September 23-25, 2013 From theory to practice - Task 39 Exhibition at SHC 2013
Task 39 showcased a range of innovative polymer based collectors and components at the SHC 2013 in Freiburg,
Germany. From 23 to 25 September, visitors had the opportunity to have a look at the latest results of Task 39
research and check out a range of polymeric products with the potential to shape the future of solar thermal
energy systems. Among the exhibition partners were the Norwegian company Aventa AS , the Israelian company
Magen Ecoenergy and the Canadian Enerconcept Technologies. Whereas Aventa AS showcased their scalable
all-polymeric solar collectors for building integration, the latter demonstrated fully polymeric collectors
for thermosiphon systems for sunny regions (Magen eco-SPARK and eco-FLARE) or solutions for a solar air heater
wall (LUBITM by Enerconcept). Further partners, the German Roth Werke and Consolar, provided space
saving and light weight polymeric storage tanks as an alternative to metal based products. A highlight of the
exhibition was the prototype of an innovative thermosiphon design conceptualized in the frame of the European
funded project SCOOP. Based on extruded PP twin wall sheets, the SCOOP thermosiphon is suitable for mass
production and a promising option for the cost-efficient manufacturing and installation around the world.
With the unique assembly of novel polymeric products, Task 39 has taken the next step towards the
implementation of the theoretical work that has been done during the last years. The showcase was well
received by the international audience and successful in promoting the confidence in novel polymer based
The theoretical groundwork of Task 39 is collected in the official Task 39 Handbook:
Koehl et. al., Polymeric Materials for Solar Thermal Applications. Weinheim: Wiley-VHC, 2012.
ISBN: 978-3-527-33246-5. More information about the
Task 39 Exhibition.
Task 39 Exhibition truck in front of the conference venue in Freiburg, Germany. (Source: Fraunhofer ISE).
Left: Fully polymeric thermosiphon based on extruded twin wall sheets (Design: EU SCOOP, built by: Fraunhofer ISE).
October 11, 2013 Austrian Task 39 Dissemination Workshop
"Kunststoffe – die Wachstumsoption für die Solarthermie" (German)
At JKU Linz major results of Task 39 and associated research projects were disseminated on October 11th, 2013.
More than 70 participants from industry and research institutions were attending the workshop.
In several presentations the highlights of the Austrian collaborative research projects SolPol-1/2 were reported.
In these projects novel collector types (e.g., with full overheating protection based on triggered backcooling)
and polymeric materials with enhanced long-term performance (e.g., for solar absorbers or liners of seasonal heat stores)
have been successfully developed. Combining the expertise of polymer and solar thermal energy research offers
a tremendous potential for innovative solar-thermal technology developments. The hosts of the workshop were the
Johannes Kepler University Linz – Institute of Polymeric Materials and Testing (JKU-IPMT), AEE – Institute for
Sustainable Technologies (AEE INTEC) and the Austrian Ministry for Transport, Innovation and Technology (bmvit).
October 17-18, 2013 Task 39 Meeting in Blumau Austria
The Task 39 Experts Meeting no. 16 was held in Bad Blumau, Austria, on October 17-18, 2013. The Meeting was hosted by AEE-INTEC at Gleisdorf and the Johannes Kepler University of Linz.
26 experts from research institutions and industry participated in the meeting.
Most of the presentations given at the meeting are summarized in the present newsletter.
Participants at the 15th Task 39 Meeting in Blumau
Fiber-reinforced polyamides for integrated storage collectors
In the EU FP7 project SCOOP special emphasis is given to injection moulded absorbers for integrated storage
collectors. Based on conceptual designs, application-relevant loading conditions and FEM modeling property
requirements have been established for the polymeric materials to be used for the absorber. Due to relatively
high mechanical loads and an operating temperature range up to 100°C fiber-reinforced engineering plastics
have been pre-selected, compounded and characterized considering different material states. The investigated
polyamide grades exhibit a high solar absorbance (> 95°C), glass transition temperatures varying from 0 to 100°C
and temperature and humidity dependent mechanical properties. The material structure is significantly affected
by the processing conditions. The average length of the short-glass fibers is ranging from 150 to 250µm.
Current research work is dealing with injection moulding, joining and testing of model components and collectors.
On material level the long-term behaviour is characterized using an advanced fracture mechanics testing approach.
