Solar heat grid: Intelligent control concept for Germany's largest solar thermal system

[Translate to English:] Bild: SWLB

As part of the climate protection model project “Solar heat grid - construction and connection of one of the largest German solar thermal plants to an optimized heat network”, Stadtwerke Ludwigsburg-Kornwestheim GmbH (SWLB) public utility is currently building Germany's largest open-air plant with a peak output of around 9 MW from a collector area of 14,800 m². This plant is combined with a 2,000 m3 heat storage tank and the merging of four heat networks.

The aim of the project is to increase the share of renewable energies in the district heating network and to actively promote climate protection and the green energy transition in Germany by reducing CO2 emissions. Completion is scheduled for May 2020 after about three years of work.

The solar heat grid project considers all facets of decentralized heat supply: generation, distribution, storage and consumption. Back in 2008 SWLB started a partnership with us in order to modernize the control technology of the district heating network and to develop a concept that is uniform and scalable for the future. How resilient this concept is today is shown in the current project, where numerous solutions had to be found in response to regulatory issues. The project planning phase is already making use of our long-standing experience in regulating heat networks and integrating large solar thermal systems into existing district heating networks, as in the case of the largest plant in Senftenberg to date.

To meet these demanding requirements and master the complexity involved, an intelligent storage management system is used to integrate the solar system and the heat storage tank into the existing heating network. This is a standard network control solution consisting of the freely configurable SE²MASTER, controller, the higher-level SE²OPERATOR control system and our unique “Cluster-Control” module option. The new solar thermal system is optimally integrated in this way and fully automated in its interaction with the overall system. The state of the solar thermal system and the entire district heating network is continuously recorded by a large number of sensors. With the decentralized control and regulation technology of the SE²MASTER, all units and actuators are controlled at the same time. The SE²OPERATOR heat network control system assumes fully automated operation of the district heating network, visualization, operation and monitoring. This combination makes operational management extremely efficient and user-friendly - saving time, costs and ultimately CO2..

The complex demands on control technology have been resolved yet again with our integrated solution for decentralized energy systems:

  • a stable heat supply ensured at all times in an extended network with now 13 unsuitable points
  • primary feed-in of CO2-neutral heat generators, solar thermal system and wood-fired power plant
  • maximum utilization of solar heat and its efficiency-optimized grid feed-in
  • intelligent storage management for control engineering optimization of the loading and unloading of heat storage
  • two of the stand-alone grids to be integrated can be switched to act as producers or consumers in the heat network
  • operation of the entire plant and system is completely automated

When the project is completed in May 2020, the combination of measures will save around 3,700 tons of CO2 per year, equivalent to around 1.6 million liters of gasoline. SWLB will then have taken another major step in the pursuit of its sustainable goals.