Operative temperature as measurement and control parameter for direct electrical heating systems.
As part of the research project “Operative temperature as a measurement and control variable for electrical direct heating systems”, the energy potential of fast-reacting electrical direct heating systems was investigated in simulations and experiments at the Hermann-Rietschel-Institute at TU Berlin. The subject of the research is the development and testing of a simple and cost-effective measurement and control method that uses the locally perceived (operative) temperature in the room instead of the air temperature as a reference variable. The new reference variable allows a more precise measurement of thermal comfort and, in combination with low-capacity heating systems, enables a more energy-efficient, demand-oriented heat supply.
As part of the research work, a test stand was equipped with PTC heating fabrics decoupled from the component mass on the ceiling and wall surfaces. In addition, heating windows with a transparent metal oxide coating just a few nanometers thick were used. A new type of infrared sensor was developed to record the operating temperature. The sensor allows immediate detection of changes in the operating temperature and thus enables precise control of rapid heating processes using radiant heating.
Model-based control enables an energy-saving reduction in the operating temperature, even in short-term non-usage phases. Depending on the dynamic boundary conditions, the control algorithm guarantees that the setpoint value is reached again within a predefined time at the start of a utilization phase. In this way, the degree of utilization of the heat transfer can be significantly increased compared to through-heating operation, while still achieving heating with an equivalent benefit.
Conventional heat transfer systems have annual efficiency rates of only 70 to 80 % due to inertia-related oversupply and therefore represent a significant energy weakness in heating systems compared to the technically very sophisticated heat generators. The measurement and control method developed as part of the project is cost-effective and enables a significant improvement in the degree of utilization of the heat transfer by using fast-reacting, electrical direct heating systems. For rooms with long periods of non-use and short periods of use, e.g. little-used offices or meeting rooms, the degree of utilization of the heat transfer could be improved by up to 45% with the new control system compared to a permanent heating operation. Compared to permanent heating operation of the floor heating, the improvement in the degree of utilization through the use of direct electric panel heating systems was up to 56%. Compared to planned set-back operation, the newly developed heating and control system also represents a significant organizational simplification.
Based on the previous investigations, dimensioning rules were developed for the efficiency-optimized design of electrical direct heating systems depending on variable boundary conditions. For practical application, a heating surface dimensioning tool was developed with which a control function can be created depending on all relevant room and heating system-specific parameters.
Funding


Project Partners
Dr. Langhein GmbH
Browatech GmbH & Co. KG
Feinwirkerei Karl Jahn GmbH
Vestaxx GmbH
WISTA Management GmbH
Vattenfall Energy Solutions GmbH
Project term | December 2018 to July 2021 |
Funding code | SWD-10.08.18.7–18.14 |
Project management | Lukas Schmitt |