April 9-11, 2014 Task 39 Meeting Askelon, Israel
The experts meeting no. 17 was held in Ashkelon, Israel, from April 9-11, 2014. The meeting was hosted by the Israeli Task 39 partner Magen eco-Energy who is pioneering the production of all polymeric solar thermal collectors with a great market share in Israel and the MENA region, the US, South America and Asia. 18 participants (including one industry partner via Skype) took part in the meeting.
April 10, 2014 Excursion to Magen Eco Energy
On April 10, the Task 39 industrial partner Magen Eco Energy invited to
an extensive factory tour to their production site at Kibbuz Magen.
The Task 39 experts had the unique opportunity being introduced to Magen's different product lines, visted the in- and outdoor test facilities.
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April 10, 2014 Excursion to National Solar Energy Center
In the afternoon of April 10, a visit of Fraunhofer ISE’s outdoor test site at the Ben Gurion University in the Negev desert near Sde Boker was arranged. An overview of the different research activities at the National Solar Energy Center was given. Two Task 39 partners are involved in on-going projects.
April 29, 2014 Concept paper workshop for new Task under IEA-SHC Programme
For the collection of ideas and possible country contributions a concept paper workshop was
arranged at the Fraunhofer ISE in Freiburg, Germany on April 29, 2014. The new task shall be
defined under the umbrella term "Optimised integration of solar thermal systems". This covers a range of topics,
which may build on expertise developed -among others- in Task 39 ... [more]
Juni 25-27, 2014 in Gleisdorf, Austria Gleisdorf Solar 2014
September 16-19, 2014 in Aix-les-Bains, France EUROSUN 2014
October 13-15, 2014 in Beijing, China SHC 2014
Group picture of Task 39 experts in the Negev desert
Michael Sessler guiding through Magen's production facility.
Excursion to Fraunhofer ISE’s outdoor test site at the Ben Gurion University in the Negev desert
Aging characterization of polyolefinic liner materials using conventional methods and photoluminescence spectroscopy
Hot water heat storages are of growing importance in large-scale solar thermal systems. Their longevity is mostly restricted by the long-term stability of the waterproofing liner that commonly consists of polyolefin-based polymeric materials. Therefore, the objective of work package 02 within the research project SolPol-1 (www.solpol.at) was the development of accelerated test and characterization methods to evaluate the long-term stability of polymeric materials in solar-thermal components.
Within the present work, two commercial polyethylene grades were exposed in hot air at 95°C and 115°C under atmospheric conditions as well as in water at 95°C at a pressure of 5 MPa of pure oxygen. To characterize their aging behavior laser-induced photoluminescence spectroscopy was applied. Additionally, aging characterization was performed by established methods such as tensile testing, infrared (IR) spectroscopy, high performance liquid chromatography (HPLC), differential scanning calorimetry (DSC) and UV-VIS spectroscopy.
For the hot air aging experiments, established methods of aging characterization (tensile tests, IR spectroscopy, HPLC) showed that the samples were still in the induction period after 1169 h of aging. Interestingly, photoluminescence centered around 450 nm started to steadily grow in intensity already within the initial stages of the aging experiments. The growth was significantly stronger at 115°C and attributed to localized oxidation-induced carbonyl build-up. The aging experiments at enhanced oxygen pressure were carried out until the detection of embrittlement after 840 h and 936 h of aging. Moreover, a significant increase in carbonyl absorbance was determined by IR spectroscopy. Photoluminescence centered around 500 nm increased until the end of the aging experiments. Based on the results of the various aging experiments, it was concluded that photoluminescence spectroscopy is a viable method to characterize oxidation-induced changes in polyolefins. Due to its higher sensitivity compared to IR spectroscopy, photoluminescence spectroscopy is able to detect localized oxidation-induced changes already within the induction period.
Klemens Grabmayer and Gernot M. Wallner, University of Linz, Austria firstname.lastname@example.org
Beate Röder, Humboldt Universität zu Berlin, email@example.com
Ulrike Braun, Bundesanstalt für Materialforschung Berlin, firstname.lastname@example.org
David Nitsche, AGRU Kunststofftechnik GmbH, email@example.com
Fig 1. Evolution of photoluminescence spectra for PE liner B upon hot air aging at 115°C.
In the last years Plastic solar collectors are being developed and manufactured. Plastic Pipes are
used in these solar systems (PP, PEX, CPVC) but storage tanks are still mainly metallic. This article
presents some ideas for manufacturing low cost thermoplastic pressure storage tanks for DHW solar systems.
1) Thermoplastic endless glass fiber wound reinforced Polyolefine Tank.
A blow molded, thin wall vessel ( 100 -120 liter volume) will be covered by a cross-wound sheath of endless
glass fibers, encapsulated in a Polypropylene coating similar to a wire. These cross-wound layers of PP and
fibers are molten by means of hot air and fused to the vessel (Leister system) and form a hybrid pressure
resistant tank. This method is similar to the process using thermoset polyester Glass reinforced resins
(GRP) but presents the advantage of a clean chemical free procedure and a recyclable product.
2) Injection molding of two half shells made from glass reinforced engineering materials
specially designed for liquid applications
No internal lining will be necessary. The shells can be welded by means of hot –plate, vibration welding or
Infrared radiation. Welding coefficients are quite strong. This will enable to make a lightweight
but pressure resistant tank .The water temperatures are moderate and do not negatively impact the pressure
resistance of these engineering materials. The material used has to have NSF 61 certification!
For both methods the pressure vessel with be insulated by means of a PU foam or mineral wool ,covered by an external injection molded or thermoformed protection and enhanced with an electric heater and thermocouple, Inlets, outlets, connection flanges etc..
