Integrated Ultra-Supercritical Power Plant

The Integrated Ultra-Supercritical Power Plant is an example model to determine the optimal operation of a pulverized coal-fired ultra-supercritical power plant integrated with a thermal energy storage system (TES) for a given electricity price. This model integrates a Solar salt charge and discharge heat exchanger in the Ultra-Supercritical Power Plant model. A flowsheet of the integrated power plant is shown in the figure below:






Reheater (\(RH_1\) and \(RH_2\))


Turbine (\(T_1\) to \(T_{11}\))


Boiler Feed Water Pump Turbine


Storage Turbine


Feed Water Heater (\(FWH_1\) to \(FWH_9\))


Condensate Mixer


Condenser Pump


Booster Pump


Boiler Feed Water Pump


Storage Pump




Charge Splitter


Discharge Splitter


Charge Storage Heat Exchanger


Discharge Storage Heat Exchanger


Boiler Feed Water


Boiler Flow Inlet (mol/s)


Condenser Flow Outlet (mol/s)


Steam Flow to Charge Storage System (mol/s)


Salt Flow to Charge Storage System (kg/s)


Boiler Feed Water Flow to Discharge Storage System (mol/s)


Salt Flow to Discharge Storage System (kg/s)

Model Structure

For the construction of the integrated power plant model, the Ultra-Supercritical Power Plant model is used as the base model to integrate the charge and discharge heat exchangers. The optimal integration point and design of both storage heat excahngers are obtained using the Design of Integrated Ultra-Supercritical Power Plant model. The integrated model is also constructed using the unit models from the power generation unit model library in addition to the IAPWS property package for steam and water, and the Solar salt property package in the storage heat exchangers. The unit models used are shown in the table below:

Unit Model

Units in Flowsheet


Turbines (\(T_1\) to \(T_{11}\)) and \(BFPT\)


Turbine Splitters


Boiler Components (\(Boiler\), \(RH_1\), and \(RH_2\))


Mixers (\(CM\) and \(DA\))


Pumps (\(CP\), \(BP\), \(BFWP\), and \(SP\))


Condenser, Feed Water Heaters (\(FWH_1\) to \(FWH_9\)), and Storage Systems (\(HXC\) and \(HXD\))

Degrees of Freedom

The integrated ultra-supercritical power plant model has a total of 4 degrees of freedom, listed below:

  1. Boiler feed water flow (\(boiler.inlet.flow_-mol\)),

  2. Steam flow to charge heat exchanger (\(HXC.inlet_-1.flow_-mol\))

  3. Condensate flow to discharge heat exchanger (\(HXD.inlet_-2.flow_-mol\)),

  4. Cooler enthalpy at outlet (\(cooler.outlet.enth_-mol\))

Notable Variables

Variable Name



Power out from the power plant in MW


Revenue in $ per hour


Total solar salt inventory in kg


Hot solar salt inventory in kg

Notable Constraints

  1. The net power is given by the sum of the power produced by the storage system and the plant as shown in the following equation:

\[NetPower = PlantPowerOut + ST.mechanical_-work\]
  1. The revenue is calculated by considering the given electricity price \(lmp_-signal\) and the amount of net power \(NetPower\) produced by the plant and the storage system. This is shown in the equation below:

\[Revenue = lmp_-signal * NetPower\]
  1. 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:

\[HotSaltInventory = HotSaltInventory + F^{charge}_{salt, outlet} - F^{discharge}_{salt, inlet}\]
\[total_-salt = HotSaltInventory + ColdSaltInventory\]