Page • The performance of an illuminated PV array or system is characterized by the system’s I-V curve. To harvest power from the system the voltage must be adjusted in order to maximize the power. This function is called Maximum Power Point Tracking (MPPT). MPPT is typically performed by the inverter or...
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ASHRAE IAM Model
Page • The simplest approach to estimating $$IAM_B\left (\theta_{AOI} \right)$$ was developed by Souka and Safat (1966) and later adopted by the American Society of Heating, Refrigeration, and Air Conditioning (ASHRAE), and is known as the “ASHRAE incidence modifier.” $$IAM_B= 1-b_{0} \left (\frac{1}{\cos \left (\theta_{AOI} \right)} -1\right)$$ This function has the benefit of...
Basic Solar Position Models
Page • Determining the relative position of the sun from any location on Earth at any time of the year involves a series of calculations, many of which are approximations. The first step to understanding these is to summarize a few basic quantities. Declination of the Sun – This is the angle between...
Bifacial PV Characterization and Rating Standards
Page • A standard module rating condition for bifacial PV modules would be a boon to the PV community as it would provide a common, accepted basis for measurement and nameplate rating of bifacial PV products. In particular, conditions that also harmonize with existing PV module rating standards are desired.Through simulation and...
Bifacial PV Performance Models
Page • The main challenge for modeling the performance of bifacial PV arrays and systems is the prediction of the irradiance hitting the array from the back side. Unlike the front side irradiance, which is usually assumed to vary little with position on the array, backside irradiance varies quite a lot with...
Bifacial PV Project
Page • Traditional AL-BSF PV cells are made to convert light hitting the front side of the cell to electricity. However newer PV cell designs (e.g., PERC, PERL, PERT, and HIT) with some minor modifications can be made so that light hitting from both sides contributes to the current produced by the...
Calculating POA Irradiance
Page • There exist many models to estimate POA irradiance from the standard components (GHI, DNI, and DHI). We describe a few of the more popular models in the next several pages.
Call for Abstracts and Sponsors for the 2024 PVPMC Workshop in Salt Lake City,UT (May 7-9, 2024)
Post, January 20, 2024 • Co-organized by Sandia National Laboratories, GroundWork Renewables and CFV Labs, this three-day workshop will examine the technical challenges and opportunities related to PV module and systems performance modeling. This year’s workshop will have a single track and will cover topics from solar resource assessment, module characterization, PV performance modeling, performance...
Call for Abstracts for the 2021 PV Performance Modeling and Monitoring Workshop (October 19-20 in Salt Lake City)
Post, July 1, 2021 • Co-sponsored by Sandia National Laboratories, GroundWork Renewables and CFV Labs, this two-day workshop scheduled for October 19th and 20th in Salt Lake City, Utah, will examine the technical challenges and opportunities related to PV module and systems modeling. The workshop this year will have a single track and will cover topics from solar resource assessment, module...
Call for Abstracts for the 2023 PVPMC Workshop – Due March 6, 2023
Post, February 28, 2023 • Co-sponsored by Sandia National Laboratories, GroundWork Renewables and CFV Labs, this two-day workshop scheduled for May 9th and 10th in Salt Lake City, Utah, will examine the technical challenges and opportunities related to PV module and systems performance modeling. The workshop this year will have a single track and will...
CEC Inverter Test Protocol
Page • 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...
Cell Temperature
Page • Cell temperature is required to calculate the IV curve of the module. Cell temperature is affected by the incident irradiance, weather conditions (such as air temperature and wind speed), and module construction and material properties.
COMSOL Models
Page • Ray Tracing Work at the University of Iowa COMSOL is a finite element method (FEM) solver and the Ray Optics Module can be used to model electromagnetic wave propagation in systems in which the wavelength is much smaller than the smallest geometric detail in the model. The electromagnetic waves are...
Contact Us
Page • This project is led by Joshua S. Stein, a Senior Scientist at Sandia National Laboratories, Albuquerque, NM. If you would like to contribute content to this site, please email Dr. Stein at jsstein@sandia.gov with your content or ideas. All contributed content will be reviewed and edited for accuracy and consistency. Contributors will...
Datasets
Page • Sandia National Laboratories has measured global normal spectral irradiance nearly continuously from August 2013 to April 2018. During this time other broadband irradiance measurements (global horizontal, direct normal, diffuse horizontal and global normal) and weather variables were also recorded. For this dataset PV Performance Labs (PVPL) has pulled together data...
DC Array IV
Page • DC wiring losses and mismatch affects how the module I-V curves are combined into an array. Series strings of modules all must carry the same current and parallel strings must operate at the same voltage. This fact means that any combined value of current and voltage may not equal the...
DC Component Health
Page • DC components in a PV system include modules, connectors, fuses, cabling, disconnects, combiner boxes, etc. Failures and/or degradation in these components can result in declines in performance. Depending on the type and location of failure or degradation the effects will differ in complex ways. An example of a simple component...
DC Module IV Characteristics
Page • This section covers topics important for modeling the IV characteristics of a PV module, including the input conditions and the various model forms.
DC to AC Conversion
Page • Conversion from DC to AC power allows this power to be tied to the AC grid. This conversion can be accomplished with high efficiencies but there are energy losses that need to be estimated. There are a number of model algorithms that are used to estimate this conversion efficiency. They...
DC Wiring Losses
Page • DC wiring losses are mainly caused by the ohmic resistance of the cabling that interconnects PV devices and strings, although losses can also occur in connections and fuses. The $$I^2\times R$$ power loss varies as a function of the array current squared. Differences in cable length or size among parallel strings can...
De Soto “Five-Parameter” Module Model
Page • The De Soto model (De Soto et al., 2006), also known as the five-parameter model, uses the following equations to express each of the five primary parameters as a function of cell temperature $$T_c$$ and total absorbed irradiance $$S$$: $${I_L}= {S\over {{S_{ref}}}}{M \over {{M_{ref}}}} \left[ {{I_{L,ref}} + {\alpha_{lsc}} \left( {{T_c} - {T_{c,ref}}} \right)} \right]...
Diffuse Horizontal Irradiance
Page • Diffuse horizontal irradiance (DHI) is the terrestrial irradiance received by a horizontal surface which has been scattered or diffused by the atmosphere. It is the component of global horizontal irradiance which does not come from the beam of the sun (where “beam” is a 5° field of view concentric around the sun). Much like...
Direct Normal Irradiance
Page • Direct Normal Irradiance (DNI) may be measured directly via an absolute cavity radiometer. Absolute cavity radiometers are considered the most accurate method of solar radiation measurement and form the basis of the World Radiometric Reference (WRR). However, absolute cavity radiometers are not designed for continuous, unattended, outdoor use. Thus, the primary method...
DIRINT Model
Page • R. Perez et. al. developed a model for determining DNI from GHI as an improvement to the DISC model. This model, “DIRINT”, improves estimation by binning zenith angle, global horizontal transmittance, and dew point temperature; or various functions of these variables, including a time derivative of the global horizontal transmittance. Each...
Document Library
Page • Audio - Calculating Model Shading Inputs from Design Data_Tarn Yates (12175 downloads ) Audio - Fleet-Wide Study of System Degradation_Mike Anderson (11875 downloads ) Audio - Quantifying Mismatch Losses in Small Arrays_Sara MacAlpine (8486 downloads ) 12th PVPMC Workshop Highlights (22734 downloads ) 11th PVPMC Factory Tours Program (12434 downloads...
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