Title

Luminescent solar concentrator structures for solar energy harvesting and radiation control

Date of Award

2017

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Science

First Advisor

Professor Kamal Alameh

Second Advisor

Dr Mikhail Vasiliev

Abstract

Luminescent solar concentrators are devices capable of converting some spectral components of solar radiation by luminescence and concentrating them before collection by photovoltaic. The aim of this thesis is to design, develop and demonstrate the principle of all-inorganic semitransparent luminescent solar concentrator (LSC) structures capable of passing most of the visible light through to provide illumination, while reflecting more than 90% of the UV and IR radiations and scattering them to the edges of the glass where they are collected by PV cells to produce electricity. All-inorganic visibly-transparent energy-harvesting clear laminated glass windows are the most practical solution to boosting building-integrated photovoltaics (BIPV) energy outputs significantly while reducing cooling- and heatingrelated energy consumption in buildings. A typical semitransparent luminescent solar concentrator is based on the integration of micro-engineered optical structures, nano-materials and IR-selective thin-film coatings, to realise stable, long-lifetime and shatterproof clear glass panels. The ability of the proposed semitransparent luminescent solar concentrators to generate electricity addresses the future net-zero-energy building demand [1, 2], making them ideal candidates for future high-rise glass buildings.

The developed semitransparent luminescent solar concentrators employ low-e thin films, which particularly, provide many benefits, including, (i) building overall aesthetic appearance, (ii) low glare and (iii) filtration of unwanted components of the incident sunlight thus increasing the energy saving rating of buildings. The low-e glass panes are typically used in a double glazing structure in order to protect the low-e film from environmental impacts and improve the insulation properties of the semitransparent luminescent solar concentrators in addition to reducing the energy consumed for cooling or heating the inside of buildings.

Multi-layer thin film coatings for solar and thermal radiation control are designed, using the Optilayer software package, developed using Physical Vapour Deposition (PVD), and tested using spectrophotometry. Experimental results show that the measured transmittance spectra for the developed structures are in agreement with simulation results and demonstrate that with the use of optimum metal-dielectric layer combination it is possible to transmit/reflect arbitrary spectral components of the incident sunlight.

In addition, two types of semitransparent luminescent solar concentrator structures are designed, developed and characterised, namely:

1. LSCs incorporating inorganic luminophore materials into the lamination interlayer. These luminophores, when used in conjunction with spectrally-selective low-e thin-film coatings and CuInSe2 solar cells, enable most of the visible solar radiation to be transmitted through the glass window with minimum attenuation and the ultraviolet (UV) radiation to be down-converted and routed together with a significant part of infrared radiation to the edges for collection by solar cells.

2. Advanced LSCs incorporating inorganic luminophore materials as well as spectrallyselective diffraction gratings as light deflector structures of high visible transparency into the lamination interlayer. For these LSCs, most of the visible solar radiation can be transmitted through the glass windows with minimum attenuation while the ultraviolet (UV) and a part of incident solar infrared (IR) radiation energy are converted and/or deflected geometrically for routing towards the vicinity of glass panel edge regions for collection by solar cells.

To boost the solar concentration capability of the laminated glass panes, functionalized epoxy interlayers are especially developed, which comprise UV-curable epoxy and inorganic luminophores with engineered absorption and emission bands. The developed functionalized interlayers demonstrate an excellent ability to scatter and concentrate sunlight within the glass structure with minimum reabsorption. Several materials and combinations of several luminophore types were investigated in order to determine the optimum interlayer structure that exhibits maximum UV and IR radiation scattering, conversion, and deflection towards the edge solar cells. Measured conversion efficiencies of 3.8% and 5.4% are achieved for 10 cm × 10cm LSCs samples without and with diffraction gratings, which correspond to output electrical power densities of 38Wp/m2 and 54 Wp/m2,respectively.

A photobioreactor based on the developed semitransparent luminescent solar concentrator technology is developed, in collaboration with Murdoch University, for microalgae growth. An Insulated Glass Units (IGU) employing a special low-e thin film is developed, which passes more than 50% of the visible light while blocking more than 90% of the UV and IR radiations, hence, reducing the temperature inside the photobioreactor and improving the microalgae growth. The growth and productivity of the microalgae in the Insulated Glass

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