Cost-effective and reliable solar systems with novel heat pipe collectors

Bert Schiebler, Dipl.-Ing. (FH)
Tel.: +49 (0)5151-999 524

Schematic drawing of a solar collector configuration with a heat pipe as an additional component between absorber plate and manifold
Prinzip Heatpipe-Kollektor mit Abschaltung
Typical collector efficiency curve of a heat pipe collector with power shut-off compared to a standard collector
Versuchsaufbau Heatpipe- und Direct-Flow-System
Test roof with both prototype and reference evacuated tube collector fields (top). Maximum temperature and pressure load in the solar circuit at a low system overpressure level of 1 bar (bottom)
Solar thermal systems are since long established on the market and can significantly contribute to covering the heat demand of buildings i.e. for space heating and domestic hot water heating. In practice, high thermal loads in case of stagnation still lead to complex hydraulic system designs, affect the operational safety and require correspondent maintenance efforts, which impair the cost-efficiency and generally the attractiveness of solar thermal installations.

In order to avoid stagnation loads in solar circuits, different approaches are usually implemented. Most of them are based on additional cooling systems or draining (drainback), which require more complex hydraulic installations and control technology respectively. The use of heat pipes, on the contrary, can avoid stagnation loads directly in the collector. The functional principle is independent of a control unit or mechanically activated components, such as valves, so that the system and the safety technology can be simplified. The temperature limitation is reached by using the physical effect of the dry-out limitation of heat pipes and is absolutely intrinsically safe.

Within the research project innovative heat pipe solutions with temperature limitation were developed for integration into evacuated tube collectors and flat plate collectors. The results are used as a basis for the transfer into industrial production. The main goal is a significant reduction of the stagnation temperature, so that evaporation of the solar fluid can be completely avoided. The collector efficiency is comparable to commercial technologies. The use of heat pipe collectors with temperature limitation simplifies the system design and reduces the effort for installation and maintenance. For typical solar thermal systems, we expect a total cost saving of 20 – 30 % compared to the use of standard collectors.


Industry partner


Duration of the project

01.09.2014 – 31.03.2018

Final report

The final report of the project can be found here!


The project “Cost effective and reliable solar systems with novel heat pipe collectors” underlying this publication is funded by the German Federal Ministry of Economy and Energy (reference number 0325550A-C) based on a decision of the German Parliament.

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