of the three ReMEC candidates and shows a high hydrogen yield (≈140 g H₂/kg), but current production via carbothermal reduction is highly carbon- and energy-intensive.

  • Electrochemical molten salt reduction offers a cleaner, more efficient Power-to-Si pathway, though it remains at a low TRL (3–4) with challenges in scalability and efficiency.

  • Silicon’s natural oxide passivation layer hinders reactivity; using powders or alkaline solutions enables effective hydrogen production from water/steam reactions.

  • ReMEC cycle comparison shows aluminium and silicon have the highest overall storage efficiencies (~59–63%, electricity → ReMEC → heat & electricity), while iron is closer to deployment (higher TRL).

  • The European and Swiss funded research project REVEAL demonstrates how these technologies could underpin a circular, scalable, and carbon-free energy system for seasonal storage and industry.