March 13-15, 2013 Recent IEA-SHC Task 39 Meeting at Mallorca
The Experts Meeting No 15 was held in conjunction with a Subtask B expert’s workshop. Both events took place at the Hotel Marina Luz in Can Pastilla, Mallorca, Spain on March 13-15, 2013. The events were hosted by Fraunhofer ISE. 27 experts participated in the meeting and the workshop, among them new experts from industrial companies and research institutes from Germany, Israel, Spain and the United States of America.
March 14, 2013 Workshop on solar thermal made from polymeric materials
During the latest meeting of the IEA SHC Task 39 on Mallorca, a workshop on solar thermal systems made
from polymeric materials was conducted within Subtask B: Collectors and components. The aim of this work
shop was to define solar thermal systems made from existing components which are already available on the
market to demonstrate that polymeric materials for solar thermal is not only wishful thinking but already
Within this workshop 4 groups were formed to discuss and define the following system configurations and
the dissemination of the results respectively:
Standard domestic hot water system (collector area approx. 5m², store volume approx. 300 l)
Low-cost thermosiphon system for sunny regions
Scalable system (with respect to collector area and storage volume)
Altogether 26 experts gathered in these 4 groups to discuss system concepts, select components and to think
about suitable dissemination measures. In the end of the work shop each group presented their ideas about the
different system configurations and also concrete proposals for the realisation of the different systems.
The work shop was closed with a final discussion of the challenges encountered defining the systems with
different components from
different manufacturers. However everybody agreed on the workshop being a success event.
The next step will be the search for sponsors donating the single components to demonstrate the different
system configurations at an appropriate location.
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) invite to 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 16-18, 2013 16th IEA-SHC Task 39 Experts meeting, Blumau, Austria
The next Task 39 Experts meeting will take place from October 16-18, 2013 in Blumau, Austria and is
organised by Johannes Kepler University, Linz, Austria.
Participants at the 15th Task 39 Meeting at Mallorca
Polymeric insulations for solar thermal components
Within a 3 year research project, the Austrian Institute of Technology evaluates the potential of new
insulations for solar thermal collectors and storages. A thorough screening of existing and new materials
was performed and yielded a list of more than 40 potentially interesting insulations
(the list can be requested by the Author Christoph Zauner). A special focus was put on
polymeric materials of various kinds and can be subdivided into foams (Fig. 1, left) and
fibre based materials (Fig. 1, right).
In order to assess the potential of the various insulations in real applications, 14 miniature
collectors (Fig. 2) were equipped with different materials and were exposed in Vienna for 6 months
(from 24.07.2012 to 15.01.2013). The total irradiation was 700 kWh/m².
By measuring the absorber temperatures it is possible to quantify the insulation behavior under
real-life conditions (Fig. 3) and monitor possible degradation effects.
An important finding relates to the use of polymeric foams that are filled with a
convection-suppressing non-air cell gas: in a real collector the foam and thus the cell gas
is heated up considerably which may drive the release of the cell gas by either foam deterioration
(breaking of cells due to temperature) or improved gas diffusion (due to higher temperatures).
As a consequence the standard data sheet thermal conductivity values are no longer valid in
real collectors or storages. Thus, one has to check if and how thermal loads may influence the
thermal conductivity of these insulation materials when designing collectors or storages that
should have constant performance over their whole service-life-time.
Development of a Polymeric Absorber: Product Design Regarding Manufacturing Techniques and Fluid Mechanics
The Centre of Excellence for Renewable Energy Research at Ingolstadt University of Applied Sciences and
Roth Werke GmbH, Dautphetal (Germany), worked on the optimisation of the design of a polymeric absorber.
The new absorber design is intended to be used in unglazed (pool) collectors as well as a basis for
upcoming polymeric flat-plate collectors. The basic requirements for the polymeric absorber design were:
- Suitability for plastics processing techniques
- High collector efficiency
- Low thermal resistance between absorber surface and fluid
- Homogenous flow distribution
Resulting from the requirements a volumetric structure producible by a thermoforming process has been developed.
