Hi Luigi,

Below are attempts to answer your questions.

>>I understand that Energy Storage is charged when there is excess supply in a given time-slice. Since Energy Storage cannot be assigned a Merit Order, How does LEAP determine when the energy stored will be dispatched to the system to meet demand?

Storage only works when using LEAP’s optimization calculations. In these calculations LEAP calculates the least cost capacity expansion and dispatch across all processes in a module, all time slices in a year and all years in a scenario, with the objective of minimizing the total cumulative discounted cost of the system. So in short, the program itself decides when to store energy, when to discharge energy (and for that matter when/whether to build any storage capacity).

>>2. If Annual and Seasonal Carryover is disabled (by default), what happens to the unused energy stored when it is not dispatched in a given season or year?

In this case I believe the battery can only store and discharge within the time slices of each day (which would be more or less reasonable assuming short term battery storage). I believe there is an internal constraint that the net charge has to be zero for each group of hours. Note of course that you likely will not be modeling individual days, but rather aggregate groups of hours (e.g. you may have 4 seasons x 24 hours).

I think you can also set a constraint on the minimum charge level for a storage process. The zero net charge constraint means there won’t be any unused charge over scenario period.

>>3. In optimization scenarios (needed to model energy storage), what is the criteria that LEAP considers when endogenously adding energy storage capacity to the system?

See above – capacity additions are also subject to the overall optimization goal of minimizing costs subject to your own additional constraints. You can specify pre-existing exogenous capacity though.

>>4. How does Capacity Credit affect Energy Storage?

The capacity credit affects the degree to which each plant’s capacity (MW) count toward your planning reserve margin, using this formula:

Planning Reserve Margin (%) = 100 * (Module Capacity - Peak Load) / Peak Load

Where Module Capacity is the sum of (Capacity * Capacity Credit) across all processes.

Note that storage processes provide capacity but because they have a round trip storage efficiency <=100% they normally provide no net annual energy generation (or even negative energy).

Hope this helps,

Charlie