The following are publications developed under Task
Industry and Research Join Forces on Reliability Testing of Collectors and Materials
December 2016 - PDF 0.13MB - Posted: 2016-12-08
Editor: Pamela Murphy
Solar thermal collectors and their components are commonly exposed to a wide range of climatic influences. Next to UV radiation, factors like humidity, wind, extremely high or low temperatures, salt, sand and other particles in the atmosphere affect the surfaces and performance of these products. Although these influences are decisive factors for the lifetime and long-term efficiency of solar thermal collectors, there are no validated or binding test procedures for reliability assessment over time or models that allow a location-specific service life prediction.
Polymer Collectors with Temperature Control - Potentials for System integration
October 2016 - PDF 2.05MB - Posted: 2016-10-03
By: Alexander Thür, Katarina Maslikova
Within the Austrian research project SolPol-4/5 it is the goal to find solutions for solar thermal systems based on cheap polymer materials but with low temperature limits in order to realize significant cost reduction potentials. Therefore one major point is to keep the temperature of the solar collector (and the complete system) below the material limits which means below 100°C for cheap polymer materials. For this, several possibilities are under investigation in many research projects. One solution is to design the collector in such a way, that the performance does not allow stagnation temperatures above 100°C (temperature limited collector – TLC). Other solutions try to keep the collector performance highest possible during operation and reduce the performance during stagnation by different technical solutions (overheat controlled – OHC) like reduction of absorption characteristic at high temperatures (Föste, 2015), reduction of transmission of the transparent cover or increasing the heat losses by activating cooling processes like internal ventilation of the collector (Harrison, 2004) or using a thermosyphon driven backcooler (Thür, 2014). This simulation study based on different parameter variations estimates how different operating conditions can influence design parameters for a solar domestic hot water system (SDHW) with different collector types. For different possible market conditions, which can potentially be situated world-wide, the goal of these investigations is to find out dependencies of different design parameters depending on specific operating conditions for solar domestic hot water systems (SDHW).
Cost Drivers and Saving Potentials
INFO Sheet C1.2
October 2016 - PDF 0.46MB - Posted: 2016-11-28
By: Karl Schnetzinger, Advanced Polymer Compounds (APC), Austria / Gernot M. Wallner, University of Linz (JKU), Austria
Due to the specific characteristics of polymeric materials (e.g., variety of property profiles, ease of processing, mass production capability, freedom of design) this material class has been used to replace metal parts and components in various industrial sectors. In this case study the cost reduction achieved by material substitution is described and discussed exemplarily for industrial pumps.
Cost Drivers and Saving Potentials
INFO Sheet C1.1
September 2016 - PDF 0.29MB - Posted: 2016-11-28
By: Alexander Thür, University of Innsbruck (UIBK-EEB), Austria
A main challenge of the solar thermal market is the reduction of the production and installation cost finally following by the reduction of the market price of solar thermal systems. Installation costs are a major share of the total costs for solar thermal systems. Good ideas for cost reduction are needed. This sheet will give input for the discussion of this topic.
Task 54 Highlights 2015
April 2016 - PDF 0.72MB - Posted: 2016-04-08
One of the greatest challenges of the 21st century is to secure a sustainable energy supply and to considerably reduce CO2 emissions and the potential serious consequences of climate change. The challenging goals with regard to the contributions of renewable energy cannot be obtained without considerable growth of the solar thermal markets worldwide. Therefore, cost-competitive, efficient and reliable solar thermal systems are required. The first of these attributes is particularly hard to achieve as the prices for the production of solar thermal systems are still far from being equalled by the prices end-users have to pay. A great number of complex, costly and oftentimes non-transparent work steps are needed in order to bring solar thermal from the factory to the actual users. Task 54 is looking for ways to optimize each of these steps and is also looking into the social political contexts in which solar thermal installations are embedded. The ultimate goal is to strengthen the solar thermal industry by finding solutions for the cost-efficient production and installation of solar thermal systems and their marketing at a competitive price.
Novel solar thermal collector systems in polymer design – Part 5: Fatigue characterization of engineering PA grades for pressurized integrated storage collectors
2016 - PDF 0.94MB - Posted: 2016-10-21
By: Joerg Fischer*, Patrick R. Bradler, Mathias Schlaeger, Gernot M. Wallner, Reinhold W. Lang
Publisher: Energy Procedia, Elsevier
A novel aging test method considering the superimposed mechanical and environmental (temperature and environmental
medium) loads representative for pressurized integrated storage collectors (ICS) is described. Engineering polyamide (PA) grades
with short glass fiber (GF) reinforcement, which are of high relevance for endcaps of steel-pipe ICS absorbers or all-polymeric
absorber/storage-tanks, are characterized on a specimen level. Therefore, specific test devices and test arrangements for fracture
mechanics specimens with or without weld-line are implemented on an electro-dynamic test machine. Fatigue crack growth
kinetics data are obtained by conducting cyclic mechanical loads under various environmental testing conditions. The
experimental results of two glass-fiber reinforced PA grades, using compact type specimens, performed at two different
temperatures (23 °C and 80 °C) and in two environmental media (air and water), are compared in terms of crack growth kinetics.
