Battery Initial SoC

Units:	%
Mode:	Input Only
Multi-band:	False
Default Value:	0
Validation Rule:	≥0
Key Property:	No
Description:	Initial State of Charge

Battery Initial SoC is the initial State of Charge of a BESS unit, at the start of the first period of the Horizon.

Example:

Storage	Property	Value	Units
Battery1	Max Power	25	MW
Battery1	Capacity	2	MWh
Battery1	Max SoC	90	%
Battery1	Min SoC	10	%
Battery1	Initial SoC	10	%

The example shows a typical set up for a BESS unit.

When the following conditions are satisfied, Initial SoC may be freely optimized by PLEXOS (any value from 0 to 100%):

Chronology is Sampled,
The battery duration (ratio of Capacity to Max Power) is short relative to the Sampling Interval.

Under the above conditions, freely optimized initial SoC generally results in lower cost, more robust solutions in comparisons to those which strictly adhere to user-defined initial SoC.

As an extreme case, consider sampling only 1 day per year with End Effects Method set to 'Recycle'. A user-defined initial SoC essentially fixes the SoC for one interval duration in each day of the year. If initial SoC is say 0% and simulations start from midnight, the battery cannot effectively be used in a solar soak application to meet nighttime demand, as it will be empty every midnight. The one-time costs of filling low-duration batteries are contextually negligible when amortised over the entire Planning Horizon.