Sandia National Laboratories is facilitating a collaborative group of photovoltaic (PV) professionals (PV Performance Modeling Collaborative or PVPMC). This group is interested in improving the accuracy and technical rigor of PV performance models and analyses. Such models are used to evaluate current performance (performance index) and determine the future value of PV generation projects (expressed…
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2021 PV Performance Modeling and Monitoring Workshop in Salt Lake City, Utah USA (19-20 October 2021) Hosted by GroundWork Renewables, CFV Labs, and Sandia National Laboratories. Call for Abstracts is out and abstracts are due by August 1, 2021. Registration and Hotel information will be forthcoming. 2020 PVPMC Webinar Series Webinar recordings and PDFs are…
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The National Solar Resource Data Base (NSRDB) compiled by NREL contains measured and modeled solar irradiance and weather data for two time periods: 1961-1990 – Original version (237 National Weather Service sites in the U.S. including sites in Guam and Puerto Rico). This data is the basis for TMY2 files. 1991-2005 – Update version (1,454…
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The performance index is the ratio of measured energy from a PV system to the predicted energy using a PV performance model. Unlike with the performance ratio, the performance index very close to 1 for a well functioning PV system and should not vary by season due to temperature variations. There are several formal definitions…
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The annual yield or energy yield is simply the number of kilowatt hours produced in a year divided by the STC DC rating of the PV system. It will change from year to year depending on the weather. It is expressed in units of kWh/kWp, where kWp is “kW peak” and is the DC STC…
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PV performance metrics are quantities that are used to evaluate and compare the performance between systems and between different sites and climates. A 2014 report by SunSpec Alliance and San Jose University entitled: PV System Performance Assessment, provides a good technical summary of a collection of PV performance metrics in use today.
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The daily AC performance ratio () is defined in IEC 61724 as: , where: is ths the AC system yield defined as the measured AC energy produced by the PV system in the day (kilowatt hours per day) divided by the rated power of the PV system. The definition of this rating is not specified in…
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Outline Definitions and Overview PV System Monitoring Monitoring Equipment Data Filtering Data Filling PV Performance Metrics Performance Ratio Performance Index Annual Yield
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Energy losses on the AC side of the inverter can be significant when the AC power is raised to distribution or transmission level voltages and is transferred any distance before the utility meter. The value of the energy produced by the plant needs to include all losses before the utility meter. For a residential system,…
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Inverter efficiency is the ratio of the usable AC output power to the sum of the DC input power and any AC input power. Typical grid-tied inverter efficiencies exceed 95% under most operating conditions. Efficiency changes as a function of AC output power, DC voltage, and sometimes inverter temperature. Sandia National Laboratories and BEW have…
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