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Development of a Broadband Antireflection Coated Transparent Silica Window for a Solar-Hybrid Microturbine System

Amsbeck, Lars and Helsch, Gundula and Röger, Marc and Uhlig, Ralf (2009) Development of a Broadband Antireflection Coated Transparent Silica Window for a Solar-Hybrid Microturbine System. SolarPACES. SolarPACES 2009, 15.-18. September 2009, Berlin, Deutschland. ISBN 978-3-00-028755-8.

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Abstract

A promising way of a solar-thermal power plant with high overall efficiency is the coupling of a Braytontype microturbine with a solar receiver. Within the SOLHYCO project, a 100kWe solar-hybrid microturbine demo system is currently under development. The compressed air is preheated up to 800°C with solar radiation using a metallic tube receiver. The tube receiver is located in a cavity with a circular opening Thermal analysis of the receiver showed that the aimed overall receiver efficiency of 80% cannot be reached with an economically sized receiver cavity. Reasons for this are high losses by infrared radiation and convection caused by high temperatures of the tubes of up to 950°C. Covering the cavity opening with a transparent window could reduce these losses. Fused silica has ideal properties to fulfill the technical needs. It is highly transparent in the solar spectrum and it can be used at high operating temperatures. Further a very low thermal expansion coefficient allows high temperature gradients. Although there are a few disadvantages: Glass is a brittle material which can not withstand high tensile stresses. Further a flat plate as a receiver window would lead to additional losses by reflected solar radiation. Within the ARTRANS project an antireflective coated fused silica window was developed. The prototype, consisting of ten pipe segments is held by a frame of insulating material. A broadband antireflective coating was developed to reduce the losses by reflected solar radiation. The segments of the prototype were coated by dip-coating from a silica sol containing solution and tempered at 900°C. Optical measurements of the resulting 110 nm porous silica coating showed that the transmission could be increased as expected from 93% to more then 97% in the solar spectrum. The overall performance of the receiver without and with transparent window was supported by numerical simulations. The simulations showed that a receiver with coating will have a 13.1% points higher receiver efficiency. Using a window without coating, the receiver efficiency will still be 9.5% points higher than without window.

Document Type:Conference or Workshop Item (Speech, Paper)
Title:Development of a Broadband Antireflection Coated Transparent Silica Window for a Solar-Hybrid Microturbine System
Authors:
AuthorsInstitution or Email of Authors
Amsbeck, Larslars.amsbeck@dlr.de
Helsch, GundulaTU Clausthal-Zellerfeld
Röger, Marcmarc.roeger@dlr.de
Uhlig, Ralfralf.uhlig@dlr.de
Date:September 2009
Refereed publication:No
In ISI Web of Science:No
Publisher:SolarPACES
ISBN:978-3-00-028755-8
Status:Published
Keywords:Solar Thermal Power Plant, Solar-hybrid System, Microturbine, Fused Silica, Antireflection Coating, Solarthermische Kraftwerke, Solar-hybrides System, Mikroturbine, Quarzglas, Entspiegelung
Event Title:SolarPACES 2009
Event Location:Berlin, Deutschland
Event Type:international Conference
Event Dates:15.-18. September 2009
Organizer:SolarPACES, Deutsches Zentrum für Luft- und Raumfahrt (DLR) e.V.
HGF - Research field:Energy
HGF - Program:Renewable Energies
HGF - Program Themes:E SF - Solar research (old)
DLR - Research area:Energy
DLR - Program:E SF - Solar research
DLR - Research theme (Project):E - Solare Hochtemperatursysteme (old)
Location: Stuttgart
Institutes and Institutions:Institute of Technical Thermodynamics > Solar Research
Deposited By: Marc Röger
Deposited On:19 Feb 2010 18:35
Last Modified:12 Dec 2013 20:48

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