Moreover, the influence of welding on the crack growth kinetics for one PA grade is shown. For all specimens (unwelded and
welded) the fatigue crack growth rates are enhanced in water compared to air. In welded specimens the fatigue crack growth
resistance is significantly reduced compared to unwelded specimens.
Novel solar thermal collector systems in polymer design – Part 3: aging behavior of PP absorber materials
2016 - PDF 0.43MB - Posted: 2016-10-21
By: Markus Povacz, Gernot M. Wallner, Michael K. Grabmann*, Susanne Beißmann, Klemens Grabmayer, Wolfgang Buchberger, Reinhold W. Lang
Publisher: Energy Procedia, Elsevier
A novel, accelerated aging test method was used to characterize the long-term stability of commercial black-pigmented
polypropylene (PP) model materials for solar thermal absorbers at elevated temperatures. The PP model materials investigated, PP-B1 and PP-B2, are based on carbon black pigmented PP block copolymer grades. Using an automatized planning technique, sliced 100 µm thick specimens were prepared, aged in hot air and heat carrier fluid (mixture of 60 vol.-% deionized water and 40 vol.-% commercial propylene glycol) at 95°C, 115°C and 135°C for up to 15,000 hours, and characterized in terms of various aging indicators (i.e., remaining primary stabilizer content, oxidation temperature, carbonyl index and ultimate mechanical properties). In general two major trends were discerned. First, the aging processes of the PP compounds depend on the stabilizer system, but even more heavily on the interaction of the stabilizers with the carbon black pigments and the structure and morphology of the polymer. Although the compound PP-B2 exhibited much faster stabilizer loss and an associated drop in oxidation temperature than PP-B1, mechanical investigations proved a better long-term stability for PP-B2. Second, it was shown for the compounds investigated that exposure to hot air causes harsher aging than exposure to hot heat carrier fluid. This is, presumably related to the reduced quantity of dissolved oxygen and triazole-based corrosion inhibitors used in the heat carrier fluid. While PP-B1 is use for absorbers in unglazed collectors and overheating-protected glazed collectors, the investigations clearly revealed that PP-B2 is a promising alternative.
Polymeric materials in solar-thermal systems - performance requirements and loads
2016 - PDF 1.91MB - Posted: 2016-10-21
By: Thomas Ramschak, Robert Hausner, Christian Fink
Publisher: Energy Procedia, Elsevier
A major basic problem in selecting appropriate polymeric materials and processing technology routes is related to the lack of
well-defined functional and performance requirements on the component level and to material property requirements on the
Hence, in a first step several reference climate regions were defined for pumped systems (continental (Graz/Austria), moderate climate (Beijing/China)) and non-pumped systems (Mediterranean (Athens/Greece), hot and dry (Pretoria/South Africa), hot and humid (Fortaleza/Brazil)), respectively. For each of these reference regions various solar-thermal plant types (e.g., domestic hotwater systems for single family houses (pumped and thermosiphon); domestic hot-water systems for multi-family houses; solar combi-systems for domestic hot-water and space heating (pumped) were pre-defined and evaluated and optimized virtually by modelling and simulation.
To determine performance requirements on the component level and to derive material property requirements on the specimen level all-purpose modelling and design tools for collectors were implemented and used which allow for the description of temperature profiles, stagnation conditions, efficiency curves, pressure losses, distribution of fluid and heat flow and the thermal and hydraulic optimisation of the whole collector.
Lifetime modeling of polypropylene absorber materials for overheating protected hot water collectors
January 2016 - Posted: 2016-10-21
By: G.M. Wallner, M. Povacz, R. Hausner, R.W. Lang
Publisher: Solar Energy, Elsevier
For the utilization of polymeric materials in high-demanding applications like solar thermal systems it is of utmost importance to define
the performance requirements and to investigate the applicability of components for defined systems under service relevant conditions.
This paper deals with the lifetime estimation of black-pigmented polypropylene (PP) absorber grades for overheating protected solar
thermal collector systems for hot water preparation in five representative climate zones. Based on experimental aging data in hot air
and heat carrier fluid at elevated temperatures (95 °C, 115 °C and 135 °C) and climatic input data, as well as deduced loading conditions
and absorber temperature distributions, the lifetime was calculated using a theoretical and an empirical extrapolation approach and
assuming cumulating damages in service relevant temperature intervals. Depending on the PP grade, the extrapolation method and the
location, endurance limits ranging from 8 to 50 years were obtained. The PP grade with ß-spherulithic structures and less carbon black
exhibited a superior performance (factor 2) compared to a well-established grade which is currently widely used for swimming pool absorbers.
Task 54: Price Reduction of Solar Thermal Systems
November 2015 - PDF 0.11MB - Posted: 2015-11-17
By: Michael Köhl, ISE Fraunhofer
Publisher: IEA SHC
Driving down the costs of solar thermal systems is not just about cheaper collector production. In fact, post-production processes, such as sales, installation and maintenance account for up to 50% of the price that end consumers pay. This new IEA SHC Task, Price Reduction of Solar Thermal Systems, will investigate these other factors and find ways to reduce systems costs. The Task’s kick-off meeting was hosted by Fraunhofer ISE in Freiburg, Germany the end of October. Researchers and industry representatives from all over the world participated.