Storage Initial Volume

Units:	GWh
Mode:	Input/Output
Multi-band:	False
Default Value:	0
Validation Rule:	≥0
Key Property:	No
Description:	Storage volume at the start of the period

Storage Initial Volume as an input sets the volume in the storage at the start of the first period of the Horizon. The units of Initial Volume are controlled by the Storage Model.

Example:

Storage	Property	Value	Units
PUMP1	Max Volume	5	GWh
PUMP1	Initial Volume	0	GWh
PUMP1 TAIL	Max Volume	5	GWh
PUMP1 TAIL	Initial Volume	5	GWh

The example show a typical set up for a pump storage system.

When the following conditions are satisfied, initial volume may be freely optimized by PLEXOS (any value from 0 to Max Volume):

Chronology is Sampled,
The storage duration (ratio of Max Volume to connected Generator Max Capacity) is short relative to the Sampling Interval.

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

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

As an output, Initial Volume is the volume in storage at the start of the period.