The fluid flow in the structure was investigated and optimised by means of CFD. The final absorber design
revealed a more uniform flow distribution in the riser ducts and a higher collector efficiency compared
to a conventional sheet-pipe absorber.
Sunlumo Technology, the green-tech company from Perg (Upper Austria) is
currently working on the implementation of the pilot series of the One World
Solar Collector, which is to be presented later this year. FEM Analyses and
Simulations for the mechanical and hydraulical leads are finished. The
production plant for the pilot series is currently being installed. For the
implementation of the One World Solar Collector, Sunlumo has taken a leading
European machine builder aboard. Sunlumo is currently studying the use of
piping, terminals and pump groups all made from polymeric materials.
Bio4Sun - Polymers for Solar Collectors – A Novel Approach
In the field of solar heat, polymers significantly gained importance over the last years. Numerous research and development activities carried out by renowned research facilities and the global players in the polymer and solar industry (e.g. activities in IEA SHC Task 39) demonstrate that polymers are the materials of choice for next generation solar thermal systems. In addition to classical polymers made from petrochemical resources biogenic polymers (i.e. polymers based on renewable resources and/or biodegradable polymers) have been introduced as a sustainable and seminal alternative. Biogenic materials are already successfully used in the automotive and electronic industry. Therefore, biogenic materials are expected to have a high potential in the solar industry as well: Solar energy can get even „greener“! However, so far no systematic and comprehensive investigation of biogenic polymers for solar applications has been carried out. Therefore a novel 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 will be 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 will be carried out in order to identify potential biogenic candidate materials for solar applications. In the next step the application relevant thermal, thermo-mechanical, mechanical and optical properties of suitable materials will be characterized and a comprehensive polymer physical property profile will be compiled. Then a systematic characterization of the degradation behavior after accelerated weathering under application relevant conditions and a first basic assessment of the lifetime will be done. After the successful project conclusion an extensive set of information on the applicability and the limitations of use of biogenic polymers for solar technologies will be available. The potential optimization requirements of the materials will also be evaluated. These results should serve to initiate innovative industrial research work in the fields of solar heat.
Plastic collector development with temperature limitation by thermosiphonal backcooling
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 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.
A prototype of this collector concept was constructed and tested at the outdoor test facility successfully. As shown in the graph for the first prototype the temperatures could be limited to less than 100°C at the absorber surface. The thermosiphonal driven backcooling resulted in collector inlet temperature of about 40°C and outlet temperature of about 90°C. In parallel CFD calculations with good agreement to the measurement results were done to simulate a thermosiphonal driven backcooling loop with several register in parallel in the absorber and backcooler.
Further work within the project now is in progress for designing and constructing the second generation prototype collector with several improvements which will be tested at the University of Innsbruck in summer 2013. The CFD model will be further developed to be used for calculating different geometries and operating conditions.
eco-SPARK® is an innovative light glazed solar collector developed and manufactured by Magen eco-Energy. Magen eco-Energy is also known for manufacturing Heliocol® - unglazed solar collector (absorber) dedicated and designed especially for pool heating at low and medium temperatures as well as pre-heating of large volumes of water.
eco-SPARK® incorporates all of Magen eco-Energy's intellectual property, 40 years of experience and proven performance; eco-SPARK's innovation lies in its design: each panel is encased in a partitioned polymeric glazing to create an internal greenhouse effect significantly enhancing the solar collectors' performance.
eco-SPARK® is perfect for either pool heating in windy areas, northern regions and is ideal when used as pre-heating system and at low income housing energy saving projects. Its unique design characteristics provide more security from overheating (manifold is not encased in the glazing), and its air gaps insulation limits stagnation temperatures.
It is a unique low cost absorber with high performance!
