The use of a two-stage concentrator with a fresnel lens primary and a non-imaging dielectric totally internally reflecting secondary, has unique advantages for photovoltaic concentration. This new design has a much larger acceptance angle than the conventional lens-cell concentrating system. In the continuation of this research, an optimally designed prototype which employs a 13.6-cm diameter flat fresnel tons as the primary focusing device, a dielectric compound hyperbolic concentrator (DCHC) as secondary and a 1-cm diameter high-concentration cell for electricity conversion has been built, tested and analyzed. Measurements under sunlight show that it has an angular acceptance of (plus minus)3.6 degrees, which is dramatically better than the (plus minus)0.5 degree achievable without a secondary concentrator. This performance agrees well with theoretical ray-tracing predictions. The secondary shows an optical efficiency of (91(plus minus)2)% at normal incidence. Combining with the primary fresnel tens which has an optical efficiency of (82(plus minus)2)%, tho two-stage system yields a total optical efficiency of (7l(plus minus)2)%. The measurement of the system electrical performance yielded a net electrical efficiency of 11.9%. No problems associated with non-uniform cell illumination were found, as evidenced by the excellent fill factor of (79(plus minus)2)% measured under concentration. The secondary geometrical properties and the optimal two-stage design procedures for various primary- cell combinations were systematical studied. A general design principle has been developed.
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