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At least 487 records · Page 27

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DOE OSTI2021

Hardware-in-the-Loop Testbed for Cyber-Physical Security of Photovoltaic Farms

In the last decades, modem grids with distributed energy resources, such as photovoltaic (PV) farms, are increasingly vulnerable to cyber-attacks that seriously affect the stability and performance of the power system. While cyber-physical security of smart grids is extensively studied, most of the existing work focuses on the grid level and neglects the modeling and features of device-level power electronics converters (PECs). Furthermore, establishing a high-fidelity simulation testbed that can simulate harmonic frequencies of the PV farm is in urgent need. In this paper, a high-fidelity and real-time hardware-in- the-loop testbed is built to simulate the harmonics of power electronics converters for cyber-physical security of PEC-enabled PV farms. Based on this testbed, the impact of typical cyber-attacks and physical faults on the PV converter can be analyzed, thus providing a foundation for cyber-attack detection, root cause diagnosis, and resilient control to mitigate the adverse effects of cyber-attacks.

14 SOLAR ENERGY↗

DOE OSTI2020

Analysis and Validation of Spectral Irradiance Simulations for 75 kW Bifacial Solar Test Field

This work investigates how the spectrum of irradiance incident on the rear of bifacial modules impacts their performance. Light incident on the rear of bifacial modules can be reflected from the ground, mounting structures, and other nearby objects, causing both the intensity and spectrum to be modified. As a result, PV cells and sensors with different spectral responses report different values for the rear irradiance, leading to increased uncertainty when modeling performance. Here, we calculate the spectral irradiance incident on the rear of modules through raytrace simulations and validate with measured field data collected from a 75kW single-axis-tracked bifacial test site. Spectral responses for different sensors and PV cells are applied and compared with field measurements for four days. Based on these results, a method for improving non-spectral simulations is proposed. In addition, a linear regression is applied to the modeled spectral results as a method to gain insight into the contributions of ground reflected light to total rear irradiance.

bifacial photovoltaics↗

DOE OSTI2020

Optimizing Bifacial PV Systems (Q3 FY2020 Project Report)

This project has four main technical objectives. Develop and improve bifacial performance models by adding the capability to evaluate electrical behavior and performance of bifacial modules and arrays under realistic field conditions including irradiance variability caused by racking, module frame, and position in the array. Instrument and monitor performance of fielded bifacial systems to validate performance models and to measure, analyze and publish on bifacial energy gain. These should include both research and commercial bifacial systems and cover a variety of deployment applications. Evaluate optimal bifacial system designs using simulations leveraging high performance computing, and also using full sized and miniaturized experimental field deployments. Establish and contribute to international test standards for bifacial system performance, testing, and safety, and work with the community to establish installation and siting best practices.

14 SOLAR ENERGY↗

DOE OSTI2021

Evaluating Cell Temperature Models and the Effect of Wind Speed in PV System Capacity Testing: Preprint

Capacity testing is a routine procedure for assessing a photovoltaic system's performance relative to expectations. The most common test method involves fitting a regression model that predicts system output power using operating weather conditions including wind speed. Structural modifications to the regression model to incorporate wind in different ways improved the model's ability to fit measured system performance, but the observed improvements were small and unlikely to change the result of a capacity test. However, the results showed that the choice of reporting wind speed and inclusion or exclusion of wind speed in the performance model used as the test benchmark can significantly change the test result.

41 EE - Solar Energy Technologies Office (EE-4S)↗

DOE OSTI2023

Collaborative R&D with First Solar on Understanding Performance Limitations in CdTe (Project 1 "CdTe" - Mods 0-10, 13, 14-A1, 17)

This CRADA involves analyses on a variety of CdTe and CdTe-PV related materials, test structures, and solar cells produced at FSLR or NREL. Single-crystal (sx) material will be primarily MBE grown and provided by FSLR. Joint activities are focused on establishing the appropriate quality metrics as a basis for high performing sx devices and to study the dopability of the material. Polycrystalline (px) materials will be provided by NREL, FSLR, or fabricated jointly. Px activities are focused on the characterization of performance limiting mechanisms including bulk defects, grain boundaries, and the hetero-interface. A combination of growth, characterization, and theory will be applied. Analysis will include techniques that are well established in CdTe research at NREL (e.g., LIV/DIV/CV, AS/DLTS, LTPL, TRPL) as well as techniques that have not been widely applied to the PV part of CdTe technology (e.g., PCD, CL, uPL, SE).

