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Determination of Correction Factors for Heat Losses at High Temperatures in Parabolic Trough Fields

Wittmann, Michael und Feldhoff, Jan Fabian und Hirsch, Tobias (2012) Determination of Correction Factors for Heat Losses at High Temperatures in Parabolic Trough Fields. SolarPACES 2012, 2012-09-11 - 2012-09-14, Marrakesch, Marrokko. (nicht veröffentlicht)

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Kurzfassung

In former and current parabolic trough solar thermal power plants, thermal oil is typically used as heat transfer medium. The thermal oil enters the irradiated absorber tube at temperatures around 300 °C and leaves the solar field with temperatures near 400 °C. The upper temperature is limited by the decomposition temperature of the oil. Due to the fact that the selective coating of the absorber tubes improved strongly, within this temperature range the total heat loss of the solar field can be calculated by simplified equations, e.g. using the arithmetic mean of the loop temperatures m=0.5 (in + out). This simplification leads to an underestimation of the heat losses in a magnitude below 3 %. For medium quality yield estimations this error is tolerated [1] in favor of calculation speed. New parabolic trough systems with different heat transfer media endeavor to higher outlet temperatures. Since radiative heat losses become more and more significant at higher temperatures, the heat loss curve converges to a characteristic corresponding to the temperature to the 4th power. In consequence, using the simplified equations in high temperature systems up to 580 °C leads to errors higher than 15 %. Additionally, medium quality yield estimations typically do not take into account the part load behavior of the solar field’s temperature distribution (see figure below). During times of low solar irradiation the main temperature rise will take place near the inlet of the solar field, thus, the mean temperature of the solar field will be raised. This leads to a further underestimation of the solar field’s heat losses such that the error cannot be tolerated anymore in future high temperature parabolic trough plants. The proposed paper will address this problem and will show how correction factors depending on heat losses, solar field temperatures and part load behavior can be defined in order to achieve both fast and accurate calculations for high-temperature parabolic trough systems.

elib-URL des Eintrags:https://elib.dlr.de/80803/
Dokumentart:Konferenzbeitrag (Vortrag)
Titel:Determination of Correction Factors for Heat Losses at High Temperatures in Parabolic Trough Fields
Autoren:
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iDORCID Put Code
Wittmann, MichaelMichael.Wittmann (at) dlr.deNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Feldhoff, Jan FabianJan.Feldhoff (at) dlr.dehttps://orcid.org/0000-0003-1636-5429NICHT SPEZIFIZIERT
Hirsch, Tobiastobias.hirsch (at) dlr.dehttps://orcid.org/0000-0003-0063-0128NICHT SPEZIFIZIERT
Datum:2012
Referierte Publikation:Ja
Open Access:Nein
Gold Open Access:Nein
In SCOPUS:Nein
In ISI Web of Science:Nein
Status:nicht veröffentlicht
Stichwörter:solar thermal power, solar field, heat losses, parabolic trough, heat collecting element, molten salt, yield calculation, yield estimation, system analysis
Veranstaltungstitel:SolarPACES 2012
Veranstaltungsort:Marrakesch, Marrokko
Veranstaltungsart:internationale Konferenz
Veranstaltungsbeginn:11 September 2012
Veranstaltungsende:14 September 2012
Veranstalter :SolarPACES
HGF - Forschungsbereich:Energie
HGF - Programm:Erneuerbare Energie
HGF - Programmthema:Konzentrierende Solarsysteme (alt)
DLR - Schwerpunkt:Energie
DLR - Forschungsgebiet:E SF - Solarforschung
DLR - Teilgebiet (Projekt, Vorhaben):E - Linienfokussierende Systeme (alt)
Standort: Stuttgart
Institute & Einrichtungen:Institut für Solarforschung > Linienfokussierende Systeme
Hinterlegt von: Wittmann, Michael
Hinterlegt am:22 Jan 2013 11:17
Letzte Änderung:24 Apr 2024 19:47

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