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 :ref:`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 :ref:`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 |
|---|---|
| NetPower_t | Net power out from the power plant at each time period in MW |
| SaltInventory_t | Solar salt inventory at each time period in kg |
- Power plant ramping is limited by including the following equations for a given ramp_-rate:
NetPower_{t-1} - ramp_-rate \leq NetPower_t
NetPower_{t-1} + ramp_-rate \geq NetPower_t
- 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:
HotSaltInventory_t = HotSaltInventory_{t-1} + F^{charge}_{salt, outlet} - F^{discharge}_{salt, inlet}
total_-salt = HotSaltInventory_t + ColdSaltInventory_t
Note that the notable constraints and variables in the multiperiod model also consider the notable variables and constraints given in :ref:`Integrated Ultra-Supercritical Power Plant`.