This newsletter summarises the topics of the
Task 39 Meeting at the Canary Islands Institute of Technology in Pozo Izquierdo, Gran Canaria,
Spain from October 15-17, 2012, organised by Fraunhofer ISE, Freiburg, Germany.
October 2012 Task 39 Handbook is available now!
Bridging the gap between basic science and technological applications, the first book devoted
to polymers for solar thermal applications is available now!
[Read more ...]
March 13-15, 2013 15th IEA-SHC Task 39 Experts meeting, Mallorca
The next Task 39 Experts meeting at Mallorca will
be organised by Fraunhofer ISE, Freiburg,
September 23-25, 2013 SHC 2013 - 2nd International Conference on Solar Heating and Cooling for Buildings and Industry
The IEA Solar Heating & Cooling Programme (IEA SHC) and the European Solar Thermal
Industry Federation (ESTIF) are pleased to announce SHC 2013, the International Conference
on Solar Heating and Cooling for Buildings and Industry, from September 23-25, 2013 in Freiburg, Germany.
More information: http://www.shc2013.org/
October 10-11, 2013 16th IEA-SHC Task 39 Experts meeting, Blumau
The 16th Task 39 Experts meeting will
take place in Blumau, Austria from October 10-11, 2013.
14th Task 39 Meeting at Gran Canaria Spain, October 15-17, 2012.
Preparation of photocatalytic optically transparent coatings from pigment dispersions
Surface cleaning of building materials like facades and glass panes, causes considerable trouble in practice,
high consumption of energy and chemical detergents and, consequently, high costs. In field of solar energy
harvesting dirty surface decrease the efficiency of module resulting in low earnings. To realize self-cleaning
material surfaces there are two principal ways: the development of so-called superhydrophobic or
Photocatalytic coatings based on anatase TiO2 pigment are well known and are mainly used as thick and optically
non-transparent coatings for mineral substrates. On the other hand, optical transparent coatings have been
introduced on the market by Pilkington (PilkingtonTM). Basically, their photocatalytical cleaning is based
on fast drop of the water contact angles to few degrees achieved in the presence of solar radiation.
Superhydrophilicity of the coatings or thin films provide smooth later of water, draining the inclined
surface and removing dirt (self-cleaning).
Due to the increasing importance of plastics in solar thermal systems, where glass panes is intended
to be replaced by stable PC sheets or plastic foils, improvements of plastic glazing is urgently needed.
Photocatalytic optically transparent coatings are of great challenge because adherence, scratch resistance,
and low haze beside the applicability on plastic substrates are difficult to achieve at the same time.
Optically transparent nanocrystalline TiO2 (anatase) coatings were prepared by following approach used
for the development of spectrally selective (TSSS) paint coatings by using proper dispersants and
selecting novel sol gel binders enabling fast curing at relatively low temperatures, close to the
temperature at which plastics are stable. Pigment dispersion were prepared from commercial P 25 TiO2
(anatase) pigment and used for the deposition of coatings. Coatings were analyzed with various techniques
(confocal Raman, XRD, DLS (dispersions), and IR) and their self-cleaning and photocatalytic efficacy was
determined using newly developed fluorescence –based method (Černigoj et al., 2010). Pigment coatings exhibited haze below 1%,
yet their efficiency was up to 10 times higher as compared to that of Pilkington TM commercial coatings on glass.
The applicability of pigment dispersions for PC and acrylic sheets were demonstrated and discussed.
Ivan Jerman, Mohor Mihelčič, Pavli Pori, Boris Orel*,
National Institute of Chemistry, Ljubljana, Slovenia
Fernando Fresno Garcia, Urška Lavrenčič Štangar**
Laboratory for Environmental Research, University of
Nova Gorica Nova Gorica, Slovenia.