In implementing its One World Solar Collector pilot phase, Sunlumo is now carrying out
a study about the weldability of polymeric materials for solar-thermal applications,
together with its academic partners. Pressure, temperature, wind and snow loads constitute
a heavy strain for all collector parts over many years. Thus welding seams must be perfectly
designed and executed. In total, six different welding technologies are tested on different
materials. These tests are carried out using standard test specimens and testing plates with
dimensions that are similar to the actual parts. The findings of this study will influence
the industrial design and other product development activities of Sunlumo. The current findings
will also be used for implementing new projects such as the solar pump group project and plastic solar tubing.
Thermotropic glazings with enhanced overheating protection performance
Thermotropic glazings providing overheating protection for solar thermal
collectors undergo a reduction of solar hemispheric transmittance upon exceeding
a pre-defined threshold temperature reversibly. Besides other thermotropic glazings,
thermotropic systems with fixed domains (abbr. TSFD) were considered promising with
regard to achievable overheating protection performance. TSFD consist of a thermotropic
additive finely dispersed in a polymeric matrix material. The optical switching process
is triggered by a change in the refractive index of the thermotropic additive at a certain
threshold temperature. However, the achieved overheating protection performance of TSFD
was inappropriate in order to protect a solar thermal collector from overheating so far.
This was primarily ascribed to inappropriate diameters of the scattering domains established
by the thermotropic additive. Thus, a process for adjustment of scattering domain diameter was
developed and successfully established. Scattering domains with diameters between 100 and
1000 nm were obtained, which is almost optimal. The TSFD containing these optimized
scattering domains exhibited a solar hemispheric transmittance reduction from 73.1 to 49.2 %
(see Fig. 4). In contrast, the same TSFD formulated with the not optimized scattering domains
(diameters between 2.8 and 116 µm) exhibited a transmittance reduction from 81.8 to 81.1 %
only. Investigations in order to enhance the overheating protection performance of the obtained
TSFD further and efforts to determine their long-term stability are currently under way.
Fig. 4. Solar hemispheric transmittance (blue: at 23 °C; red: at 70 °C) of thermotropic
layers formulated with scattering domains that were either not optimized or optimized with regard to scattering domain diameter.
Evaluation of thermosiphon systems by adopting a total cost accounting approach
To assess suitability of using polymeric materials in solar thermosiphon systems versus
those with more traditional materials, a total cost case study is conducted in Task 39 by
analysing differences in thermal performance related to a traditional thermosiphon system,
investment cost, operation and maintenance cost, reliability and long-term performance,
climatic and environmental performance and cost. Two polymeric based solar thermosiphon
systems have been selected for study, one designed by Aventa Solar and one designed by
Fhg ISE, and most reasonable process trees and associated inventory data for those are
presently defined for the purpose of Life cycle analyses, LCA. The results will be used
for assessment of climatic and environmental performance and cost of the two polymeric
systems in relation to that of a traditional thermosiphon system. For the LCA study,
inventory data from the Ecoinvent data base, is selected as a first approximation.
End-of-life scenarios including both recycling and no recycling are considered. Estimating
reasonable end-user costs for investments, O&M and end-of-life will be an important
part of on-going work as well as analysis of importance of durability on cost for which
results from the SCOOP project would be taken advantage of.
Bo Carlsson, Linnaeus University, Sweden;
in collaboration with Aventa AS, Norway
As an outcome of the research performed in the EU FP7 project SCOOP by partners and material suppliers several prototypes of
new polymeric collectors for emerging markets were prepared in the first half-year of 2013. Two partners have protected their design in a joint patent. During the Solar Heating and
Cooling Conference SHC2013 in Freiburg from September 23-25, one version was displayed to the public at the
Task 39 Exhibition in front of Konzerthaus Freiburg. The new solar collector concepts are based on the
thermosiphon principle and the absorbers on extruded polymeric sheets with intrinsic channel structure
for the circulation of the heat carrier. A group of experts in SCOOP is testing the sustainability of the
processed materials in the application as solar collector. Further the thermal performance of the complete
systems is investigated in laboratory and outdoor tests.
