Task 39 - Polymeric Materials for
Solar Thermal Applications
Newsletter No. 10 - June
Task 39 Newsletter
This newsletter summarises the topics at the
Task 39 Meeting in Berlin, Germany, May 15, 2012
hosted by Prof. Beate Roeder, Humboldt University zu Berlin in collaboration with Fraunhofer ISE, Freiburg, Germany.
May 15, 2012 Recent IEA-SHC Task 39 Meeting in Berlin, Germany
The 13th Task 39 experts meeting took place at Grand Hotel Esplanade, Berlin Germany on May 15, 2012.
2012 Open Workshop Berlin
The open workshop in connection with the 13th Task 39 meeting "Chancen und Anforderungen für Kunststoffe
in der Solarthermie" took place at Grand Hotel Esplanade, Berlin, on May 16, 2012 under the organisation of Fraunhofer ISE, Freiburg.
July 9-11, 2012 SHC 2012: San Francisco 1st International Conference on Solar Heating and Cooling for Buildings and Industry
On 9-11 July 2012, San Francisco will host the International Conference on Solar
Heating and Cooling for Buildings and Industry – SHC 2012. The scientific conference
is organized by the International Energy Agency's Solar Heating and Cooling
Programme (IEA SHC), which coordinates research on solar thermal technologies.
More information: http://www.shc2012.org/cms/
October 15-17, 2012 14th IEA-SHC Task 39 Experts meeting, Gran Canaria
The next Task 39 Experts meeting on Gran Canaria will
be organised by Fraunhofer ISE, Freiburg,
Sunlumo initiated and conducted the research and development for the One World Solar Collector.
Plastic collectors are significantly lighter in weight, making them easier to install. Their
low weight also reduces the costs of logistics and installation. Additionally, the materials
are suitable for environmentally friendly recycling and inexpensive to produce. The fully automatic
production plant for synthetic collectors represents a revolution in technology. Operating at a
30-second work cycle that is typical in factory automation, the plant can produce approximately
500,000 square metres of solar collectors per year. Over the coming ten years, the global annual
demand for solar collectors will increase from its current level of 50 million square metres to
approximately 400 million,” says Robert Buchinger. The new mass-market product can meet the
requirements of this volume market. Many industrial enterprises all over the world have already
expressed their interest in realising the One World Solar Collector. Sunlumo is currently
conducting exploratory talks prior to awarding licences. The One World Solar Collector is modular in
structure and tailored towards supporting hot water production and heating systems. Sunlumo was
able to leverage an outstanding competence network and top know-how in solar thermal technology
during the research and development phase of this unique product for the volume market.
Ryton®PPS and Xtel®PPS alloys: High Performance Plastics - Portfolio
Poly(p-phenylene sulfide) (PPS) by Chevron Phillips Chemicals is a highly
stable polymer with a remarkable degree of molecular stability toward both
thermal degradation and chemical reactivity. When blended with glass fibers
and other fillers, PPS produces engineering plastics having a unique combination of properties.
The product portfolio consists of a series of Ryton®PPS compounds and Xtel®
PPS based alloys. The latter offer an increased flexibility and ductility and enhanced
impact resistance. Grades are available for injection molding and extrusion applications.
Ryton®PPS competes successfully with metals because it often eliminates expensive secondary
operations and because it offers greater design flexibility. Part integration lowers
weight and cost and also eases manufacturing and assembly. Metals replacement is advantageous
mainly due to Ryton®’s long-term predictability of performance properties over a wide
range of temperatures and environments.
An updated report from Norway on new development of solar thermal systems with polymer
collectors was presented. The feasibility of the preferred system architecture, based
on drain-back and low pressure hydraulic system and heat store, has been demonstrated over
a period of 35 years.
A recently installed systems with polymeric solar collectors from the company Aventa is monitored,
and is compared with the performance of an air – water heat pump, installed in an identical house.
Both have passive house standard.
The growth of the solar market in Europe is decreasing. Polymeric products can be one key for new
market expansion. A closer collaboration with the building industry aiming to introduce polymeric
collectors as regular modular building elements that can replace conventional façade or roof covers
is progressing. The flexibility with regard to dimensions and shapes, combined with low weight are
important aspects. The figure to the right shows examples of possible integration of solar collectors
with multiple functions.
