Qatar study reveals seasonal shifts in tracker efficiency for desert solar farms

Field testing in Qatar is offering new insights, suggesting that horizontal single-axis trackers combined with bifacial modules might outperform fixed-tilt solar panels in desert environments. But, interestingly enough, these advantages don’t seem to be steady throughout the year.

Researchers at Hamad Bin Khalifa University carried out a 20-month trial at the Qatar Environment and Energy Research Institute. They found that, in some cases, tracker-based bifacial systems produced up to 13.5% more electricity than similar fixed-tilt setups. Their findings, published in Renewable Energy, looked into how factors like module type, ground coverage, string layouts, and weather conditions influence energy output in one of the toughest climates in the region.

This kind of study is pretty important for developers working across the Gulf and the broader Middle East, where scorching heat, intense sunlight, and dust can make system design quite the challenge. You see, in these harsh settings, even a small percentage increase in yield can significantly impact project costs, component choices, and land-use strategies.

Now, the researchers pointed out that their test setup was unusually large for this sort of field research. They used seven rows of SOLTEC-SF7 trackers, various string configurations, different pitches, and 13 types of commercial PV modules. Their system employed astronomical single-axis tracking with asymmetric backtracking, a method meant to minimize shading between rows while maintaining output efficiency.

For comparison, they set up a fixed-tilt array inclined at 22 degrees facing south, laid out as similarly as possible to the tracker system. Both arrays were installed on natural gravel ground, which mimics the desert terrain common in the region.

They measured rear-side temperatures with embedded sensors and monitored different irradiance components, like plane-of-array irradiance, global horizontal irradiance, diffuse horizontal irradiance, and rear-side irradiance. This approach allowed them to determine how much of the system’s energy was coming from direct sunlight versus reflected or diffuse light, a key factor for understanding bifacial performance.

The results showed that the tracker setup gave an average annual boost of around 15.5% in plane-of-array irradiance, and about 13.5% higher energy yield compared to the fixed-tilt system. The peak performance occurred in early July 2024, with daily gains reaching roughly 36%. However, that advantage wasn’t consistent all year.

Seasonally, from February through September, the tracking system generally performed better, thanks, partly, to the high direct sunlight and the sun’s angle during summer. But from October to January, the fixed-tilt configuration actually outperformed the trackers by as much as 7.2%. This was mainly due to the lower sun angles in winter, which reduce tracking effectiveness and favor fixed setups.

This kind of fluctuation really matters for solar projects in the Gulf. It suggests that tracker systems aren’t automatically better every single month, even in a desert climate with tons of sunshine. Instead, the optimal choice really depends on how the sun moves through the sky, the kind of sunlight (direct vs. diffuse), and specific operational conditions.

And, interestingly enough, the study also highlighted how diffuse light plays a role. On overcast days, the performance difference between the two systems shrank because both were capturing more scattered irradiance rather than direct beam sunlight. During winter, the fixed-arrays captured midday sun more effectively, but in the brighter months, the trackers had an edge during early mornings and late afternoons.

Module type was just as critical as how the array was mounted. Among the tested options, silicon heterojunction modules yielded the highest overall energy output, especially during periods of intense sunlight and heat. The researchers noted that this matches their known resilience to temperature increases and their strong bifacial response. N-type PERT and high-efficiency bifacial PERC modules also did well, which hints that a good rear-side response can compensate for some temperature-induced losses.

This is a big deal, particularly in hot climates where module efficiency often drops as the temperature rises. For developers, say in the UAE, where similar high temperatures and dust are common, these results emphasize choosing modules that keep performing well under stress rather than just chasing the highest nominal efficiency ratings.

Another point they found was that the position of the strings relative to the tracker’s torque tube didn’t significantly impact output. That’s helpful because it gives system designers more leeway when laying out bifacial trackers in desert areas, where practical constraints like cost and maintenance can influence setup choices.

HBKU’s broader research continues to explore how PV systems behave in arid environments. Past studies have looked into early degradation of silicon heterojunction modules in desert conditions and how vertical east-west bifacial systems respond to dust and energy harvesting. Those efforts are part of a bigger push to adapt and optimize PV deployments tailored specifically for Gulf climates rather than simply copying designs from cooler, temperate regions.

For the solar industry, what this means isn’t exactly a straightforward verdict. Sure, trackers can provide clear benefits in Qatar-like conditions, but only if engineers and project planners factor in seasonal variations, the nature of sunlight, and the types of modules used. During winter months, the fixed-tilt setups still hold strong. Come summer, bifacial trackers have a real edge by making better use of the abundant direct sunlight.

Overall, the takeaway is pretty clear: desert solar isn’t a one-size-fits-all affair. Achieving the highest yields hinges on tuning mounting structures, choosing appropriate module types, and spacing, everything suited to the local climate rather than assuming one approach dominates year-round.