Poly2Facade – Overheating Protection by Polymers in Solar Facade Modules
The integration of solar thermal collectors into the facades of e.g. offices buildings (multifunctional facades)
requires protection against overheating at the backside of the module (inner wall) to maintain thermal comfort in
the room if the collector is in stagnation. The national project Poly2Facade (Austrian Program "Neue Energien",
FFG-Projekt 833717) was launched this year to develop overheating protected solar thermal modules by following two
strategies: storage of the excess heat in a PCM material behind the absorber and shading of the absorber by a
Simulations of the heat transfer by CFD on a preliminary model geometry carried out at the Austrian Institute of
Technology (AIT) proof that a significant temperature reduction can be attained with both concepts (see Fig. 1). The
upcoming variations will define the optimal geometry and material parameters (e.g. phase change and switching temperature)
of an overheating protected module. After the CFD design phase polymer based materials will be developed at the
Montanuniversität Leoben and the Polymer Competence Center Leoben (PCCL). At the end of the project the modules
will be installed in the test room of the Forschungszentrum für Integrales Bauwesen (FIBAG) and monitored to
evaluate the performance of the overheating protection.
Fig. 1 Simulations of the heat transfer by CFD on a preliminary model geometry
show that a significant temperature reduction can be attained with PCM and TTL
(REF= reference case, PCM=phase change material, TTL=thermotropic layer).
Canary Islands Institute of Technology (ITC) experiences in desalination with renewable energies
The archipelago of the Canary Islands is an outermost EU region located close to the West African coast.
This Spanish territory lacks of conventional fossil fuels and limited fresh water resources; however, these
islands have important amounts of wind and solar resources. This situation is the starting point to couple
renewable energies and desalination. The Canary Islands Institute of
Technology (ITC) has been researching on this topic since 1996; sixteen 100% renewable energy (RE) powered
autonomous desalination systems have been tested using different RE generation systems (PV, small and medium
size wind turbines, solar thermal collectors) and different desalination processes (Reverse osmosis (RO),
electrodialysis reversal (EDR), membrane distillation (MD)) among others. This long experience of ITC in this
field has allowed passing from the laboratory to the real world, offering a solution to water supply in remote
inland areas based on the international patent DESSOL® (Reverse Osmosis by Photovoltaic Energy), currently
transferred to a private company (www.drglobe.net). Thanks to the economic
support of the Spanish International Cooperation Agency, the Canary Islands Government and the EU
(MEDA-Water Program) 5 PVRO systems were installed in the North of Africa (one in Tunisia, with a capacity
of 2.08 m³/h, commissioned in May 2006, and four in Morocco (0.5 – 1 m³/h), commissioned along 2008).
Furthermore the ITC has complemented those actions with training, and has been offering the e-learning course "
Introduction to desalination by renewable energies" since 2010.
Within the research project SolPol-2, Sunlumo Technology is engaged in a concept study of novel,
plastics based, large-area film collectors. The ambition of the study is to elaborate scenarios
for a future implementation of film collectors, be it a temporarily special application or an
energy supply solution for modern membrane architecture. In doing so, collector design concepts
as well as facade integration concepts are developed. After having narrowed down the spectrum of
possible application scenarios to the most purposeful and demand-orientated, the definite
identification, selection and characterization of adequate materials and semi-finished products
follows as the preliminary stage of a precise product development.
Thermomechanical Properties of Polymeric Liner Materials for Long-Term Heat Storages
Large-scale solar thermal systems are of growing importance for district heating. Seasonal heat storage enables solar
thermal heating without the need for auxiliary heating. The objective of work package 05 within the research project
SolPol-2 (www.solpol.at) is the development of improved polyolefin formulations
for liner materials used in hot water heat storages. Selected polyolefin materials were characterized by tensile
testing and dynamic mechanical analysis (DMA) as to their thermomechanical material properties with a special
focus on material stiffness.
The stiffness (modulus) of the investigated polymeric materials is in the operating temperature range up to 90°C
significantly dependent on temperature. The E-moduli decreased by up to 25 % with an increase of the ambient
temperature from 20°C to 30°C and up to 85 % with an increase from 30°C to 95°C (i.e., maximum service temperature).
DMA (s. Fig. 2) revealed a decrease of the storage modulus of up to 40 % from 5°C to 30°C, which are the ambient
temperatures during the installation of heat storages in the field. Thus, the flexibility required for proper
laying and welding is significantly dependent on temperature. The reason for the change in stiffness is the
temperature dependent inner mobility of polymeric materials (glass transition in the amorphous phase (TG)
and mobility transition within the crystalline phase (Tα)).