ExKoll – Market research and cost optimization calculations for extruded solar thermal collectors made of polymers
Investigating the production of polymeric collectors from an economic point of view, different questions dealing with potential advantages of polymeric collectors were addressed. A combined approach of market study and technical cost calculation was performed in a concept study within the BMU Project ExKoll. Based on a market study, the possible market size for polymeric collectors was estimated and used for scaling a virtual production line in which polymeric collectors are produced continuously. Further, the cost distribution of conventional, metal-based collectors was analyzed and the most price-driving factors were identified.
Based on state-of-the-art materials, technology and design calculations two different collector designs were chosen and optimized towards cost optimization. For these concepts the individual production steps were investigated, with labor, energy and machinery cost taken into account. Scale effects on solar thermal systems, but also on a collector level, by variation of the collector´s length, were investigated for further analysis. Different collector efficiencies and life times were taken into account.
In summary, cost reductions of 8-16% on a system level can be considered realistic. Polymeric materials and production via extrusion hold much higher potential, but the low share of production cost on the market price of collectors is the limiting factor.
Polymer based solar collectors are one of the important parts of modern architecture. Market demands are oriented to the colored absorbers to fulfil the demand of architects and integrate the collectors in new buildings. One of the options for production of colored collectors is usage of the Thickness Insensitive Spectrally Selective (TISS) paints. In the past TISS paints were based on petroleum based solvents. Industrial production of unglazed solar collectors and polymer based solar façades is faced with problematic emission of Volatile Organic Compounds (VOC) during production, drying and curing process. In order to decrease the emission and fulfil the demands of new environmental regulations alternative low VOC binders are used for development of TISS paints.
It was shown that low VOC TISS paints can compete with standard TISS paints in optical and mechanical properties. For industrial application the paints must sustain environmental material stresses during service life time.
Ervin Šest, Ivan Jerman, NIC - National Institute of Chemistry, Slovenia,
THE ART OF STABILIZATION:
Analytical Evaluation of Stabilization Efficiencies for Stabilizer-Systems
Without proper stabilization, polymers are susceptible to degradation caused by reactions with oxygen or UV-light, which lead to undesirable changes in the properties of the polymer. A stabilization system is normally added to the polymeric material, which is responsible for maintaining mechanical properties like strength and toughness. Usually additive formulations consist of several stabilizers from different chemical classes to ensure the best possible protection of the polymer. These combinations may show antagonism as well as synergism. Due to these unpredictable effects, the rating of stabilizer efficiencies is rather complicated. Obviously the investigation of interactions between stabilizers from different chemical classes is very important as they can be critical to their functionality.
A highly sensitive HPLC-MS method was developed to detect and identify stabilizers and their degradation pathways. Studies using different model formulations aged in the polymer mimicking squalane visualized a strong antagonistic effect between phenolic antioxidants and HALS as shown in Figure 1. The reaction mechanism between HALS and thiosynergists as proposed in the literature also would suggest a strong antagonism, as acidic degradation products of the thiosynergist deplete the protection efficiency of the HALS. In the present study no antagonistic effects were observed and combination of these two stabilizers was rather favourable to extend the service life of the polymer. Of all investigated formulations the ternary combination HALS/phenol/thiosynergist showed the highest protection efficiency for the polymeric material 1.
1 S. Beißmann, K. Grabmayer, G. Wallner, W. Buchberger, Polymer Degradation and Stability, to be submitted
Materials and model components for injection moulded storage collector
In the EU FP7 project SCOOP injection moulded absorbers for integrated storage collectors are developed. By FEM modeling property requirements were defined for the pressurized integrated storage component. Due to relatively high mechanical loads and an operating temperature range up to 100°C fiber-reinforced engineering plastics were preselected and characterized as to application relevant properties. To check the long-term performance and to screen various materials pressure cooker testing (in water at 135°C) was performed. Depending on the material formulations significant differences in the hydrolysis resistance were obtained.
Miniaturized model absorbers were manufactured by injection moulding and joining of half-shell parts (s. Fig. 1). Various joining techniques were used and evaluated. Besides mechanical sealing and fixturing using O-rings and screws, rivets or clamps, 1K and 2K-glueing systems and frictional welding were investigated. While the evaluated mechanical joining or glueing techniques did not allow for pressure tight model absorbers, better results were obtained for welded model absorbers. Ongoing work deals with the long-term performance testing on specimen and subcomponent level.
Gernot M. Wallner, University of Linz, Austria, firstname.lastname@example.org;
Coauthors: Thomas Lüftinger, Polytec; Karl Schnetzinger, APC, Austria
Injection moulding tool for half-shell absorber subcomponents for integrated storage collectors.
ECO-DESIGN and ENERGY LABELING for Polymeric Systems
Domestic hot water and space heating systems have to receive energy labels in the EU within the next years. This also applies for solar thermal systems using polymeric solar collectors.
In order to get an idea how polymeric collectors influences the Energy Label of various heating systems, we investigated different examples for space heating and domestic hot water preparation.
In a special example for domestic hot water preparation, we looked at 9 different domestic hot water systems (2 fossile, 1 air heat pump each combined with 3 different thermal storages (Energy Labels A, B and D) and a state-of-the-art polymeric solar collector (η0 = 64.2%, a1 = 4.167, a2 = 0.051, IAM = 0.89).
The results are depicted in the lower figure and show that it is crucial to use a very good thermal storage (Label B or better), otherwise it’s possible that the usage of polymeric solar collectors even decrease the overall system performance and worsen the Energy Label.