Comparative study of soiling effect on CSP and PV technologies under semi-arid climate in Morocco

Soiling of solar collectors reduces the efficiency of both concentrating solar power (CSP) and photovoltaic technologies (PV), and increases the operations and maintenance (O&M) costs. Many countries with significant solar potential such as Morocco are located in regions characterized by dry and harsh climatic conditions, dust storms and high pollution. This study investigates the impact of soiling on PV and CSP technologies under a semi-arid climate in BenGuerir city of Morocco. For this purpose, one year of data collected from two types of soiling sensors, a Tracking Cleanliness Sensor (TraCS) and DustIQ, was evaluated. A meteorological station installed at Green Energy Park (Morocco). A period with red rain events and a dry period were selected to quantify the impact of soiling on both technologies during these periods. It is found that the soiling effect for CSP mirrors with an annually averaged soiling rate of -1.18%/day is around 5 to 6 times higher than for PV (-0.23%/day). The loss due to soiling during red rain events has been observed more pronounced compared to the dry period

A Comparative Study of Soiling on Solar Mirrors in Portugal and Morocco: Preliminary Results for the Dry Season

Soiling is a factor of major importance regarding any solar energy conversion technology, as in Photovoltaic (PV) panels and, namely, in concentrated solar power (CSP), since scattering due to particle deposition severely reduces the mirror’s reflectance. Concerned with this problem, a collaboration between the Renewable Energies Chair, University of Évora, Portugal and the Institut de Recherche en Energie Solaire et Energies Nouvelles, Morocco, was created to investigate and compare soiling in mirrors in both locations. This research enables the comparison between particle deposition effects in the two climates, crucial to implement mitigation measures. Southern Portugal and Northern Africa have considerable potential for future CSP installations, which makes this study relevant from an economical point of view, as it may influence the maintenance procedures and expected energy production of such CSP plants

Parallel soiling measurements for 4 mirror samples during outdoor exposure with TraCS

The upgraded version of the Tracking Cleanliness Sensor, the so-called TraCS4, which determines the realtime cleanliness and soiling rate of four mirror samples simultaneously is presented. Using this device, different materials can be intercompared at the site of interest which is the main advantage as the performance of anti-soiling-coatings is usually dependent on local weather conditions. A detailed uncertainty analysis of the TraCS4 device results in a cleanliness measurement uncertainty of about 0.019 cleanliness points. The uncertainty for the intercomparison of different materials is derived to be 0.012 cleanliness points. Exemplary soiling measurements with different anti-soiling and reference coatings at PSA are presented

The enerMENA Meteorological Network – Solar Radiation Measurements in the MENA Region

International audienceFor solar resource assessment of solar power plants and adjustment of satellite data, high accuracy measurement data of irradiance and ancillary meteorological data is needed. For the MENA region (Middle East and Northern Africa), which is of high importance for concentrating solar power applications, so far merely 2 publicly available ground measurement stations existed (BSRN network). This gap has been filled by ten stations in Morocco, Algeria, Tunisia, Egypt and Jordan. In this publication the data quality is analyzed by evaluating data completeness and the cleanliness of irradiance sensors in comparison for all of the stations. The pyrheliometers have an average cleanliness of 99.2 % for week-daily cleaning. This is a 5 times higher effort than for Rotating Shadowband Irradiometer (RSI) stations which even have a slightly higher average cleanliness of 99.3 % for weekly cleaning. Furthermore, RSI stations show a data completeness of 99.4 % compared to 93.6 % at the stations equipped with thermal sensors. The results of this analysis are used to derive conclusions concerning instrument choice and are hence also applicable to other solar radiation measurements outside the enerMENA network. It turns out that RSIs are the more reliable and robust choice in cases of high soiling, rare station visits for cleaning and maintenance, as usual in desert sites. Furthermore, annual direct normal and global horizontal irradiation as well as average meteorological parameters are calculated for all of the stations

A Benchmark of Simple Measurement Systems for Direct Irradiance

Accurate direct normal irradiance (DNI) measurements are essential for the design and the operation of concentrating solar power systems. Several measurement systems for DNI are available to users, but all commonly used systems still have drawbacks. Sun trackers with pyranometers and a pyrheliometer are expensive and require permanent checks and maintenance by qualified personnel, for example due to tracking errors and soiling effects. Simpler, i.e. more economic and robust sensors may have shortcomings regarding accuracy under various atmospheric conditions and might not be significantly less susceptible to soiling and user errors. Validations and benchmarking of simple radiometers for solar energy applications have been presented. To the best of our knowledge, no benchmarking study is available which evaluates some more recent simple measurement systems which are relevant for solar applications in 2023. Furthermore, most previous benchmarking studies did not measure atmospheric parameters like circumsolar irradiance which may directly influence the measurements of these sensors. We close this gap by benchmarking relevant measurement systems (Rotating Shadowband Irradiometer RSI and Rotating Shadowband Pyranometer RSP 4G; Delta-T SPN1, EKO MS-90, PyranoCam, Sunto CaptPro) at multiple sites. We also evaluate the influence of relevant atmospheric parameters which we measure with dedicated instruments at one site. We include the PyranoCam system in our benchmarking, a novel radiometer system suitable for all solar irradiance components including DNI. It consists of a pyranometer and a fisheye camera that takes photos of the whole sky and employs a combined physical and machine-learning model. The results of the study provide improved estimates of the sensors’ accuracies for a specific application and climatic condition and can assist in the development of corrections for the sensor technologies