14 SOLAR ENERGY↗

DOE OSTI2020

Comparative study on the overall energy performance between photovoltaic and Low-E insulated glass units

In this report a novel semi-transparent building integrated photovoltaic (BIPV) laminate was developed and introduced in this paper. It was produced by cutting standard mono-crystalline silicon solar cells into small strips and then making electrical connections between each strip before laminating the cells between two layers of glass. The overall energy performance and energy saving potential of the BIPV insulated glass unit (IGU) under real world conditions were identified through a side by side comparative study. Compared to the reference IGU, the BIPV IGU had lower solar heat gain coefficient (SHGC) but much higher U-factor. The average HVAC electricity saving of the BIPV IGU was about 10% relative to the reference IGU. Daylighting measurement and analysis were carried out to evaluate the trade-offs associated with the BIPV IGU between daylight, glare, and lighting energy use. The results indicated that the BIPV IGU is better than the reference IGU in reducing discomfort glare. However, if the most conservative viewpoint near the window is used for the assessment, a lower transmittance BIPV IGU is required to bring the overall discomfort levels below the perceptible level. Lastly, the net energy saving potential associated with the novel BIPV IGU was identified based on the power, thermal and daylighting performance. On average, the BIPV IGU saved 16.8% of the total electricity use of the room. Further studies and improvement on the energy conversion efficiency of solar cells, the optimal transmittance as well as the thermal properties would make this technology more energy-efficient and affordable.

14 SOLAR ENERGY↗

DOE OSTI2020

LCOE*: Re-Thinking LCOE for Photovoltaic Systems

Solar industry is working towards reducing the levelized cost of energy (LCOE). The LCOE formulation includes various implicitly connected cost and physical design parameters. This entails complex cost analyses by economists, and electrical analysis and energy yield calculations of solar farms by device physicists/technologists. The standard formulation requires a constant exchange of information to optimize the design of a specific farm. In this paper, we present a fundamental reformulation of LCOE (in terms of LCOE*) to deconvolve the cost vs. energy yield analysis so that economists and technologists can work independently towards minimizing LCOE. We validate our LCOE* formulation by comparing LCOE calculated by the traditional vs. new method. We further provide a global analysis of LCOE* as an illustrative example. This LCOE* will accelerate new technology development (e.g. bifacial PV) by allowing a rapid and transparent analysis of its cost-performance trade-off.

14 SOLAR ENERGY↗

DOE OSTI2022

Spectral Rear Irradiance Testing and Modeling for Degradation and Performance of Solar Fields

This work investigates how the spectrum of irradiance incident on the rear of solar modules impacts the degradation and performance of backsheets. We model the spectral irradiance incident on the rear of modules through raytrace simulations and validate with measured field data collected from a 75kW single axis-tracked bifacial test site. A generic equation to estimate relative degradation is proposed, and we show that current acceleration factors for UV damage in chambers can be sub-estimate up to 4.5% absolute from the usually assumed 10% dosage on the rear surfaces.

bifacial performance↗

DOE OSTI2022

Demonstration of a modeling toolkit for the design of building electrical distribution systems

The deployment of building equipment (e.g., lighting, security) and miscellaneous electrical loads that fundamentally require DC power for operation is increasing. Powering these DC loads has traditionally required an AC/DC converter, but the installation of photovoltaic (PV) and battery energy storage systems that primarily produce DC power eliminates the need for AC/DC converters at each end-device. However, analyzing system energy efficiency and cost for different electrical distribution architectures can be challenging as software tools that support this are not readily available. This paper presents preliminary results from a laboratory verification of the Building Electrical Efficiency Analysis Model (BEEAM) toolkit that was developed to address this gap. Three different eight-luminaire lighting systems comprised of market-available products were designed and modeled: one that used traditional AC distribution, a second that used a hybrid AC -to- centralized DC electrical distribution architecture, and a third that used a hybrid AC -to- distributed DC architecture. Notably, AC/DC conversions are required in all three systems. BEEAM models for LED drivers as well as Power-over-Ethernet (PoE) switches were created using laboratory characterization data. The lighting systems were simulated in Modelica, and the results were compared with each other and physics-based expectations. Simulation results show that PoE system energy efficiency is highly dependent on both device specification (e.g., LED driver and PoE switch efficiency) and system architecture (e.g., PoE switch loading) choices, as expected. For the products and system architectures selected for this study, the two DC systems were found to be less efficient than the AC system over the course of typical operation. In future work, simulation results will be compared with laboratory measurements to validate the usefulness of this software for design, and lighting systems with integrated PV and battery energy storage will be simulated to quantify the energy performance improvements that result from the elimination of some AC/DC converters.

