Polymeric Materials for Solar Thermal Applications E-Book
151,99 €
Mehr erfahren.
- Herausgeber: Wiley-VCH
- Kategorie: Fachliteratur
- Serie: Solar Heating and Cooling
- Sprache: Englisch
Bridging the gap between basic science and technological applications, this is the first book devoted to polymers for solar thermal applications. Clearly divided into three major parts, the contributions are written by experts on solar thermal applications and polymer scientists alike. The first part explains the fundamentals of solar thermal energy especially for representatives of the plastics industry and researchers. Part two then goes on to provide introductory information on polymeric materials and processing for solar thermal experts. The third part combines both of these fields, discussing the potential of polymeric materials in solar thermal applications, as well as demands on durability, design and building integration. With its emphasis on applications, this monograph is relevant for researchers at universities and developers in commercial companies.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 529
Veröffentlichungsjahr: 2012
Ähnliche
Cover
Related Titles
Title Page
Copyright
About the Editors
List of Contributors
IEA Solar Heating and Cooling Programme
Acknowledgments
Part I
Chapter 1: Principles
1.1 Introduction
1.2 Solar Irradiance in Technical Applications
1.3 Quantifying Useful Solar Irradiation
1.4 Solar Thermal Applications
1.5 Calculating the Solar Contribution
1.6 Conclusions
Chapter 2: Solar Thermal Market
2.1 Introduction
2.2 Collector Types
2.3 Regional Markets
2.4 Market Trends
Links Providing Updated Market Data and Forecasts
References
Chapter 3: Thermal Solar Energy for Polymer Experts
3.1 Solar Thermal Systems and Technical Requirements
3.2 Overview of Solar Thermal Applications
3.3 Solar Thermal Collectors
3.4 Small to Medium Size Storages
3.5 Sources of Further Information
References
Chapter 4: Conventional Collectors, Heat Stores, and Coatings
4.1 Collectors
4.2 Material Properties of Insulations
4.3 Heat Store
4.4 Other Components
4.5 Analysis of Typical Combisystems
4.6 Definition of Polymeric Based Solar Thermal Systems
4.7 Life Cycle Assessment Based on Cumulated Energy Demand, Energy Payback Time, and Overall Energy Savings
4.8 Cumulated Energy Demand, Energy Payback Time, and Overall Energy Savings for Conventional and Polymeric Based Domestic Hot Water Systems
References
Chapter 5: Thermal Loads on Solar Collectors and Options for their Reduction
5.1 Introduction
5.2 Results of Monitoring Temperature Loads
5.3 Measures for Reduction of the Temperature Loads
References
Chapter 6: Standards, Performance Tests of Solar Thermal Systems
6.1 Introduction
6.2 Collectors
6.3 Solar Thermal Systems
6.4 Conclusion
Part II
Chapter 7: Plastics Market
Reference
Chapter 8: Polymeric Materials
8.1 Introduction
8.2 Material Structure and Morphology of Polymers
8.3 Inner Mobility and Thermal Transitions of Polymers
8.4 Polymer Additives and Compounds
References
Chapter 9: Processing
Chapter 9.1: Structural Polymeric Materials
9.1.1 Introduction to Polymer Processing
9.1.2 Extrusion Based Processes
9.1.3 Injection Molding
9.1.4 Thermoforming
9.1.5 Fiber Reinforced Polymer
References
Chapter 9.2: Paint Coatings for Polymeric Solar Absorbers and Their Applications
9.2.1 Outline of Content
9.2.2 General Remarks about Selective Paint Coatings
9.2.3 Preparation of Selective Paints
9.2.4 Application Techniques for Spectrally Selective Paints
9.2.5 Conclusions
References
Chapter 10: Polymer Durability for Solar Thermal Applications
10.1 Introduction
10.2 Polymeric Glazing
10.3 Polymeric Absorbers and Heat Exchangers
10.4 Conclusion
References
Chapter 11: Plastics Properties and Material Selection
11.1 Introduction
11.2 How to Select the Right Material
11.3 Material Databases
11.4 Selection Criteria
11.5 Real Life Example: Standard Collector in Plastic (1:1 Substitution)
11.6 Summary
Part III
Chapter 12: State of the Art: Polymeric Materials in Solar Thermal Applications
12.1 Solar Collectors
Acknowledgment
12.2 Small to Mid-Sized Polymeric Heat Stores
12.3 Polymeric Liners for Seasonal Thermal Energy Stores
References
Chapter 13.1: Structural Polymeric Materials – Aging Behavior of Solar Absorber Materials
13.1.1 Introduction and Scope
13.1.2 Methodology
13.1.3 Results, Discussion, and Outlook
References
Chapter 13.2: Thermotropic Layers for Overheating Protection of all-Polymeric Flat Plate Solar Collectors
13.2.1 Introduction
13.2.2 Materials and Sample Preparation
13.2.3 Physical Characterization of the Polymers
13.2.4 Results and Discussion
13.2.5 Effect of Thermotropic Layers on Collector Efficiency and Stagnation Temperatures
13.2.6 Outlook
Acknowledgments
References
Chapter 13.3: Application of POSS Compounds for Modification of the Wetting Properties of TISS Paint Coatings
13.3.1 Introduction
13.3.2 Wetting of Surfaces
13.3.3 POSS Nanocomposites as Low Surface Energy Additives for Coatings
13.3.4 Anti-wetting Properties of Coatings with Smooth Surfaces – Lacquers for Polymeric Glazing
13.3.5 Anti-wetting Properties of Coatings on Rough Surfaces – TISS Paint Coatings
13.3.6 Conclusions
References
Chapter 14: Conceptual Design of Collectors
14.1 Introduction
14.2 Calculation of Collector Efficiency
14.3 Flow Optimization
14.4 Optimization of the Fluid Dynamics in Polymeric Collectors
14.5 Collector Mechanics
14.6 Conclusion
References
Chapter 15: Collectors and Heat Stores
15.1 Introduction
15.2 Solar Absorber Made of High-Performance Plastics
15.3 Flate Plate Collector with Overheating Protection
15.4 Flat Plate Collectors with a Thermotropic Layer
15.5 Solar Storage Tank with Polymeric Sealing Technology with Storage Volumes from 2 to 100 m3
Reference
Chapter 16: Durability Tests of Polymeric Components
16.1 Introduction
16.2 Twenty Years Outdoor Weathering of Polymeric Materials for use as Collector Glazing
Acknowledgments
16.3 Accelerated Lifetime Testing of a Polymeric Absorber Coating
16.4 Evaluation of Temperature Resistance of a Polymer Absorber in a Solar Collector
Acknowledgments
16.5 Determination of Water Vapor Transport through Polymeric Materials at Raised Temperatures
References
Chapter 17: Architecturally Appealing Solar Thermal Systems – A Marketing Tool in Order to Attract New Customers and Market Segments
17.1 Introduction
17.2 Architectural Integration as a Marketing Tool
17.3 Web Database
17.4 Examples
I-Box concept, Storelva/Tromsoe, Norway
Penthouse Vienna, Austria
“Home for Life” Concept House, Aarhus, Denmark
Bjoernveien 119, Oslo, Norway
Social housing in Paris, France
References
Chapter 18: Obstacles for the Application of Current Standards
18.1 Introduction
18.2 Internal Absorber Pressure Test
18.3 High-Temperature Resistance and Exposure Tests
18.4 Mechanical Load Test
18.5 Impact Resistance Test
18.6 Discontinuous Efficiency Curves
Reference
Glossary
Polymeric Materials
Abbreviations
Terms and Definitions
Solar Thermal Systems
Abbreviations
Terms and Definitions
Index
Related Titles
Wolf, E. L.
