Dish-based CPV-T for rooftop generation

Christian Davila-Peralta, Justin Hyatt, Dan Alfred, Morgan Struble, Frank Sodari, J Roger P Angel

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Hybrid CPV-T with combined electrical and thermal output is well suited to solar generation from fixed limited areas, such as on the roof of an industrial or commercial facility with need for heat. This application will become especially attractive once overall electrical conversion efficiency of 40% is reached, as is projected for REhnu CPV systems using multijunction cells of 50% efficiency, anticipated in a few years. We outline here a configuration of dish- based CPV trackers optimized for close packing on a flat roof in a triangular grid, with a mirror area-to-ground area ratio of 50%. When the geometry of shadowing averaged over a year is taken into account, 80% of all the sunlight that would strike the rooftop is directed into the receivers. Such an array on a given area of flat roof will generate more electrical energy than would be possible with conventional PV panels, even if covering the entire rooftop, because of silicon's relative inefficiency. For example, in Tucson, the annual average global flux of 5.7 kWh/m2/day on a horizontal surface covered with 22% silicon modules will yield 1.25 kWh/m2/day. We show that a CPV system collecting 80% of all the direct sunlight of 7.0 kWh/m2 and converting it with 40% efficiency will yield 2.24 kWh/m2/day of rooftop area, nearly twice as much4. Thermal power will double again the total energy yield. A dual axis CPV-T tracker designed specifically very close spacing has been built to carry a single dish mirror of the standard type used in REhnu's M-8 generator, described by Stalcup et al in these proceedings1,2. Sunlight is collected and focused by a single square paraboloidal mirror, 1.65 × 1.65 m with focal length of 1.5 m. For closest possible packing without mechanical interference, and for broad distribution of load on a rooftop, the mirror and receiver are mounted to a C-ring structure, configured such that the elevation and azimuth axes intersect at a virtual pivot, at the center of the sphere that just clears the receiver and the corners of the mirror. Initial tests of closed loop tracking show an accuracy of 0.03°rms under calm conditions, and 0.04°rms in 6 m/sec wind.

Original languageEnglish (US)
Title of host publication13th International Conference on Concentrator Photovoltaic Systems, CPV 2017
PublisherAmerican Institute of Physics Inc.
Volume1881
ISBN (Electronic)9780735415614
DOIs
Publication statusPublished - Sep 6 2017
Event13th International Conference on Concentrator Photovoltaic Systems, CPV 2017 - Ottawa, Canada
Duration: May 1 2017May 3 2017

Other

Other13th International Conference on Concentrator Photovoltaic Systems, CPV 2017
CountryCanada
CityOttawa
Period5/1/175/3/17

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ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Davila-Peralta, C., Hyatt, J., Alfred, D., Struble, M., Sodari, F., & Angel, J. R. P. (2017). Dish-based CPV-T for rooftop generation. In 13th International Conference on Concentrator Photovoltaic Systems, CPV 2017 (Vol. 1881). [080002] American Institute of Physics Inc.. https://doi.org/10.1063/1.5001440