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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 559 records · Page 31
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DOE OSTI2016

Coordination of International Standards with Implementation of the IECRE Conformity Assessment System to Provide Multiple Certification Offerings for PV Power Plants

To help address the industry's needs for assuring the value and reducing the risk of investments in PV power plants; the International Electrotechnical Commission (IEC) has established a new conformity assessment system for renewable energy (IECRE). There are presently important efforts underway to define the requirements for various types of PV system certificates, and publication of the international standards upon which these certifications will be based. This paper presents a detailed analysis of the interrelationship of these activities and the timing for initiation of IECRE PV system certifications.

14 SOLAR ENERGY↗
DOE OSTI2016

Voltage Support Study of Smart PV Inverters on a High-Photovoltaic Penetration Utility Distribution Feeder

This paper reports on tools and methodologies developed to study the impact of adding rooftop photovoltaic (PV) systems, with and without the ability to provide voltage support, on the voltage profile of distribution feeders. Simulation results are provided from a study of a specific utility feeder. The simulation model of the utility distribution feeder was built in OpenDSS and verified by comparing the simulated voltages to field measurements. First, we set all PV systems to operate at unity power factor and analyzed the impact on feeder voltages. Then we conducted multiple simulations with voltage support activated for all the smart PV inverters. These included different constant power factor settings and volt/VAR controls.

14 SOLAR ENERGY↗
DOE OSTI2018

Defining the Value of IECRE Certifications for Providing Confidence in PV System Performance

The International Electrotechnical Commission (IEC) established a new conformity assessment system for renewable energy (IECRE) to address the industry's need to assure investors of the value of their PV power plants. There has been significant activity in the past three years devoted to defining the requirements for several types of PV system certificates, and publication of the international standards upon which these certifications are based. Now the IECRE system faces the challenge of defining the value proposition for certification and convincing stakeholders that it should be a standard requirement in the marketplace. This paper presents a detailed analysis of the present situation and the plan for promotion of IECRE certifications to help achieve wider market penetration of PV power generation.

14 SOLAR ENERGY↗
DOE OSTI2020

Impact of Aggregated PV on Subsynchronous Torsional Interaction: Preprint

This paper investigates induced oscillation (specifically subsynchronous torsional interactions) in power systems arising from photovoltaic (PV) power modulation. Time domain simulations of a modified IEEE first-benchmark system are presented and analyzed. In the IEEE benchmark system, a PV generator was added at the same bus where the synchronous generator is connected. The impact of different parameters of the PV inverters volt-volt-ampere reactive (volt-var) curve on SSTI is examined. The most severe impact found arises from the time response of the inverters reactive power change. A second-order time response with natural frequency matching the rotor speed deviation oscillation frequency and low-damping ratio quickly drives the system to an unstable region. Although it is highly unlikely that conditions necessary for distributed energy resource-induced oscillations would occur in the field, with knowledge of this vulnerability in mind, inverters' control parameters can be designed to avoid it.

aggregated↗
DOE OSTI2022

A Sparse and Low Rank Penalized Signal Decomposition Model with Constraints: Anomaly Detection in PV Systems

Recently, robust PCA has seen its wide application in various industries for its ability to perform the task of anomaly detection. The essence of robust PCA approach is to break down the signal into a low rank component and sparse component. In many applications, a simple breakdown of the signal without accounting for the signs of low rank components and sparse components would violate the physical constraints of the decomposed signal. In addition, often times, the signals in the real world collected for a long duration has smooth changes within a day and between days. As an example, the power signals collected in a photovoltaic (PV) system are cyclostationary, exhibiting these characteristics. Neglecting the smoothness of signals would result in miss detection of anomalous signals which are smooth within a day but non-smooth between days and vice versa. In this paper, we developed a signal decomposition approach for the purpose of anomaly detection based on the idea of low rank and sparse decomposition taking into consideration the signs of the decomposed low rank and sparse components and the within-day and between-day smooth changes in the original signals. The proposed unsupervised approach for fault detection eliminates the need for faulty samples required by other machine learning methods. It does not require the full I-V characteristics to work. Furthermore, there is no need for complex modelling of PV systems as in the case of power loss analysis. Using Monte Carlo simulations, we demonstrate the ability of our proposed approach for detecting anomalies of different duration and severity in PV systems.