Nanophysics of Solar and Renewable Energy
2012
ISBN: 978-3-527-41052-1
Vogel, W., Kalb, H.
Large-Scale Solar Thermal Power
Technologies, Costs and Development
2010
ISBN: 978-3-527-40515-2
Keyhani, A., Marwali, M. N., Dai, M.
Integration of Green and Renewable Energy in Electric Power Systems
2010
ISBN: 978-0-470-18776-0
Armaroli, N., Balzani, V.
Energy for a Sustainable World
From the Oil Age to a Sun-Powered Future
2010
ISBN: 978-3-527-32540-5
Pagliaro, M., Palmisano, G., Ciriminna, R.
Flexible Solar Cells
2008
ISBN: 978-3-527-32375-3
Mathers, R. T., Meier, M. A. R. (eds.)
Green Polymerization Methods
Renewable Starting Materials, Catalysis and Waste Reduction
2011
ISBN: 978-3-527-32625-9
Stolten, D., Emonts, B. (eds.)
Fuel Cell Science and Engineering
Materials, Processes, Systems and Technology
2012
ISBN: 978-3-527-33012-6
All books published by Wiley-VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.
Library of Congress Card No.: applied for
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
Bibliographic information published by the Deutsche Nationalbibliothek
The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at http://dnb.d-nb.de.
© 2012 Wiley-VCH Verlag & Co. KGaA, Boschstr. 12, 69469 Weinheim, Germany
All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.
Print ISBN: 978-3-527-33246-5
ePDF ISBN: 978-3-527-65963-0
ePub ISBN: 978-3-527-65962-3
mobi ISBN: 978-3-527-65961-6
oBook ISBN: 978-3-527-65960-9
ISSN: 2194-0665
eISSN: 2194-8135
Composition Thomson Digital, Noida, India
About the Editors
Dr.-Ing. Michael Köhl, physicist, has been actively involved in the field of solar energy conversion since 1977. He presently works on service-life analysis of solar collectors and photovoltaic modules in the department Weathering and Reliability at Fraunhofer ISE. He was the coordinator of the EU projects SUNFACE and SOLABS and leader of Subtask 5 of the IP PERFORMANCE. Dr. Köhl is the current Operating Agent of the Task 39 “Polymeric Materials for Solar Thermal Applications”of the Solar Heating and Cooling Programme of the International Energy Agency IEA.
Dr. scient. Michaela Meir, physicist, has been working with R&D on solar thermal and energy systems for more than 15 years, with particular focus on the development of solar collectors using polymeric materials. She is presently employed part-time by the University of Oslo and by Aventa AS. She is Chairman of the Norwegian Solar Energy Society board and leader of Subtask A “Information”of IEA SHC Task 39.
Sandrin Saile, M.A. received her M.A. in British and North American Cultural Studies from the University of Freiburg. She joined the Fraunhofer ISE's department “Weathering and Reliability” in 2009 where she is responsible for the management and dissemination of the department's solar thermal activities, in particular the projects SCOOP and SpeedColl. Within IEA SHC Task 39 she is mainly active in Subtask A “Information” and played an active role in establishing the Solar Heating and Cooling Series.
Prof. Dr. mont. Gernot M. Wallner, graduated with a “Diplomingenieur” degree in Polymer Engineering and Science at the University of Leoben (Austria) in 1994, and he obtained a PhD degree in the same field at the University of Leoben in 2000. In 2008 Prof. Wallner obtained a Venia Docendi in the field of “Functional Polymeric Materials” with special focus on solar energy applications. Since 2010, Prof. Wallner has been Deputy Head at the Institute of Polymeric Materials and Testing (IPMT) at the Johannes Kepler University Linz (JKU, Austria). Prof. Wallner is a member and leading person in several solar related working groups and committees. Since the establishment of IEA SHC Task 39 in 2006, he has been leader of the Subtask C “Materials”.
Dr.-Ing. Philippe Papillon has been a senior expert in the field of solar thermal energy at INES (Institut National de l'Energie Solaire - CEA) since December 2005. He has been active in the field of thermal solar energy for more than 20 years, and has experience as coordinator as well as WP leader in European projects and also large national research projects. Beyond his research activities within INES, he is also an expert in European and French standardization committees, and is a member of the European Technology Platform on Renewable Heating and Cooling board. From 2006–2010 he acted as leader of the IEA SHC Task 39 Subtask B “Collectors”.
List of Contributors
Stephan Bachmann
University of Stuttgart
Institute for Thermodynamics and Thermal Engineering (ITW)
Pfaffenwaldring 6
70550 Stuttgart
Germany
Andreas Bohren
University of Applied Sciences Rapperswil HSR
Institute for Solar Technology SPF
Oberseestr. 10
8640 Rapperswil
Switzerland
Jay Burch
1617 Cole Blvd.
MS 52/2
Golden, CO 80401
USA
Stefan Brunold
University of Applied Sciences Rapperswil HSR
Institute for Solar Technology SPF
Oberseestr. 10
8640 Rapperswil
Switzerland
Jane H. Davidson
University of Minnesota
Department of Mechanical Engineering
111 Church Street SE
Minneapolis, MN 55455
USA
Harald Drück
University of StuttgartInstitute for Thermodynamics and Thermal Engineering (ITW)
Pfaffenwaldring 6
70550 Stuttgart
Germany
Ulrich Endemann
BASF – The Chemical Company
Segment Management Universal
BASF SE, E-KTE/IU-F 206
67056 Ludwigshafen
Germany
Stephan Fischer
University of Stuttgart
Institute for Thermodynamics and Thermal Engineering (ITW)
