Iec 61724

[Arabella Kochanski]

The2021 version of the standard recognises that the solar irradiance measurement is one of the weakest links in the measurement chain. For Class A systems, it specifies the Class of pyranometer that may be used, including requirements for dew and frost mitigation, azimuth and tilt angle accuracy. It also defines cleaning and calibration intervals for pyranometers. Furthermore, the standard defines requirements for measurement of module- and air temperature, wind speed and direction, soiling ratio, and (AC and DC) current and voltage.

IEC 61724-1:2021 requires pyranometer dew and frost mitigation for class A monitoring systems. Why? Pyranometer domes are made of glass. When facing the sky on a clear night, glass temperature tends to go below dewpoint, so that water condenses on the dome. Heating and ventilation of solar radiation sensors keep the glass temperature above dewpoint and free from dew and frost deposition. This significantly increases the reliability of the measured data. There is an exception for locations where dew and frost is expected for less than 2 % of annual GHI hours.

The following tables offer an overview of the main elements of the IEC 61724-1 monitoring classification system, its requirements for solar radiation measurement and which pyranometers comply in which accuracy class.

You may have heard of the IEC 61724-1 standard to promote international uniformity in PV (photovoltaic) system performance monitoring. But why was it created, and what does it mean for you? In this interview with PES (Power & Energy Solutions), Matt Perry, Technical Product Manager for the Renewable Energy Group, details what you should know about the IEC 61724-1 Class A standard.

It may seem trivial to quantify with high accuracy and low uncertainty the amount of solar radiation that reaches the PV module surface given recent advancements in satellite and radiometric technologies; however, one must consider the seemingly random nature of solar radiation.

The behavior of solar modules is, of course, directly related to the amount of solar radiation that reaches the solar module, but it is also dependent on other meteorological parameters such as ambient temperature and wind. The power performance of PV modules is rated under standard test conditions, typically defined as 1000 W/m2, 25 Deg C cell temperature, and AM 1.5 spectrum. Short circuit current, open circuit voltage, cell temperature, and maximum power performance coefficients are all typically determined in controlled laboratory settings. However, modules rarely, if ever, operate under STC conditions. The only way to predict or verify performance of a PV system is to correct power-producing expectations to the weather.

Therefore, for analysts or grid/plant operators to produce high-confidence performance analytic or ground-truthing of satellite data, they rely on on-site measured data for input into their respective PV modelling exercise.

The IEC 61724-1 standard is the second revision of a guideline established to promote international uniformity in PV system performance monitoring. The completely revised and updated version introduces a monitoring system classification that specifies measurement parameters and sensor requirements, according to PV project size or monitoring objectives. The revised standard may be the first to present standardized methodologies for performing soiling measurements and calculating soiling loss indices.

In the previous answer, I mentioned several areas that if not properly mitigated will lead to lower-quality data sets, but perhaps one common mistake seen in monitoring would be lack of redundancy, particularly in plane of array irradiance on single-axis tracker sites and back of module temperature measurements.

This is one benefit of IEC 61724-1. In attempts to help eliminate this mistake, it provides guidance on the relation between system size and the minimum number of pyranometers and back of module sensors necessary to achieve Class A accuracies.

To name a few, in the near future, I expect to see new soiling measurement and analysis techniques, more distributed generation or microgrid sites using an all-sky camera combined with system management, and more spectral measurements as PV module developers develop ways to utilize this data.

But, I still see people in both science and industry, dedicating their work to making a difference in the world, and this is what I enjoy most, this comradery I enjoy with my community, making better sensors and dataloggers, working toward higher-value data, streamlining cost and implementation.

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This is another two-part article, which I would like to share with you. This time we will look at weather data acquisition according to the IEC 61724-1 standard. This part contains some basic knowledge of this standard, especially regarding class A systems. The second part will speak about a set of sensors we use along with our data logging system to fulfill the requirements of this standard.

Regardless of the size of the photovoltaic (PV) applications the performance ratio (PR) is an important quality characteristic and indicates the health of a PV system. The PR is the ratio of the actual and the maximum possible power output.

The urge to achieve the highest possible efficiency for utility PV systems is even more important compared to smaller systems. Therefore, the IEC 61824-1 defines 3 different classes of PV performance monitoring, class A with the highest and class C with the lowest requirements. The applicable class is depending on the PV system size and the user objectives. This article will pinpoint the advantages of a class A performance monitoring system, which is intended to be applied for utility scale installation.

But the standard is not just speaking about sensor accuracy. It speaks also about how the data acquisition and data storage is realized. Class A systems have higher requirements regarding the sampling interval as well as for the recording interval. The recording interval is limited to 1 minute. The sampling time is limited to 3 seconds for the more relevant data like irradiance, temperature, wind and electrical output. This might not have the highest influence on the PR, but enables new possibilities regarding the detection of defects or anomalies, which is also a purpose of the standard. In a nutshell, the standard also indicates requirements which must be implemented in the software of the data acquisition and processing system and is therefore a topic of applicational requirements.

I hope this short article was interesting for you and I would like to have an open discussion on the topic of performance monitoring of PV systems. Are you already familiar with this standard? Do you keep the compliance for Class A system in your utility scale applications?

IEC 61724-1 was launched in March 2017 and has some comparisons with the new ISO 9060:2018 standard that is planned to be launched this year. Both standards define Class A, B and C but with a different meaning

There are two reasons for the extra steps prescribed by IEC 61724-1 to comply with an optimal Class A: reliability of data and availability of data. To achieve this, dew, frost, soiling and instrument deposition as such should be prevented, and customers have to do good product maintenance. You should at least do all of the below:

If you are aiming for the IEC 61724-1 Class A we have the perfect product bundle for you: the new CVF4 ventilation unit combined with the SMP10 smart pyranometer. With this combination your solar monitoring will be 100 % IEC compliant.

Have all jaws drop as people lay eyes on you wearing the spectacular long style 61724 by Alyce Paris. The corset bodice is detailed with exposed boning and is enclosed along the back with a lace tie to bring a natural accentuation to the bodice. From top to the very bottom of the sweep train is reflective sequin that will illuminate perfectly in every photo you take.

This part of IEC 61724 outlines equipment, methods, and terminology for performance monitoring and analysis of photovoltaic (PV) systems. It addresses sensors, installation, and accuracy for monitoring equipment in addition to measured parameter data acquisition and quality checks, calculated parameters, and performance metrics. In addition, it serves as a basis for other standards which rely upon the data collected.

The cost to purchase this Standard varies depending on whether you are ordering a hardcopy, PDF or combination of the two. We also offer two different types of subscriptions: a one year and a three year.

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