State of charge (SOC)
For thermal stores, state of charge (SOC) describes the stored energy relative to a defined usable energy range. In PCM coolant packs, it depends on factors including the solid and liquid fractions and the temperature. A percentage requires a definition of which condition counts as fully charged for the application.
What does the condition of a PCM tell you?
- Remaining solid material is relevant to heat absorption during melting. Liquid material is needed to release heat during solidification.
- During a phase change, temperature may remain almost unchanged even though the solid and liquid fractions change substantially.
- A suitable surface temperature therefore demonstrates neither complete conditioning nor a particular remaining protection duration.
How is a reproducible starting condition achieved?
Pre-conditioning specifies the temperature, duration and loading arrangement. A verified process brings the packs to their intended initial condition. A reliable SOC percentage, however, requires an appropriate measurement or calculation method; it cannot be read from a thermometer alone.
Related terms: PCM · Hibernation / controlled intermediate storage