Pfaffenwaldring 6
70550 Stuttgart
Germany
Robert Hausner
AEE-Institute for Sustainable
Technologies
Feldgasse 19
8200 Gleisdorf
Austria
Steffen Jack
Bäckerstr. 50
31785 Hameln
Germany
Ivan Jerman
National Institute of Chemistry
L02 Laboratory for the Spectroscopy of Materials
Hajdrihova 19
1000 Ljubljana
Slovenia
Suanne Kahlen
Polymer Competence Center Leoben
GmbH Roseggerstr. 12
8700 Leoben
Austria
and
Borealis Polyolefine GmbH
St. Peter-Str. 25
4021 Linz
Austria
Matjaž Koželj
National Institute of Chemistry
L02 Laboratory for the Spectroscopy of Materials
Hajdrihova 19
1000 Ljubljana
Slovenia
Roman Kunic
Faculty of Civil and Geodetic
Engineering
Jamova 2
1000 Ljubljana
Slovenia
Reinhold W. Lang
Johannes Kepler University
Institute of Polymeric Materials and Testing
Altenberger Str. 69
4040 Linz
Austria
Andreas Mägerlein
BASF – The Chemical Company
Segment Management Universal
BASF SE, E-KTE/IU-F 206
67056 Ludwigshafen
Germany
Susan C. Mantell
University of Minnesota
Department of Mechanical Engineering
111 Church Street SE
Minneapolis, MN 55455
USA
Michaela Meir
University of Oslo
Department of Physics
Post Box 1048 Blindern
0316 Oslo
Norway
Axel Müller
HTCO GmbH
Rabenkopfstraße 4
79102 Freiburg i.Br.
Germany
Maria Christina Munari Probst
Ecole Polytechnique Federale de Lausanne
LE 0 04 (Building LE)
Station 18
1015 Lausanne
Switzerland
Fabian Ochs
University of Stuttgart
Institute for Thermodynamics and Thermal Engineering (ITW)
Pfaffenwaldring 6
70550 Stuttgart
Germany
Boris Orel
National Institute of Chemistry
L02 Laboratory for the Spectroscopy of Materials
Hajdrihova 19
1000 Ljubljana
Slovenia
Philippe Papillon
Institut National de l'Energie Solaire
Commissariat à l'Energie Atomique et aux Energies Alternatives
50 avenue du Lac Leman
73377 Le Bourget du Lac
France
Markus Peter
dp2 – Intelligent use of Energy
Mengeweg 2
59494 Soest
Germany
Lidija Slemenik Perše
National Institute of Chemistry
L02 Laboratory for the Spectroscopy of Materials
Hajdrihova 19
1000 Ljubljana
Slovenia
Micha Plaschkes
MAGEN-ECOENERGY
Product and Process Development
Kibutz Magen-85465
Israel
Christoph Reiter
Ingolstadt University of Applied Sciences
Esplanade 10
85049 Ingolstadt
Germany
John Rekstad
University of Oslo
Department of Physics
Post Box 1048 Blindern
0316 Oslo
Norway
Katharina Resch
University of Leoben
Institute of Materials Science and Testing of Plastics
Otto-Glöckel-Str. 2
8700 Leoben
Austria
Florian Ruesch
University of Applied Sciences Rapperswil HSR
Institute for Solar Technology SPF
Oberseestr. 10
8640 Rapperswil
Switzerland
Sandrin Saile
Fraunhofer Institute for Solar Energy Systems ISE
Department Weathering and Reliability
Heidenhofstr. 2
79110 Freiburg
Germany
Karl Schnetzinger
Advanced Polymer Compounds
Kurzheim 22
8793 Gai
Austria
Ingvild Skjelland
Aventa Solar/Aventa AS
Trondheimsveien 436a
0962 Oslo
Norway
Elke Streicher
University of Stuttgart
Institute for Thermodynamics and Thermal Engineering (ITW)
Pfaffenwaldring 6
70550 Stuttgart
Germany
Beate Traub
University of Stuttgart
Institute for Thermodynamics and Thermal Engineering (ITW)
Pfaffenwaldring 6
70550 Stuttgart
Germany
Christoph Trinkl
Ingolstadt University of Applied Sciences
Esplanade 10
85049 Ingolstadt
Germany
Jens Ullmann
Institute for Thermodynamics and Thermal Engineering (ITW)
Pfaffenwaldring 6
70550 Stuttgart
Germany
Helmut Vogel
University of Osnabrück
Albrechstr. 30
49076 Osnabrück
Germany
Gernot M. Wallner
Johannes Kepler University
Institute of Polymeric Materials and Testing
Altenberger Str. 69
4040 Linz
Austria
Karl-Anders Weiß
Fraunhofer Institute for Solar Energy Systems ISE
Department Weathering and Reliability
Heidenhofstr. 2
79110 Freiburg
Germany
Claudius Wilhelms
University of Kassel
Kurt-Wolters-Str. 69
34125 Kassel
Germany
Christoph Zauner
AIT Austrian Institute of Technology
Giefinggasse 2
1210 Vienna
Austria
Christoph Zimmermann
Institute for Thermodynamics and Thermal Engineering (ITW)
Pfaffenwaldring 6
70550 Stuttgart
Germany
Wilfried Zörner
Ingolstadt University of Applied Sciences
Esplanade 10
85049 Ingolstadt
Germany
IEA Solar Heating and Cooling Programme
The Solar Heating and Cooling Programme was founded in 1977 as one of the first multilateral technology initiatives (“Implementing Agreements”) of the International Energy Agency. Its mission is to “advance international collaborative efforts for solar energy to reach the goal set in the vision of contributing 50% of the low temperature heating and cooling demand by 2030.”
The member countries of the Programme collaborate on projects (referred to as “Tasks”) in the field of research, development, demonstration (RD&D), and test methods for solar thermal energy and solar buildings.
A total of 47 such projects have been initiated to date, 38 of which have been completed. Research topics include:
solar space heating (Tasks 19, 26, 44),solar heat for industrial or agricultural processes (Tasks 29, 33, 34, 49),solar district heating (Tasks 7, 45),solar cooling (Tasks 25, 38, 48),solar buildings/architecture (Tasks 11, 13, 20, 21, 22, 23, 28, 31, 37, 41, 47),materials/components for solar heating and cooling (Tasks 10, 18, 27, 32, 39, 42),standards, certification & test methods (Tasks 14, 34, 43),resource assessment (Tasks 17, 36),storage of solar heat (Tasks 7, 42).In addition to the project work, several special activities – Memorandum of Understanding with solar thermal trade organizations, statistics collection and analysis, conferences and workshops – have been undertaken. An annual international conference on Solar Heating and Cooling for Buildings and Industry was launched in 2012. The first of these conferences, SHC2012, was held in San Francisco.
Current members of the IEA SHC are:
AustraliaFinlandSingaporeAustriaFranceSouth AfricaBelgiumItalypainCanadaMexicoSwedenDenmarkNetherlandswitzerlandEuropean CommissionNorwayUnited StatesGermanyPortugalFurther information:
For up to date information on the IEA SHC work, including many free publications, please visit the web site www.iea-shc.org
Acknowledgments
The process of compiling this handbook was a collaborative effort involving the experience and expertise of many people. While the handbook consists of separate chapters with individual authors responsible for their own contents, it is also the product of a progressive development process to which all participating Task 39 experts (see, for example, http://www.iea-shc.org/about/members/task.aspx?Task=39) contributed either during discussions in experts meetings or by sharing their experience and the results of numerous funded research projects.
As it is not possible to thank all of the many people involved, we hereby acknowledge the essential support from funding agencies and the industry as a whole. Furthermore, we thank the Task 39 experts for their active and inspiring work – their contributions greatly added to the vivid and dynamic nature of Task 39 and naturally also to the contents of this book.
As is the case with every publication, the final result would have not been feasible without the help of a great number of people working hard behind the scenes. We would like to take this opportunity to acknowledge their passion and endurance, which have allowed the project to come to fruition. The editors and authors are very grateful to Bente Flier, Lesley Belfit, Dr. Frank Weinreich, and the rest of the Wiley-VCH team for their patient and constructive support throughout the project as well as to Sarah Greuter and Raphael Präg for their tireless assistance in preparing the manuscript.
Michael Köhl, Freiburg, GermanySandrin Saile, Freiburg, GermanyMichaela Meir, Oslo, NorwayPhilippe Papillon, Chambery, FranceGernot M. Wallner, Linz, Austria
Part I
1
Principles
Markus Peter
1.1 Introduction
Apart from fossil and nuclear energy sources, so-called renewable energy is available. The already located and predicted resources of fossil fuels and fissile materials evidently underline that in a limited system like the earth only renewable energy can assure a long-lasting existence. Three categories of renewable energies, based on different primary sources, are available:
solar energy: thermonuclear (fusion) processes in the sun;geothermal energy: residual heat from the genesis of earth and decay of isotopes inside the earth;tidal energy: gravity caused by planetary (orbs) motion.Within the ability and experience of humankind only these energy sources are inexhaustible.
