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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Exploring the Performance and Reliability of Screen-Printable Fire-Through Copper Paste on PERC Solar Cells

For 40 TW of PV required to transition our planet to 100% renewables, the silver (Ag) should disappear from PV production. Advantages of copper (Cu) over silver (Ag) include 1) bulk Cu has a similar conductivity to Ag (1.7 mu O-cm for Cu, 1.6 mu O-cm for Ag) and 2) Cu is approximately 100 times cheaper than Ag, making it an excellent potential replacement. Problems associated with copper (Cu) contacts include 1) easy oxidation and 2) diffusion into the Si cell and recombination activity.

copper paste↗
DOE OSTI2023

Real-Time Regional PV Spinning Reserve Estimator with AGC Look-Ahead Windows

Curtailed PV generation is a zero-marginal cost spinning reserve that can be used for a number of active power control services. However, unlike the traditional spinning reserve providers, i.e., fossil-fueled generators, who have well-defined operating characteristics, e.g., available headroom or potential high limit (PHL), PV plants have by nature variable and uncertain operating characteristics. To ensure the effective coordination between PV plants and the system operator during an active power control event, accurate forecasts of the PV PHL are essential. A novel reference-control grouping based scaling method has been proposed by NREL to estimate the PV PHL in real-time. This work further enhances the methodology by: 1) improving the model accuracy through machine learning; 2) considering look-ahead windows introduced by the computation and communication latencies; 3) applying the method to regional spinning reserve estimation. A significant performance improvement, over 99% of estimation error reduction, has been observed based on real-world data collected by CAISO and PV plant operators.

potential high limit↗
DOE OSTI2022

Record Efficiency Multijunction Solar Cells with Strain-Balanced Quantum Well Superlattices

The absorption edge of a GaAs solar cell can be tuned to longer wavelengths with strain-balanced quantum wells, as an alternative to metamorphic epitaxy. For one-sun photovoltaic applications, an optimum bandgap for both single and multijunction solar cells is near the broad water absorption peak at 930 nm and can be accessed by a Ga0.9In0.1As alloy. This alloy is strained with respect to the GaAs substrate, and so only very thin ~10 nm layers can be grown without relaxation via dislocation formation. However, solar cells require significant thickness for complete absorption of the incoming solar spectrum, requiring many such layers. We have designed quantum well superlattices with up to 300 sets of carefully tuned strain-balanced GaInAs/GaAsP pairs by limiting composition modulation and material degradation. We have incorporated quantum well solar cells into multijunction devices to achieve record 32.9% two-junction and 39.5% three-junction solar cells under standard one-sun illumination. We will describe the physics of the quantum well devices and the growth conditions that lead to sharp interfaces and good material quality, as well as the characterization of the efficiencies.

GaAs↗
DOE OSTI2023

Real-Time Regional PV Spinning Reserve Estimator with AGC Look-Ahead Windows: Preprint

Curtailed PV generation is a zero-marginal cost spinning reserve that can be used for a number of active power control services. However, unlike the traditional spinning reserve providers, i.e., fossil-fueled generators, who have well-defined operating characteristics, e.g., available headroom or potential high limit (PHL), PV plants have by nature variable and uncertain operating characteristics. To ensure the effective coordination between PV plants and the system operator during an active power control event, accurate forecasts of the PV PHL are essential. A novel reference-control grouping based scaling method has been proposed by NREL to estimate the PV PHL in real-time. This work further enhances the methodology by: 1) improving the model accuracy through machine learning; 2) considering look-ahead windows introduced by the computation and communication latencies; 3) applying the method to regional spinning reserve estimation. A significant performance improvement, over 1.6% of estimation error reduction, has been observed based on real-world data collected by CAISO and PV plant operators.

potential high limit↗
DOE OSTI2020

Synchronverter-based Control of Multi-Port Autonomous Reconfigurable Solar Plants (MARS)

