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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 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Establishment of a PID Pass/Fail Test for Crystalline Silicon Modules by Examining Field Performance for Five Years: Preprint

In an experiment with five module designs and multiple replicas, it is found that crystalline silicon cell modules that can pass a criterion of less than 5 percent power degradation in stress test conditions of 60 degrees Celsius, 85 percent relative humidity (RH), 96 h, and nameplate-rated system voltage bias show no power degradation by potential induced degradation in the range of 4-6 years duration in the Florida, USA environment. This data suggests that this chamber stress level is useful as a pass/fail criterion for PID, and will help ensure against degradation by system voltage stress in Florida, or less stressful climates, for at least 5 years.

14 SOLAR ENERGY↗
DOE OSTI2018

Photovoltaic system with improved AC connections and method of making same

An alternating current (AC) harness for a photovoltaic (PV) system includes a wire assembly having a first end and a second end, the wire assembly having a plurality of lead wires, and at least one AC connection module positioned at a location along a length of the wire assembly between the first end and the second end. Further, the at least one AC connection module includes a first connection terminal electrically coupled to the plurality of lead wires of the wire assembly and constructed to electrically couple the wire assembly with an output of a first PV module of the PV system. The at least one AC connection module also includes a second connection terminal electrically coupled to the plurality of lead wires of the wire assembly and constructed to electrically couple the wire assembly with an output of a second PV module of the PV system.

14 SOLAR ENERGY↗
DOE OSTI2018

Integrating More Solar with Smart Inverters: Preprint

In Hawai'i, the relatively high cost of electricity costs coupled with various incentives have made it cost-effective to install solar photovoltaics (PV) on residential homes and larger central-station PV plants. On some of the islands, PV has reached over 50% of the installed generation capacity base. To make sure these inverter-based PV plants can maintain stable and safe operations, new smart inverter functionality is being evaluated and demonstrated at significant scale across the islands This paper describes research conducted to validate high PV penetration scenarios with smart inverters and recent progress on the use of these advanced inverter grid support functions in actual power grids in Hawai'i.

14 SOLAR ENERGY↗
DOE OSTI2018

Design of a Microgrid Transition Controller II: System Recovery Under Abnormal Conditions: Preprint

This paper presents a microgrid transition controller for managing emergency operation when the microgrid experiences a system blackout caused by an internal or external fault. The developed transition controller consists of various application function blocks, including normal operation, emergency operation, and coordination between them. The developed microgrid transition controller is validated by a sample microgrid, and two test cases are investigated: islanded black start and grid-connected black start. The simulation results demonstrate the feasibility and effectiveness of the proposed microgrid transition controller for handling emergency operation and transitioning to normal operation.

14 SOLAR ENERGY↗
DOE OSTI2019

Effects of Reactive Power on Photovoltaic Inverter Reliability and Lifetime

For predicting the reliability and lifetime of Photovoltaic (PV) inverters, thermal cycling is considered the most important stressors in the inverter system. To realize this, a detailed electrothermal model of the PV inverter was developed along with the controllers. The model was verified by developing an in-house inverter, which was placed inside a thermal chamber to verify the losses and temperature rise within the system at various temperatures. After the verification of the model, a reduced order model of the inverter was implemented which can translate the mission profile of ambient temperature and solar irradiance into load profile of junction temperatures of the switches. The estimated junction temperature data was used to identify the reliability indices and predict the useful lifetime of the inverter system. After developing the models to predict useful lifetime of the system, the impact of reactive power on the overall reliability of the system was studied. Experiments show that lifetime and reliability of the inverter decreases as the operating power factor decreases from unity. The results are presented and discussed here.

14 SOLAR ENERGY↗
DOE OSTI2019

Bifacial PV System Performance: Separating Fact from Fiction

The performance of bifacial PV systems depends greatly on the installed conditions. Previous simulations and results have shown very high bifacial gain improvement, but this may not be the case for all conditions, particularly for large-scale systems with self-shading, lower-cost PV modules (PERC) which might have lower bifaciality coefficient, and field deployments over natural ground cover. But not to worry! Financial models indicate that even with these lower performance conditions, and with bifacial gain of 4%-9%, bifacial modules can still provide improved LCOE.