Renewable energy like heat in the upper lithosphere or wind is a mixture of two or more primary sources. In the case of heat in the upper lithosphere geothermal and solar energy are relevant, for wind the rotation of earth, planetary motion, and solar irradiance are important.
The largest flux of energy available on earth is solar irradiation. The total power emitted by the sun is approximately 380 × 1018 MW. This corresponds to 62.6 MW m−2 related to a surface calculated from the diameter of the sun. Even sources with high capacity too, the potential of geothermal and tidal energy are orders of magnitude smaller than that of solar irradiation.1
The energy emitted by the sun results from different fusion processes (mainly the fusion of 4H+ to 1He). Owing to the distance between the sun and earth (approximately 1.5 × 108 km) the electromagnetic radiation arrives at the outer atmosphere highly diluted, with a power density of approximately 1367 W m−2. This so-called solar constant, measured outside the atmosphere, has a fluctuation range of about ±3.5% that is mainly caused by the variation of the distance between the sun and the earth, sun activity, and sunspots (Figure 1.1).
Figure 1.1 Geometrical proportions between the sun and the earth.
The fraction of energy reaching the earth is only 0.045 · 10−6% of the amount emitted by the sun. Related to this the actual worldwide primary energy consumption is less than 0.01%.
Outside the atmosphere electromagnetic radiation from the sun consists of wavelengths in a range 10−20 to 104 m. However, solar radiation is mainly emitted in wavelengths between 0.2 and 5 µm. Approximately 90% of the radiation is emitted with wavelengths between 0.3 and 1.5 µm, reaching from the near UV-B to UV-A, visible light, and near-infrared. The sun radiates similarly to a black body with a temperature of approximately 5800 K. For most of the radiation the atmosphere is practically opaque; however, an optical window that is transparent for wavelengths in the range 0.29–5 µm enables radiation with a total power of approximately 1000 W m−2 to pass. While even further diluted while passing through the atmosphere, the aforesaid optical window enables more than 90% of visible light within the solar spectrum to reach earth's surface. In the range 0.38–0.78 µm visible light represents almost 50% of the transmitted energy. This range is most important for the biosphere and also for technical use.
Figure 1.2 gives the spectral distribution of solar radiation outside the atmosphere. The range shown contains approximately 95% of the radiation power of the solar spectrum.
Figure 1.2 Spectral distribution of solar radiation outside the atmosphere.
Extraterrestrial solar radiation (outside the atmosphere) is the sole direct radiation coming from the direction of the sun. Direct solar radiation is characterized by the capability to cause shadow and the possibility to be concentrated. On entering the atmosphere, part of this direct radiation is reflected (scattered) or absorbed by aerosols, dust, and diverse molecules (e.g., H2O and O3). The measure of extinction within the atmosphere depends on the amount and kinds of particles and the length of the path. In this respect and for calculating of the solar irradiation that is available on earth, the so-called air mass is an important figure. For solar radiation with perpendicular (normal) incidence an air mass of 1 is defined. An air mass of 1.5 corresponds to an incidence angle, θZenith of 48.19 ° (Figure 1.3).
Figure 1.3 Path of solar radiation through the atmosphere.
The scattered part of the direct radiation becomes diffuse radiation. Different to direct radiation, diffuse radiation (idealised) has no defined direction and for this reason is not capable of causing shadow and cannot be concentrated.
The total irradiance that is available on earth is given by:
(1.1)
where
The ratio between the radiation that is reflected to outer space by the atmosphere or after striking earth's surface and the radiation reaching the atmosphere is called albedo. The albedo ranges from less than 10% for forest areas to approximately 90% for fresh snow. Mainly depending on properties of the atmosphere and changes of earth's surface (e.g., ice/snow), the average albedo is around 30%. Besides the different amounts of solar energy reaching the diverse areas of the globe, particularly high values of the albedo in the Arctic and Antarctic regions are driving forces of the climate. Changes of the albedo, for example, due to melting of ice or snow, seem to cause significant climatic changes.
1.2 Solar Irradiance in Technical Applications
The energy emitted by the sun introduces different forms of appearance of solar energy on earth. Evaporation, rainfall, and melting of ice, ocean current and waves, movements and heating of the atmosphere and earth's surface, as well as the production of biomass are typical forms where solar energy appears, often indirectly. Photovoltaics and solar thermal systems represent almost direct ways of using solar irradiance by involving technical equipment. While photovoltaic is the direct conversion of sunlight into electricity, the thermal utilization of solar energy is versatile and characterized by numerous different applications. Solar thermal systems are applicable even where heat up to several hundreds degree centigrade is needed, for instance in industrial processes. Compared to photovoltaics, thermal applications often show advantages in efficiency and the comparatively simple feasibility of storage, even on large scales.
As described above, the fraction of extraterrestrial radiation hitting earth's surface, and hence technical equipment for using solar irradiance, depends on the air mass, that is, on the length of the optical path through the atmosphere in combination with the cloudiness and haze. After passing through the atmosphere the available irradiance consists of a direct and a diffuse part. In general, technical applications might use both direct and diffuse irradiance. In particular constructions, such as concentrating collectors or facilities with heliostats and central receivers, only direct irradiance can be utilized.
1.3 Quantifying Useful Solar Irradiation
For solar thermal applications and photovoltaic systems, but also with regard to passive use of sunlight in buildings, the amount of irradiation on surfaces with different orientations can be calculated. With respect to detailed performance predictions, particularly for solar thermal systems, the fractions of direct and diffuse irradiance on any surface have to be determined separately. As discussed, in the case of concentrating systems, knowledge of the direct irradiation is most important.
For direct irradiation, equations mainly referring to geometrical relations are available. For diffuse irradiation, geometric basics have been combined with correlations and models derived from empirical investigations and findings. In general the solar irradiance available on a horizontal surface ranges from around 100 W m−2 for a totally dull sky with only diffuse sunlight to more than 1000 W m−2 under clear sky conditions. Between these values the available amount of irradiance depends on the position of the sun in the sky, the cloudiness, and extinction processes within the atmosphere. In Central Europe, during a year roughly half of the irradiation is direct while the other half is diffuse irradiation. During winter the fraction of diffuse irradiance might reach 70%; however, approximately 75% of the irradiation reaches Central Europe between April and September. The amount of solar irradiation on one square meter horizontal surface per year is approximately 900 kWh in Northern Europe, around 1100 kWh in Central, and about 1400 kWh in Southern Europe. Within the sunbelt of the globe the yearly solar irradiation may exceed 2200 kWh m−2. Notably, independent of the location or time within the year the irradiance perpendicular (normal) to a surface might exceed 1000 W m−2. This is valid for all areas of the globe, whether having lavish sunshine like Africa or lower irradiation like regions at higher latitudes, for example, in Central or Northern Europe. Evidently, the differences in annual irradiation on a horizontal surface in various regions are caused mainly by the angle of incidence at the locations, the hours of sunshine, and the fraction of diffuse irradiance.
As the availability of solar irradiation on the globe is different between regions, the average ambient temperature differs as well. A rough classification reveals a correlation between regions with high solar irradiation and high ambient temperatures and regions with lower solar irradiation and lower ambient temperatures. Nevertheless, exceptions in both directions are common. For example, according to Meteonorm 5.1, with approximately 3.3 °C the average ambient temperature of Davos in Switzerland is quite low, while the irradiation on a horizontal surface reaches 1380 kWh m−2 h−1 – a fairly high value – for Central Europe.2
With respect to solar thermal collectors, as well as the irradiance the ambient temperature, inducing heat losses, is an important parameter.
