# Designing a Conceptual Digital Twin Architecture for High-Temperature Heat Upgrade Systems
## 4 High-Temperature Heat Upgrade Use Case
### Data Flow and Process Modeling  
The concept presented above is completed with a control system that integrates all the components and decides which and how much energy from every resource is used to charge the two thermal storage systems, according to their availability, energy requirements, and constraints of specific industries.  
The diagram in Figure 8 presents the information flow between system entities, processes, and data stores for a possible arrangement of the high-temperature heat upgrade system. The diagram represents system entities using rectangles (Waste Heat, HT-HP, TES, Electric Heater, and Heat Exchanger) while processes are defined with rounded rectangles (Transfer Heat, Charge, Discharge, Produce Heat, Request Heat). The most important input and output parameters that are transferred in the system are represented by data store elements (\(Q_{WH}\), \(Q_{TES,CL}\), \(Q_{TES,HL}\), \(Q_{CL}\), \(Q_{HL}\), \(COP\), \(Q_{EH}\), \(Q_{HE}\)) and connected to the process by information flow arrows. For a better understanding of the information flow, we also display the energy flow generated by the physical processes using the color-coded arrows, yellow for the cold loop and red for the hot loop.  
The external industrial process, denoted as Waste Heat in the diagram, Transfers Heat into our system and generates a production of energy curve that is saved into the datastore as \(Q_{WH}\). The same is true for the Fresnel collectors, represented by the Electric Heater. The Heat Exchanger is also an external industrial process that can request high-temperature heat at any moment, based on the demand curve, \(Q_{HE}\). As these entities and processes are dependent on environmental data that we cannot control, we can only collect data from them.  
Figure 7: A 3D model of the high-temperature heat upgrade system prototype.  
The TESes from both hot and cold loops can Charge and Discharge with energy. We consider them as passive entities equipped with sensors that can measure the stored energy at a given moment. The TES sensor readings are saved in \(Q_{TES,CL}\) and \(Q_{TES,HL}\) datastores.  
The Upgrade Heat process, controlled by the HT-HP, uses low thermal energy as input from either industrial heat or from a TES and outputs high thermal energy that can be used directly in the Transfer Heat process of the Heat Exchanger or can be stored in a TES through its Charge process.  
The Control System acts as an orchestrator for the system's processes. Based on the current heat demand, and the other entities' information, it ensured the thermal energy equilibrium in the system. It controls when the surplus thermal energy is stored in a TES through a Charge process and when to supply this energy through the Discharge process. It also configures the Upgrade Heat process of the HT-HP by providing information about the demand. Based on past data and sensor readings, the Control System creates forecasts of the different energy inputs and measurements of the system so it can provide relevant information to the high heat demand regarding its energy request.