title: Dish-based high concentration PV system with Köhler optics.
abstract: We present work at the Steward Observatory Solar Lab on a high concentration photovoltaic system in which sunlight focused by a single large paraboloidal mirror powers many small triple-junction cells. The optical system is of the XRX-Köhler type, comprising the primary reflector (X) and a ball lens (R) at the focus that reimages the primary reflector onto an array of small reflectors (X) that apportion the light to the cells. We present a design methodology that provides generous tolerance to mis-pointing, uniform illumination across individual cells, minimal optical loss and even distribution between cells, for efficient series connection. An operational prototype has been constructed with a 3.3m x 3.3m square primary reflector of 2m focal length powering 36 actively cooled triple-junction cells at 1200x concentration (geometric). The measured end-to-end system conversion efficiency is 28%, including the parasitic loss of the active cooling system. Efficiency ~32% is projected for the next system.
authors.forename: Blake M
authors.initials: BM
authors.lastname: Coughenour
authors.forename: Thomas
authors.initials: T
authors.lastname: Stalcup
authors.forename: Brian
authors.initials: B
authors.lastname: Wheelwright
authors.forename: Andrew
authors.initials: A
authors.lastname: Geary
authors.forename: Kimberly
authors.initials: K
authors.lastname: Hammer
authors.forename: Roger
authors.initials: R
authors.lastname: Angel