Effect of surface active substances and nucleating agent on the overheating protection
performance of thermotropic overheating protection glazings
Thermotropic glazings providing overheating protection for solar thermal collectors undergo a reduction of solar hemispheric transmittance upon exceeding a pre-defined threshold temperature reversibly. Recent work within the project “Smart Windows – Smart Collectors: Development of Overheating Protection Glazings for Façades and Solar-Thermal Collectors” (State Government of Styria, Department Zukunftsfonds Steiermark; Project number 5019) revealed significant optimisation potential of thermotropic systems with fixed domains (two-phase mixture of a thermotropic additive finely dispersed in a matrix material, abbr. TSFD) for overheating protection purposes. TSFD established so far did not reflect the high light-shielding efficiency predicted by numerical simulation, which was attributed to inappropriate scattering domain shape and/or size. Thus, strategies for adjustment of scattering domain size/shape were employed in order to improve overheating protection performance of TSFD. One strategy was to manipulate matrix/additive interaction by addition of surface active substances or nucleating agents during manufacturing process. Whereas the addition of surfactants did not improve the light-shielding efficiency of an epoxy acrylate based TSFD, a nucleating agent enhanced overheating protection performance significantly (see Fig. 6). However, optimal scattering domain shape and size were not achieved upon addition of these substances. Furthermore, inhomogeneities were observed in layers formulated with anionic surfactant or nucleating agent because these substances were not solubilised upon the employed manufacturing conditions. Thus, further effort in adjustment of scattering domain size and shape are necessary in order to improve the overheating protection performance of TSFD.
Development of a Low-cost Solar Water Heating System using Polymeric Materials
Installed cost has been identified as a major market barrier for solar water heaters (SWHs). NREL is working with an innovative industry partner, RhoTech Solar (USA), to address this barrier by developing a solar water heater that can be installed for approximately $1,000. This SWH is a thermosiphon design made primarily of polymeric materials. Three unglazed prototypes (one is shown below) have been fabricated and are undergoing field trials. This prototype consists of an integrated absorber and storage tank made of thin-film polyethylene (PE). A heat exchanger is located in the storage tank and is also made of polymeric materials. The next step in this design is to develop a thin-film glazing that will improve the performance of the SWH. The glazed prototype will begin testing in September 2013. This project will address key issues associated with using polymeric materials for solar thermal applications; primarily overheat protection and materials durability.
In addition to working directly with RhoTech Solar to develop a marketable product, NREL is also proposing to start an IEA SHC task to develop multiple innovations aimed at reducing the cost of solar water heating systems and increasing the global market for this technology.
Ryton®PPS and Xtel®PPS alloys: Coolant ageing at 140°C and hot water approvals
In solar thermal applications an excellent resistance against hot water and glycol solutions is required.
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.
CPChem has carried out several ageing tests on Ryton® and Xtel® compounds in different automotive coolants,
glycol and hot water at different temperatures. Test results of 5000h coolant ageing in Glysantin G40 at 140°C
were presented. For the glass filled injection molding grades, a drop in mechanical properties occurs during
the first 1000h of ageing, after 1000h a plateau is reached. For the unfilled Xtel® XE4500BL there’s a slight
increase in tensile strength. Tensile elongation is reduced by 40% after 3000h of ageing at 140°C.
There’s no visual difference in surface appearance observed of the aged test bars compared to the reference bars.
TSC is a company founded in 2006 with the aim of developing advanced solar thermal solutions.
The main project of the company is the CCStaR, a collector based on the Fixed Mirror Solar
Concentrator concept, addressed to medium temperature applications (100ºC to 200ºC) for industrial
and commercial applications. The basic module has an aperture of 37 m2. In the current design polymeric
materials are used both in the hydraulic circuit where relative motions are required (for tracking purposes
and thermal expansions) and in the reflector design which consists of a polyurethane foam sandwich panel.
Further cost reductions can be achieved by using carbon based polymers to form the reflective layer.
Suitability of using polymeric materials in solar thermosiphon systems
To assess suitability of using polymeric materials in solar thermosiphon systems versus those with more
traditional materials, a case study will be performed in Task 39 as a complement to a previous case study
conducted on assessment of suitability of polymeric materials in solar thermal collectors for DHW production
and heating of buildings. As in the previous case study, assessment of suitability will be made based on a
total cost accounting approach taking into account thermal performance, investment cost, operation and
maintenance cost, reliability and long-term performance, climatic and environmental performance and cost.
