The Multiperiod Integrated Ultra-Supercritical Power Plant is an example model to determine the optimal schedule and operation of a pulverized coal-fired ultra-supercritical power plant integrated with thermal energy storage system (TES) for given electricity prices over a time horizon. The multiperiod model uses the Integrated Ultra-supercritical Power Plant model for each period in the horizon. A more detailed description of the model is given in the sections below.
The multiperiod power plant model is developed by creating multiple instances of Integrated Ultra-Supercritical Power Plant model, where every instance is indexed by a time period, along with two coupling variables to link each time period. These coupling variables are: the optimal power produced by the power plant and the amount of storage material available at the end of each time period. A scheme showing how the multiperiod model is constructed is shown in the figure below:
The multiperiod model has a total of 4 n degrees of freedom, where n represents the number of time periods. The degrees of freedom for each time period are listed below:
- Boiler feed water flow (boiler.inlet.flow−mol),
- Steam flow to charge heat exchanger (HXC.inlet−1.flow−mol)
- Condensate flow to discharge heat exchanger (HXD.inlet−2.flow−mol),
- Cooler enthalpy at outlet (cooler.outlet.enth−mol)
| Variable Name | Description |
|---|---|
| NetPowert | Net power out from the power plant at each time period in MW |
| SaltInventoryt | Solar salt inventory at each time period in kg |
- Power plant ramping is limited by including the following equations for a given ramp−rate:
NetPowert − 1 − ramp−rate ≤ NetPowert
NetPowert − 1 + ramp−rate ≥ NetPowert
- The salt inventory SaltInventory is given by the hot salt and total salt material balances, the latter involving a fixed amount of salt total−salt. The material balances are shown in the following equations:
HotSaltInventoryt = HotSaltInventoryt − 1 + Fsalt, outletcharge − Fsalt, inletdischarge
total−salt = HotSaltInventoryt + ColdSaltInventoryt
Note that the notable constraints and variables in the multiperiod model also consider the notable variables and constraints given in Integrated Ultra-Supercritical Power Plant.