How accurate is a commercial monitoring system for photovoltaic plant? (original) (raw)
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Data quality processing for photovoltaic system measurements
International Journal of Electrical and Computer Engineering (IJECE), 2024
The operation and maintenance activities in photovoltaic systems use meteorological and electrical measurements that must be reliable to check system performance. The International Electrotechnical Commission (IEC) standards have established general criteria to filter erroneous information; however, there is no standardized process for the evaluation of measurements. In the present work we developed 3 procedures to detect and correct measurements of a photovoltaic system based on the single diode model. The performance evaluation of each criterion was tested with 6 groups of experimental measurements from a 3 kWp installation. Based on the error of the 3 procedures performed, the most unfavorable case has been prioritized. Then, the reduction of errors between the estimated and measured value has been achieved, reducing the number of measurements to be corrected. For the clear sky categories, the coefficient of determination is 0.9975 and 0.9961 for the high irradiance profile. Although an increase of 2.5% for coefficient of determination has been achieved, the overcast sky categories should be analyzed in more detail. Finally, the different causes of measurement error should be analyzed, associated with calibration errors and sensor quality. This is an open access article under the CC BY-SA license.
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Broadband (0.3-3.0/~m) global solar irradiance measurements are used in the evaluation of solar energy conversion devices. The uncertainty at. tached to such measurements is important in evaluating whether conclusions associated with the measurements are statistically valid. A standardized uncertainty analysis method, developed over the past 15 years in the arena of consensus standards and professional society organizations, is described and applied. The results of the uncertainty analysis for the instrument calibration and field data measurement process indicate that the total measurement uncertainty in pyranometry (i.e. the measurement of global solar irradiance) can approach 5%. Thus comparisons of results between laboratories using different pyranometers can have a total uncertainty of up to 10%. Statistically valid conclusions on a conversion device's performance may be drawn only if such results account for known bias errors or exceed the uncertainty limits derived using this methodology.
Quality control test for unreliable meteorological and electrical photovoltaic measurements
International Journal of Electrical and Computer Engineering (IJECE), 2023
Meteorological and electrical measurements using predictive computational techniques have been used in the analysis of photovoltaic system operation and maintenance. International standards establish general and no standardized criteria on the quality control and validation of these measurements. In the present work, a methodology has been developed to correct erroneous photovoltaic experimental measurements: radiation, temperature, current, and voltage. We validated the proposed approach with 12 case studies with more than 5,000 meteorological and electric measurements from an experimental 3 kWp photovoltaic system. The approach is based on a set of non-intrusive criteria developed from the one diode model, the approach allowed to correct about 80% of the erroneous data, 30% more using polynomial regression. As for the regression methodology, we have shown that the proposed methodology includes 4 meteorologicalelectrical variables allowing a more rigorous analysis. For 75% of the cases evaluated, the proposed methodology achieves a better data correction. This is an open access article under the CC BY-SA license.
Renewable Energy, 2013
This work represents the Photovoltaic section of the European Project PERSIL, which includes also the study of solar thermal plants. The activity is twofold: the results of 1-year monitoring and checking of thirteen PV systems; the consequent guidelines for the design, installation and maintenance of grid connected PV systems. For accurate estimation of the energy production a two-year analysis of solar radiation has been conducted on the basis of pyranometer measurements in all the Project locations. The checking of energy performance has been carried out by a suitable improvement of a conventional method, that includes the assessment of the energy availability. The corresponding results are excellent for three PV plants, whereas they are strongly negative for five old PV plants which exhibit poor availability (62e78%). The remaining plants behave with acceptable performance ratios (0.65e0.78). Within the guidelines for design, the optimum coupling array/inverter and the related protections have been discussed in detail. About the guidelines for installation, the PV module/inverter cooling, the electric cables and enclosures have been dealt with. Then, concerning the guidelines for maintenance, the main items are the energy production assessment, the glass dirt checking and the maintenance of motors in sun-trackers. Finally, all these guidelines help to maximize the energy availability.
Uncertainties of Laboratory Measurements for Energy Rating
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Laboratory measurement of irradiance and temperature behaviour of PV modules are widely used to predict energy produced by PV modules or systems. The inherent measurement uncertainties have so far not been an essential part of the discussion. In this contribution, we investigate how the uncertainty of laboratory characterization propagates to rated energy on an exemplary basis. For three typical modules (c-Si, CdTe, CIS) and three locations, the irradiance and temperature losses were simulated. The input data used for the simulation were module characteristics as measured and modified according to the possible influence of measurement uncertainties. Statistical uncertainties as well as systematic uncorrected offsets were considered. The resulting uncertainty for expected real world losses is dependent on the location. For irradiance, it is roughly ±1.0 for c-Si, ±1.5% for the CIS module under investigation, and ±2.5% for CdTe. Uncertainty of temperature losses was ±0.1% for the locations with low temperature and ±0.4% for higher temperatures for all technologies. The values apply, if measurement uncertainties are minimized. As a consequence of these results, thorough PV module energy rating or PV system yield prediction is possible only with reliable laboratory measurements.
Uncertainty Analysis of Solar Monitoring Station: A Case Study
Proceedings of the ISES Solar World Congress 2019, 2019
The present work describes the type B uncertainty analysis for the environmental quantities monitored by a solar station. Type B in our case represents the random effects of sensor and data logger on the measuring system by rounding resolution and noise, and should be as low as possible. It is performed in order to comply with ISO technical recommendations and also academic purposes. Special care should be taken if this report is used as an example for uncertainty analysis of similar stations because it depends on configuration, calibration certificates, data loggers specs, acquisition setup and so on. By the end of work it will be possible to include the determined system uncertainty to the overall measured repeated data.
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This paper deals with the uncertainty analysis of parameters estimated during long-term monitoring of photovoltaic plants. A specifically developed data-acquisition system is briefly described, which has been conceived to be easily calibrated and, if necessary, adjusted to compensate for measuring-chain drifts, in order to assure the traceability of the estimated parameters. The measurement capabilities of the acquisition system are reported in terms of measured quantities and expected uncertainty. Results that refer to a three-year monitoring of ten photovoltaic plants based on different technologies and architectures are reported. The obtained uncertainty is suitable to distinguish the behavior of the different plants, thus allowing a preliminary comparison to be performed among technologies and architectures. Experimental results highlight an important difference between crystalline silicon devices and thin film technologies in regards to degradation.
Measurement Science and Technology
This paper describes the traceability chain for photovoltaic devices and the measurement methods employed to perform the various transfer steps. The measurement uncertainties are analysed in detail based on the accreditation of the European Solar Test Installation (ESTI) for the calibration of photovoltaic devices. The various contributions to the overall uncertainty are critically analysed for various traceability chain options. A major contribution is the uncertainty in the calibration of the primary reference device. The overall measurement uncertainty is reduced using the ESTI reference cell set compared to the traceability from the world photovoltaic scale. For the maximum power of photovoltaic modules, the expanded combined uncertainty is reduced from ±2.6% to below ±2%. Recommendations are made on the scope for further reduction of uncertainty and for the best calibration strategy for various PV technologies.