The first step will be a Life Cycle Analysis (LCA), to assess the difference in environmental characteristics
between a thermosiphon system based on polymeric materials and corresponding solar systems with more
traditional materials. For the assessment, the following environmental impact indicators will be used:
IPCC, Ecoindicator99 and ReCiPe.
Participants of the case study will be Linnaeus University, Aventa AS, and Fraunhofer Institut für Solare
SCOOP – Qualification of New Materials, Absorbers and Other Components
In order to achieve the goal to produce cost-efficient and flexible collector systems made of polymers suitable
materials need to be developed. This, however, requires a set a specialised testing methods and analytical routines.
In order to identify the first indicators of material degradation induced by accelerated ageing methods a set of
standard testing methods is adjusted to the requirements of the envisaged solar thermal application.
The presented routine is based on a correlation of data acquired by spectroscopic measurements and mechanical
testing. Additionally, a third dimension of data acquisition on a molecular level based on mass spectrometric
methods is being developed. Identifying the first indicators of material degradation is the first step for
material modifications leading to an improved service life time.
One step further towards the testing of absorbers and components is made by developing a destructive
testing method for twin wall sheets. This approach focuses on examining the pressure resistance during
collector stagnation, but can also help to optimize the production process. The work is done in the
project SCOOP and funded by the European Commission within the Seventh Framework Programme.
The need for polymers suitable for solar thermal hot water flat plate collectors requires engineering thermoplastics capable of withstanding high temperatures under different conditions (e.g. stagnation). The products based on these polymers will be exposed to pressure, hot water and/or air during operation. Polyphenyl ether (PPE)/polysterene (PS) blends, which are fully miscible polymer systems, are amorphous polymers having a good hydrolytic stability and, therefore, used in a wide range of hot water fluid engineering applications. A challenge of these blends is their resistance against oxidation during aging in hot air (Olivares et al. 2008, Kahlen et al. 2010). To overcome this challenge, a novel NORYLtm PPE/PS resin is developed by SABIC Innovative Plastics. The improved NORYLtm resin demonstrates reduced oxygen uptake compared to the NORYL resin tested by Olivares et al. and Kahlen et al. (Olivares et al. 2008, Kahlen et al. 2010). Currently the mechanical properties of the resin are under evaluation and the results will be presented at the SHC 2013 in Freiburg.
Unisol – universal solar system for pre-heating water
The UNISOL project main goals are to provide an efficient and low-cost heat storage system, for domestic hot water (DHW) and/or room heating (RH). The main targets of this system will be apartment buildings with a maximum individual floor area of 250 m2. The easy integration with collective systems in these apartment buildings is also a priority. Thus the design of this universal, innovative, independent and intelligent system that manages the accumulation of heat that can use almost any type of solar collector is being tested and refined.
The schematic 3D drawing (figure) shows the UNISOL second prototype that was designed in order to concentrate all the required hydraulic, electric and electronic circuits in a single vertical section of the individual storage tank. The primary experimental tests of this system, for a DHW profile are already done. The graph shows one result of those experiments, giving information about the thermal response of the system in order to recover from a specific consumption (80 L). It is worth to notice that this systems works using the drain-back model and these data is required to design the algorithm required for the electronic controller which is being developed.
Aging behavior of black pigmented polypropylene model materials
Within the collaborative research project SolPol-2 “Solar-thermal systems based on polymeric materials –
Development of collectors and plastics-compounds” (www.solpol.at) commercially available black pigmented
polypropylene materials are investigated as to their aging behavior considering solar absorber applications.
