40% Efficient Sunlight to Electriity Conversion

Keith Emery, Martin Green, Mark Keevers, Ian Thomas, John Lasich, Richard King

Research output: Contribution to journalArticlepeer-review

79 Scopus Citations

Abstract

Increasing sunlight conversion efficiency is a key driver for on-going solar electricity cost reduction. For photovoltaic conversion, the approach most successful in increasing conversion efficiency is to split sunlight into spectral bands and direct each band to a dedicated solar cell of an appropriate energy bandgap to convert this band efficiently. In this work, we demonstrate conversion of sunlight to electricity in a solar collector with an efficiency value above 40% for the first time, using a small 287-cm2 aperture area test stand, notably equipped with commercial concentrator solar cells. We use optical band-pass filtering to capture energy that is normally wasted by commercial GaInP/GaInAs/Ge triple junction cells and convert this normally wasted energy using a separate Si cell with higher efficiency than physically possible in the original device. The 287-cm2 aperture area sunlight-concentrating converter demonstrating this independently confirmed efficiency is a prototype for a large photovoltaic power tower system, where sunlight is reflected from a field of sun-tracking heliostats to a dense photovoltaic array mounted on a central tower. In such systems, improved efficiency not only reduces costs by increasing energy output for a given investment in heliostats and towers but also reduces unwanted heat generation at the central tower.

Original languageAmerican English
Pages (from-to)685-691
Number of pages7
JournalProgress in Photovoltaics: Research and Applications
Volume23
Issue number6
DOIs
StatePublished - 2015

Bibliographical note

Publisher Copyright:
Copyright © 2015 John Wiley & Sons, Ltd.

NREL Publication Number

  • NREL/JA-5J00-63397

Keywords

  • concentrator
  • CPV
  • energy conversion efficiency
  • photovoltaic efficiency
  • solar cell efficiency
  • split spectrum

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