Joshua S Stein

Sandia National Laboratories · Photovoltaic Systems Evaluation Laboratory

Concentrating solar power (CSP) plants with integrated thermal energy storage (TES) have successfully been coupled with photovoltaics (PV) + chemical battery energy storage (BES) in recent commercial-scale projects to balance system cost and diurnal power availability. Sandia National Laboratories has been tasked with designing an advanced solar en...

Perovskite solar cells have shown a strong increase in efficiency over the last 15 years. With a record power conversion efficiency on small area above 34%, perovskite/silicon tandem solar cells already exceed the efficiency limit of silicon solar cells and their efficiency is expected to increase further. While predicted to take large markets shar...

All freely available plane‐of‐array (POA) transposition models and photovoltaic (PV) temperature and performance models in pvlib‐python and pvpltools‐python were examined against multiyear field data from Albuquerque, New Mexico. The data include different PV systems composed of crystalline silicon modules that vary in cell type, module constructio...

Different data pipelines and statistical methods are applied to photovoltaic (PV) performance datasets to quantify the performance loss rate (PLR). Since the real values of PLR are unknown, a variety of unvalidated values have been reported. As such, the PV industry commonly assumes PLR based on statistically extracted ranges from the literature. H...

The International Energy Agency PVPS Task 13 has assembled an international team of photovoltaic (PV) researchers from government labs, academia, and industry to study the specific application of bifacial PV modules deployed on tracking systems. This configuration is of particular interest as it has been identified as the PV system design with the...

The Photovoltaic (PV) Performance Modeling Collaborative (PVPMC) organized a blind PV performance modeling intercomparison to allow PV modelers to blindly test their models and modeling ability against real system data. Measured weather and irradiance data were provided along with detailed descriptions of PV systems from two locations (Albuquerque,...

The accurate quantification of the performance loss rate of photovoltaic systems is critical for project economics. Following the current research activities in the photovoltaic performance and reliability field, this work presents a comparative assessment between common change point methods for performance loss rate estimation of fielded photovolt...

Metal halide perovskite solar cells (PSCs) and modules offer promise as an ultralow-cost, high-performing renewable energy source due to their high-power conversion efficiency (PCE), low materials cost, diverse deposition routes (e.g., vapor phase, solution-processable fabrication), and potential use in tandem configurations, due to their bandgap t...

Low levelized cost of electricity (LCOE) has been identified as critical for widespread adoption of photovoltaics (PV) without subsidies. Maintaining decades-long high energy production is often an under-recognized opportunity in meeting cost goals because component lifetimes are not fully quantified at the time of manufacture. Whereas certain stan...

Perovskite solar cells (PSCs) promise high efficiencies and low manufacturing costs. Most formulations, however, contain lead, which raises health and environmental concerns. In this review, we use a risk assessment approach to identify and evaluate the technology risks to the environment and human health. We analyze the risks by following the tech...

Cloud cover significantly affects the solar irradiance incident on a photovoltaic (PV) module, so identifying and predicting cloud motion is useful for PV applications, such as informing tracker movements and predicting short-term power. This work presents two algorithms to aid in real-time weather predictions, i.e., a convolutional autoencoder (CA...

Irradiance transposition models seem to perform well, except the Isotropic with -11.25 W/m² underestimation. Most temperature models could not capture behavior when ΔΤ between module and ambient is negative. Uncertainties due to derate factors: modelers overbudgeted resulting in significant power underestimation; maybe ~10% is appropriate for comme...

Photovoltaic (PV) performance is affected by reversible and irreversible losses. These can typically be mitigated through responsive and proactive operations and maintenance (O&M) activities. However, to generate profit, the cost of O&M must be lower than the value of the recovered electricity. This value depends both on the amount of recovered ene...

The cost of photovoltaic (PV) modules has declined by 85% since 2010. To achieve this reduction, manufacturers altered module designs and bill of materials; changes that could affect module durability and reliability. To determine if these changes have affected module durability, we measured the performance degradation of 834 fielded PV modules rep...

PV module operating temperature is the second-most important factor influencing PV system yield—after irradiance—and a substantial contributor to uncertainty in energy system yield predictions. Models commonly used to predict operating temperature in system simulations are based on a simplified energy balance that lumps together different heat loss...

Classification machine learning models require high-quality labeled datasets for training. Among the most useful datasets for photovoltaic array fault detection and diagnosis are module or string current-voltage (IV) curves. Unfortunately, such datasets are rarely collected due to the cost of high fidelity monitoring, and the data that is available...

PV module operating temperature is the second most important factor influencing system yield, after irradiance. A variety of temperature models are used within yield simulation software to predict module operating temperature, which then determines operating efficiency. Four temperature models are frequently used: PVsyst, Faiman, SAPM and SAM NOCT....

PV module operating temperature is the second most important factor influencing system yield, after irradiance. A variety of temperature models are used within yield simulation software to predict module operating temperature, which then determines operating efficiency. Four temperature models are frequently used: PVsyst, Faiman, SAPM and SAM NOCT....

Metal halide perovskites are not only established as champion materials for conversion of solar energy to electricity but are also one of the promising candidates for solar driven fuel generation. In this paper, we report the photovoltaic devices' operational stability investigation in dry and humid nitrogen (N2) and carbon dioxide (CO2) environmen...

