The Uncertainty of the HelioClim-3 DNI Data Under Moroccan Climate

The purpose of this study is to evaluate the uncertainty of the DNI satellite-derived data from HelioClim-3 against those measured at ground level by calculating the classical statistical performance indicators for different time resolutions (hourly, daily and monthly). Correlations between the errors and the Aerosol optical depth (AOD) data measured by an AERONET sun photometer station at the University of Oujda were performed. Results show that the DNI data derived from Helioclim-3 can be considered as acceptable for satellite data with an RMSE of 19.7 % and a bias of 7.9 % for the hourly data. HelioClim-3 systematically over-estimates the daily DNI sums for the investigated site. The correlation to AOD at 550 nm can only be one of the reasons for the deviation. Corrections or site adaptation could help to increase the accuracy of the data base for that pixel

Monitoring of Mirror and Sensor Soiling with TraCS for Improved Quality of Ground based Irradiance Measurements

Meteorological stations for solar irradiance measurements are mainly utilized for resource assessment of possible sites for future solar power plants and for thermal efficiency calculation and control of operating power plants. These stations consist of a solar tracker, two pyranometers and a pyrheliometer (MHP) for irradiance measurements. The accuracy of the MHP instrumentation is usually specified to be better than 2% if cleaned on a daily basis. However, soiling frequently exceeds other error influences significantly, reducing irradiance values and accuracy. Due to the high sensitivity to soiling shown by pyrheliometers, especially DNI measurements are affected. Reductions of measured DNI values exceeding 25% in only a few weeks are not unusual. In order to improve this situation, the soiling level of each individual sensor can be determined by following a special sequence of sensor cleaning and brief breaks combined with a close examination of the sensor responses. This allows for an approximate post processing correction of the irradiance data measured since the last cleaning (if recent). The corrections applied are cross- checked by means of an improved version of the TraCS asset. It can be used to control the sensor soiling correction procedure. The TraCS's improvement consists in rotating the mirror within its plane with the pyrheliometer thus scanning its surface instead of just viewing the same small spot on the mirror. Hence, a better accuracy of the mirror soiling level is achieved by deriving more reliable average values. Finally, the results of an examination of sensor soiling rates at several meteorological stations set up in the MENA region and cleaned following the described protocol is presented. This gives an idea about the range of regional differences in soiling rates to be expected in the North African region

Investigation of soiling effect on different solar mirror materials under Moroccan climate

This paper presents some first results of the effect of dust on different solar mirror materials in Morocco. For this purpose, thirteen glass and aluminum mirrors were exposed at the University of Oujda (Eastern Morocco) for a period of three months (from April to June). For each type of the mirrors, one sample mirror was installed horizontally and twelve mirrors were installed in the so called “mirrors sphere” in four different directions (North, South, East and West) with three tilt angles relative to the vertical plane: +45°(facing the sky), 0° (vertical) and -45° (facing the ground). The drops in specular reflectance were measured after each month of exposition for both mirror materials. Furthermore, X-ray diffraction analyses were performed for the dust collected from the mirrors to identify the mineralogical components of the dirt settled on the mirror surfaces. For both mirror materials, the drop on cleanliness per time interval was quite the same for all the mirrors and over all the test periods. The highest average cleanliness drop per month for the horizontal mirrors was 45 % and 33 % for the glass and aluminum mirrors respectively. The +45° mirrors come in the second position with a cleanliness drop of about 14 % for both reflectors. However, the mirrors installed on the 0° and -45° angles remained cleaner with a cleanliness average of about 97 % for both mirrors. These first results can be of high importance to motivate scientists and actors in the field of solar energy to further investigate the soiling of CSP mirrors and add it as a parameter in solar resource assessment

A Novel Method for Automatic Real-Time Monitoring of Mirror Soiling Rates

The effect of soiling of solar concentrators influences the output of solar thermal power plants significantly. The literature values estimate the loss in specular reflectivity due to dust on the mirrors to be as high as 14% or even 26% after a few months [1], [2]. It varies significantly with location [3]. Given the fact that these numbers are quite high and very broadly spread in the literature, project planners and plant operators demand better methods to measure soiling loads in running power plants as well as in resource assessment measurement campaigns. In this paper we introduce a new measurement setup named “TraCS” (Tracking Cleanliness Sensor) that allows for an easier, supposedly more precise and more cost effective measurement of the soiling level of solar mirrors. It will assist power plant operators and maintenance teams to optimize their cleaning cycles based on a real time measurement. At the same time the setup paves the way to including cleanliness as a standard parameter in solar resource assessment. It enables more sophisticated research on the most important weather parameters influencing the soiling rates at different plant sites and on upcoming new coating materials [4]

Water Scenarios Modelling for Renewable Energy Development in Southern Morocco

Water and energy are two pivotal areas for future sustainable development, with complex linkages existing between the two sectors. These linkages require special attention in the context of the energy transition. Against this background, this paper analyses the role of water availability in the development of solar thermal and photovoltaic power plants for the case of the Draa Valley in southern Morocco. Located in a semi-arid to arid mountainous area, the Draa Valley faces high water stress - a situation expected to worsen due to climate change. At the same time, the region has one of the greatest potentials for solar energy in the world. To examine whether limited water availability could accelerate or delay the implementation of solar thermal and photovoltaic power plants, this paper compares regional water availability and demand in the Draa Valley for different scenarios, paying particular attention to potential socio-economic development pathways. The Water Evaluation and Planning System software is applied to allocate the water resources in the study region. The water supply is modelled under the Representative Concentration Pathway 8.5 climate scenario, while the water demand for the Draa Valley is modelled for a combination of three socio-economic and two energy scenarios. The climate scenario describes a significant decrease in water availability by 2050, while the socio-economic and energy scenarios show an increase in water demand. The results demonstrate that during a sequence of dry years the reservoirs water availability is reduced and shortages in water supply can result in high levels of unmet demand. If this situation occurs, oasis farming, water for drinking and energy production could compete directly with each other for water resources. The energy scenarios indicate that the use of dry cooling technologies in concentrated solar power and photovoltaic hybrid systems could be one option for reducing competition for the scarce water resources in the region. However, given that energy generation accounts for only a small share of the regional water demand, the results also suggest that socio-economic demand reduction, especially in the agricultural sector, for example by reducing the cultivated area, will most likely become necessary

CSP performance assessment including soiling measurements for Morocco and Portugal reveals similar electricity yield and cost in both countries

The objective of this research work is to understand the impact of soiling on the thermal performance, electrical production and Levelized Cost of Electricity of possible Concentrating Solar Power plants in both Morocco and Portugal. For this matter, a joint soiling measurement campaign, following the same protocol, has been conducted in the two countries to assess and evaluate the impact of dust on the optical properties of soiled solar mirrors. After that, and using high-quality irradiation data measured at ground level, simulation of a 3.6 MWth molten-salt test facility has been conducted with and without taking soiling into consideration for both sites. Results show that soiling in Morocco is three times higher than in Portugal. The daily Soiling rate average is around 1.6% and 0.06% for both sites, respectively. In addition, results show that both sites are favorable for CSP implementation. The simulated electrical output for a clean field is ~1.4 GWeh and ~1.3GWeh with a Levelized Cost of Electricity of ~0.194V/kWh and ~0.205V/kWh for Morocco and Portugal, respectively. Nevertheless, when soiling is taken into consideration both sites produce similar amount of electricity of ~1.25GWeh with a similar Levelized Cost of Electricity of ~0.231V/kWh