14 SOLAR ENERGY↗
DOE OSTI2024

Simulation-Based Analysis of Feeder Operation with Different PV Smart Inverter Functions on an Actual Distribution System: Preprint

High penetration of photovoltaics (PV) in distribution feeders can cause problems, such as overvoltage, reverse power flow, and large net load changes. Traditional voltage regulation devices, such as capacitors and voltage regulators, can solve some of these problems but might have some delays. Today, smart inverters are gradually being used to provide voltage regulation and frequency support in distribution systems. Different smart inverter settings have been recommended in various rules and standards; however, the potential benefits and their impacts on distribution system operation are not well compared and studied. This paper presents a comparison of different smart inverter settings as applied to a distribution system. An actual feeder model from San Diego Gas & Electric Company is used to conduct the simulation. Additionally, a load disaggregation method is proposed to disaggregate the load and PV profile for each load location using advanced metering infrastructure net load measurements. Then, different smart inverter settings are applied to the PV systems in the feeder, and the simulation results are compared. The results show that the implementation of specific functions of smart inverters can reduce voltage exceedances, and the utility can determine the specific inverter setting based on its operational requirements.

distribution system↗
DOE OSTI2017

Model Development of Degradation of PV Modules Backsheet with Locating Place of Module

Performance of a photovoltaic (PV) module is related to the micro-environment around the module. The position of photovoltaic modules in an array row have a large effect on the yellowing and gloss of PV module backsheet exposed in Dfa climatic zone (Gaithersburg, MD) with a polyethylene naphthalate (PEN) outer layer. Stress/Response models of yellowing and gloss-losing as function of location parameters of module, including the shed, row, measurement position in a same module and the distance of module location to the row center, are under development. The module installation height had the greatest influence on degradation of PEN PV backsheet in the Dfa climatic zone. The module backsheets at the end of an array have higher degradation rate (edge effect). The edge effect decreases with increasing of module installation heights.

14 SOLAR ENERGY↗
DOE OSTI2012

Development of a Visual Inspection Data Collection Tool for Evaluation of Fielded PV Module Condition

A visual inspection data collection tool for the evaluation of fielded photovoltaic (PV) modules has been developed to facilitate describing the condition of PV modules with regard to field performance. The proposed data collection tool consists of 14 sections, each documenting the appearance or properties of a part of the module. This report instructs on how to use the collection tool anddefines each attribute to ensure reliable and valid data collection. This tool has been evaluated through the inspection of over 60 PV modules produced by more than 20 manufacturers and fielded at two different sites for varying periods of time. Aggregated data from such a single data collection tool has the potential to enable longitudinal studies of module condition over time, technologyevolution, and field location for the enhancement of module reliability models.

14 SOLAR ENERGY↗
DOE OSTI2013

Estimating Rooftop Suitability for PV: A Review of Methods, Patents, and Validation Techniques

A number of methods have been developed using remote sensing data to estimate rooftop area suitable for the installation of photovoltaics (PV) at various geospatial resolutions. This report reviews the literature and patents on methods for estimating rooftop-area appropriate for PV, including constant-value methods, manual selection methods, and GIS-based methods. This report also presents NREL's proposed method for estimating suitable rooftop area for PV using Light Detection and Ranging (LiDAR) data in conjunction with a GIS model to predict areas with appropriate slope, orientation, and sunlight. NREL's method is validated against solar installation data from New Jersey, Colorado, and California to compare modeled results to actual on-the-ground measurements.

14 SOLAR ENERGY↗
DOE OSTI2014

BEopt-CA (Ex): A Tool for Optimal Integration of EE, DR and PV in Existing California Homes

Opportunities for combining energy efficiency, demand response, and energy storage with PV are often missed, because the required knowledge and expertise for these different technologies exist in separate organizations or individuals. Furthermore, there is a lack of quantitative tools to optimize energy efficiency, demand response and energy storage with PV, especially for existing buildings. As technology costs evolve (e.g., the ongoing reduction in the cost of PV), design strategies need to be adjusted accordingly based on quantitative analysis.

14 SOLAR ENERGY↗
DOE OSTI2016

Residential PV-Energy Storage Testing Collaboration with SunPower: Cooperative Research and Development Final Report, CRADA Number CRD-14-569

Residential scale energy storage devices have shown great promise to add value and improve the ability to integrate distributed and variable generation into the distribution grid. Battery energy storage systems combined with PV and advanced inverters can provide many services. These include extended backup power in case of grid failure, reductions in feeder and system level peak load, system level net load ramp reduction, grid management services both locally (e.g., voltage management) and bulk system (e.g., reserves) level, and improved grid reliability through grid voltage and frequency support. Even though the cost of the energy storage systems are decreasing, one of the main challenges related to the widespread deployment of energy storage, as found by the U.S. Department of Energy (DOE), is utility acceptance of storage technologies. Various interconnection challenges exist when connecting distributed PV-energy storage into the electrical distribution grid in terms of safety, reliability and stability of the electric power systems. Some of the urgent challenges, as seen by the manufacturers and installers are: safety of the battery cells and the packs, performance of the power conversion systems, effect of bidirectional power flow on existing utility equipment and qualification of solutions such as volt-ampere reactive (VAR) support and frequency regulation. Under this project, National Renewable Energy Laboratory (NREL) researchers will work with SunPower to address these challenges by research, testing and analysis at Energy System Integration Facility (ESIF) and energy storage testing laboratory at NREL. NREL's unique power hardware-in-the-loop (PHIL) capability will be utilized to evaluate system-level issues such as reverse power flow and VAR support (if available) for these PV-energy storage systems. Through the analysis of test results, the proposed project will demonstrate use of ESIF capabilities in a way that advances both the DOE and SunPower's goals of moving clean, renewable energy technologies onto the electrical grid.

