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The influence of climate and location on collector performance
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
2002 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 25, no 4, p. 499-509Article in journal (Refereed) Published
Abstract [en]

The influence of annual climate variations on the performance of solar thermal collectors in the northern part of Europe has been investigated. The annual solar collector energy output has been calculated with the MINSUN simulation program using hourly, measured climatic data for the years 1983–98 for three cities situated in the south (Lund), central (Stockholm) and north (Luleå) of Sweden. A synthetic year created with the Meteonorm weather simulation program was also used in the simulations. Two solar thermal collectors were modelled: a flat plate solar collector and a tubular vacuum collector, both of commercial standard.

The thermal energy output is strongly correlated to the annual global irradiation at a horizontal surface. The annual average energy delivered from the flat plate collector was 337 kWh/m2 for Stockholm (337 for Lund and 298 for Luleå), and from the vacuum tube collector 668 kWh/m2 for Stockholm (675 for Lund and 631 for Luleå) at an operating temperature of T=50°C. Maximum deviations from the average value for this 16-year period are around 20% for the flat plate and 15% for the vacuum tube collector, at T=50°C.

The relation between global irradiation on a horizontal surface and the annually collected thermal energy at a constant operating temperature could be fitted to a linear equation: qu=aG(0°)+bT, where qu is the energy output from the collector, G(0°) the global irradiation at a horizontal surface, T the average temperature of the collector fluid, and a and b fitting parameters in a double linear regression analysis.

Place, publisher, year, edition, pages
2002. Vol. 25, no 4, p. 499-509
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-89753DOI: 10.1016/S0960-1481(01)00091-X,OAI: oai:DiVA.org:uu-89753DiVA, id: diva2:161486
Available from: 2002-04-05 Created: 2002-04-05 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Solar Thermal Collectors at High Latitudes: Design and performance of non-tracking concentrators
Open this publication in new window or tab >>Solar Thermal Collectors at High Latitudes: Design and performance of non-tracking concentrators
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Solar thermal collectors at high latitudes have been studied, with emphasis on concentrating collectors. A novel design of concentrating collector, the Maximum Reflector Collector (MaReCo), especially designed for high latitudes, has been investigated optically and thermally. The MaReCo is an asymmetrical compound parabolic concentrator with a bi-facial absorber. The collector can be adapted to various installation conditions, for example stand-alone, roof- or wall mounted. MaReCo prototypes have been built and outdoor-tested. The evaluation showed that all types work as expected and that the highest annually delivered energy output, 340 kWh/m2, is found for the roof MaReCo. A study of the heat-losses from the stand-alone MaReCo lead to the conclusion that teflon transparent insulation should be placed around the absorber, which decreases the U-value by about 30%.

A method was developed to theoretically study the projected radiation distribution incident on the MaReCo bi-facial absorber. The study showed that the geometry of the collectors could be improved by slight changes in the acceptance intervals. It also indicated that the MaReCo design concept could be used also at mid-European latitudes if the geometry is changed.

A novel method was used to perform outdoor measurements of the distribution of concentrated light on the absorber and then to calculate the annually collected zero-loss energy, Ea,corr, together with the annual optical efficiency factor. A study using this method indicated that the absorber should be mounted along the 20º optical axis instead of along the 65º optical axis, which leads to an increase of about 20% in Ea,corr. The same absorber mounting is suggested from heat loss measurements. The Ea,corr at 20º absorber mounting angle can be increased by 5% if the absorber fin thickness is changed from 0.5 to 1 mm and by 13% if two 71.5 mm wide fins are used instead of one that is 143 mm wide. If the Ea,corr for the standard stand-alone MaReCo with 143 mm wide absorber mounted at 65º is compared to that of a collector with a 71.5 mm wide absorber mounted at 20º, the theoretical increase is 38%.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2002. p. 78
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 697
Keywords
Materials science, Solar thermal collectors, concentrators, CPC, high latitudes, Materialvetenskap, Solfångare, koncentratorer, höga latituder
National Category
Materials Engineering
Research subject
Solid State Physics
Identifiers
urn:nbn:se:uu:diva-1925 (URN)91-554-5274-4 (ISBN)
Public defence
2002-04-29, Polhemssalen, Uppsala, 10:15 (English)
Opponent
Available from: 2002-04-05 Created: 2002-04-05 Last updated: 2009-04-29Bibliographically approved

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