Control of integrated photovoltaic (PV) plants with energy storage systems (ESSs) has become an important research and development topic in recent times. In this context, a Multi-port Autonomous Reconfigurable Solar (MARS) plant that integrates PV and ESS to alternating current transmission grid and high-voltage direct current (HVdc) link is studied in this paper. With penetration of power electronic based resources in the grid, the grid’s capability to recover from frequency or voltage disturbances are reduced. Therefore, one of the vital objectives of any new grid integrated power electronic resource is to provide advanced control functions like voltage and frequency support to the grid during disturbances. In this research work, a detailed implementation of a synchronverter-based control algorithm of MARS is presented. The proposed control algorithm and the MARS control architecture are evaluated through simulations on PSCAD/EMTDC simulation platform to showcase the performance in different operating conditions. In addition, they are evaluated in Opal-RT offline simulation models which can also be used to perform control-hardware-in-the-loop (cHIL) tests.

Marthi, Phani Ratna Vanamali↗
DOE OSTI2022

Forecasting Distributed PV Adoption in Barranquilla, Colombia [Slides]

The objective of the dGen Colombia project is to provide projections to 2050 on distributed PV deployment by sector for a range of scenarios for Barranquilla, Colombia. NREL used the open-source Distributed Generation Market Demand Model (dGen) adapted for international projects for this analysis. As part of this analysis, technical potential, economic potential, and adoption projections of rooftop and groundmount PV for the city of Barranquilla are presented. Five main scenarios and their combinations were modeled to provide insight on the impact of increased demand from electric vehicles, air conditioning, and time-of-use tariffs.

14 SOLAR ENERGY↗
DOE OSTI2021

Solar +: Clean Energy Strategies for the Sunshine State (Final Technical Report (FTR) of the Florida Alliance for Accelerating Solar and Storage Technology Readiness (FAASSTeR))

This reports on a four-year effort to provide foundational research, analysis, strategies and assistance to help Florida, and other states that might learn from this work, to grow solar energy in conjunction with other distributed energy resources by addressing and overcoming existing barriers, and in way that delivers increased value. The start of this effort coincided with an inflection point of sorts into a new dawn for solar energy in Florida, where the Sunshine state’s national ranking in total installed solar, according to the Solar Energy Industries Association (SEIA), has rose from 13th to 4th. Florida has now become the national leader in annual utility-scale solar growth as dozens of large plants have come online. Also, during this time, Florida utilities have expressed a strong and growing interest in understanding the role of energy storage and how to best plan for and deploy this unique resource as part of strategies to grow solar. The utility-scale solar growth experienced has been fueled by the economics of solar cost-parity with natural gas combined cycle plants and Florida Public Service Commission’s (PSC) approval of cost-recovery for the Investor-Owned Utilities (IOU’s), primarily through the Solar Base Rate Adjustment (SoBRA) mechanism. This has led to gigawatts (GW’s) of rate-based solar capacity additions over several years, along with fairly significant amounts of energy storage. Meanwhile, municipal electric utilities, which, collectively, are the third largest source of power in the state, have been increasing solar considerably through power purchase agreements (PPA’s) and are on track to have close to 1 GW of grid-connected solar by 2024. Florida’s municipal utilities and the Florida Municipal Electric Association (FMEA) have been key partners in the Florida Alliance for Accelerating Solar and Storage Technology Readiness (FAASSTeR), formed to carry out this effort. The six largest of these have been Core Team utilities, engaging throughout the project in weekly calls, discussions, and project direction, participating in and hosting workshops and benefiting from technical assistance in several areas.