Final monitoring results: Polymeric collectors competing with heat pump
Energy monitoring has been performed for two passive houses in Oslo during 2012-2013. One house is heated by a solar heating system, the other with an air-to-water heat pump. The objective has been to investigate the need for additional energy supply in order to provide the required indoor comfort and prepare domestic hot water. If corrected for differences in domestic hot water consumption and indoor temperature the two houses require almost equal amounts of auxiliary energy. The solar energy gain would increase significantly if the solar collectors were placed more appropriate, with less shading due to neighbouring buildings and vegetation. Both heating technologies could improve performance with minor system adaptations. It was shown that solar thermal heating can compete with heat pump technology even for locations as far north as Oslo, Norway.
M. Meir, E.Murtnes, A.Dursun, J. Rekstad
University of Oslo and
Aventa AS, Norway;
Market Scenarios for the Solar Thermal Industry and Potentials for Polymers based on 100%-Regenerative Energy Scenarios
In order to estimate the future demand for polymeric materials used for solar thermal systems, the
Institute of Polymeric Materials and Testing at JKU Linz (AT) and the AEE-Institute for Sustainable
Technologies (Gleisdorf, AT) have analysed scenarios that aim for a 100% renewable energy supply by 2050
(on a global, European and Austrian scale). Those scenarios were compared to European market scenarios
established by ESTIF (European Solar Thermal Industry Federation). Assuming an average polymeric material
demand of 10 kg/m² installed collector a cumulated worldwide demand for polymeric materials of about 80
to 300 Mio. tons up to 2050 (in 37 years) was calculated. In 2011 (1 year) the global plastic production
was about 280 Mio. tons. Hence, it was concluded that no material shortages are to be expected for future
polymer based solar thermal technologies. However, the demand will be significant, why R&D focus should
be put on optimized system technologies avoiding overheating and allowing for cost- and performance-optimized
plastics such as the polyolefins polypropylene or polyethylene.
K. Holzhaider, G. Wallner, H. Kicker, R.W. Lang, Institute of Polymeric Materials and Testing, JKU Linz, Austria
Fig. 6. Cumulated global demand for polymeric materials up to 2050
Performance Optimisation of Polymeric Collectors by Means of Dynamic Simulation and Sensitivity Analysis
The Institute for New Energy Systems at Technische Hochschule Ingolstadt and Roth Werke GmbH,
Dautphetal (Germany), are analysing production processes and collector designs for polymeric
collectors against the background of cost reduction for solar-thermal heating systems.
This includes the fields of collector technology, materials and production. For a cost-effective collector
the maximum temperature loads of the parts has to be lowered to allow the use of commodity plastics.
One solution could be the adjustment of the collector efficiency by simultaneous cost savings from fewer
production steps and material effort.
Thus, the balance between collector efficiency and part temperatures should enable decreasing collectors manufacturing
costs as well as heat production costs of solar-thermal systems.
For that case various collector and system design approaches were developed. In a simulation study, the
designs were analysed with regard to stagnation temperatures, collector efficiency and system output. The
results are basis for the evaluation of the proposed collector designs, the system sizes and the thermal
requirements of polymeric materials.
Christoph Reiter, Mathias Ehrenwirth, Dr. Sebastian Brandmayr, Dr. Christoph Trinkl, Institute for New Energy Systems, Technische Hochschule Ingolstadt, Germany,
Bioplastics for Solar Thermal Applications – Potential and Prospects
Bioplastics (i.e. polymers based on renewable resources and/or biodegradable polymers) are already successfully
used in the automotive and electronic industry. Therefore, bioplastics are expected to have a high potential in the
solar industry as well, yielding further greening of solar thermal systems. However, so far no systematic and
comprehensive investigation of bioplastics for solar applications has been carried out. Therefore project “Bio4Sun –
Bioplastics for Solar Applications” was initiated at the Department Polymer Engineering and Science at the University
of Leoben and the Polymer Competence Center Leoben. The project is funded by Austrian Klima- und Energiefonds and was
launched in April 2013. Bio4Sun aims at evaluating and testing the potential and applicability of biogenic polymers
for the use as components for solar thermal devices. Based on material requirements and specifications an extensive
literature and market survey was carried out in order to identify potential biogenic candidate materials for solar
applications. In total around 40 potential bioplastic candidate materials for solar applications were identified.
In the next step bioplastics were extruded into films with a thickness around 400µm on a Dr. Collin Laboratory extruder.
