East-west vertical PV as antidote for soiling in desert regions

From pv magazine Global

Researchers at the Hamad Bin Khalifa University (HBKU) in Qatar have investigated the potential of bifacial east-west-oriented vertical PV installations for mitigating soiling in desert regions and have found these systems may have up to 9.2% higher power generation compared to conventional arrays.

In the paper “Assessing vertical east-west bifacial photovoltaic systems in desert environments: Energy yield and soiling mitigation,” published in Solar Energy, the researchers explained that their approach is intended to reduce cleaning costs and levelised cost of energy (LCOE) in projects located in desert environments.

“This research is crucial for optimising energy production and reducing maintenance expenses in arid regions, where the impact of soiling is substantial,” they emphasised.

The research team conducted a series of tests at the Outdoor Test Facility (OTF) at the Qatar Environment and Energy Research Institute (QEERI) in Doha. The experimental setup consisted of four n-type bifacial, 60-cells, 270 W, glass-glass frameless modules. Two of the modules were installed in the conventional latitude-tilt, around 1.1 m above ground level, while the other two were deployed in the vertical east-west configuration, approximately 0.8 m from the ground.

The academics cleaned one module of each configuration weekly, with the others being left intentionally soiled. The tests showed that, from September to March, the tilted setup received 11.4% higher irradiation than the vertical module, while the vertical module received 5.2% higher irradiation between April and August.

“This pattern corresponds to the seasonal trajectory of the sun in Doha, favoring tilted modules during the winter, and vertical modules during the summer,” the academics pointed out, noting that in the whole of 2022 the tilted module received approximately 4.5% higher irradiation than the vertical module.

The test also showed, however, that over about three years tilted modules had soiling losses of up to 60% for monofacial modules and up to 45% for bifacial modules, while the vertical modules experienced “negligible” soiling losses.

“Additionally, during the summer months, when the soiling rates reach the highest values in Qatar, clean vertical bifacial modules showed the capacity to generate 3.8% on average, and up to 9.2% more energy than clean tilted bifacial modules,” the researchers stressed.

They concluded by saying that vertical PV installations represent a real alternative to conventional PV systems in desert climates, as in these locations “soiling and high temperatures coincide with the peak energy demand.”

“Future research includes further exploration into the long-term performance, durability, and economic feasibility of larger vertical bifacial PV systems in desert climates and other environments with high-soiling rates,” they added.

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