Waghale, Anay S.↗

DOE OSTI2022

Testing Asoleyo Decorative Solar Cell and Modules: Cooperative Research and Development, CRADA Number CRD-20-16732 (Final Report)

Team Asoleyo is transforming the utilitarian rectangular grid that dominates the visual style of standard solar panels by re-designing solar cells’ silver contact grid using principles of symmetry, rhythm, and line. Our designs use well-established manufacturing equipment, techniques, and materials, achieving similar manufacturing costs but far superior aesthetic effect- without the need for additional layers or occlusion. This project will test new decorative PV Cell front contact designs, individually and interconnected within modules, for their performance characteristics.

14 SOLAR ENERGY↗

DOE OSTI2023

2023 Annual Technology Baseline (ATB) Cost and Performance Data for Electricity Generation Technologies

These data provide the 2023 update of the Electricity Annual Technology Baseline (ATB). Starting in 2015 NREL has presented the ATB, consisting of detailed cost and performance data, both current and projected, for electricity generation and storage technologies. The ATB products now include data (Excel workbook, Tableau workbooks, and structured summary csv files), as well as documentation and user engagement via a website, presentation, and webinar. Starting in 2021, the data are cloud optimized and provided in the OEDI data lake. The data for 2015 - 2020 are can be found on the NREL Data Search Page. The website documentation can be found on the ATB Website.

Array↗

DOE OSTI2020

Divanadium substituted keggin [PV 2 W 10 O 40 ] on non-reducible supports-Al 2 O 3 and SiO 2 : synthesis, characterization, and catalytic properties for oxidative dehydrogenation of propane

Molecular metal oxide cluster, K 5 [α-1,2-PV 2 W 10 O 40 ] (PV 2 W 10 ), was found to have intrinsic catalytic activity for the oxidative dehydrogenation of propane with high selectivity (> 80%) to propylene at low propane conversion (0.3%). Synthesis of dispersed PV 2 W 10 in non-reducible supports, γ-Al 2 O 3 and SiO 2 , was done by incipient wetness impregnation. The supported catalysts were characterized by IR, Raman spectroscopy, nitrogen adsorption, x-ray powder diffraction (PXRD), elemental analysis, hydrogen temperature-programmed reduction (H 2 –TPR), and ammonia temperature-programmed desorption (NH 3 –TPD). Catalytic testing of the supported PV 2 W 10 at equimolar cluster concentration revealed that when supported in γ-Al 2 O 3 it is more active (sevenfold increase in propane conversion) but in SiO 2 it is more selective to propylene (94%). The observed performance was due to both an increase in reducibility and higher concentration of strong acid sites for PV 2 W 10 supported in γ-Al 2 O 3 versus SiO 2 . Lastly, PV 2 W10 was shown to remain intact under reaction conditions indicating its thermal and oxidative stability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Indoor and Outdoor Test Results for 'DUSST', a Low-Cost, Low-Maintenance PV Soiling Sensor

Soiling can cause significant losses to photovoltaic systems, and therefore it is often measured for the purposes of predicting long-term energy forecasts or for monitoring real time performance and triggering maintenance events as needed. Currently, the most common soiling monitoring technologies are soiling stations that use the electrical outputs of a regularly cleaned PV device and of a naturally soiled PV device to quantify soiling. As part of a new class of low-cost and low-maintenance soiling stations NREL has previously presented 'DUSST'. DUSST projects a collimated monochromatic light source through a glass surface (exposed similarly to the PV modules that need to be monitored) and on to a light detector to measure the intensity of the transmitted light. As the glass surface naturally soils, the losses are quantified by comparing this soiled reading with a calibrated reading under baseline clean condition. This work presents the ongoing improvement of DUSST and the ongoing indoor and outdoor validation of this new soiling sensor.

14 SOLAR ENERGY↗

DOE OSTI2026

Performance measurement of emerging 3- and 4-terminal tandem solar cells

Tandem solar cells are not limited to the conventional two-terminal (2-T) configuration. Multi-terminal designs like three-terminal (3-T) and four-terminal (4-T) devices have gained increasing attention in the PV community due to their relaxed current-matching requirement between subcells and their potential for enhanced energy yield. However, reliable and standardized methods for evaluating the performance of multi-terminal tandems remain underdeveloped. This work addresses this gap by providing comprehensive measurement guidelines tailored to these advanced configurations. We examine key coupling mechanisms between subcells, including the shared electrical load in 3-T devices and optical luminescent coupling in both 3-T and 4-T devices, to enable accurate and consistent performance evaluation. Furthermore, we propose two stabilized measurement methods for emerging 3-T tandem cells incorporating perovskite subcells: (1) a two-dimensional maximum-power-point tracking (MPPT) approach that continuously tracks both subcells' maximum power points (P MAX ) until convergence to stabilized outputs, and (2) a hybrid approach that combines MPPT for one subcell with stabilized current recording under fixed voltage biases near the P MAX of the other, allowing robust extraction of the overall stabilized P MAX (termed “MPPT + asymptotic P MA X scan” method). These methods directly address the dynamic current responses inherent to perovskite-containing tandems, providing a foundation for meaningful and reproducible performance comparisons.