1.4 Solar Thermal Applications
In combination with solar thermal systems the available amount of solar irradiation enables an economic use of solar energy and significant savings of conventional energy sources. In particular in a temperature range below 130 °C, which is the main focus for solar collectors equipped with polymers, space heating, domestic hot water preparation, and approximately 50% of the heat that is demanded by industry can be supported.
However, solar thermal systems are used over a much wider temperature range. On the basis of different operating temperatures in IEA-SHC Task 33, Solar Heat for Industrial Processes (http://www.iea-shc.org/task33/), three different fields of thermal applications for solar energy have been defined (Figure 1.4):
Figure 1.4 Global solar irradiation on a horizontal surface in Central Europe and differentheat demands in households and industry in schematic manner.
Low temperature, below 20 up to 250 °C:
pool heating,domestic hot water,space heating and cooling,solar drying, distillation, pasteurization, sterilization (e.g., of potable water),food, paper, textile, and chemical industry.Medium temperature, 250–400 °C:
solar cooling and air conditioning,process heat in various industry sectors,power stations for electricity generation,petroleum industry and heat treatment of metals.High temperature, from 400 up to approximately 1700 °C:
heat treatment of metals, metallurgy,process heat for cement, glass, and refractory industry,power stations for electricity generation, for example, tower concepts.In all solar thermal applications solar irradiance is absorbed and converted into thermal energy. With respect to the particular ways of utilizing solar irradiance, passive and active use can be distinguished. A typical example for passive use is heating of buildings with solar irradiance entering the house through windows. This well-known kind of solar heating is particularly effective if the windows are equipped with glass. As glass is much more transparent to visible light and other high-energy wavelengths emitted by the sun, than for infrared radiation emitted by the floor, walls, and furniture in a house that have been heated by absorbing solar irradiance, solar energy is trapped. This so-called greenhouse effect is also present considering the globe, with the earth's surface as absorber and the atmosphere as transparent cover; technically it is applied and optimized in all kinds of solar thermal collectors featuring transparent covers.
From the absorber of a solar collector the heat is in most cases removed through a heat transfer medium, while in a few cases solar irradiance is directly absorbed by the heat transfer fluid. Commonly used fluids for heat transfer in solar heating systems for houses are water or mixtures of water and antifreeze/anticorrosion, in particular applications air or specific oils are employed. On leaving the collector, the heat is either transferred directly to the consumer and consuming devices, such as radiators or floor heating, or it is transferred to a heat store. Heat stores are introduced to decouple the supply of energy from the sun and other heat sources from the demands. Heat stores enable a level, high availability of energy at times without equal demand and vice versa; furthermore, they can supply energy with a power exceeding that of the original energy source. The capacity of heat stores range from several hours up to some days or a few weeks. In the case of pool heating, the pool water is a store with high capacity. A particular approach is the construction of seasonal stores designed to keep solar heat from summer for space heating and domestic hot water preparation during winter.
In some industrial applications and in the case of floor or wall heating an instantaneous supply of heat directly from a solar thermal system to the consumer might be possible.
In most applications the connection between the collector and the store or directly to the consumer is made by insulated pipes – in the case of air as heat transfer medium in the form of air ducts. Unless the motion of the heat transfer fluid is caused by gravity, introduced by differences in the density of the fluid between the collector and the store or consumer due to temperature differences, a circulation pump (or fan) has to be present in the collector loop.3 A controller determines the starting and stopping of this device as well as other temperature or time dependent operations. Thus, apart from the collector and the store the controller is another important component of many solar heating systems.
In cases where the amount of solar energy is not sufficient, auxiliary heating might be installed.
1.5 Calculating the Solar Contribution
The amount of heat delivered by a solar heating system can either be measured or calculated. Measurements are common for billing, system investigation and optimization, and, furthermore, for trouble-shooting in exiting set-ups. Calculation and numerical simulation of solar thermal systems are helpful to support general decisions during planning and design and in general cases of building and (re)construction.
Besides calculation “by hand”, personal computers with simple spreadsheet programs and programs for numerical system simulation are available. Owing to interactions of the components in solar heating systems and the dependency of system performance on different transient parameters, for example, weather conditions and loads, the applicability of static calculations is limited. For several decades numerical simulation has been a well-established method that can take various system designs, load structures, and climatic conditions into account.
In cases where solar energy is not the only source supplying heat, the fraction of energy delivered by the sun and the amount of energy delivered by other sources are of interest. To define the fraction of energy delivered by the solar part of a heating system and thus, for example, the savings of conventional energy, depending on varying system designs, different methods are proposed. As a general and simple approach, universal for all kinds of solar heating systems, the fraction of energy delivered by the solar part, fsol can be calculated as:
(1.2)
where
In many cases Qaux is the auxiliary heat delivered to the system if the solar contribution is not sufficient.
In this definition the kind of auxiliary heating and its individual performance are included and not taken into account separately. The solar fraction fsol typically accounts for net energy and allows a rough and easy understandable calculation of the solar contribution. In the literature, other performance indicators are defined, such as the fractional energy savings fsav. Particularly for solar heating systems for houses, detailed information is given in the results of IEA-SHC Task 26.
1.6 Conclusions
The energy content of solar irradiation that is available on earth is several orders of magnitude larger than world's energy consumption of today. Even in countries not situated in the sunbelt of the globe, the most of the needed energy can be provided by solar irradiance using available techniques.
With respect to Europe almost half of the final energy consumption is connected to the production of heat, the major part for heating of buildings. In the European Union currently approximately 75% of energy consumption in buildings is related to space heating and the preparation of domestic hot water. Besides the housing sector, considering industry within Europe, approximately of energy consumption is in the form of heat. About 30% of this heat is used at temperatures below 100 °C – which is easy to provide with solar thermal systems.
Notes
1. Solar energy approximately 5.6 × 106 EJ a−1; geothermal energy approximately 9.7 × 102 EJ a−1; tidal energy approximately 9.4 × 101 EJ a−1.
2. Meteonorm is a global meteorological database for applied climatology, developed by Meteotest in Bern, Switzerland (http://meteonorm.com/).
3. Circulation caused by gravity (thermosiphon effect) can only be achieved in cases where the store or the consumer is located above the collector. Today, for most technical applications in Central or Northern Europe the opposite is the case.
2
Solar Thermal Market
Karl-Anders Weiß, Christoph Zauner, Jay Burch, and Sandrin Saile
2.1 Introduction
The international solar thermal market has shown strong development over the last years. Especially in China, the United States, and Europe the manufacturing and commissioning of solar thermal systems has grown rapidly. According to Sarasin 2011 there are currently 70 million households with a solar hot water supply and current market forecasts suggest that there will be a considerate number of additional systems in the years to come.1 Despite this overall positive development a glance at the global distribution of solar thermal systems shows that their market penetration is inhomogeneous as it varies not only with ecological awareness but also due to climatic and political conditions, which appear to be even more powerful in shaping the solar thermal landscape. The aim of the European Union to reach 20% renewable energies by 2020, for example, goes hand in hand with consumers' attentiveness towards the expected price increase for fossil fuels and has already shown a range of positive effects. Whereas some countries have readily jumped on the environmental bandwagon, others put less effort into paving the way for renewable heat with the result being a low or non-existent solar thermal involvement.
