SA study busts US claims that solar systems kill one bird per minute

Africa’s first concentrated solar power plant tower, the Khi Solar One near Upington, is not killing birds at rates previously thought, a groundbreaking study has revealed. 

Stellenbosch University conservation ecologist HP van Heerden conducted the first study ever to focus on birdlife around the solar facility. 

Media reports in the US claim that up to one bird per minute, or 28,000 birds per year, die because of solar systems. These claims are exaggerated and likely based on anecdotal rather than factual evidence. 

Photo: Heli SCSP website

Renewable energy solutions must be built while bringing the environment, namely plants and animals, into consideration, Van Heerden said, with his study revealing that although the solar tower does have an impact on bird populations in the area, both seasonally and throughout the year, it was less than expected. 

The Khi Solar One site is 315 hectares, and has an adjacent open Nama Karoo veld that receives very little rain – around 150mm per year. 

During his surveys, modelled on similar studies conducted in Spain and the US, van Heerden recorded 57 different bird species during summer and winter, and 49 species in winter. More species were observed in the veld than around the solar tower site, and most species except pied crows, Egyptian geese and korhaan did not fly higher than 10m. 

The Khi Solar One tower. Photo: Abengoa

But there were fatalities and injuries. 

Van Heerden counted 324 injured or dead birds, from 34 different species, around the solar tower. 285 of these were found inside the solar field, called the heliostat area, with the remaining dead or injured birds found around the power generation unit and evaporation ponds. 

Heliostats are movable mirrors used to reflect sunlight.

Movable mirrors, or heliostats. Photo: Heli SCSP website

61% of the injuries and deaths were caused by birds colliding with structures, but 14% of the birds were singed. 

The singeing of the birds occurs due to the ‘solar flux’, which is a concentrated beam of sunlight from the heliostats that can reach temperatures of up to 800 degrees Celsius. 

Van Heerden explained that the bight light from the mirrors of the towers attract insects, and by proxy, insect-eating birds. If a moving bird flies through the solar flux, it can be singed due to the mirrors converting sunlight into thermal energy. 

These incidents took place most during the plant’s downtime, when the mirrors were in a standby position, which created “a kind of halo effect” and a solar flux above the tower. 

Luckily, van Heerden provided recommendations to the facility’s operators, saying that heliostats should not be positioned at 90 degrees in the early mornings and late afternoons. He advised that the intensity of the solar flux can also be reduced when mirrors are in standby positions, and that they should preferably be set in a horizontal position during the plant’s downtime. 

“Some impact by solar towers on the environment is almost unavoidable, but can be minimised if managed right,” van Heerden said.

(Compiled by Nica Richards)

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