Thermodynamics seminars

Nanofluid Optical Filters for Photovoltaic/Thermal Collectors

2:00–3:00pm Thursday 10 May 2018

Venue: Level 3 seminar room, Department of Mechanical Engineering

Natasha Hjerrild

Abstract

Sunlight can be captured to produce both electricity and thermal energy using hybrid photovoltaic/ thermal (PV/T) collectors to sustainably address rising energy demand. However, the thermal component of these systems is currently limited to the delivery of low outlet temperatures (<<100°C) to prevent thermal degradation of the PV cells. Spectrum splitting hybrid photovoltaic/ thermal (PV/T) systems can offer greater combined electrical/ thermal efficiencies and higher thermal output than conventional (thermally-coupled) PV/T systems. This presentation highlights recent advancements in mid-temperature range optically filtering nanofluids, which absorb the portions of the solar spectrum that are poorly converted into electricity by underlying PV cells.

These nanofluids were fabricated by suspending visible light absorbers (silica-coated silver nanoplates, or Ag-SiO2) and near-infrared absorbers (silica-coated gold and bimetallic gold-copper nanorods) in various base fluids to meet the spectral and thermal requirements of the PV/T system. Because nanofluids in concentrating PV/T systems are exposed to harsh environmental conditions including strong ultra-violet (UV) irradiation and high temperatures, the nanofluids underwent accelerated photothermal testing to ensure nanofluid stability. After stable nanofluids were developed, the nanofluids were used to filter light for three PV cell types (monocrystalline silicon, gallium arsenide, and germanium) in an indoor test. Several litres of the highest performing nanofluid (aqueous Ag-SiO2) were produced to filter light for a monocrystalline silicon PV array in a prototype PV/T system for outdoor testing. An economic analysis confirms that Ag-SiO2 nanofluids are a strong candidate for low cost, high-efficiency optical filtration of silicon solar cells, though the commercial viability of such PV/T systems is subject to local natural gas and grid electricity prices.

Presenter

Natasha Hjerrild has recently finished her PhD in the School of Photovoltaic and Renewable Energy Engineering at the University of New South Wales. She was awarded an Endeavour Scholarship to pursue her PhD research on nanofluid development for combined photovoltaic/ solar thermal technology. Prior to her time at UNSW, she received her Master’s in Materials from the University of Oxford for her research on alternative transparent conductors applied to solution-processed, quantum dot solar cells. She received her Bachelor’s degree in Materials Science and Engineering from Cornell University in 2012. Her primary research interest combines nanomaterial synthesis and characterization with performance enhancement of solar energy and energy storage technologies.

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