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DOE OSTI2023

DuraMAT Technology Scouting Report: Assessing Module Reliability Risks Associated with Projected Technological Changes

Maintaining the reliability of photovoltaic (PV) modules in the face of rapidly changing technology is critical to maximizing solar energy's contribution to global decarbonization. Our presentation describes expected changes in PV technology and their impacts on performance and reliability. We leverage PV market reports, interviews with PV researchers and other industry stakeholders, and peer-reviewed literature to narrow the multitude of possible changes into a manageable set of 11 impactful trends likely to be incorporated in near-term crystalline-silicon module designs. We group the trends into four categories (module architecture, interconnect technologies, bifacial modules, and cell technology) and explore the drivers behind the changes, their interactions, and associated reliability risks and benefits. Our analysis identifies specific areas that would benefit from accelerating the PV reliability learning cycle, to assess emerging module products and designs more accurately. We recommend that researchers continue tracking module technologies and their reliability implications so efforts can be focused on the most impactful trends. As the rapid technological turnover continues, it is also critical to incorporate fundamental knowledge into models that can predict module reliability. Predictive capabilities complete the PV reliability learning cycle-reducing the time required to assess new designs and mitigating the risks associated with large-scale deployment of new products.

bifacial↗

DOE OSTI2018

Estimating the Effects of Module Area on Thin-Film Photovoltaic System Costs

We investigate the potential effects of module area on the cost and performance of photovoltaic systems. Applying a bottom-up methodology, we analyzed the costs associated with thin-film modules and systems as a function of module area. We calculate a potential for savings of up to 0.10/Wand0.13/W in module manufacturing costs for CdTe and CIGS respectively, with large area modules. We also find that an additional 0.04/W savings in balance-of-systems costs may be achieved. Sensitivity of the /W cost savings to module efficiency, manufacturing yield, and other parameters is presented. Lifetime energy yield must also be maintained to realize reductions in the levelized cost of energy; the effects of module size on energy yield for monolithic thin-film modules are not yet well understood. Finally, we discuss possible non-cost barriers to adoption of large area modules.

14 SOLAR ENERGY↗

DOE OSTI2018

Q3/Q4 2017 Solar Industry Update

This technical presentation provides an update on the major trends that occurred in the solar industry in the Q3 and Q4 of 2017. Major topics of focus include global and U.S. supply and demand, module and system price, investment trends and business models, and updates on U.S. government programs supporting the solar industry.

14 SOLAR ENERGY↗

DOE OSTI2024

PV Modules Temperature Variation and Patterns in Medium and Utility-Scale Floating PV Systems

This paper presents the preliminary results and findings of the four operational Floating PV systems across the USA. At each site, temperature of five PV modules located at North-West, North-East, Middle, South-West, and, South-East have been monitored through the Resistant Temperature Detector (RTD) sensors. Three RTDs were attached to each PV module on the rear-side along the diagonal at top, middle and bottom cells. The preliminary results reveal wide temperature differences among the inter and intra PV modules. Besides this, wave pattern temperatures were observed in a few PV modules. The final results, findings, and, factors responsible will be investigated during the next few months. Index Terms - photovoltaic module, floating PV systems, string, array, temperature, mismatch, utility scale.

ENGINEERING,SOLAR ENERGY↗

DOE OSTI2019

Q2/Q3 2019 Solar Industry Update

This technical presentation provides an update on the major trends that occurred in the solar industry in the first three quarters of 2019. Major topics of focus include costs and deployment, the global and U.S. supply and demand of PV, module and system price, investment trends and business models, and updates on U.S. government programs supporting the solar industry.

14 SOLAR ENERGY↗

DOE OSTI2018

III-V/Si Tandem Cell to Module Interconnection - Comparison Between Different Operation Modes

III-V/Si tandem solar cells have the potential to surpass the theoretical efficiency limit of silicon solar cells. On the cell level it was shown at this conference that three-terminal tandem (3T) devices consisting of III-V top and Si bottom cell perform as well as operating the subcells independently. However, integrating these 3T devices in a module requires voltage matching of the top and the bottom cell. Here we investigate the robustness of 3T III-V/Si tandem devices in comparison with independently operated and current matched two terminal devices with respect to spectral and thermal effects. Under most conditions, interconnected voltage matched devices are able to perform as well as those with independent operation of the top and bottom cell, and prove that 3T devices significantly outperform current matched devices.

