New heat transfer fluid and pump test stand at DLR site in Cologne
- DLR and industrial partners test new heat transfer fluid for use in solar power plants and industrial facilities.
- The new test stand in Cologne-Porz makes it possible to demonstrate and research novel heat transfer fluids on a pilot plant scale with limited effort.
- Experiments take place within the framework of the SING project.
In a newly constructed "Mobile Heat Transfer Fluid and Pump Test Stand" (MOPUW), DLR, in cooperation with industrial partners, is testing the functionality of the entire system up to temperatures of 480 degrees Celsius in continuous operation. According to the operating parameters, this is the hottest thermal oil system in the world. DLR’s industrial partners are the pump manufacturer Dickow, the plant manufacturer heat 11, the chemical company Wacker Chemie AG and TÜV NORD.
The new test stand makes it possible to demonstrate and research new types of heat transfer fluids on a pilot plant scale with limited effort. Such system demonstrations provide insights into how a thermal oil ages over time under high temperatures and which degradation products have to be specifically removed from the closed oil circuit so that stable operation is possible in the long term.
Heat transfer oils must be able to withstand permanently high temperatures
Heat transfer fluids play a central role in solar thermal power plants. They conduct the thermal energy gained from concentrated sunlight to the heat storage tank or to the power block, where a steam turbine drives a generator that produces electricity. A higher temperature of the heat transfer fluid improves the efficiency of converting heat to electricity, which lowers the cost of generating electricity.
Industrial plants also need heat transfer fluids, for example to heat a reactor for the production of plastics. Both in the solar power plant and in the industrial plant, heat transfer fluids are exposed to high temperatures over a long period of time.
Where the optimum operating temperature lies depends on the type of plant and the application. Parabolic trough power plants with a comparatively long service life of 25 years and a large "oil inventory" of up to several thousand tonnes are currently still operated with state-of-the-art thermal oil at temperatures of around 400 degrees Celsius. At higher temperatures, the organic oil would decompose after a shorter period of time and would have to be replaced much sooner. According to calculations by DLR and TSK Flagsol, the use of more temperature-resistant silicone fluids is profitable even at operating temperatures of up to 440 degrees Celsius.
Many industrial process plants use one hundred to one thousand times less thermal oil than solar power plants. For this reason, it could be beneficial to operate the processes at temperatures above 450 degrees Celsius and to replace the degraded oil at an earlier stage. Possible areas of application are melamine production, lye concentration (NaOH, KOH) or bauxite digestion, a sub-step in aluminium production.
New silicone oil for particularly high temperatures
At the new test rig, the project partners will first test HELISOL®XLP, a new silicone fluid developed by WACKER, and the Dickow pump.
With its NMX pump series, Dickow has developed the world's only magnetically coupled and self-venting pump that operates continuously at up to 500 degrees Celsius and 50 bar without cooling and with a very compact design. This advance is made possible by the use of high-temperature-resistant materials and the corresponding design of the inner plain bearing as well as the magnetic coupling.
WACKER has developed the HELISOL® XLP silicone fluid for temperature ranges into which no other heat transfer fluids have penetrated to date. Chemists from WACKER and DLR have already determined the properties and temperature resistance of the new HELISOL® XLP heat transfer fluid in the laboratory. To demonstrate that the entire system can withstand the high temperatures, the plant will be operated for 3000 hours at 450 degrees Celsius and later for 1000 hours at higher temperatures.
Heat 11, a specialist for heat transfer systems, has designed the mobile heat transfer medium and pump test stand according to the specifications of DLR and Dickow.
The safety experts from TÜV NORD supervised the design and manufacture of the test stand and are also available to answer safety questions during operation.
Project SING
Scientists from the Institute for Future Fuels operate the MOPUW test facility as part of the SING (Silicone Fluid Next Generation) project. The primary goal of the project is to reduce the electricity production costs of solar thermal parabolic trough power plants. DLR is the project coordinator, the Dickow company is the owner of the plant. Other project partners in the SING project are WACKER Chemie AG, flucon, TÜV NORD and Senior Flexonics. Associated partners are heat 11, Flagsol, Rioglass, RWE, STEAG and the Spanish research centre CIEMAT on behalf of DLR.
The project is funded by the German Federal Ministry for Economic Affairs and Climate Action.