Update on two-year performance of 120 kWp concentrator PV systems using multi-junction III–V solar cells and parabolic dish reflective optics

Abstract

Multi-junction III–V solar cells have been in operation for the last two years in several 500X dish concentrator PV systems using reflective optics. The performance monitoring of these CPV systems on a 15-second basis has accumulated a very large amount of data and allowed for analysis of the influence of atmospheric parameters to the system efficiency. Dense array modules are assembled into large receivers of approximately a quarter of square meter in size and with a typical efficiency of 31.7% and power output of 36.5kWp under Standard Operating Conditions (SOC, 1000W/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , AM1.5D, low AOD and 21°C cell temperature). At Normal Operating Cell Temperature (NOCT 53°C), the receiver efficiency and power output become 30% and 35.4kW. The DC efficiency of the dish unit is 24.5% at SOC. More interestingly, the specific Energy Production Rate (EPR) of each dish, being the ratio of the daily energy output and the daily incident direct-beam energy (DNR), was measured. In average, over a two-year period and over four dishes, the EPR was 27.5 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , corresponding to the equivalent aperture of a 100%-efficient solar energy converter. The annualised efficiency of these CPV systems is 21.1%. A new generation of dense array modules have demonstrated efficiency of 36.1% at 50W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 21°C. Also, a new redesigned optics has recently been implemented on one of the dishes and has demonstrated a significant boost in efficiency, bringing the SOC efficiency to 26.2% and an expected EPR of 30 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . We expect that combining the 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> generation modules with the redesigned optics would improve the DC efficiency to 28% at SOC.