It was concluded, that stiffness characterization by tensile testing (single-point data) should be combined
with thermomechanical stiffness characterization by DMA in order to thoroughly describe the material stiffness properties.
Klemens Grabmayer and Gernot M. Wallner, Institute of Polymeric Materials and Testing, University of Linz, Austria,
David Nitsche, AGRU Kunststofftechnik GmbH, email@example.com
Fig. 2 Dynamic mechanical characterization of selected polyolefin-based liner materials
Polymeric façade collectors or heat pump: Experiences and energy monitoring
– Rudshagen passive houses, Oslo
In Norway's first single-family house field "Rudshagen" (Oslo)
with passive house standard, two identical residences were selected for energy monitoring. The present
study compares the performance of two passive houses, each 116 m², one heated by polymeric solar
collectors and one with an air-to-water heat pump. The polymeric collectors (19.5 m²) are facade integrated
and contribute to domestic hot water (DHW) preparation and space heating. The energy monitoring started in early
spring 2012, will continue for one year and record all relevant parameters necessary to compare for the energy
consumption in each building and evaluate the dynamic performance of each technology during all seasons.
In spite of the rainy summer 2012, the electric energy consumption for DHW- and space heating is 12% lower for
solar- relative to the heat pump heated house in the period from January 24 - September 18, 2012.
The final study is part of a master project at the
University of Oslo. Financial support by the Research Council of Norway through the project SILVER and the support by OBOS and Aventa is kindly
Evaluation of overheating protection potential of thermotropic glazings: A holistic approach
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. In order to evaluate the theoretical overheating protection potential
of thermotropic systems with fixed domains (abbr. TSFD; i.e. a two-phase mixture of matrix/thermotropic
additive), a numerical model with optimal layer morphology was implemented. The hypothetical TSFD comprised
spherical scattering domains with diameters between 200 and 400 nm. Input parameters for the model were
refractive indices of matrix and additive below and above the switching threshold, respectively. Several
combinations of matrix and thermotropic additive displayed promising transmittance reduction capability
upon exceeding the threshold temperature. Fig. 3 displays hemispheric transmittance of a representative
TSFD below (blue) and above (red) the threshold temperature. Hatched bars indicate computed transmittance
of the hypothetical model at a wavelength of 589nm (left). Solid bars represent actually measured
transmittance at 590nm (middle) and the integral solar transmittance (right). Theoretically, this TSFD
exhibits a reduction in transmittance from 86% to 59% (589 nm). However, in effect the transmittance changes
from 85% to 77% (590 nm). Solar transmittance declines from 81% to 75%. Micrographs of this formulation revealed
spherical scattering domains with diameters between 12 and 62 µm. Hence, the moderate reduction in transmittance
compared to the computed values is attributable to inappropriate scattering domain size. Thus, further efforts
in adjusting scattering domain size are necessary in order to improve the light shielding performance.
Analysis of Production Processes and Collector Design of Polymeric Collectors
The Centre of Excellence for Renewable Energy Research at Ingolstadt University of Applied Sciences
and Roth Werke GmbH, Dautphetal (Germany), have started a new project in the field of polymeric
collector development in spring 2012. The 3-year project is funded by the German Federal Ministry
for the Environment, Nature Conservation and Nuclear Safety. The objective is the development
of a polymeric collector to reduce the manufacturing costs compared to state-of-the-art flat-plate
collectors. Therefore, a new design suitable for polymeric processes will be created and will be
optimised by simulation regarding part temperatures and efficiency. A comparison of the life
cycle costs of the adapted solar-thermal system and a state-of-the-art system by annual system
simulation should prove the cost advantage. Finally, prototypes of the designed collector will
be investigated in test rig measurements and an annual system test.
