A Dynamic Optimization Tool to Size and Operate Solar Thermal District Heating Networks Production Plants

Abstract

The aim of the ISORC/OPTIMISER project is to increase and improve the use of solar thermal energy in district heating networks. One of the main tasks of the project is to develop an optimization tool for the sizing and operation of a solar district heating network. This is the first optimization tool using an open-source interface (Julia, JuMP) and solver (Ipopt) to solve nonlinear problems. This paper presents the multi-period optimization problem which is implemented to consider the dynamic variations in a year, represented by four typical days, with an hourly resolution. The optimum is calculated for a total duration of 20 years. First, this paper presents the modeling of the different components of a solar district heating network production plant: district network demand, storage and three sources, i.e., a fossil (gas) and two renewable (solar and biomass) sources. In order to avoid prohibitive computational time, the modeling of sources and storage has to be fairly simple. The multi-period optimization problem was formulated. The chosen objective function is economic: The provided economic model is accurate and use nonlinear equations. Finally the formulated problem is a nonlinear Programming problem. Optimization of the studied case exhibits consistent operating profiles and design. A comparison is made of different types of storage connection at the production site, highlighting the relevance of placing the storage at the solar field outlet. The optimum configuration supplies 49% of demand using solar energy, achieving a renewable rate of 69% in combination with the biomass boiler.

Robust Optimization of the Energy Concept of an Industrial Plant w.r.t. Uncertain Energy Costs and Environmental Conditions

“…To determine the output of the solar thermal unit, a single equivalent solar panel is usually considered, for which the inlet and outlet temperatures w.r.t a given the mass flow are calculated, [7]. However, to find an appropriate design an optimization of the mass flow in the panels is required, which may necessary for an operational consideration, but not for the design.…”

Analysis and future perspectives for the application of Dynamic Real-Time Optimization to solar thermal plants: A review

“…The optimal trajectories determined during this planning phase can be tracked by controllers only if the error between the forecasts and the actual measures is small. Delubac et al used a dynamic multi-period approach to determine the best design and also the optimal operation strategy of a DHN using solar energy in association with a biomass plant and backup gas boilers (Delubac et al, 2021). This planning determines the optimum energy mix and particularly the use of the solar thermal plant.…”

Efficient District Heating in a Decarbonisation Perspective: A Case Study in Italy

“…The models that include hydraulic and thermal dynamic analysis do not account for environmental and economic aspects [23]. Or, again, other tools do not have a general scope of application, because they can be applied to particular typologies of networks, such as solar district heating, as in [25]. Finally, literature studies usually relate to the thermal network or relate to the user side (i.e., the building).…”