Fault detection and classification in photovoltaic (PV) systems through real-time monitoring is a fundamental task that ensures quality of operation and significantly improves the performance and reliability of operating systems. Different statistical and comparative approaches have already been proposed in the literature for fault detection; howev...

In the last decade and longer, photovoltaic module manufacturers have experienced a rapidly growing market along with a dramatic decrease in module prices. Such cost pressures have resulted in a drive to develop and implement new module designs, which either increase performance and/or lifetime of the modules or decrease the cost to produce them. I...

Operation and maintenance (O&M) and monitoring strategies are important for safeguarding optimum photovoltaic (PV) performance while also minimizing downtimes due to faults. An O&M decision support system (DSS) was developed in this work for providing recommendations of actionable decisions to resolve fault and performance loss events. The proposed...

This article presents a notable advance toward the development of a new method of increasing the single-axis tracking photovoltaic (PV) system power output by improving the determination and near-term prediction of the optimum module tilt angle. The tilt angle of the plane receiving the greatest total irradiance changes with Sun position and atmosp...

A linear performance drop is generally assumed during the photovoltaic (PV) lifetime. However, operational data demonstrate that the PV module degradation rate (Rd) is often nonlinear, which, if neglected, may increase the financial uncertainty. Although nonlinear behavior has been the subject of numerous publications, it was only recently that sta...

Failure diagnosis (detection and classification) in photovoltaic (PV) systems through data diagnostic algorithms is a fundamental task that ensures quality of operation and significantly improves the performance and reliability of operating PV systems. The scope of this work is to present the development of Failure Diagnosis Routines (FDRs) and Tre...

Accurate quantification of photovoltaic (PV) system degradation rate (RD) is essential for lifetime yield predictions. Although RD is a critical parameter, its estimation lacks a standardized methodology that can be applied on outdoor field data. The purpose of this paper is to investigate the impact of time period duration and missing data on RD b...

Corrective maintenance strategies are important for safeguarding optimum photovoltaic (PV) performance while also minimizing downtimes due to failures. In this work, a complete operation and maintenance (O&M) decision support system (DSS) was developed for corrective maintenance. The DSS operates entirely on field measurements and incorporates tech...

The advent of bifacial PV systems drives new requirements for irradiance measurement at PV projects for monitoring and assessment purposes. While there are several approaches, there is still no uniform guidance for what irradiance parameters to measure and for the optimal selection and placement of irradiance sensors at bifacial arrays. Standards a...

The IEA PVPS Task 13 group, experts who focus on photovoltaic performance, operation, and reliability from several leading R&D centers, universities, and industrial companies, is developing a framework for the calculation of performance loss rates of a large number of commercial and research photovoltaic (PV) power plants and their related weather...

b>Accepted Manuscript (Postprint): L. Micheli et al., “Improved PV Soiling Extraction through the Detection of Cleanings and Change Points,” IEEE Journal of Photovoltaics, Volume: 11, Issue: 2, March 2021.

b>Accepted Manuscript (Postprint): L. Micheli et al., “Improved PV Soiling Extraction through the Detection of Cleanings and Change Points,” IEEE Journal of Photovoltaics, Volume: 11, Issue: 2, March 2021.

This paper presents the first systematic comparison between south-facing monofacial and bifacial photovoltaic (PV) modules, as well as between south-facing bifacial and vertical east-west facing bifacial PV modules in Alaska. The state’s solar industry, driven by the high price of energy and dropping equipment costs, is quickly growing. The challen...

The IEC 61853 photovoltaic (PV) module energy rating standard requires measuring module power (and hence, efficiency) over a matrix of irradiance and temperature conditions. These matrix points represent nearly the full range of operating conditions encountered in the field in all but the most extreme locations and create an opportunity to develop...

Photovoltaic (PV) soiling profiles exhibit a sawtooth shape, where cleaning events and soiling deposition periods alternate. Generally, the rate at which soiling accumulates is assumed to be constant within each deposition period. In reality, changes in rates can occur because of sudden variations in climatic conditions, e.g., dust storms or prolon...

The photovoltaic (PV) energy rating is related to the energy yield performance of a PV module. Unlike the power rating, which is only related to the performance at a single operating point at 25°C, 1000 W/m , and AM1.5 spectrum (Standard Test Conditions, STC), the energy rating considers several characteristics of the PV module that affect the amou...

Dust accumulation significantly affects the performance of photovoltaic modules and its impact can be mitigated by various cleaning methods. Optimizing the cleaning frequency is essential to minimize the soiling losses and, at the same time, the costs. However, the effectiveness of cleaning lowers with time because of the reduced energy yield due t...

The virtual bifiPV Workshop was held in July 2020 to provide the solar industry with a forum for sharing and discussing research into bifacial PV technology. This report outlines major insights from the workshop to give the reader an overview of the latest developments in bifacial PV technology worldwide, from the lab to the field. Citations are dr...

Data integrity is crucial for the performance and reliability analysis of photovoltaic (PV) systems, since actual in-field measurements commonly exhibit invalid data caused by outages and component failures. The scope of this paper is to present a complete methodology for PV data processing and quality verification in order to ensure improved PV pe...

Different data pipelines and statistical methods are applied to photovoltaic (PV) performance datasets to quantify the PV module degradation rate. Since the real value of degradation rate is unknown, a variety of unvalidated values has been reported in the literature. As such, the PV industry commonly treats this metric in an assumptive manner base...