Film specimens were prepared and characterized as to application relevant thermal, thermo-mechanical, mechanical and
optical properties applying Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), tensile
testing and UV/Vis/NIR spectroscopy. The generated polymer physical property profiles indicate that bioplastics
in general possess a high potential for application in solar thermal devices. For example Cellulose polymers, PLA
and Bio-PA turned out to exhibit excellent optical properties, which make them interesting as glazing materials or
as materials for air collectors, and Bio-PE, PTT, and PHB may be appropriate materials for swimming pool collectors,
for piping or framings. Current focus is on investigating ageing characteristics and long-term stability. Material
characteristics after exposure to application relevant external stress factors such as ultraviolet (UV) radiation,
humidity and temperature will be tested.
Polymeric solar collectors with integrated overheating protection
Within the Austrian SolPol consortium (www.solpol.at) research is done at the University of Innsbruck for
supporting the development of solar thermal collectors based on low price polymeric materials with low temperature
limits. The main topic of research is to keep the temperature below the critical temperature of about 95°C during
stagnation. The investigated concept is thermosyphonal driven backcooling directly integrated into the collector.
A first small-scale prototype of this collector concept was constructed and tested 2012 at the outdoor test facility
successfully. The temperatures could be limited to just below 100°C at the absorber surface.
Following up a second generation “full-scale” prototype collector with several improvements was designed and
constructed during winter by the industry partner Greiner and again tested at the University of Innsbruck in summer
2013. The tests showed that at solar irradiation of 950 W/m² and ambient temperature of 20°C the maximum absorber
temperature reached a maximum of only 85°C, which is significantly less than the first prototype showed. Based on
this result low price polymeric materials with low temperature limit (<95°C) can be used and therefore further
improvements of the design will be done in order to enable cheap production and reliable long term lifetime in the end.
Alexander Thür, Claudia Hintringer, Alexander Richtfeld, Norbert Hauer, Wolfgang Streicher; University of Innsbruck, Austria,
Novel latent heat storages for overheating protection
Utilizing façades for energy conversion, distribution and storage is a major opportunity of increasing the energy efficiency of buildings due to the very large areas available, in particular for multi-storey buildings in “smart cities” of the future. A prototype of such a multifunctional façade is being realized in the course of the Austrian K-Project “Multifunctional Plug & Play Façade” (MPPF). A high degree of prefabrication of various functional, inter-exchangeable modules for energy conversion, air conditioning, shading, IT and control ensures economic viability in the long run. However, one year of intense monitoring of the fully integrated solar thermal modules revealed the major obstacle for the widespread use of flat plate collectors in aluminium/steel-glass-façades: in the unavoidable case of stagnation, the temperatures at the room-sided-panel of the façade exceed values that can be considered comfortable for inhabitants. Simulations clearly demonstrated that effective overheating protection is achieved by applying functional polymers, such as latent heat storages, as insulating materials (also within the collector). However, appropriate latent heat storages with storage temperatures between 60 and 90°C are not available so far. Thus, within the project “Poly2Facade - Innovative thermal self-regulating solar facades by means of functional polymers” (carried out within the framework of the program Haus der Zukunft Plus, which is a science and technology program of the Austrian Ministry of Traffic, Innovation and Technology) novel tailor-made latent heat storages with high storage temperatures based on polymeric materials for overheating protection of buildings with integrated solar thermal modules are developed and investigated. Various phase change materials (PCM) with different storage temperatures were selected and compounded with polymer matrix Polypropylene. Compounds were found to be highly effective in terms of storage capacity. Moreover, production of latent heat storages with various storage temperatures and geometric shapes is feasible. By means of heat exposure tests also long-term stability of compounds was approved. Current investigations focus on characterization of long-term stability applying thermo-mechanical load and thermal cycling. Finally, test rig measurements in solar simulators and application demonstration in the real MPPF test building with solar thermal façade elements shall prove the overheating protection efficiency of the developed materials.
New generation of coloured Thickness Insensitive Spectrally Selective paint coatings for polymeric solar absorbers.
