Thermal Battery State of Charge Calculator
Translate hot and cold tank temperatures into a deterministic state-of-charge percentage and remaining deliverable energy for molten-salt or concrete-based thermal batteries.
Engineering planning aid. Validate thermal measurements and loss estimates against calibrated sensors and energy balance checks before making dispatch commitments.
Examples
- Nominal capacity 120 MWh, design hot 565 °C, design cold 290 °C, current 500 °C, losses 4 MWh ⇒ State of charge 73.03% with 87.64 MWh available and 32.36 MWh headroom.
- Nominal capacity 80 MWh, design hot 500 °C, design cold 280 °C, current 320 °C, losses left blank ⇒ State of charge 18.18% with 14.55 MWh available and 65.45 MWh headroom.
FAQ
How should I measure the current average hot tank temperature?
Use a stratified average across multiple thermocouples or fibre-Bragg grating sensors spaced through the tank height. Simple single-point readings can miss thermal layering and distort the state-of-charge estimate.
Can the calculator handle sensible and latent thermal batteries?
The default formulation targets sensible two-tank systems. Latent or thermochemical storage requires enthalpy lookups across phase changes; approximate the state of charge with equivalent energy fractions before applying those more complex corrections.
Why subtract documented losses separately if the temperature already dropped?
Operators often track parasitic draws and flare losses explicitly. Subtracting them preserves audit trails and keeps the temperature-based ratio comparable across reports even when measurement windows differ.
Additional Information
- Result unit: percentage of nominal MWh plus deliverable energy in MWh.
- Losses default to 0 MWh when no telemetry is supplied, keeping the calculation conservative.
- Clamp logic ensures the temperature ratio never exceeds 0%–100%, preventing overstatement when sensors read slightly above design targets.