14 SOLAR ENERGY↗

DOE OSTI2018

Elucidating potential-induced degradation in bifacial PERC silicon photovoltaic modules

This paper elucidates the behavior and underlying mechanism of potential-induced degradation (PID) on the rear side of p-type monocrystalline silicon bifacial passivated emitter and rear cell (PERC) photovoltaic modules. At 50 degrees C, 30% relative humidity, and -1000 V bias to the solar cells with aluminium foil on the rear glass surface, the rear-side performance of bifacial PERC modules at standard testing conditions degraded dramatically after 40 hours with a 40.4%, 36.2%, and 7.2% loss in maximum power (Pmpp), short-circuit current (Isc), and open-circuit voltage (Voc), respectively. The front-side standard testing condition performance, on the other hand, showed less degradation; Pmpp, Isc, and Voc dropped by 12.0%, 5.2%, and 5.3%, respectively. However, negligible degradation was observed when the solar cells were positively biased. Based on I-V characteristics, electroluminescence, external quantum efficiency measurements, and the effective minority-carrier lifetime simulation, the efficiency loss is shown to be caused by the surface polarization effect; positive charges are attracted to the passivation/antireflection stack on the rear surface and reduce its field effect passivation performance. Extended PID testing to 100 hours showed an increase in device performances (relative to 40 hours) due to the formation of an inversion layer along the rear surface. In addition, replacing ethylene-vinyl acetate copolymer with polyolefin elastomer films significantly slows down the progression of PID, whereas a glass/transparent backsheet design effectively protects the rear side of bifacial PERC modules from PID. Furthermore, PID on the rear side of bifacial PERC modules is fully recoverable, and light greatly promotes recovery of the observed PID.

14 SOLAR ENERGY↗

DOE OSTI2025

Spatially resolved charge-transfer kinetics at the quantum dot–microbe interface using fluorescence lifetime imaging microscopy

Integrating the optoelectronic properties of quantum dots (QDs) with biological enzymatic systems to form microbe-semiconductor biohybrids offers promising prospects for both solar-to-chemical conversion and light-modulated biochemical processes. Developing these nano–bio hybrid systems necessitates a deep understanding of charge-transfer dynamics at the nano–bio interface. Photoexcited carrier transfer from QDs to microbes is driven by complex interactions, with emerging insights into the relevant thermodynamic and kinetic factors. The heterogeneities of both microbes and QD ensembles pose significant challenges in mechanistic understanding, which is critical for designing advanced nano–bio hybrids. We used fluorescence lifetime imaging microscopy to analyze charge transfer between a CdSe QD film andShewanella oneidensismicrobes. We correlated the spatiotemporal fluorescence data with an analytical model. Our analysis revealed two distinct distributions of QD de-excitation pathways. The characteristics of these distributions: 1) a faster transfer rate ( k ¯ E T 1 = 1.5 10 9 s - 1 ), with a lower acceptor number ( N ¯ a 1 = 0.03 ) and 2) a slower transfer rate ( k ¯ E T 2 = 4.1 10 8 s - 1 ) with a higher acceptor number ( N ¯ a 2 = 0.18 ). We assign these distributions to the indirect and direct electron transfer mechanisms, respectively. Our findings demonstrate how spectroscopic imaging can uncover fundamental electron transfer mechanisms at complex interfaces, offering valuable design principles for future nano–bio hybrids.

Science & Technology - Other Topics↗

DOE OSTI2021

Technology Evaluation of the Yotta SolarLEAF: A Panel-Based Thermally Managed Battery Module

In 2019, the United States installed 13.3 gigawatts of solar energy production capacity. This demand for solar will continually increase as the phasing out of fossil fuels continue. As the demand for solar energy grows, so does the demand to store this generated energy. It is projected that by 2035 the global demand for stationary energy storage will reach the terawatt scale. So, scalable solutions with suitable thermal management systems are required to meet future demand. Yotta Solar has developed an ESS system, the Yotta LEAF, that provides solar energy storage without increasing the footprint of solar arrays. This is particularly useful in applications with limited space (e.g., building roof) and where large scale batteries require strong requirements for fire suppression systems. As part of the Wells Fargo Innovation Incubator (IN2), the National Renewable Energy Laboratory (NREL) has conducted a third-party technology validation of Yotta's alpha prototype. The report includes the objectives, technology description, methodology, and results from experiments conducted at the Thermal Transfer Facility (TTF) at NREL.