Evaluation of Aerosols Impact on global and direct irradiance attenuation under clear sky condition: A case study in Morocco

In order to reduce the consumption of fossil fuels, solar energy is a promising alternative. However, solar potential depends on several atmospheric parameters. In the absence of clouds, aerosols are the primary source of solar radiation attenuation. This study aims to examine the impact of aerosol optical depth on the attenuation of solar irradiance under clear sky conditions. For this purpose, aerosol data from satellite database and irradiance data from high-performance meteorological stations installed in two sites in Morocco were exploited. Under clear sky conditions, the results showed a decrease in global horizontal irradiance relative to the global irradiance at the top of the atmosphere of 24% for aerosol optical depth values of 0.02 and exceeding 53% for 0.6. Aerosols have a more significant impact on the direct normal irradiance under clear sky conditions; over the test data, a decrease of 66% was observed for the direct normal irradiance according to the extraterrestrial irradiance for aerosol optical depth of 0.2 and reaching 92% for 0.6

Detection of clear sky instants from high frequencies pyranometric measurements of global horizontal irradiance

Solar resource assessment by clear sky models is of great importance in the solar energy field: verifying the performance of photovoltaic systems during stable conditions, clouds effects evaluation, the determination of geographical areas where irradiation is more uncertain and the preparation of forecasts with sky cameras. But before using these models they must be validated against high performances soil measurements. Since there is no radiometric sensor that measures clear-sky radiation, then historical clear-sky time periods must be identified only from long-term allsky irradiation records. The contribution of this study is to exploit the ground measurements, analyze them and retrieve the information they contain concerning the clear sky instants. The study will be performed by comparing the clear sky instants identified by an algorithm proposed by Reno and Hansen with a physical clear sky model. This comparison is made using high frequency global horizontal irradiation (GHI) data from high performances meteorological station installed at Benguerir in Morocco

AATTENUATION-The Atmospheric Attenuation Model for CSP Tower Plants: A Look-Up Table for Operational Implementation

Attenuation of solar radiation between the receiver and the heliostat field in concentrated solar power (CSP) tower plants can reduce the overall system performance significantly. The attenuation varies strongly with time and the average attenuation at different sites might also vary strongly from each other. If no site specific attenuation data is available, the optimal plant design cannot be determined and rough estimations of the attenuation effect are required leading to high uncertainties of yield analysis calculations. The attenuation is caused mainly by water vapor content and aerosol particles in the lower atmospheric layer above ground. Although several on-site measurement systems have been developed during recent years, attenuation data sets are usually not available to be included during the plant project development. An Atmospheric Attenuation (AATTENUATION) model to derive the atmospheric transmittance between a heliostat and receiver on the basis of common direct normal irradiance (DNI), temperature, relative humidity, and barometric pressure measurements was developed and validated by the authors earlier. The model allows the accurate estimation of attenuation for sites with low attenuation and gives an estimation of the attenuation for less clear sites. However, the site-dependent coefficients of the ATTENUATION model had to be developed individually for each site of interest, which required time-consuming radiative transfer simulations, considering the exact location and altitude, as well as the pre-dominant aerosol type at the location. This strongly limited the application of the model despite its typically available input data. In this manuscript, a look-up table (LUT) is presented which enables the application of the AATTENUATION model at the site of interest without the necessity to perform the according complex radiative transfer calculations for each site individually. This enables the application of the AATTENUATION model for virtually all resource assessments for tower plants and in an operational mode in real time within plant monitoring systems around the world. The LUT also facilitates the generation of solar attenuation maps on the basis of long-term meteorological data sets which can be considered during resource assessment for CSP tower plant projects. The LUTs are provided together with this manuscript as supplementary files. The LUT for the AATTENUATION model was developed for a solar zenith angle (SZA) grid of 1◦, an altitude grid of 100 m, 7 different standard aerosol types and the standard AFGL atmospheres for mid-latitudes and the tropics. The LUT was tested against the original version of the AATTENUATION model at 4 sites in Morocco and Spain, and it was found that the additional uncertainty introduced by the application of the LUT is negligible. With the information of latitude, longitude, altitude above mean sea level, DNI, relative humidity (RH), ambient temperature (Tair), and barometric pressure (bp), the attenuation can be now derived easily for each site of interest