Thermochemical storage

Reversible reactions that soak up heat and give it back later.

Storage · Chemical · No. 90

• Storage
• Duration: Days to seasons

Heat split into two chemicals and kept apart leaks almost nothing, so summer sunshine could warm a home in winter.

Chart: Illustration: Thermochemical storage

Where it comes from

Chart: Map of where it comes from

Heat drives a reaction apart, such as lime from CO2 or a salt from water vapour; calcium looping holds 390 to 490 kWh per tonne of limestone.

Three things to know

1. A typical West European home needs about 7 to 12 GJ of seasonal heat, roughly 10 m3 of reactor at 1 GJ per m3.
2. Natural limestone wears out fast in calcium looping, with one model assuming only 7.5% stays reactive.
3. Adding 10% iron oxide to manganese oxide raised its re-oxidation from 6% to 100%, a key research fix.

The journey

1. 1 Heat inSolar heat or cheap electricity
2. 2 SplitCompound breaks into two parts
3. 3 Store apartKept separate at room temperature
4. 4 RecombineProducts react again, releasing heat
5. 5 Heat outWinter home heating or industrial heat

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