Thus, one can see that the potential to increase solar thermal on a worldwide scale is there; the only question is how this may be accomplished. Next to awareness raising activities on political and personal grounds, cost reduction and scale effects are one possible path to pursue. Current technology for solar thermal systems is based primary upon metals and glass, with associated processing methods and costs. The costs of these conventional systems are not likely to be reduced significantly in the future, as the current technology has nearly exhausted the most promising routes to cost reduction. Considering the spectrum of reasonable alternatives, polymer technology is a promising path to radical cost reduction for solar thermal systems [2]. Plastics offer a wide range of adaptable features, highly automated manufacturing can be very inexpensive, and innovative processing can produce multiple integrated features in a single step. Previous results in solar thermal and in analogous cost/weight reduction in other areas indicate that this promise might be achievable, leading potentially to a new low-cost market niche for solar thermal systems [3] and multi-functional collectors with additional use, e.g. for the building technology. To provide a basis for subsequent discussion of the potential of polymers for solar thermal systems, the next sections give an overview of the most important collector types, their regional distribution, and discuss possible future market trends.
2.2 Collector Types
Each object that converts solar radiation into heat can be considered a solar thermal collector. As such, the earth itself or even human beings are prominent examples.
In a more technical sense, however, a solar thermal collector is a device that converts incoming radiation into some technically useful form of heat such as, for example, a warm fluid.
A very simple realization of this principle is a garden hose. A clever combination of several such hoses can already be viewed as a simple unglazed collector. Minimizing convection losses leads directly to glazed collectors (flat plate collectors, tube collectors) of various types and further improvement can be achieved by using mirrors to concentrate the solar radiation. In such a way, it is possible to reach temperatures up to some 3500 °C in a so-called solar furnace.
One way of measuring the performance of a collector is by comparing the heat, Q, actually produced with the total incident solar energy, G. The collector efficiency η is given by:
(2.1)
The warmer the collector is compared to the environment, the more heat losses occur. Thus, the efficiency depends on the operating temperature of the system (Figure 2.1).
Figure 2.1 Efficiency of various collector types and their usual application. Source: Austrian Institute of Technology.
The following subsections give a concise overview of the main types of collectors. More detailed and comprehensive descriptions can be found in various books and reports, such as References [4–7].
2.2.1 Unglazed Collectors
Especially when the operating temperatures are low (up to a few degrees above ambient temperature, see Figure 2.1), such as for swimming pool heating, one is often well off using an unglazed collector. These black pipes or mats are most commonly made of plastics (mostly EPDM, but also PE and PP), offer a reasonable performance, and make up a reasonable share of the total solar thermal energy yield.
2.2.2 Flat Plate Collectors (FPC)
A flat plate collector (FPC) consists of a frame construction (wood, metal, polymers) and a transparent cover (glass, polymer) that houses the main collector parts (Figure 2.2). Usually, a layer of thermal insulation (mineral wool, foam) is placed at the backside and/or laterally. Atop of this insulation resides the main functional part of the device, the absorber, which converts the incoming solar radiation into heat. In conventional collectors this absorber consists of a (spectral selectively) coated metal sheet (copper, aluminium), which is connected (e.g., welded, pressed) to a network of pipes filled with a certain heat transfer medium (e.g., water, water/glycol mixture).
Figure 2.2 Scheme of a flat plate collector. Source: Austrian Institute of Technology.
In this way, it is possible to convert solar radiation into a form of energy that can subsequently be used for domestic hot water preparation, space heating, solar cooling, process heat, and so on.
The main heat losses in a flat plate collector occur through the front cover via thermal radiation, convection, and conduction. The first of these can be reduced by using so-called selectively coated absorbers that emit only approximately 5% in the relevant spectral region (near-IR, mid-IR), while convection may be almost eliminated by evacuating the collector. Chapter 4 gives a more detailed description of FPCs.
2.2.3 Evacuated Flat Plate Collector (EFPC)
In evacuated flat plate collectors it is desirable to reduce the internal pressure to less than 1 kPa, which minimizes convective losses.
To sustain the structural integrity and the vacuum for an operational period as long as 20 years, sophisticated technical solutions are needed. Especially critical issues are out-gassing materials, vacuum-sealed fittings, and structure-stabilizing elements.
There have also been several attempts to use inert gases (Ar, Kr) instead of air. Owing to their specific physical properties (different atomic mass and size lead to different mean free paths, viscosities, and thus conductive and convective heat transfer coefficients), this route provides another way to improve collector efficiency.
2.2.4 Evacuated Tube Collectors (ETC)
A different realization of evacuated collectors applies the principle of “thermo flasks:” in evacuated tube collectors, the header pipe is connected to evacuated (<1 kPa) glass-tubes housing the absorber-unit. One can classify ETCs (evacuated tube collectors) into two main types: direct flow tubes and heat pipe tubes (Figure 2.3).
Figure 2.3 Scheme of a heat pipe collector. Source: Austrian Institute of Technology.
In the former, the fluid of the solar loop is directly circulated through the piping of the absorber, which is embedded in an evacuated glass tube. The latter concept utilizes solar energy by evaporating a certain fluid mixture (water, alcohol) that rises to a heat exchanger attached to the collection tube. At that condenser the solar fluid is heated while the fluid mixture inside the tube liquefies.
2.2.5 Concentrating Collectors
By focussing the incoming solar radiation one can achieve higher energy densities that allow for higher collector fluid temperatures. Furthermore, in such a concentrating system (scheme is depicted in Figure 2.4), the total area of hot surfaces (absorber) is decreased compared to conventional FPCs, thereby minimizing energy losses.
Figure 2.4 Scheme of a concentrating collector. Source: Austrian Institute of Technology.
Various forms of concentrating collectors are available or under development: parabolic trough collectors, concentrating linear Fresnel collectors, solar dishes, and compound parabolic concentrators (for a detailed description see Reference [1]). In 2010, various large-scale installations of such systems were either already installed or under development (for a list of solar thermal power stations, for example, see Reference [7]).
2.2.6 Air Collectors
In most FPCs water or water/glycol mixtures are used as heat transfer medium. Nevertheless, air is a viable fluid for certain applications, too (e.g., drying, but also air conditioning).
Advantages of solar air collectors are, for example, leakages are less harmful, air cannot boil or freeze [although condensation may cause problems (cf. hygienic issues)]. Owing to the lower heat capacity of air (1 J g−1 K−1 at T = 20 °C), larger fluid-volumes are needed, which requires special collector and system design (Figure 2.5) [8].
Figure 2.5 Air collector scheme. Source: Austrian Institute of Technology.
2.2.7 Market Share of Different Collector Types
Evacuated tube collectors dominate the worldwide market (Figure 2.6) with a share of about 56%, followed by flat plate collectors, which account for about of the market. The share of unglazed collectors is about 11% while air collectors are in the range of 1%. The domination of ETCs is due to the big Chinese market while unglazed collectors dominate the Australian and US market and flat plate collectors are mainly installed in Europe and the rest of the world. A worldwide reduction of the number of different collector types on a short or medium time scale does not seem to be realistic due to the different systems of hot water preparation and technological conditions.
Figure 2.6 Distribution of the worldwide capacity in operation by collector type for 2009 [9].