14 SOLAR ENERGY↗

DOE OSTI2019

Progress and Challenges in Absorber and Interface Fabrication of Polycrystalline CdTe Photovoltaics

Polycrystalline thin-film CdTe device efficiency of over 19% has been achieved at Colorado State University using a highly repeatable and scalable sublimation process. Record efficiency for research scale CdTe photovoltaics has been reported to be over 22% and highest reported module efficiency is over 18% by First Solar Inc. Use of Se alloying with CdTe to form a lower band-gap CdSexTe1-x (CST) alloy has led to higher devices efficiencies with better current collection. Recent materials characterization has revealed that Se may be responsible for more than just reduction of band-gap. With CdCl2 treatment Cl is known to very effectively passivate defects at CdTe grain boundaries. Recent materials and electrical characterization have shown that Se has a very similar behavior to Cl at the grain boundaries of polycrystalline CdTe. These include Se decorating the grain boundaries like Cl in the diffusion region between CST and CdTe while cross-section cathodoluminescence maps show substantially higher signal intensity in regions with Se. Double heterostructures fabricated using CdSeTe with Al2O3 as a passivating oxide have been measured to have several hundred nanosecond bulk recombination lifetime. These films were also measured to have surface recombination velocity of under 100 cm/s. These results among others emphasis that Se also helps in passivation of grain boundaries. High absorber quality may help in mitigating the voltage deficit that has traditionally been the largest limiting factor in CdTe photovoltaics in achieving efficiency closer to Shockley-Queisser limit. In addition to graded absorber devices and double heterostructures, replacing the traditional Cu doping with more advanced group V doping is an important research effort that maybe critical for future improvements in device efficiency. Nitrogen, Phosphorous, Arsenic and Antimony doping has been investigated by several research groups. Advanced co-sublimation hardware developed at Colorado State University provides researchers with a unique capability of depositing films for group V doping with Cd overpressure. Such deposition under Cd overpressure causes formation of CdV which is known to be favorable for incorporation of group V dopant and activation. Utilizing the high absorber and interface quality material and higher doping, efforts are in progress to fabricate polycrystalline devices with open-circuit voltage over 1V and device efficiency over 24%.

Munshi, Amit↗

DOE OSTI2017

One Year Performance Results for the Prism Solar Installation at the New Mexico Regional Test Center: Field Data from February 15 2016 - February 14 2017.

A 9.6 kW test array of Prism bifacial modules and reference monofacial modules installed in February 2016 at the New Mexico Regional Test Center has produced one year of performance data. The data reveal that the Prism modules are out-performing the monofacial modules, with bifacial gains in energy over the twelve-month period ranging from 17% to 132%, depending on the orientation and ground albedo. These measured bifacial gains were found to be in good agreement with modeled bifacial gains using equations previously published by Prism Solar. The most dramatic increase in performance was seen among the vertically mounted, west-facing modules, where the bifacial modules produced more than double the energy of monofacial modules in the same orientation. Because peak energy generation (mid- morning and mid-afternoon) for these bifacial modules may best match load on the electric grid, the west-facing orientation may be more economically desirable than traditional south-facing module orientations (which peak at solar noon).

14 SOLAR ENERGY↗

DOE OSTI2017

Q4 2016/Q1 2017 Solar Industry Update

This technical presentation provides an update on the major trends that occurred in the solar industry in the fourth quarter of 2016 and the first quarter of 2017. Major topics of focus include global and U.S. supply and demand, module and system price, investment trends and business models, and updates on U.S. government programs supporting the solar industry.

14 SOLAR ENERGY↗

DOE OSTI2023

Fall 2023 Solar Industry Update [Slides]

Each quarter, the National Renewable Energy Laboratory (NREL) conducts the Quarterly Solar Industry Update, a presentation of technical trends within the solar industry. Each presentation focuses on global and U.S. supply and demand, module and system price, investment trends and business models, and updates on U.S. government programs supporting the solar industry. This quarter we also provide additional analysis on the domestic content of U.S. PV installations.