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 OSTI2025

Characterization of dangling bond defects at the crystalline Si/SiO x interface in a polycrystalline Si passivating contact solar cell at room temperature with electrically detected magnetic resonance spectroscopy

Monocrystalline silicon solar cells can achieve photoconversion efficiencies exceeding 26%; however, performance-limiting defects that trap carriers continue to be a challenge. In this work, we have characterized Si solar cells with tunneling SiO x /polycrystalline-Si (poly-Si) passivating contacts (TOPCon) on As-doped Czochralski Si wafers with electrically detected magnetic resonance (EDMR) spectroscopy. We fabricated 2 × 20 mm 2 TOPCon-like mini solar cells with edge passivation alongside larger 4 cm 2 sister cells and obtained similar device characteristics. We performed EDMR spectroscopy at 300 K on two minicells with different degrees of surface passivation based on the recombination parameter, J o , values of 40 and 310 fA/cm2. We optimized the resolution and the signal-to-noise ratio of the EDMR response of the minicells by varying the forward bias voltage and the magnetic field modulation amplitude. We detect two distinct signals with EDMR spectroscopy, an axial-like signal at g = 2.009, 2.0087, and 2.0015, and an isotropic signal at g = 2.0024, which we attribute to Si dangling bonds (P b0 and P b centers) and boron–oxygen related defects, respectively, at or near the c-Si/SiO x interface. The EDMR signals were lower for the cell with a lower value of J o , while the ratio of the two defect populations was very similar. The EDMR signal increases with forward bias but drops to zero at bias voltages >0.5 V, consistent with interface defects within or near the boron-doped emitter depletion region. Our study demonstrates a method to fabricate minicells that can be characterized with EDMR spectroscopy to detect industrially relevant defects in TOPCon cells.

14 SOLAR ENERGY↗
DOE OSTI2021

Effect of Dopant Compensation on the Conductivity of the Intrinsic poly-Si Isolation Region in Passivated IBC Silicon Solar Cells

The performance of IBC solar cells depends on the ability of this region to electrically isolate the doped fingers so that shunting does not occur and reduce the cell fill factor. We report on simulations which model the region between the p- and n-type poly-Si fingers of interdigitated back contact (IBC) solar cells as a series of resistors extending from one doped finger to the other. We demonstrate that the existence of a well compensated region between the doped fingers is enough to prevent shunting and loss of cell performance, despite contamination of dopants from the opposing dopant fingers. We show through these simulations that a net doping concentration below ~1018 cm-3 will enable a high resistivity and identify the conditions under which this highly resistive region forms despite imperfect finger edges. Additionally, we apply this analysis to tails measured by time-of-flight secondary ion mass spectrometry and confirm this hypothesis for our experimentally measured tails.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2022

Room Temperature, Dip Coating Organic Passivation for c-Si Surfaces

Surface passivation of crystalline Si (c-Si) to reduce recombination rate is crucial to obtain high-efficiency c-Si solar cells. A fast passivation technique that can be performed at room temperature is needed when studying the degradation behaviors using various characterization methods to not destroy the degraded states. In this contribution, we explore Nafion via dip coating on n-type Cz wafers. We show that both the Nafion concentration and the conditions of surface and edge affect the passivation quality, and we achieve excellent passivation quality of iVoc of 716 mV, with a saturation current density (J0) of 7 fA/cm2. Additionally, electron paramagnetic resonance (EPR) shows Nafion can be used under cryogenic temperature and reveals the reduction of Si dangling bond after Nafion treatment.

dielectric solar cell↗
DOE OSTI2023

Vegetation Management Lessons Learned and Helpful Tools

The InSPIRE Project is investigating questions around vegetation management and agrivoltaics at solar sites across the US. Results from research at three Enel Green Power pollinator-friendly solar sites in Minnesota have shown that the success of different pollinator-friendly seed mixes depend on the ecoregion and can vary from site to site. Results from the Enel Green Power sites also showed that weed coverage decreases dramatically by three years post seeding. The InSPIRE project has also created resources like The 5 C's of Agrivoltaics and an online agrivoltaics financial calculator to help farmers, land owners, developers, and facility operators with vegetation management at solar facilities. The PV-SMaRT calculator was created by the University of Minnesota in partnership with NREL to help with questions surrounding storm-water runoff at PV sites.

agrivoltaic↗
DOE OSTI2020

Activation Energy for End-of-Life Solder Bond Degradation: Thermal Cycling of Field-Aged PV Modules