14 SOLAR ENERGY↗
DOE OSTI2017

Using Residential Solar PV Quote Data to Analyze the Relationship Between Installer Pricing and Firm Size

The vast majority of U.S. residential solar PV installers are small local-scale companies, however the industry is relatively concentrated in a few large national-scale installers. We develop a novel approach using solar PV quote data to study the price behavior of large solar PV installers in the United States. Through a paired differences approach, we find that large installer quotes are about higher, on average, than non-large installer quotes made to the same customer. The difference is statistically significant and robust after controlling for factors such as system size, equipment quality, and time effects. The results suggest that low prices are not the primary value proposition of large installer systems. We explore several hypotheses for this finding, including that large installers are able to exercise some market power and/or earn returns from reputations.

14 SOLAR ENERGY↗
DOE OSTI2017

Native Vegetation Performance under a Solar PV Array at the National Wind Technology Center

Construction activities at most large-scale ground installations of photovoltaic (PV) arrays are preceded by land clearing and re-grading to uniform slope and smooth surface conditions to facilitate convenient construction access and facility operations. The impact to original vegetation is usually total eradication followed by installation of a gravel cover kept clear of vegetation by use of herbicides. The degree to which that total loss can be mitigated by some form of revegetation is a subject in its infancy, and most vegetation studies at PV development sites only address weed control and the impact of tall plants on the efficiency of the solar collectors from shading.This study seeks to address this void, advancing the state of knowledge of how constructed PV arrays affect ground-level environments, and to what degree plant cover, having acceptable characteristics within engineering constraints, can be re-established.

14 SOLAR ENERGY↗
DOE OSTI2017

Using Residential Solar PV Quote Data to Analyze the Relationship Between Installer Pricing and Firm Size

We use residential solar photovoltaic (PV) quote data to study the role of firm size in PV installer pricing. We find that large installers (those that installed more than 1,000 PV systems in any year from 2013 to 2015) quote higher prices for customer-owned systems, on average, than do other installers. The results suggest that low prices are not the primary value proposition of large installers.

14 SOLAR ENERGY↗
DOE OSTI2017

Evaluating the Technical and Economic Performance of PV Plus Storage Power Plants

The decreasing costs of both PV and energy storage technologies have raised interest in the creation of combined PV plus storage systems to provide dispatchable energy and reliable capacity. In this study, we examine the tradeoffs among various PV plus storage configurations and quantify the impact of configuration on system net value.

14 SOLAR ENERGY↗
DOE OSTI2018

Expanding PV Value: Lessons Learned from Utility-led Distributed Energy Resource Aggregation in the United States

Distributed PV capacity in the United States has increased from about 0.4 Gigawatts (GW) in 2010 to 10.5 GW in 2017 (GTM Research and SEIA 2018). When distributed PV is coupled with other emerging distributed energy resources (DERs) like battery storage and electric vehicles (EVs) they can provide demand response, voltage regulation, and other grid services. When many DERs are aggregated and called upon to provide these services simultaneously they may offer the same or more value than large, centralized power producers. In the United States, utility efforts to aggregate DERs are in the nascent stage. If initial DER aggregation programs prove successful, it could open new value streams for PV and other emerging DERs, thereby expanding deployment and transforming the energy market. The literature on the scope, performance, and lessons learned from utility-led DER aggregation programs is limited. This report fills this research gap, first by surveying utility-led DER aggregation programs nationwide, and then providing a deeper analysis of five utility pilots. We compare lessons learned across the five cases to develop a list of common challenges and related solutions that other utilities might consider when developing next generation programs.

14 SOLAR ENERGY↗
DOE OSTI2018

Grid Ready: Strategies for Interconnecting Large-Scale PV in New York City

This Grid Ready Solar project is intended to help create transparency for building owners and developers, so they can better understand and more quickly navigate the interconnection process for large-scale photovoltaic (PV) projects on Con Edison's electrical grid in New York City. Phase 1 of the project provided high-level technical screens of grid interconnection requirements in an attempt to streamline the interconnection of large-scale solar PV systems to the New York City grid. In Phase 2 of the Grid Ready project, the focus of this report, Sustainable CUNY worked with NREL to evaluate a range of solutions for improving the economics of large-scale (over 200 kW) PV within the five boroughs of New York City that are in Con Edison's service territory, as identified on the NY Solar Map.

14 SOLAR ENERGY↗