2 Volume Thermal Storage -title

2 Volume Thermal Storage Component Model

2 Volume Thermal Storage - Model overview

Model Overview

Author / organization: Matthildi Apostolou / EDF

Domain: Thermal storage

Intended application: Optimisation processes

Modelling of spatial aspects: Discretized (single device)

Model dynamics: Quasi-static

Model of computation: To be used by an optimization algorithm

Functional representation: Implicit

2 Volume Thermal Storage - Input and output

Input and Output

Input variables :

  • Real Pdemand: thermal demand (kW)
  • Real Tdemand,in: input temperature of the demand (degC)
  • Real Tdemand,out: output temperature of the demand (degC)
  • Real Psource,max: maximum power of the heat source (kW)
  • Real Tsource,in: input temperature of the source (degC))
  • Real Tsoure,out: output temperature of the source (degC)

Output variables:

  • Real Vtot: total volume (m3)
  • Real Vup: Upper layer’s volume at every time step (m3)
  • Real Vdown: Lower layer’s volume at every time step (m3)
  • Real Vload: Volume of water corresponding in the exchange during the loading phase(m3)
  • Real Vunload: Volume of water corresponding in the exchange during the unloading phase (m3)
  • Real Tup: Upper layer’s temperature (degC)
  • Real Tdown: Lower layer’s temperature (degC)
  • Real MC: heat mass of the cold flow (corresponding to the loading phase) (kW/K)
  • Real MH: heat mass of the hot flow (corresponding to the unloading phase) (kW/K)

2 Volume Thermal Storage - related documents

2 Volume Thermal Storage - description

Short Description

A simple model of a thermal storage tank with two layers (hot and cold volume). The temperature of each layer is stable (not varying during the study period), whereas the volume of each layer is varying in order to meet the charging/ discharging requirements.

This system is intended to be used for optimisation processes. Temporal resolution depends on the component: for daily storage resolution can go up to an hour/minute range; for seasonal storage representative days have to be used.

The model is an equivalent circuit model including lookup tables. Equations describing the state of the battery are time-continuous, while the sensors measuring the real-time status are discrete event-based.

In test configuration, the production unit and the storage tank are the two elements to be sized in order to satisfy the demand. The total power produced by the production unit is therefore equal to the total energy demand. The total volume of the storage tank is obtained accordingly, in order to store the energy when available and discharge it when needed. The initial state of the storage must be equal to its final state for the optimisation’s time horizon, in order to ensure that no extra energy is supplied to the system. The optimal volume implies that the storage tank is emptied and fully charged at least once during the time horizon given.

Present use / development status

The model allows, by considering the energy conservation in each layer, the sizing of the storage tank (in terms of total volume and temperature level of each zone) and the optimisation of its operation (charging/discharging). The model is therefore useful for the sizing of this component at the design phase of the optimisation of multi-energy systems.


Model Details