14 SOLAR ENERGY↗

DOE OSTI2022

Quantifying Energy Flows in PV Circularity Processes: Preprint

As sustainability and end-of-life management become a hot topic to timely address in the PV community, a proper evaluation of the benefits of circular pathways such as recycling, reuse, and remanufacturing has not been performed holistically beyond material flows or LCA analysis. Energy flows are critical for evaluating energy generation technologies. Previously they have been used to compare renewables to fossil generation and then between PV technologies. This paper brings energy flows to bear on reaching circular pathways for PV. The energy flows to track energy usage, generation, and losses complementary to the mass flows are presented for silicon through the leverage of the PV ICE framework.

circular economy↗

DOE OSTI2025

A Convolution Neural Network for Voltage Event Classification at a Photovoltaic Inverter

This paper presents a convolutional neural network (CNN) developed to identify voltage events in photovoltaic (PV) inverters. The CNN is trained on synthetic data generated using the IEEE 13-bus distribution feeder model and evaluated on field measured data collected from Energy Northwest’s Horn Rapids Solar, Storage, and Training (HRSST) facility. The study focuses on two common voltage events: faults and voltage sags. The CNN is configured to analyze voltage and current waveforms from three-phase PV systems, demonstrating excellent accuracy during training. Field data from the HRSST facility is employed to assess its real-world performance, where the CNN achieves perfect identification of faults and voltage sags in a sample of nine events. This work highlights the potential of the proposed method to enhance PV protection schemes, providing a robust foundation for improved voltage event detection and grid reliability.

Cornachione, Matthew A.↗

DOE OSTI2022

PV Hosting Capacity Estimation: Experiences with Scalable Framework

Hosting capacity is an indication of the amount of solar photovoltaics (PV) that can be hosted in a distribution system without additional changes to infrastructure or oper-ations. This paper presents a framework for estimating the PV hosting capacity at scale. First, we analyze computational, modeling and other key challenges of performing relevant, large-scale simulations, provided along with the experiences and lessons learned. Then, we develop two open-source Python-based software tools to conduct repeatable distribution analyses: the Distribution Integration Solution Cost Options (DISCO) for configuring and analyzing simulations and the Job Automation and Deployment Engine (JADE) for parallelizing jobs on high-performance computing clusters. A case study of hosting capacity estimation for the SMART-DS San Francisco (SFO) 2000+ synthetic feeders, is used to demonstrate the capability of the developed DISCO+JADE framework and tools. The framework and tools can help utilities assess the overall hosting capacity of their service territory, which can help them better plan for the overall upgrade costs to integrate more PV in the future. The experiences are shared to aid the tool users and researchers to conduct relevant studies and research.

distributed energy resources↗

DOE OSTI2022

A Two-Level Model Predictive Control-Based Approach for Building Energy Management including Photovoltaics, Energy Storage, Solar Forecasting and Building Loads

This paper uses a two-level model predictive control-based approach for the coordinated control and energy management of an integrated system that includes photovoltaic (PV) generation, energy storage, and building loads. Novel features of the proposed local controller include (1) the ability to simultaneously manage building loads and energy storage to achieve different operational objectives such as energy efficiency, economic cost efficiency, demand response and grid optimization through the design of specific power trajectory tracking performance functionals, (2) an energy trim function that minimizes the impact of solar forecasting errors on system performance, and (3) the design of a state of charge controller that uses day-ahead forecast of solar power and building loads to intialize energy storage at the start of each day. The local controller is tested in simulation using an exemplary system with PV generation, energy storage and dispatchable building loads. Two sample days with different PV forecasts and multiple case scenarios are considered, and the performance of the algorithm in managing the real and reactive net building load trajectories and the ramp rate of PV injections into the utility network are evaluated. The simulations are based on actual forecasted and measured PV data, and the results show that the local controller meets the tracking requirements for real and reactive power within the operating constraints of the building.

14 SOLAR ENERGY↗