Importance of environmental performance and cost on suitability of using polymeric materials in solar collectors
To assess suitability of solar collector systems with polymeric materials versus those with
more traditional materials a case study has been undertaken in Task 39 in which one solar
heating system with polymeric solar collectors were compared with two equivalent but more
traditional solar heating systems, one with flat plate collectors and one with evacuated
tube solar collectors. In the comparison made, a total cost accounting approach was adopted.
Life Cycle Assessment (LCA) results obtained in this analysis clearly indicated that the polymeric
solar collector system is the most favourable as regards climatic and environmental performance.
In terms of climatic and environmental costs per solar heat collected, the differences between
the three kinds of collector systems, however, are small when compared with existing energy prices.
With present tax rates it is seems not likely, thus, that those differences will have any significant
influence on the choice of which system is the most favourable from a total cost point of view.
In the choice between a renewable heat source and a heat source based on the use of a fossil fuel,
which was also analysed in the present study, the conclusion was that for climatic performance to be
an important economic factor, the rate of carbon dioxide emission must be considerably increased
above the level given by the present EU carbon dioxide emission trade rate. An alternative to an
increase in this trade rate would be to introduce a tax system based on environmental cost,
making use of e.g. Ecoindicator99, to include also other
impacts on the environment not just the greenhouse effect.
Bo Carlsson, Linnaeus University, Sweden, email@example.com
Helena Persson, Linnaeus University, Sweden, firstname.lastname@example.org
M. Meir, Aventa AS, Norway;
J. Rekstad, University of Oslo, Norway.
Solar COllectors made Of Polymers: European FP7 Project SCOOP
What needs to be done to ensure that the high potential of plastics in the field of
low-temperature solar-thermal energy supply can be used to obtain marketable products?
This question is dealt with in the project Solar COllectors made Of Polymers (SCOOP).
The project is funded by the Seventh Framework Programme of the European Commission
and was officially launched on December 1, 2011 and runs for 3.5 years.
The main goals of the project are:
• Development of innovative polymer absorber designs with optimized heat transfer competitive to metal absorbers
• Development of new polymer material grades with promising cost performance ratio
and proven long-term durability for absorbers used in thermo-siphon systems suitable
for injection moulding or extrusion as production technology
• Design of innovative thermo-siphon solar-thermal systems suitable for polymer components
• Design of innovative solar-thermal systems suitable for polymer components using flat-plate
collectors appropriate for the integration into the building envelope;
Partners within SCOOP are Fraunhofer ISE (coordination), AEE INTEC, HSR Hochschule fuer
Technik Rapperswil, University of Oslo, Humboldt-University of Berlin and Johannes Kepler
University of Linz as research institutions and the industrial partners GREENoneTEC, HTCO,
PPI, APC, DS Smith Kaysersberg and Aventa. The project is funded by the European Commission
within the Seventh Framework Programme (FP7).
Reliability of solar thermal collectors under extreme climatic conditions: German project SpeedColl
Solar thermal collectors are installed in very different climates almost all over the world and have to stand
harsh operational conditions. In the project SpeedColl, collectors and components are exposed and monitored o
n different test sites including extreme climatic conditions to evaluate the occurring loads and the degradation
effects. The exposure sites are:
- moderate: Freiburg & Stuttgart, Germany
- alpine: Schneefernerhaus, Zugspitze, Germany
- arid: Sede Boker, Negev Dessert, Israel
- tropical: Kochi, India
- maritime: Pozo Izquierdo, Gran Canaria, Spain
Accelerated ageing and qualification tests for collectors and components will be developed on the
basis of the outdoor data and indoor screening tests. The project is funded by the German Ministry
for the Environment, Nature Conservation and Nuclear Safety and the industrial partners. Partners in
SpeedColl are the Fraunhofer Institute of Solar Energy Systems (coordination), the Institute of
Thermodynamics and Thermal Engineering (ITW) of the University of Stuttgart, Bosch, Viessmann and
Vaillant with collectors, Almeco Tinox, Alanod, BlueTec, Centrosolar Glas, Kömmerling, OTTO Chemie and
DSM with components and Wagner, Monier, GeneralSolar, Interfloat, Dt. Kupferinstitut and Ritter as passive
partners. The project was launched in April 2011 and runs for four years.