Christoph Reiter, Dr. Christoph Trinkl, Centre of Excellence for Renewable Energy Research,
Ingolstadt University of Applied Sciences, Germany
Basic characterization of extrudable black PP-Absorber Materials
Polypropylene exhibits high potential for solar absorbers in overheating protected collectors. Currently,
some PP-grades with appropriate stabilization and pigmentation are commercially available and used for swimming
pool absorbers or pressurized pipe applications. An objective within the research project SolPol-2 “Solar-thermal
systems based on polymeric materials” is the identification and polymer-physical characterization of black
pigmented PP grades. In this study focus was given to two commercially available PP-Block-Copolymer grades
(PP-B) and one PP-RCT (Polypropylene-Random Copolymer, Crystalline, Temperature resistance) development grade
(see Figure). The supplied materials were characterized on specimen level in the unaged state by UV-Vis-NIR
spectroscopy, differential scanning calorimetry (DSC) and tensile testing at ambient temperature. The results
revealed that pigmentation with carbon black is a suitable technique to fulfill high absorbance requirements
(solar absorbance > 95%). Depending on the copolymer type and the additive package melting peak temperatures
ranging from 135 to 170°C were obtained. Regarding the mechanical properties significant differences in the
ultimate properties (e.g. strain-at-break) were detected. Promising grades were selected for further material
development and optimization in SolPol-2.
Plastic collector development with temperature limitation by thermosyphonal backcooling
Within the Austrian SolPol consortium (www.solpol.at) at the University of Innsbruck research is done for supporting
the development of solar thermal collectors based on cheap plastic material 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. First calculations
with a simple excel tool showed a sufficient high potential of cooling power at reasonable thermosyphonal driven flow
rates and stagnation temperatures. Motivated by these results a CFD model was generated for detailed calculations of
flow distribution and peak temperatures in critical positions of the collector. In parallel a prototype of this
collector concept was constructed and tested at the outdoor test facility successfully. Further work now is in
progress for developing a detailed tool for theoretical calculation of the collector efficiency curve for such
collector types in order to be able to optimize this concept further.
Alexander Thür, Claudia Hintringer, Norbert Hauer, Wolfgang Streicher; University of Innsbruck, Austria
Monitoring the exposure of plastic materials to the environment:
Identification and quantitation of stabilizers and their degradation products
The project SolPol-2 aims at the development of polymeric materials and components for solar thermal systems
(www.solpol.at). Since polymeric materials used in solar thermal applications
are prone to degradation by sunlight and oxygen, the addition of different stabilizers is essential. Unfortunately,
it is not yet fully clear which combination of stabilizers provides the best performance for a specific application.
Furthermore, one must also take into account that the additives themselves may degrade and therefore lose their
protective function. However, characterization of degraded additives is important to provide insight into the
mechanism of an additives stabilization process.
The applicability of different analytical methods for the determination of polymer stabilizers and their
degradation products in plastic materials following accelerated aging tests was investigated. Frequently
used antioxidants have been examined to determine possible migration and chemical reactions during aging in
several polyolefin materials in different environments and at elevated temperatures (95°C-135°C). The
degradation of additives was monitored by analysis of the polymer samples aged in air or water using HPLC
with UV and tandem mass spectrometric (MS/MS) detection. After sample preparation, the amount of residual
intact stabilizers in the polymeric matrices was determined using HPLC with UV detection. For materials
containing sterically hindered phenols (used as antioxidants) some previously unknown degradation products
could be identified using highly sensitive MS/MS detection. These included compounds with a quinone-type
structure, hydrolysis products, or products generated by reaction with hydroxy radicals.
Optical overheating protection for solar thermal collectors
Today’s solar thermal systems are often associated with high initial capital investment.
Significant portions of the overall costs are associated with the component materials and their assembly into
the collector panel. SABIC Innovative Plastics recently launched a program to investigate the
feasibility of an cost effective solar thermal collector incorporating polymers. The polymeric
components have the potential to enable lower costs through mass production of complex parts.
One of the challenges is to maintain the efficiency of such a solar thermal collector while
simultaneously ensuring that the collector does not exceed the useful working temperatures of the
plastic components under “stagnation conditions”.
In order to limit the stagnation temperature, an optical solution has been developed by The University
of Amsterdam (Ronald Giessen, Martin Slaman) known as the ‘optical switch’, which is based on the
principle of total internal reflection (Snell’s law). SABIC Innovative Plastics has an exclusive license
on this invention and has the intention to further investigate this temperature limiting method for its