Production of non-black selective surfaces is highly desirable because of their decorative property. Good examples of their use are façade solar absorbers, passive cooling systems or military applications. Coloured Thickness Sensitive Spectrally Selective (TSSS) paint coatings are not practical, because they inevitably need low emitting (metallic) substrate, which is difficult to make on industrial scale on polymeric absorbers made by extrusion. Thus, (TISS) paint coatings, which are applied on the polymeric absorbers by spraying and exhibit various colours than black, represent a viable option for making selective and coloured polymeric absorbers. Despite the extensive trials and by using polyurethane and/or polysiloxane resin binders, the best non-black (i.e. blue) TISS paint coatings, which were prepared exhibited solar absorptance of about as 0.85-0.86 and even though eT of these coatings remained between 0.40-0.35, the spectral selectivity did not assure high enough collection of solar radiation and stagnation temperatures were low (Tstag< 130°C).
During the last few years a major break –through have been made due to the use of special dispersant (alkylalkoxysilanes), adequate aluminium flake pigments and black manganese spinel pigments, which have been combined with pigments of other than black colours. The key component for the new generation of the coloured TISS coatings was perfluoropolymer based resin binder, which was combined with organic flake- like blue pigment, stable up to 170°C. The corresponding blue TISS paint coatings showed αs= 0.92 and εT = 0.38, which selectivity was higher as compared to the black TISS coatings of the previous generation of the TISS paint coatings. This we attributed to the flake –like blue organic pigment, which strongly reflected just a narrow portion of blue light, giving rise metric chroma value of about C* = 10 (see Figures) and contributed significantly to the high solar absorptance of the coating. Expectedly, the mixture of the black and blue pigments finely dispersed within the paint provided a complete coverage of the aluminium flakes and solar absorptance values higher than 0.90, which has not been not been obtained yet for the coloured TISS coatings. The corresponding blue TISS paint coatings exhibited distinguished water repellent properties (water contact angle ~1300 and excellent UV light stability (30 years) attributed to the inherent hydrophobicity of the perfluoropolymeric resin binder. Other colours (brick red, green), are available on request.
Mohor Mihelčič, Lidija Slemenik, Boris Orel,
National Institute of Chemistry, Ljubljana, Slovenia,
Alajž Vilčnik, Chemcolor, Sevnica, Slovenia
Fig. 9. Cross –section SEM micrographs of black (above) and blue (below) TISS paint coatings.
The 2013 edition of the SHC Programme’s Solar Heat Worldwide shows a number of international trends.
2011, installers set up a total capacity of 48.1 GWth: 14.3% increase compared to 2010. Despite
the high global growth rate of the solar thermal market, the wind energy- and photovoltaic industries
are more progressive.
With respect to pumped and thermosiphon systems, more than three quarters of all solar thermal systems installed use
natural flow and the rest are pumped solar heating systems. Worldwide, thermosiphon systems are more common which is
due to the growing importance of the Chinese market. In Europe the Trend is reversed. The share of thermosiphon
systems is decreasing from 19% of the total installed capacity, to only 14% of newly installed capacity.
What both markets have in common is that the segment of large solar domestic hot water applications is on the rise.
Climbing form 10% in the total installed capacity to 17% in the newly installed capacity. Solar domestic hot water
applications for single family houses are already a mature market segment but world-wide the share tend to decrease
because the overall market becomes more sophisticated.
Thomas Ramschak, AEE - Institut für Nachhaltige Technologien, Gleisdorf, Austria,
Performance requirements for polymeric materials in different solar thermal systems
The knowledge of performance requirements is essential for proper selections and developments of adequate polymers for different components in diverse solar thermal systems. In the framework of a national project (SOLPOL-1) investigations were made to find out figures for temperature and pressure loads for the main components of such systems. Calculations with different simulation tools for five of the main climatic zones of the world, for different applications, different system types and collector types were done. On an annual basis statistical load profiles for polymeric collectors and there components are existing now.
As an example in the diagram typical temperature loads of collector components for the continental zone (Graz) of two systems are presented. For the reference system with a standard collector (selective coated absorber) the temperature statistics of absorber, cover and insulation (dashed lines) and for the polymeric system with a black absorber without overheating protection the temperature statistics of absorber, insulation (both nearly the same) and both sheets of a twin-sheet cover (continuous lines) are shown. This example figures were calculated under the complicating assumption that the collectors were mounted on a newly built house and the system has to withstand one year insolation without operation as maximum possible temperature load.
Robert Hausner, AEE - Institut für Nachhaltige Technologien, Gleisdorf, Austria,