Bridging the gap between basic science and technological applications, the Task 39 handbook
discusses the requirements, conditions and benefits of polymeric materials in solar thermal
applications and it does so in a format that is still to be missed among other publications in
the field. As the first of its kind, the book specifically caters to two expert groups.
Part one explains the subject “solar thermal energy” for representatives of the plastics
industry and research. The second part provides information about polymeric materials and processing
for solar thermal experts - a know-how which is fused in part three of the publication. With its
twofold focus the handbook is relevant for researchers, scientists, engineers and technicians
active in the solar thermal field and/or polymer sector. ”Polymeric Materials for Solar Thermal
Applications” is published by Wiley-VCH and will be available in October 2012.
Effect of cyclic thermal treatment on overheating protection performance of thermotropic glazings
Thermotropic glazings provide overheating protection for solar thermal collectors and façades.
They reduce solar radiation passing through the thermotropic glazing upon exceeding a pre-defined
threshold temperature reversibly. During operating life thermotropic glazings are exposed to numerous
transitions from temperatures below to temperatures above the threshold temperature and vice versa.
Hence within this research work the light-shielding capability upon several heating/cooling cycles
(up to 100) of selected thermotropic glazings was evaluated. Fig. 1 displays solar hemispheric
transmittance of thermotropic glazings prior to thermal cycling (number of cycles 0) and after
100 cycles. Data were recorded at room temperature (black) and at 70°C (red) for each number of cycles,
respectively. With increasing number of cycles deterioration of switching performance was observable for
investigated layers 2, 3 and 4. Nevertheless, layer 1 displayed an enhanced performance after 100 cycles
compared to the initial state. Furthermore our investigations – details are available from the Journal of
Polymer Research (DOI: 10.1007/s10965-012-9888-3) – revealed a significant effect of a single thermal cycle
on the morphology of thermotropic glazings. Theoretical considerations and our findings concurrently suggest
a close correlation of light-shielding efficiency and morphology. Thus, future work will focus on a
detailed survey of the effect of thermal cycling on morphology. However further efforts are necessary in
order to improve long-term stability of thermotropic glazings.
Within the collaborative research project SolPol-2 “Solar-thermal systems based on polymeric materials –
Development of collectors and plastics-compounds” (www.solpol.at) a variety of polymer grades
is investigated as to their applicability for black solar absorbers of collectors with and
without overheating control. The materials selected include commodity plastics
(e.g. polyolefines (PO)), engineering plastics (e.g. polyamides (PA)) and high-performance
plastics (e.g. polyphenylene sulfide (PPS)). As black pigments various types of carbon black,
graphite and carbon nanotubes are considered. Furthermore, the effect of various inorganic
particles (e.g., fillers or fibers) on the solar absorbance is evaluated. As shown in the
representative figure the solar absorbance of the black-pigmented plastics-compounds
(plaques with a thickness of 2 mm) is ranging from 89% to 96%. While black-pigmented
polyolefins or engineering polyamides exhibit high solar absorbance values, high performance
materials with a high density of aromatic groups are characterized by lower solar absorbance.
The modification of high performance plastics with inorganic particles (e.g. glass) allows
for an enhancement of the solar absorbance.
Aging testing of heat storage liner materials using micro-sized specimens
The current approach to develop accelerated aging test methods for polymeric
materials used in solar thermal applications within the basic research project
SolPol-1 (www.solpol.at) focuses on micro-sized specimens with thicknesses in
the micrometer range. To evaluate the influence of thickness on the long-term
thermal stability of polymers, in a first series of experiments, micro-sized
specimens with thicknesses of 50 µm, 200 µm and 500 µm (s. Fig. 2) were prepared
from extruded sheets by automated planning on a CNC milling device. As model
materials selected polyolefin formulations for heat storage applications were used.
The micro-sized specimens were aged in hot air at 135°C. A clear dependence of the
aging behaviour (decrease in oxidation temperature TOX
and strain-at-break values εB)
on the thickness could be found, with thinner specimens degrading faster than thicker
specimens (s. Fig. 3). For the investigated materials and the applied aging parameters
an acceleration factor of aging of 1.5 was obtained by reducing specimen
thickness by a factor of 10 (500 µm to 50 µm).
Polysol: Development of a modular, all-POLYmer SOLar thermal collector for
domestic hot water preparation and space heating
The project focus is to develop a novel modular, all-polymer glazed solar thermal collector that can directly
substitute a conventional metallic solar thermal collector for domestic heating and hot water applications.
