Solar panel installations might have been wrong all this time
A study by Dutch scientists has shown that the conventional slanted horizontal installation of photovoltaic (PV) solar panels might not be the best way to harness energy from the sun.
Typically, single-sided PV solar panels are installed at a 30 to 45-degree north angle in the Southern Hemisphere or the same angle south in the Northern Hemisphere.
This is to ensure optimal exposure to the sun throughout the year — including the winter — when the sun will appear lower in the sky and be available for a shorter period than in the summer.
However, for several years, some solar energy experts have claimed that installing vertical bifacial solar panels would make them more efficient.
The Netherlands Organisation for Applied Scientific Research’s (TNO’s) study on the potential of vertical solar panels, published in EPJ Photovoltaics in November 2023, supports these assertions.
The researchers used data from a PV solar park with nine rows of eight bifacial PV panels in an east-west orientation, all angled at 90 degrees to the ground, to create a digital twin to simulate performance over a year.
They unexpectedly found the panels would have generated 2.5% more energy during the year than when in the conventional configuration.
While this might not seem like much, the difference can be substantial in large-scale installations where economies of scale come into play.
It’s all about heat
The efficiency difference could be explained by the vertical panels’ operating temperatures being about half what they would have been in the conventional horizontal orientation.
The lower temperatures positively affected the operating voltage and the total energy generation, particularly under high irradiance conditions.
“For a standard system, we observed that under high irradiance conditions, the increase due to the light is offset by the decrease due to the higher operating temperature,” corresponding author Bas B. Van Aken told pv magazine.
“However, for the vertical system, we observed that the operating temperature is not increasing so much and the voltage increase and decrease are more or less balancing.”
It is important to note that the findings were measured against the rated capacity of the panels. That means the fact that they sported double the surface area did not contribute to their performance being better than a single-sided horizontal solar panel.
In addition to the lower operating temperatures, the angle of the panels also means that at least one side is exposed to the sun for a longer time during the winter.
Sunzaun Farm in Somerset, California, with a row of vertical solar panels
While the study was done using the typical weather conditions in the Netherlands, South Africa has a much sunnier climate.
With the corresponding higher local irradiance, the differences in energy efficiency could theoretically be even higher.
PV solar panels start becoming less efficient once their surface temperature reaches 25°C. This number is likely exceeded for many days during the hot summer months in South Africa.
Vertical solar installations would perhaps not be suited for home rooftops, but they could be of significant benefit in other configurations.
Where a home has run out of space on its roof, for example, it might have a wall with lots of exposure to the sun that could support such panels. Alternatively, the panels themselves could act as a wall.
The more obvious application is in commercial and utility-scale solar plants, where the installations must make the best possible use of their available land.
This could be of huge help to the agricultural sector, as farmers would be able to grow crops on the same land where they plant the vertical solar panels.
In addition to the Netherlands, bifacial vertical solar installations have already popped up at farms in the US and Japan.
However, until the study’s findings were published, the main purpose of these installations was to make optimal use of land. The potential efficiency benefits were unknown.
For a more detailed look at the study’s findings, YouTuber Matt Ferrell’s explainer video is worthwhile to watch.
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