John Gabriel

A high concentration photovoltaic module utilizing micro-transfer printing and surface mount technology

We describe a high concentration photovoltaic (CPV) module utilizing micro-transfer printed (µ-TP) dual-junction GaInP/GaAs solar cells and an ELO (Epitaxial Lift-Off) process used to fabricate very small cells (<0.5 mm2) using 1st use and reused GaAs substrates. The benefits of this technology include high efficiency, simple distributed heat transfer at high concentration ratios, and short optical paths. This approach enables the use of low cost, high reliability surface mount assembly of large backplanes for integration into CPV modules. To minimize compound semiconductor use and maximize cell efficiency, we combine plano-convex primary and spherical secondary optics to concentrate sunlight 1000X over a +/−0.8 degree angle of acceptance. Receiver efficiencies of ELO dual-junction GaInP/GaAs cells of >30% at 1,000 sun concentration are reported. Coupled with a >80% efficient optical train, module efficiencies greater than 24% have been achieved with dual-junction µ-TP solar cells.

HCPV Characterization: Analysis of Fielded System Data.

Sandia and Semprius have partnered to evaluate the operational performance of a 3.5 kW (nominal) R&D system using 40 Semprius modules. Eight months of operational data has been collected and evaluated. Analysis includes determination of Pmp, Imp and Vmp at CSTC conditions, Pmp as a function of DNI, effect of wind speed on module temperature and seasonal variations in performance. As expected, on-sun Pmp and Imp of the installed system were found to be ∼10% lower than the values determined from flash testing at CSTC, while Vmp was found to be nearly identical to the results of flash testing. The differences in the flash test and outdoor data are attributed to string mismatch, soiling, seasonal variation in solar spectrum, discrepancy in the cell temperature model, and uncertainty in the power and current reported by the inverter.. An apparent limitation to the degree of module cooling that can be expected from wind speed was observed. The system was observed to display seasonal variation in performance, li...

Performance of a micro-cell based transfer printed HCPV system in the South Eastern US

Printed micro-cells are the basis of a more cost effective and highly efficient HCPV module design. Module efficiencies of 33.9% at STC have been demonstrated for modules designed for commercial use. An array of these modules were deployed in a 3.5 kW system in Huntsville, AL to validate the design, demonstrate the reliability of the system and collect on-sun data to understand system performance. The first six months of performance data is presented along with results from soiling experiments.

On‐Sun Performance of a Novel Microcell Based HCPV System Located in the Southwest US

Semprius has developed a novel microcell based, highly scalable HCPV module that addresses performance, cost and reliability requirements for utility scale solar installations. Semprius has fabricated dual junction cell based engineering prototype modules with 1000X concentration based on this technology. A 1 kW HCPV system using these modules was installed in Tucson to validate the technology and acquire on‐sun data. Eight months of on‐sun results from this system are presented.

Ultrahigh Efficiency HCPV Modules and Systems

Semprius manufactures high-concentration photovoltaic (HCPV) modules and systems. Module characterization and quality control methods are described in this paper. Module efficiency distribution for thousands of modules is presented, currently showing an increase in average efficiency from 33% in 2013 to 35%. Data from modules and systems in the field are presented showing consistent performance over all seasons and no apparent degradation after 3 years. Finally, the effect of ambient temperature and wind speed on performance was studied.

Semprius field results

Semprius has increased its printed micro-cell module efficiency to 35.5% at CSTC. This design has been field tested for more than two years with no measurable signs of degradation. Three different commercial ready CPV systems have been designed, installed and characterized. The pointing error of all three trackers is ±0.1°, well within the module angle of acceptance (AOA) of ±0.8°. The on-sun performance of these systems is consistent with expectations. The peak AC efficiency of the systems was ∼30%.

Ultra high efficiency HCPV modules

Semprius manufactures HCPV modules and systems. Module characterization and QC methods are described in this paper. Module efficiency distribution for thousands of modules is presented, showing an increase in average efficiency from 33.2% in 2013 to 34.9% currently. Data from modules and systems in the field is presented showing no measureable degradation after three years and consistent performance over different seasons. Finally, the effect of ambient temperature and wind speed on performance was studied.

Multi-physics circuit network performance model for CPV modules/systems

Advanced empirical models have been developed to analyze or predict the performance of flat-plate or concentrator photovoltaic modules/systems in the outdoor environment [1]. These models typically rely on the use of empirical equations driven by several coefficients which are empirically determined through regression analysis of large sets of experimental data collected in the field. For instance, the performance model developed by Sandia Laboratories can be used to predict the performance of a photovoltaic module/system under varying (direct normal) irradiance, air mass, ambient temperature or wind speed. As the model empirically-determined coefficients are derived from averaged data sets (filtering out most transient effects), it is not always possible to link these coefficients to specific module design parameters. Moreover, since the detailed internal module wiring configuration is typically neglected, these empirical models cannot be used to accurately predict the performance of modules/systems when modules are partially shadowed. To overcome this limitation, specific models have been developed for predicting the non-linear effect of partial shading on PV systems [2,3]. This paper presents a generalized multi-physics performance model relying on the use of physical equations and elementary electrical circuit network models. This model can be used for predicting, comparing or analyzing the performance of concentrated photovoltaic modules or systems. The model is particularly useful for predicting the impact of a design change in the module/system materials, wiring configuration, solar cell type, or of the concentrator optics. Following a presentation of the model architecture, a first example presents how this performance model can be effectively used to optimize the module internal wiring configuration in order to minimize the impact of receiver current mismatch an reduce string losses at the system level. The model can also be used to determine the impact of shorts/opens defects on module performance. This performance model can also be used to determine the optimum method for binning and placing an array of individual receivers onto the backplane of micro-cell based concentrator photovoltaic modules [4,5]. A second example illustrates how the model can be easily extended through the use of high level analytical equations in order to perform multi-physics simulations. The impact of thermal expansion on the performance of a CPV module is studied using semi-empirical optical throughput equations of the CPV module optics coupled to thermal equations. Finally, a last example highlights the intrinsic capability of the model to accurately predict the non-linear effect of partial shading. Experimental data are presented to support these analyses.