PTES (sometimes called a Carnot battery) uses electricity to drive a heat pump that moves heat from a cold store to a hot store. On discharge the cycle reverses and a heat engine turns the temperature difference into electricity.
Round-trip efficiency depends on machinery efficiency and temperatures; configurations using Brayton or Rankine cycles, with salts, rock, water or ice as stores, are at development and demonstration stage.
Key facts
- Charge
- Heat pump (compressor)
- Discharge
- Heat engine (turbine)
- Stores
- Hot + cold reservoirs
- Maturity
- Development / demonstration
Cycle options4
- Brayton (gas) cycle PTES
- Rankine / transcritical CO₂ PTES
- Liquid-air-assisted configurations
- Hybrid with CSP or waste heat
Key components6
- Compressor and expander
- Hot store (salt, rock, concrete)
- Cold store (water, ice, chilled media)
- Recuperators and heat exchangers
- Motor-generator and grid connection
- Control system
Integration opportunities4
- Solar PV and wind firming
- Retrofit of retiring thermal plants
- CSP plants
- Grid services where market rules permit
Evaluate project by project
Performance and commercial suitability of PTES must be assessed for each project; several configurations are still under development.
Related calculators
Calculators are available to staff / admin only.
Related topics
- Heat-to-PowerSteam Rankine, ORC, sCO₂ and closed-cycle gas turbines convert stored or recovered heat into electricity.
- Heat PumpsIndustrial and large heat pumps upgrade low-grade heat to useful temperatures; storage lets them run at the best hours.
- Thermal BatteryIntegrated systems that turn electricity — often cheap renewable power — into stored high-temperature heat for steam, hot air or power.
Project & partnership desk
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