Nanostructured black, ceramic and composite high temperature spectrally selective coatings for solar receivers

Noč, Luka (author), Jerman, Ivan (mentor), Genorio, Boštjan (co-mentor)

This thesis describes research on coatings for concentrated solar power (CSP) receivers, conducted to increase their efficiency for solar-to-thermal energy conversion and prolong their service lives. The coatings for CSP receivers include a black spinel pigment with a high absorptance for sunlight. With aim to develop pigments with an even higher solar absorptance (αS), metal ions were added to the commercial pigment and, using solid-state synthesis, new compositions were formed. The pigment doping resulted in a reduction of the thermal emissivity (εT) and therefore the efficiency of the receiver increased. The prepared coatings were thermally aged for 1300 hours at 800 °C in air, and the characterization was performed at uniform time intervals. Excellent results were obtained with the coatings made from the Cr-doped pigment. Coating-reliability testing was conducted to evaluate the service life of the high solar absorptive (HSA) coating under conditions simulating those in industry. To improve the corrosion resistance of the CSP receiver at high temperature, while maintaining the low thermal emission of the coating, ultra-thin (1–3 nm) mono-, di- and trilayers of hybrid organic-inorganic polyhedral oligomer silsesquioxanes (POSS) were prepared with the Langmuir-Blodgett (LB) technique. Alumina thermal barrier coatings with a low εT were fabricated using the sol-gel process and HSA coatings on the basis of a SiO2 inorganic binder were deposited on them. Alumina coatings were also laser-cured, which increased their thermal stability. New, two-dimensional materials such as MXenes were used in the preparation of the coatings to improve their functionality.

• Language: English
• Keywords: concentrated solar power, spectrally selective coatings, reduced thermal emittance, spinel pigment, metal ion diffusion
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2020
• PID: 20.500.12556/RUL-124688
• COBISS.SI-ID: 51428099
• Publication date in RUL: 09.02.2021

Secondary language

• Language: Slovenian
• Title: Nanostrukturirane črne, keramične in kompozitne visokotemperaturne spektralno selektivne prevleke za sončne sprejemnike

Abstract

V pričujoči disertaciji so opisane raziskave prevlek za sprejemnike koncentratorskih sončnih elektrarn (CSP) z namenom povečati njihovo učinkovitost pretvorbe sončne energije v toploto in podaljšati njihovo življenjsko dobo. V prevlekah za CSP sprejemnike se uporablja spinelni pigment črne barve z visoko absorptivnostjo sončnega sevanja. Komercialnemu spinelnemu pigmentu so bili dodani kovinski ioni in s sintezo v trdnem stanju so bile pridobljene nove sestave pigmentov. Z dopiranjem pigmenta je bilo doseženo znižanje termične emisije (εT) in ob ne-znižani sončni absorptivnosti (αS) povišan termični izkoristek CSP sprejemnika. Pripravljene prevleke so bile termično starane 1300 ur pri 800 °C na zraku in na vmesnih enakomernih časovnih intervalih so bile izmerjene optične lastnosti. Izjemni rezultati so bili doseženi pri prevlekah, v katerih je bil pigment dopiran s Cr. Izvedeno je bilo testiranje zanesljivosti prevleke za oceno servisne dobe prevleke z visoko absorptivnostjo sončnega sevanja (HSA) v pogojih, ki simulirajo tiste v industriji. Za izboljšanje korozijske odpornosti CSP sprejemnika pri visoki temperaturi in hkrati ohranjanje nizke toplotne emisije prevleke, so bile z Langmuir-Blodgett (LB) tehniko pripravljene ultra tanke (1-3 nm) mono-, di - in triplasti hibridnih organsko-anorganskih poliedričnih oligomernih silseskvioksanov (POSS). Po sol-gel postopku so bile izdelane termične zaporne plasti iz Al2O3 z nizko εT, na katere smo nanesli HSA prevleke na osnovi anorganskega veziv a SiO2. Prevleke iz aluminijevega dioksida so bile tudi lasersko utrjene, kar je povečalo njihovo termično stabilnost. Za izboljšanje funkcionalnosti prevlek so bili pri pripravi le-teh uporabljeni novi 2D materiali kot so MXene.

• Keywords: koncentratorske sončne elektrarne, spektralno selektivne prevleke, zmanjšana toplotna emisija, spinelni pigment, difuzija kovinskih ionov