2.3 Regional Markets
As the previous subsections show, the types of collectors produced and put into service vary decisively and are heavily dependent on the regional and economic conditions of the respective areas they are put into operation. The inhomogeneity of collector types and regional markets can be seen in Figure 2.7, which shows the total capacity of water collectors in ten leading countries towards the end of 2009. Figure 2.8 provides information about the percentage share of the different regional markets.
Figure 2.7 Total capacity of water collectors in operation in ten leading countries at the end of 2009 [9].
Figure 2.8 Share of total collector installations (glazed and unglazed water and air collectors) by economic region at the end of 2009 [9].
China, with a total capacity of about 101 000 MWth (58.9%), dominates the solar thermal market. Other than in the USA or most European countries, evacuated tube collectors make up the largest proportion of the total capacity, followed by glazed collectors with a capacity of about 7100 MWth.
Whereas China thus shows an immense market volume of collector types that are hardly represented in other leading markets, the US American market is dominated by a type that does not play a role in China's solar thermal market at all. Here, about 12.100 MWth unglazed pool collectors were in operation in 2009, a capacity in the face of which the comparatively small amount of glazed and evacuated tube collectors hardly carries any weight. The similar distribution of Australia can be explained by partly comparable climate zones and a similar demographic structure.
In Europe, the share of unglazed collectors can hardly be compared to their domination in the Anglophone regions. Whilst Germany and Austria are the only countries where unglazed and evacuated tube collectors play a role, a larger part is made up of flat plate collectors for domestic hot water preparation or combisystems (Chapter 3).
Considering the total capacities of the biggest solar thermal markets, a closer look at the distribution per inhabitant (Figure 2.9) reveals astonishing results. In 2009, it was Cyprus, Israel, and Barbados that showed the highest total installed capacity per head. With roughly 554 000 (Cyprus), 391 000 (Israel) and 323 900 (Barbados) kWth per 1000 inhabitants these three countries, which are not even counted among the world's top ten, turn out to be frontrunners when it comes to a comparison of the markets per capita.
Figure 2.9 Total capacity of glazed flat-plate and evacuated tube collectors in operation at the end of 2009 in kWth per 1000 inhabitants [9].
Especially with regard to this parameter Austria is a very promising example, too. This small country in the middle of Europe not only manages to outdo its next-door neighbor Germany but also the solar thermal market's leading nations USA, China, and Australia. With a total capacity of about 315 000 kWth/1000 inhabitants Austria ranks fourth and shows that solar thermal energy has very big potential, even in mid-European countries with a relatively low yearly insolation.
The comparison of Cyprus, Israel, Barbados, and Austria with other countries of similar climatic and economic conditions shows enormous differences in the total capacity per capita around the globe but also illustrates the considerable potential of solar thermal energy in general (Figure 2.9). The differences can be explained by different socio-political factors that have the power to either boost or inhibit the market penetration of solar thermal systems decisively.
Political awareness and readiness to support solar thermal is one of the key catalysts for the rise and fall of the market and will probably also be in the long run. Two extreme cases where the funding/market relation becomes very apparent are illustrated in Figure 2.10, which focuses on the overall development of the installed capacity between 1974 and 2010 in the USA. Highlighting the removal of incentives in 1984, it shows that radical cuts not only marginally weaken production and installation in the following year but may also lead to a complete collapse of the market.
Figure 2.10 Collector sales in the USA in the period 1974–2010. The market collapsed after incentives were removed. There was a modest market recovery when a 30% federal rebate began in 2006. Source: Solar Energy Industries Federation SEIA.
Likewise, political measures in favor of solar thermal energy might have the exact opposite effect. In the case of Austria, for example, the notably large number of installations per capita has been brought about by an immense range of awareness-raising activities on the part of media and politics (see, for example, initiatives like the klima aktiv-Programm http://www.klimaaktiv.at), funding and other market incentive programmes, developments and investments in R&D, the foundation of lobbies and organizations (e.g., ASTTP, European RHC platform, ESTIF), the introduction of certification councils and institutes (EN 12975, DIN-CERTCO, “Solar Keymark-Label”) on national and international level, or enhanced training and education measures in the industrial sector.
2.4 Market Trends
The annually installed capacity of flat plate and evacuated tube collectors around the world has shown continuous growth over recent years, with an increasing growth rate (Figure 2.11). Again, Asia seems to be the driving force behind the rapid development of the global solar thermal market, and yet not all countries show a similar development. As can be derived from Figure 2.11 significant differences between the major markets are also seen in terms of the annual installation of solar thermal systems. While the European market is fluctuating – some years even showing decreasing installation rates – China and Taiwan almost managed to double their overall capacity each year in the last decade. Interestingly, neither Australia nor the USA show comparable development rates up to now, even though their climates are very suitable for the use of solar thermal energy systems. Regarding examples like Austria or Cyprus, there is still an enormous potential for considerable growth rates in most regions all over the world.
Figure 2.11 Annually worldwide installed capacity of flat plate and evacuated tube collectors 2000--2009 [9].
2.4.1 Global Market Development
Despite the generally positive development on a global scale, experience has shown that the national solar thermal markets are far from stable. According to Sarasin 2009 and 2010 the comparative growth rates of 2007, for instance, differ greatly from those of 2008. Whereas Australia and New Zealand grew strongly in 2007 with a rate of about 40% and Europe (−9%) had to face a negative development, the negative trend for Europe was radically reversed in the following year. In 2008, a growth rate of about 60% (compared to 50% in the USA and 41% in China) turned losers into leaders and made Europe a frontrunner in the solar thermal business. Catalyzed by a generally affirmative global average growth of 40% it seemed that the European solar thermal market would remain a major player, on top of the list. And yet, though the global installations continued to grow in 2009, now reaching about 34 GWth (+23%), the regional markets of 2009 showed entirely different developments once more. While Australia/New Zealand (+50%), Africa (+43%), and China (+29%) displayed a thoroughly positive development, Europe (−10%) and USA/Canada (−15%) declined once again [10–12].
The figures for 2010, then, appear to be fairly moderate in contrast. A slow growth continued to stabilize leading markets such as China (+17%) and the USA (+5%). Other players remained in low regions, noting negative growth rates of −29% (Germany), −23% (Australia), −21% (Austria), or −3% (Israel). The market fluctuation in the world's leading markets can be derived from Figure 2.12. Figure 2.13 shows a more detailed depiction of the European development, that is, a comparison between Austria and Germany [1].
Figure 2.12 Annual growth rates of the world's leading markets between 2002 and 2010. Figure: Fraunhofer ISE; data derived from Fawer et al. [11–18].
Figure 2.13 Annual growth rates of Austria and Germany between 2002 and 2010 with two radical crashes in 2007 and 2009 in Germany. Figure: Fraunhofer ISE; data derived from Fawer et al. [11–18].
2.4.2 Global Market Forecast
For the global market, few data is available but Sarasin 2011 expects an average growth rate of approximately 12% per annum until 2020, and also for the time beyond 2020 a stable market growth is expected, in which case the global market would reach 186 GWth of newly installed collectors in 2020. Especially, the sunbelt regions of the USA and Asia, Southern Europe, Australia, Brazil, Mexico, and South Africa are expected to contribute strongly to long-term global growth. For the markets with a high penetration of solar thermal systems, experts expect decreasing annual growth rates after 2020 due to the large market volume in these countries at that time [1].