In order to achieve this we propose the following innovations:
1. A novel selective physical vapour deposition (PVD) coating with a high thermal emittance
(temperature dependent) over 80°C. The coating will increase absorption of incident solar radiation
to levels comparable to PVD coating metallic collectors (i.e. 95%) whilst simultaneously serving as
in-built overheating protection to avoid polymer softening;
2. A novel, modular polymer composite absorber profile capable of operating at pressures
up to 6 bars. The decrease in thermal conductivity due to increased absorber thickness (required to
withstand high operating pressure) will be overcome by selectively dispersing nano-dopants within the
polymer(s), effectively creating a nano-composite layer;
3. A co-extrusion process capable of producing a modular absorber with selectively doped sections
(only top absorber surface);
4. A novel, low cost collector casing composed of up to 85% recycled mixed waste polymers.
The recycled polymer casing will contain a blown core of mixed waste polymer which will partially
serve as thermal insulation thereby reducing the need for typical insulation material by 50%.
At present the first prototypes are manufactured. After finalization of the prototypes collector
tests according to EN 12975 will be carried out by ITW as well as field tests in the following countries:
Spain, Turkey, Republic of Macedonia (formerly a federal unit of the Socialist Federal
Republic of Yugoslavia) and Germany.
The Polysol project (Grant Agreement Number 2010-1 /262149) is supported by the European Commission
through the Seventh Framework Program for Research for SMEs.
Revision of the European Standard EN 12975 "Thermal solar systems and components – Solar collectors"
Regarding the revision of the European Standard EN 12975 “Thermal solar systems and components
– Solar collectors” the following issues are important:
- A joined (CEN and ISO) Standard EN ISO 9806 will replace the current EN 12975.
- The enquiry (time to deliver comments on the draft of the Standard) is running
from 23.4. – 23.9.12 (up to 26.6.12 on national level).
- Comments (in English language) to the draft can be given by anybody through
the national mirror committees by using the official comment templates.
- If you want to give comments contact your national mirror committee.
- German translation of the draft standard can be assessed under
for other language contact your national mirror committee.
Unisol – universal solar system for pre-heating water
In any solar thermal system, between the absorption, accumulation and distribution parameters, accumulation
should be the one that controls all mechanisms and therefore the global efficiency. Thus, we intend with the
Unisol project to develop an integrated a set of R"D activities to design a universal, innovative, independent
and intelligent system that manages the accumulation of solar heat that can use almost any solar collector.
This system is intended for pre-heating domestic hot water (DHW), simultaneous application of pre-heat
domestic hot water and space heating, and also to simplify integrated systems (SI) for the support of subsystems
in multifamily housing buildings. The project displays several novel peculiarities, such as its unique principles
of universality and integration inside and outside buildings and the test of a exchanger circuit with double logic.
This project begins in January 2012. The main promoter is JPrior Lda, a private Portuguese company, Aveiro
University and LNEG. Luis Godinho, Pedro Graça and John Rekstad are persons, from Task39, that are directly involved
in this project.
Pedro Graça, Aveiro University – Physics Department, Portugal, email@example.com
ISOlar – Screening and Lang-Term-Prognosis of Thermal Properties of Insulation Materials for Solar-Thermal Collectors and Heat Storage:
Funded from the Austrian Research Promotion Agency (FFG), the ISOlar project started in April 2011. The aim is to substitute
conventional thermal insulating materials by improved ones. From more than 100 identified insulating materials about 40
became candidate status for screening tests. Thermal conductivity, thermal degradation under ambient gas conditions and
change of mass during thermal loads up to incineration level were investigated. As received status was
documented by ATR spectroscopy and stereo microscopy.
Fiber materials, Aerogel doted materials, glassy foams, and lots of synthetics as Polyethylene, or Polyol-Isocyanat
based materials were tested. As illustrated no thermal conductivity values lower than 0.03 W/mK could be detected.
Corresponding to the observed mass loss thermal degradation was detected in a temperature range from ~160°C up to ~400°C.
In many cases an initial mass loss could be observed at temperatures slightly below 100°C what is drawn back to a loss of
humidity or residual solvents. As a result of the screening tests 6 materials became subject to a detailed characterisation
as shown in the TABLE to the right. Further 6 materials will become subject of different aging tests. Parallel weathering test will be
performed in mini collectors.