Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
This is really a question about EnergyPlus rather than OpenStudio. Usually you'd find such information in the I/O reference guide (see I/O: ThermalStorage:Ice:Detailed) but in this case it's not terribly clear. Thankfully, the Engineering reference can be used, see here.
The Charging and Discharging Equation section will make you learn that x is either the Fraction charged or Fraction decharged. And yes, x**2 = x²