14 SOLAR ENERGY↗
DOE OSTI2018

Disaggregating Smart Meter Data to Identify Electric Loads and Control Opportunities

As utility data, such as smart meter data, becomes more broadly available, there is general interest in using it to improve utility operations and enable adoption of other advanced technology - such as solar photovoltaics (PV), energy storage, and controls. We explore one such use case - identifying electric resistance water heaters from smart meter data, as well as characterizing their potential for load-shifting to support grid voltage stability under high-penetration PV adoption. This paper shows the limitation of typical 15-minute data, and how shortterm capture of additional 1-minute data is needed to enable the desired application. Results indicate about 4 kWh water heating load can be shifted to align with peak sun hours in a low use home. This methodology is an example, and can be adapted to other grid-integrated efficient building use cases.

14 SOLAR ENERGY↗
DOE OSTI2019

Bifacial PV System Mismatch Loss Estimation

Nonuniform rear-irradiance on bifacial PV systems can cause additional mismatch loss, which may not be appropriately captured in PV energy production estimates and software. A simplified empirical relationship is presented that links the spatial variation of irradiance (to the resulting mismatch loss factor).

14 SOLAR ENERGY↗
DOE OSTI2019

Levelized-Cost-of-Electricity-Driven Design Optimization for Medium-Voltage Transformerless Photovoltaic Converters: Preprint

Design approaches for power electronics are typically focused on efficiency and power density; however, these strategies do not guarantee cost optimality in any well-defined sense. To overcome this shortcoming, we propose a design framework that yields circuit parameters that minimize the levelized cost of electricity (LCOE) of a generation system. LCOE serves as a meaningful metric since it captures total lifetime costs -- including hardware, balance of system, and maintenance costs\textemdash and includes the impacts of power conversion efficiency and revenue from harvested energy. To obtain a tractable design problem, we formulate an approximate LCOE improvement model that quantifies the changes in LCOE resulting from a candidate converter design. We apply this framework to a multilevel cascaded topology for low-voltage dc to medium-voltage ac conversion without line-frequency transformers. An example 200-kW commercial-scale system is studied and the solution yields a design with 15 cascaded stages, 98.89% efficiency, and an LCOE reduction of 3.6%.

14 SOLAR ENERGY↗
DOE OSTI2020

Grid-Following Inverters and Synchronous Condensers: A Grid-Forming Pair?: Preprint

As power systems across the globe continue to achieve higher instantaneous penetrations of power electronic converterinterfaced renewable sources, the stability of these power systems is challenged because of the removal of synchronous machines, from which stability is traditionally derived. Although technological solutions to these stability challenges are on the horizon, such as the use of grid-forming inverters, they are not yet widely applied to larger power systems, which presents operational challenges for power systems achieving these high instantaneous penetrations today. An interim solution using existing technologies is to pair synchronous condensers with grid-following inverters, which might prolong the stability of an operating power system while synchronous generators are turned off during periods of high renewable energy availability. This work examines the transient stability of such a solution using PSCAD simulations of a two-bus system coupled to a variedlength transmission line, with a synchronous condenser at one bus and a grid-following inverter with grid-support functionality at the other. The system is exposed to load step, balanced fault, and unbalanced fault perturbations. It was found that this simple system returned to a steady state for transmission line lengths up to 125 km after 10% load steps, or a variety of fault types.

14 SOLAR ENERGY↗
DOE OSTI2020

Machine Learning-Based PV Reserve Determination Strategy for Frequency Control on the WECC System

This paper proposes a machine learning based strategy, that is suitable for real-time operation, to determine the optimal photovoltaic (PV) power plants reserve for frequency control. The proposed machine learning algorithm is trained and tested on 1,987 offline simulations of a 60% renewable penetration Western Electricity Coordinating Council (WECC) system. On a realistic 1-day operation profile of the WECC system, the ML model demonstrates a savings of more than 40% PV headroom compared to a conservative approach.

14 SOLAR ENERGY↗
DOE OSTI2019

EFRC 10@10: Tackling the Energy Storage Problem for Grid-Scale Solar Power

Power from the electric grid that is generated by solar panels is already less expensive in many areas than that generated by fossil fuels. But as solar power facilities expand, the clean energy movement faces a difficult problem: while such facilities can generate more power than is needed in the middle of the day when the sun is shining, they can’t power the electrical grid in the evening or overnight. Storing grid-scale power in batteries would be extremely expensive. But what if solar energy could be stored cheaply as heat, and the heat converted to electricity when needed? That potential was among the reasons why the U.S. Department of Energy’s Office of Science funded an Energy Frontier Research Center (EFRC), the Solid-State Solar-Thermal Energy Conversion Center.

14 SOLAR ENERGY↗
DOE OSTI2023

Flexpower and Hydro-Hybrids

This is a presentation, given at the SETO visit on 6/21. It summarizes the GMLC Flexpower results and project as well as the Hydro-Hybrids results and project.

13 HYDRO ENERGY↗