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-cm 2 aperture area test stand, notably equipped with commercial concentrator solar cells. We use optical bandpass 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-cm 2 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.

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Solar Systems has more than 10 years experience with grid-connected CPV systems using large reflective optics. Over the last 7 years, Solar Systems has deployed 47 dish units, of which 23 are with multijunction solar cells, in five different commercial CPV power plants and two testing facilities, for a total installed capacity of 1.5 MWp. Recently, Solar Systems has designed and built a 140kWp Heliostat Concentrator PV (HCPV) system at its new Testing and Training Facility in Bridgewater, Victoria. The demonstration of the performance of the HCPV system met all the specification targets. The system reached a power output of 140kW with a DC efficiency of 240/0 to 260/0 and an optical efficiency of 840/0, measured on two different days, four months apart, around solar noon. This is the first utility-scale Heliostat CPV system ever built. It is also for Solar Systems the first demonstration of a new technology to be deployed in a large 154-MWp power plant in Northern Victoria.

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 36.5kWf under Standard Operating Conditions (SOC, 1000W/m , 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 2 , 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 2 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 2 . We expect that combining the 2 nd generation modules with the redesigned optics would improve the DC efficiency to 28% at SOC.