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An On-Line Low-Cost Irradiance Monitoring Network with Sub-Second Sampling Adapted to Small-Scale PV Systems
摘要： Very short-term solar forecasts are gaining interest for their application on real-time control of photovoltaic systems. These forecasts are intimately related to the cloud motion that produce variations of the irradiance field on scales of seconds and meters, thus particularly impacting in small photovoltaic systems. Very short-term forecast models must be supported by updated information of the local irradiance field, and solar sensor networks are positioning as the more direct way to obtain these data. The development of solar sensor networks adapted to small-scale systems as microgrids is subject to specific requirements: high updating frequency, high density of measurement points and low investment. This paper proposes a wireless sensor network able to provide snapshots of the irradiance field with an updating frequency of 2 Hz. The network comprised 16 motes regularly distributed over an area of 15 m × 15 m (4 motes × 4 motes, minimum intersensor distance of 5 m). The irradiance values were estimated from illuminance measurements acquired by lux-meters in the network motes. The estimated irradiances were validated with measurements of a secondary standard pyranometer obtaining a mean absolute error of 24.4 W/m2 and a standard deviation of 36.1 W/m2. The network was able to capture the cloud motion and the main features of the irradiance field even with the reduced dimensions of the monitoring area. These results and the low-cost of the measurement devices indicate that this concept of solar sensor networks would be appropriate not only for photovoltaic plants in the range of MW, but also for smaller systems such as the ones installed in microgrids.
关键词： pyranometer,irradiance monitoring network,very short-term solar forecasting,microgrids,cloud enhancement,wireless sensor network,lux-meter
更新于2025-09-23 15:21:01
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Calibration of the Pyranometer Sensitivity Using the Integrating Sphere
摘要： The pyranometer for observing the solar radiation reaching the surface of the earth is manufactured by various companies around the world. The sensitivity of the pyranometer at the observatory is required to be properly controlled based on the reference value of the World Radiometric Center (WRC) and the observatory environment; otherwise, the observational data may be subject to a large error. Since the sensitivity of the pyranometer can be calibrated in an indoor or outdoor calibration, this study used a CSTM-USS-4000C Integrating Sphere by Labsphere Inc. (USA) to calibrate the sensitivity of CMP22 pyranometer by Kipp&Zonen Inc. (Netherlands). Consequently, the factory sensitivity of CMP22 was corrected from 8.68 μV·(Wm?2)?1 to 8.98 μV·(Wm?2)?1, and the result from the outdoor calibration according to the observatory environment was 8.90 μV·(Wm?2)?1. After the indoor calibration of the pyranometer sensitivity, the root mean square error (RMSE) of the observational data at the observatory on a clear day without clouds (July 13, 2017) was 7.11 Wm?2 in comparison to the reference pyranometer. After the outdoor calibration of the pyranometer sensitivity based on these results, the RMSE of the observational data was 1.74 Wm?2 on the same day. Periodic inspections are required because the decrease of sensitivity over time is inevitable in the pyranometer data produced at the observatory. The initial sensitivity after indoor calibration (8.98 μV·(Wm?2)?1) is important, and the sensitivity after outdoor calibration (8.90 μV·(Wm?2)?1) can be compared to the data at the Baseline Surface Radiation Network (BSRN) or can be used for various studies and daily applications.
关键词： Sensitivity,Pyranometer,Solar radiation,Indoor?outdoor calibration,Integrating sphere
更新于2025-09-10 09:29:36
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Performance Evaluation of Radiation Sensors for the Solar Energy Sector
摘要： Rotating Shadowband Irradiometers (RSI) and SPN1 Sunshine Pyranometers allow determining the diffuse and direct components of solar radiation without sun trackers; they can be deployed in networks for continuous field operation with modest maintenance. Their performances are evaluated here by analyzing their errors with respect to well characterized references. The analysis is based on 1-minute data recorded over a 15-month period at the Payerne BSRN station in Switzerland. The analysis was applied both to the whole dataset and data subsets reflecting particular conditions to allow a better understanding of how instrument performance depends on such conditions.
关键词： accuracy,RSI,rotating shadowband irradiometer,shortwave radiation,pyranometer,SPN1,uncertainty
更新于2025-09-04 15:30:14