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July 07, 2023
By
VALERIE THOMPSON
Ground mounted agrivoltaics have minimal impact on
grassland carbon-water cycling
A US-Spanish research team studied the ecological
effect of a solar photovoltaic array located on a managed grassland
plot using a hydraulic and soil hydrology model and field
measurements. They found minimal effect on the plants’ carbon-water
cycling, which they attributed to plant photosynthetic traits changing
to take advantage of the dynamic shading under the panels.
![](images/images_07_12_2023/pic4%20copy.jpg)
Image: University of Colorado
An
international research group has investigated the impact of ground
mounted solar plants on grassland plots and has found it has a
negligible impact on grassland carbon-water cycling.
The scientists also sought to answer questions about water retention
and grassland ecosystem resistance to weather extremes such as
droughts or heat waves but the answer to this was not clear at the end
of the study.
“Indeed, we did not find that the agrivoltaic array increased
grassland resistance to drought,” the corresponding author Steven A.
Kannenberg told pv magazine. “However, as noted in the paper, I would
like to clarify the possibility that this is because the structure of
the model does not allow the grass to die back and then regrow after
drought, which is commonly observed in natural settings,”
To discover more about the impact of the reduction in light
availability caused by solar photovoltaic arrays on grassland
photosynthesis, the researchers used a combination of field
measurements and a well-established plant hydraulic and soil hydrology
model to simulate grassland physiology and hourly carbon-water fluxes
over a 23-year time period.
They found that although the agrivoltaic array reduced light
availability by 38%, photosynthesis and above ground net primary
productivity were reduced by 6 to 7%. Another metric analyzed by the
researchers, evapotranspiration, showed a 1.3% decrease compared to a
reference land plot with no solar plant.
The grassland plot in the study is dominated by smooth brome (Bromus
inermis), a common C3 pasture grass, said the researchers. It is
located in Colorado with an east-west oriented 1.2 MW plant equipped
with single-axis trackers, installed at a flat panel height of 1.8 m
with 5.2 m between rows. The paper notes that care was taken to
minimize the impact on soils and vegetation. For example, the land was
not graded for installation.
The
researchers said the minimal changes in carbon-water cycling occurred
largely because plant photosynthetic traits underneath the solar
panels changed to take advantage of the dynamic shading environment.
They conclude that agrivoltaic systems can serve as a scalable way to
expand solar energy production while maintaining ecosystem function in
managed grasslands, especially in climates where water is more
limiting than light.
“We are planning to continue this research. This paper is one of the
first of hopefully many that will come out of work done in Colorado.
And we would always be interested in hearing about research from
industry on this topic,” corresponding author Steven A. Kannenberg
told pv magazine.
The scientists presented their findings in “Grassland carbon-water
cycling is minimally impacted by a photovoltaic array,” published in
communications earth environment. They come from Colorado State
University and the Technical University of Madrid in Spain.
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