14 SOLAR ENERGY↗

DOE OSTI2024

Winter 2024 Solar Industry Update

14 SOLAR ENERGY↗

DOE OSTI2024

Spring 2024 Solar Industry Update

Each quarter, the National Renewable Energy Laboratory (NREL) conducts the Quarterly Solar Industry Update, a presentation of technical trends within the solar industry Each presentation focuses on global and U.S. supply and demand, module and system price, investment trends and business models, and updates on U.S. government programs supporting the solar industry.

14 SOLAR ENERGY↗

DOE OSTI2024

Fall 2024 Solar Industry Update [Slides]

14 SOLAR ENERGY↗

DOE OSTI2019

Model for Characterization and Optimization of Spectrally Selective Structures to Reduce the Operating Temperature and Improve the Energy Yield of Photovoltaic Modules

Many existing commercially manufactured photovoltaic modules include a cover layer of glass, commonly coated with a single layer antireflection coating (ARC) to reduce reflection losses. As many common photovoltaic cells, including c-Si, CdTe, and CIGS, decrease in efficiency with increasing temperature, a more effective coating would increase reflection of sub-bandgap light while still acting as an antireflection coating for higher energy photons. The sub-bandgap reflection would reduce parasitic sub-bandgap absorption and therefore reduce operating temperature. This reduction under realistic outdoor conditions would lead to an increase in annual energy yield of a photovoltaic module beyond what is achieved by a single layer ARC. However, calculating the actual increase in energy yield provided by this approach is difficult without using time-consuming simulation. Here, we present a time-independent matrix model which can quickly determine the percentage change in annual energy yield of a module with a spectrally selective mirror by comparison to a baseline module with no mirror. The energy benefit is decomposed into a thermal component from temperature reduction and an optical component from increased transmission of light above the bandgap and therefore increased current generation. Time-independent matrix model calculations are based on real irradiance conditions that vary with geographic location and module tilt angle. The absolute predicted values of energy yield improvement from the model are within 0.1% of those obtained from combined ray-tracing and time-dependent finite-element simulations and compute 1000x faster. Uncertainty in the model result is primarily due to effects of wind speed on module temperature. Optimization of the model result produces a 13-layer and a 20-layer mirror, which increase annual module energy yield by up to 4.0% compared to a module without the mirror, varying depending on the module location and tilt angle. Finally, we analyze how spectrally selective mirrors affect the loss pathways of the photovoltaic module.

14 SOLAR ENERGY↗

DOE OSTI2023

Life-cycle costing assessment of back contact doping and encapsulation alternatives for increasing the life expectancy of CdTe PV modules (Final Report)

Contribution of Research to the State-of-Knowledge This research produced comparative sustainability evaluations of back contact doping and encapsulation alternatives considered by First Solar for decreasing degradation and increasing the life of the cadmium telluride (CdTe) photovoltaic (PV) modules. Technical Effectiveness and Economic Feasibility of Methods Investigated A holistic life-cycle-assessment of the alternatives considered for longer module operational lives, showed that they add between 0.2% and 2% to environmental impact indicators at the cradle-to-gate module level, but at the cradle-to-grave system level, alternative materials offer only benefits (i.e., environmental impact indicator decreases) to the public and the environment. Parallel experimental studies at First Solar showed that the use of the considered alternative materials did not impact the effectiveness of the current module recycling separations and material recovery processes. Furthermore, the increment on the module manufacturing cost due to using alternative materials was estimated to be negligible (i.e., >1%) and longer module lives more than compensate cost increases. Specifically, increase of the current warranted module life of 30 years to 50 years, would decrease the levelized cost of electricity (LCOE) from $40/MWh to $24/MWh for utility-scale installations in the US-SW, the economic feasibility of the considered alternatives is assured. Benefit to the Public With decreasing degradation from the current ~0.3%/year of Series 6 modules to less than 0.2%/year, the public will be benefited by longer photovoltaic operational lives, and therefore. In addition, the requirement for end-of-life management is shifted from 30 years to 40 or 50 years, with profound benefits to the public and the environment.

14 SOLAR ENERGY↗