Interview: Green Energy Park talks soiling and its effects on PV systems


pv magazine: How much solar PV has Green Energy installed to date? What type of installations do you work with, i.e. large-scale, C&I, off-grid, and/or residential?

Dr. Ahmed Alami Merrouni: The PV capacity installed to date at GEP is 250kWp of residential installations from different technologies.

In which regions does Green Energy operate?

Figure 1: Green Energy Park research facility.

Image: Green Energy Park

Green Energy Park is a research center, a training platform and a testing facility located in the green city of Ben Guerir, mid-south of Morocco, (latitude=32.23°N; longitude=−7.95°W; altitude=449 m). GEP was developed by the Research Institute of Solar Energy and New Energies (IRESEN) with the support of the Ministry of Energy, Mines, Water and Environment and the OCP Group.

What are the main PV challenges and opportunities in this region?

Since GEP is located in an area with a semi-arid climate, the main challenges for PV are soiling and temperature. These two parameters impact the efficiency of the electricity production; besides, they contribute to the degradation of the PV modules.

Regarding the opportunities, GEP is located in a well irradiated area with an average yearly GHI value of 2100 kWh/m², which is considered as very good for PV operation. In addition, the weather properties of the area are similar to different locations in MENA region, therefore, the results of the technologies and coatings testing, in this area, can be representative and close to the ones if installed in similar locations in MENA.

What are the average soiling rates in these regions? Do they differ significantly from location to location?

The average soiling rate measurements are around 96.3%. Of course, soiling is a very specific phenomenon and it highly depends on the location. Also, the daily soiling rate depends on the season and the specific climatic conditions like red rain event.

Figure 2: Daily Soiling Rate values measured at Green Energy Park.

Image: Green Energy Park

Figure 2 presents the daily SR values during the period from May 6 until June 7, 2017. As it can be seen, in most cases, the daily drop of SR is less than 0.2%, but this drop can reach 3.8% like on May 24.

I need to mention that the SR values were measured by dividing the Isc values from two PV modules. The first one was cleaned every day and the other in different periods.

What effect does soiling have on PV plants, in terms of performance, costs, ROI and O&M? Does it vary for the different types of systems?

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This is a very good question. Generally, sites with high irradiation records are located in deserts, which is linked to the presence of dust and the lack of water. This increases the OPEX and the O&M costs, thus, it is crucial for any project developer to assess and measure the SR values in the candidate sites for PV plants hosting and for long time (at least two years).

For the case of Green Energy Park, we are working on the evaluation of the impact of soiling on the production and the O&M costs. In fact, we are trying to use the long-term SR measurements and some specific parameters (technical and economical) to develop a software that can run different cleaning scenarios and provide the most optimal one for a specific location. Until now, we have almost one year of data and we hope to publish the results soon.

What measures does Green Energy take, specifically, to combat soiling (i.e. panel tilt angles, cleaning, monitoring software)?

For the moment, we just monitor the soiling rate values every day and based on them we take the decision for cleaning the field or not.

Why did you choose Kipp & Zonen’s DustIQ solution?

Kipp&Zonen is one of the biggest actors in the metrology and meteorological sensors market worldwide. It is known inside the scientific community with the high accuracy and reliability of it sensors. From my experience, and since I’m working on the meteorology and solar resource assessment, I used to work with irradiometers and other sensors from Kipp&Zonen and I’m so happy with their quality and accuracy.

Regarding the new DustIQ system, we choose this device, because it is a very practical soiling measurement system. It is very easy to install compared to other soiling systems and it can be installed at any location in the PV park. Furthermore, it uses an optical approach for the SR measurement which make it better than the two modules measurement method that is representative for only one specific technology.

What does it offer that other soiling solutions do not?

As mentioned above, the DustIQ uses an optical approach for the SR measurement, which makes it better than the two modules method that is representative for only one specific technology. The system can also provide nighttime measurements which very helpful and important for power plants operators, that can detect specific phenomenon, like red rain or dust storms if happens during the night, thus, they can take optimal, smart and proactive cleaning decisions, which will lead to decrease the O&M costs and increase the efficiency of the PV plants. And I think that DustIQ with this feature is the best Soiling measurement device for running power plants and those in commissioning or under study.

What are the next PV projects Green Energy is set to work on?

In the Frame of OLEA project, we worked on the sizing, the installation, the commissioning and now on the operation of a 400kWp PV plant installed in an olive farm. Furthermore, we are also setting up the frames of the installation of a PV testing facility (similar to the one at GEP) in Ivory Coast.

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