Along with the expected global growth over the next decades, the shares of the different collector technologies are likely to change. Technical developments, such as the ongoing research on polymer based collectors, for example, might contribute to these shifts. Additionally, it must be assumed that the demand for high-quality solar thermal systems is going to increase rapidly. Especially, newly industrialized countries such as China and India are in need of a continuous and reliable hot water supply, meaning that high-efficiency solar thermal systems are required.
2.4.3 Focus on Europe
While the predictions give us an idea about possible future developments, it is important to note that they are based on rough estimates that include past developments and simultaneously take into account political conditions. Since these are hard to predict, most studies providing European market forecasts use different scenarios.
The pessimistic scenario, for instance, anticipates “business as usual,” which means no further political support or incentives. For this scenario the European Solar Thermal Industry Federation (ESTIF) expects a total installation of approximately 500 GWth until 2050 [17]. For an optimistic scenario, which requires strong support from politics for the market and the R&D in the sector, an additional installation of more than 2.5 TWth up to 2050 is predicted, which corresponds to more than 2.5 billion m2 collector area (Figure 2.14).
Figure 2.14 Total installed capacity 2005–2050 according to three scenarios [18].
Links Providing Updated Market Data and Forecasts
Solar Heating and Cooling Programme SHC of the International Energy Agency IEA: http://www.iea-shc.org/statistics/index.html
European Solar Thermal Industry Federation ESTIF: http://www.estif.org
Global Solar Thermal Energy Council: http://www.solarthermalworld.org/
Note
1. With about 220 GWel/th cumulated capacity towards the end of 2011, solar thermal provides the biggest energy contribution of all solar technologies (compare 60 GWel/th for PV) and ranks second only to wind power (246 GWel/th) [1].
References
1. Fawer, M. and Magyar, B. (2011) Sarasin Solarwirtschaft – Kampf um die Spitzenplätze, Bank Sarasin & Cie AG, Basel.
2. U.S. Department of Energy (March 2006) DOE Solar Energy Program FY 2005 Annual Report. National Renewable Energy Laboratory (NREL). http://www.nrel.gov/csp/troughnet/pdfs/38743.pdf (accessed 24 January 2012).
3. U.S. Department of Energy (May 2009) DOE Solar Energy Technologies Program FY 2008 Annual Report. National Renewable Energy Laboratory (NREL). http://www.nrel.gov/docs/fy09osti/43987.pdf (accessed 24 January 2012).
4. Weiss, W. and Rommel, M. (eds) (2008) Process Heat Collectors: State of the Art within Task 33/IV. Availlable at http://www.iea-shc.org/publications/downloads/task33-Process_Heat_Collectors.pdf (accessed on 21 June 2012).
5. Duffie, J.A. and Beckman, W.A. (2006) Solar Engineering of Thermal Processes, 3rd edn, John Wiley & Sons, Inc., Hoboken.
6. Goswami, D.Y., Kreith, F., and Kreider, J.F. (2000) Principles of Solar Engineering, 2nd edn, Taylor & Francis, Philadelphia.
7. Ramlow, B. and Nusz, B. (2006) Solar Water Heating – A Comprehensive Guide to Solar Water and Space Heating Systems, 1st edn, New Society Publishers, Gabriola Island.
8. Hastings, R.S. (1993) IEA SHC Task 19, Solar Air Systems: Overview. http://www.iea-shc.org/task19/index.html (accessed 17 January 2012).
9. Weiss, W. and Mauthner, F. (2011) Solar Heat Worldwide: Markets and Contribution to the Energy Supply 2009, IEA Solar Heating and Cooling Programme. http://www.iea-shc.org/publications/downloads/Solar_Heat_Worldwide-2011.pdf (accessed 17 January 2012).
10. Fawer, M. and Magyar, B. (2009) Sarasin Solarwirtschaft – Grüne Erholung in Sicht: Technologien, Märkte und Unternehmen im Vergleich, Bank Sarasin & Cie AG, Basel.
11. Fawer, M. and Magyar, B. (2010) Sarasin Solarwirtschaft – unterwegs in neue Dimensionen: Technologien, Märkte und Unternehmen im Vergleich, Bank Sarasin & Cie AG, Basel.
12. Weiss, W. and Mauthner, F. (2010) Solar Heat World Wide: Markets and Contribution to the Energy Supply 2008, IEA Solar Heating and Cooling Programme.
12. Fawer-Wasser, M. and Plinke., E. (2003) Solarenergie – heiter oder bewölkt?, Bank Sarasin & Cie AG, Basel.
14. Fawer-Wasser, M. (2004) Solarenergie – ungetrübter Sonnenschein?, Bank Sarasin & Cie AG, Basel.
15. Fawer, M. (2005) Solarenergie 2005 – Im Spannungsfeld zwischen Rohstoffengpass und Nachfrageboom, Bank Sarasin & Cie AG, Basel.
16. Fawer, M. (2006) Solarenergie 2006 – Licht- und Schattenseiten einer boomenden Industrie, Bank Sarasin & Cie AG, Basel.
17. Fawer, M. (2007) Solarenergie 2007 – Der Höhenflug der Solarindustrie hält an, Bank Sarasin & Cie AG, Basel.
18. Fawer, M. and Magyar, B. (2008) Solarenergie 2008 – Stürmische Zeiten vor dem nächsten Hoch, Bank Sarasin & Cie AG, Basel.
19. Weiss, W. and Biermayr, P. (2009) Potential of Solar Thermal in Europe, European Solar Thermal Industry Federation (ESTIF), Brussels.
3
Thermal Solar Energy for Polymer Experts
Philippe Papillon and Claudius Wilhelms
3.1 Solar Thermal Systems and Technical Requirements
Philippe Papillon and Claudius Wilhelms
Solar thermal energy offers a wide range of applications for heat production. According to these applications, mainly driven by the temperature level required, the technology will differ in order to optimize the useful gains from solar energy, but also to reduce the auxiliary energy consumption.
In the following sections the main solar thermal applications will be first introduced and then the focus will be put on the major components like the solar collector and the thermal storage. Finally, some technical requirements for collectors are expressed.
3.2 Overview of Solar Thermal Applications
Philippe Papillon
Before introducing solar thermal applications, some key figures should be introduced for a better understanding of the market, applications, and potential future of this technology. These key figures relate to the heat demand among energy consumption, the main solar thermal applications related to the level of temperature required, and the technological maturity.
Heat demand – In 2006 in Europe, low temperature heat represented 4640 TWh, which was 34% of the final energy consumption (Figure 3.1). This sector is particularly well adapted to thermal solar energy, which offers a significant potential for reducing non-renewable energy consumption.
Figure 3.1 Total final energy consumption in the EU 27 and the share of heat (2006). ESTIF 2009 – Potential of Solar Thermal in Europe. Copyright 2009 European Solar Thermal Industry Federation (ESTIF).
Within the low temperature heat sector, space heating and industrial process heat represent the major consumption (Figure 3.2). Air conditioning still has a low impact on energy consumption; however, this sector has experienced strong growth during the last decade, and should be significant in the future:
Operating temperature: Operating temperature (Figure 3.3) is a major criterion for the design of solar applications and especially collectors. It should always be taken into account to select the most appropriate technology to offer the service required as well as to obtain an energy cost as low as possible. Regarding the level of operating temperature, collector technologies differ from the simplest one to the most sophisticated product.Market deployment of the technologies: Nowadays, some applications are already entering the mass market (Figure 3.4