The longevity of solar photovoltaic modules depends on the durability and reliability of their components, one of which is the solder bonds in interconnect ribbons. The solder joints experience stresses from thermal cycling and constant elevated temperatures (40 °C-70 °C) in regular field operation leading to thermo-mechanical fatigue and intermetallic compound formation. To study the end-of-life wear-out mechanisms and to obtain activation energy of solder bond degradation, here two field-aged modules from Arizona-a 21-year-old Solarex MSX60 module (with Sn62Pb36Ag2 at the solder joints) and an 18-year-old Siemens M55 module (with Sn60Pb40 at the solder joints)-underwent 800 and 400 modified thermal cycles, respectively. Using three heating blankets, each module had three temperature zones maintained at 85, 95, and 105 °C during the 15-min hot dwell time of the thermal cycle. Cell-level series resistance data obtained from three temperature zones enabled the calculation of activation energy for solder bond degradation for the MSX60 and the M55 modules to be 0.12 eV and 0.35 eV, respectively. From each temperature zone in both modules, busbar-solder samples were obtained, imaged through SEM, and analyzed with energy-dispersive X-ray spectroscopy. In the MSX60 module with traces of Ag in the solder material, phase segregation and growth were primarily observed at high temperatures. For M55 modules without Ag in the solder material, major phase segregation was observed in all temperature zones. The IMC thickness for both modules increased with increasing module temperature. The beneficial effect of Ag in solder material on mitigating solder bond degradation is presented.

14 SOLAR ENERGY↗
DOE OSTI2022

Enabling Floating Solar (FPV) Deployment: Policy and Operational Considerations

Floating solar photovoltaics, or "floating PV", offer an opportunity for scaling up the deployment of renewable energy on inland and offshore bodies of water. Floating PV presents the opportunity to: increase clean energy generation to help meet growing demand; lessen the potential for land-use conflicts; help existing hydropower systems optimize their operation; and adapt to increasing temperatures and drought events by reducing the rate of evapotranspiration of waterways. There is significant promise for floating PV deployment in several Southeast Asian countries, especially those rich in hydropower resources, such as Laos and Thailand, but deployment remains limited. This slide deck presents an overview of NREL's research on (1) the policy, economic, environmental, and cultural barriers that currently exist, (2) recently completed modeling exercise on the potential operational benefits of pairing floating PV and hydropower, (3) international best practices that can be adopted to Southeast Asia, and (4) plans for high-resolution floating PV technical potential assessment.

Asia Clean Energy Forum↗
DOE OSTI2021

Is 3D/2D Passivation a Secret to Success for Polycrystalline Thin-Film Solar Cells?

Three leading thin-film photovoltaic (PV) technologies - cadmium telluride (CdTe), CuIn1-xGaxSe2 (CIGS), and perovskite solar cells (PSCs) - are all polycrystalline, but otherwise appear to have little in common. A comprehensive examination of these technologies, however, reveals a common theme: the formation of two-dimensional (2D) van der Waals materials at three-dimensional (3D) absorber interfaces and grain boundaries. In CdTe, the 2D compound is CdCl2; in CIGS, it is XInSe2 (X= K, Rb, Cs) with X depending on the heavy-alkali post-deposition treatment used; and in lead halide PSCs, PbI2 forms naturally, but many new, more stable, 2D perovskites have also been incorporated. Generally, these 2D interfacial materials are present not by design, but instead have evolved from their 3D counterparts during standard device processing. Here, new data, together with evidence compiled from the literature, are presented to illustrate both the existence of 3D/2D interfaces in CdTe, CIGS, and PSCs, and their correlation with improved passivation and device performance. This suggests that 3D/2D passivation may be a heretofore unappreciated key to successful polycrystalline thin-film PV. Finally, the desired attributes of successful low-dimensional layers are presented with rational design strategies for next generation polycrystalline solar cells.

3D/2D↗