On Shifted Passivity of Multi-Producer Heating Networks with Storage (I): (Extended abstract)

We present a nonlinear ODE-based thermo-hydraulic model of a district heating system with multiple heat producers, consumers and storage devices. We analyze the conditions under which the hydraulic and thermal subsystems of the model exhibit shifted passivity properties. For the hydraulic subsystem, our claims on passivity draw on the monotonicity of the vector field associated with the district heating system's flow dynamics, which mainly codifies viscous friction effects on the system's pressures. For the temperature dynamics, we propose a storage function based on the ectropy function of a thermodynamic system, recently used in the passivity analysis of heat exchanger networks.