Therefore, a novel accelerated aging testing method is used based on micro-sized specimen. Slices with
varying thickness in the µm range (100, 200 and 500µm), which are planed from 2 mm thick sheets, are exposed
in hot air and heat carrier fluid at 95°C, 115°C and 135°C. As aging indicators the remaining stabilizer
content, the oxidation temperature and ultimate mechanical properties are determined. Two commercially
available polypropylene (PP) model materials (PP1 and PP2) are investigated, which are based on carbon
black pigmented PP block copolymer grades. In Fig. 1 the time-to-failure for 100µm thick specimen of the
material grades PP1 and PP2 exposed in hot air at 135°C are compared as to the aging indicators (primary
phenolic antioxidants content < 0.03m%, oxidation temperature < 220°C, strain-at-break < strain-at-yield).
While in PP1 the primary antioxidants threshold was obtained at shorter aging time, the time-to-embrittlement
was significantly longer. Hence, it is concluded that besides the antioxidants package also the chemical and
physical structure of the material and the specimen is of relevance. In the next meeting further data will be
presented and discussed for other aging conditions.
New automated production line for welding of polymeric collectors
In February 2013 Aventa has arranged a mini-workshop together with Task 39 partners from Fraunhofer ISE and Chevron Phillips Chemicals
in connection with the opening of a new automated welding line for polymeric collectors at Aventa's production site in Norway.
The production system has been produced by a leading Austrian plant manufacturer for diverse branches of industry. The new system automatizes essential parts of the production process for Aventa, reproducibility secures a high part quality level, as well as an annual capacity for 40 000 solar collectors per shift. Production line manufacturer FILL characterizes the development of the complete application solution as pioneering work.
Relevance of Plastics for Future Solar-Thermal Markets (Europe and Austria)
Within the collaborative research project SolPol-1 “Solar-thermal systems based on polymeric materials – Scientific and Methodological Aspects and Economical and Ecological Impact Assessment” (www.solpol.at) the market potential and economical effects of various polymer based solar-thermal plant types (incl. collector types and systems principles) for different world regions are assessed. To establish reference scenarios existing non-polymeric and polymeric collector systems and their future market projections (business as usual (BAU)) were analyzed and compared.
As shown in Figure 7, the actually installed capacity of solar-thermal collectors in Austria is developing according to the BAU scenario established by ESTTP/ESTIF in 2006. For Austria, but also for Europe, the current market development is significantly deviating from the advanced market penetration (AMD) and full R&D and policy (RDP) scenario. Hence, the measures defined in the past have to be reevaluated and adopted. Systems based on highly pre-manufactured components with optimized function integration, reduced collector weight and ease of installation (plug&function), high reliability and lifetime, attractive design and appearance, and reduced costs/prices as well as an improved cost/performance ratio are needed. As revealed in other industrial sectors, polymer based product technologies allow to fulfill the above mentioned criteria. For the indicated upper and lower bound scenarios up to 2020 compound annual growth rates of 16 and 23% are required for Europe, respectively. Innovations based on a shift from conventional solar-thermal systems utilizing primarily various metals and glass to all-polymeric and hybrid systems for worldwide markets are of utmost importance.
Processability of engineering plastics to hollow profiles
Within the collaborative research project SolPol-2 “Solar-thermal systems based on polymeric materials – Development of collectors and plastics-compounds” (www.solpol.at) engineering plastics are investigated as to their processability to hollow profiles for solar absorbers. The materials selected include various polyamide (PA) grades, syndiotactic polystyrene (sPS), polyphenylene oxide blends (PPO) and polyphenylene sulfide (PPS). Besides black pigments various types of impact modifiers or reinforcing particles (e.g., glass fibers) were considered. To evaluate the processability two tool geometries (twin-wall sheet and rectangular profile) were designed, manufactured and implemented at a lab extruder by Greiner Technology and Innovation (GTI, Eberstalzell, Austria). The extrusion parameters were varied systematically to achieve profiles with defined geometry and low internal stresses. In addition to high melt viscosity, small amounts of fibers or fillers had an advantageous impact on the extrudability of various engineering plastics, which are usually optimized for injection molding processes. Representative profiles with good and poor surface and geometrical quality are depicted in the representative figure. The profiles were further used to implement model collectors for solar-thermal drainback systems. Therefore, joining technologies based on glueing and welding processes were evaluated and applied.