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Remarkable agrivoltaic influence on soil moisture, micrometeorology and water-use efficiency

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Power demands are set to increase by two-fold within the current century and a high fraction of that demand should be met by carbon free sources. Among the renewable energies, solar energy is among the fastest growing; therefore, a comprehensive and accurate design methodology for solar systems and how they interact with the local environment is vital. This paper addresses the environmental effects of solar panels on an unirrigated pasture that often experiences water stress. Changes to the microclimatology, soil moisture, water usage, and biomass productivity due to the presence of solar panels were quantified. The goal of this study was to show that the impacts of these factors should be considered in designing the solar farms to take advantage of potential net gains in agricultural and power production. Microclimatological stations were placed in the Rabbit Hills agrivoltaic solar arrays, located in Oregon State campus, two years after the solar array was installed. Soil moisture was quantified using neutron probe readings. Significant differences in mean air temperature, relative humidity, wind speed, wind direction, and soil moisture were observed. Areas under PV solar panels maintained higher soil moisture throughout the period of observation. A significant increase in late season biomass was also observed for areas under the PV panels (90% more biomass), and areas under PV panels were significantly more water efficient (328% more efficient).
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RESEARCH ARTICLE
Remarkable agrivoltaic influence on soil
moisture, micrometeorology and water-use
efficiency
Elnaz Hassanpour AdehID*, John S. Selker, Chad W. Higgins
Department of Biological and Ecological Engineering, Oregon State University, Corvallis, Oregon, United
States of America
*hassanpe@oregonstate.edu
Abstract
Power demands are set to increase by two-fold within the current century and a high fraction
of that demand should be met by carbon free sources. Among the renewable energies,
solar energy is among the fastest growing; therefore, a comprehensive and accurate design
methodology for solar systems and how they interact with the local environment is vital. This
paper addresses the environmental effects of solar panels on an unirrigated pasture that
often experiences water stress. Changes to the microclimatology, soil moisture, water
usage, and biomass productivity due to the presence of solar panels were quantified. The
goal of this study was to show that the impacts of these factors should be considered in
designing the solar farms to take advantage of potential net gains in agricultural and power
production. Microclimatological stations were placed in the Rabbit Hills agrivoltaic solar
arrays, located in Oregon State campus, two years after the solar array was installed. Soil
moisture was quantified using neutron probe readings. Significant differences in mean air
temperature, relative humidity, wind speed, wind direction, and soil moisture were observed.
Areas under PV solar panels maintained higher soil moisture throughout the period of obser-
vation. A significant increase in late season biomass was also observed for areas under the
PV panels (90% more biomass), and areas under PV panels were significantly more water
efficient (328% more efficient).
1 Introduction
Global energy demand will be doubled by mid-century due to population and economic
growth [1,2]. Renewable and environmental-friendly energies will play a vital role to meet this
demand.
Among all renewable energies, solar power is the most abundant and available source [3].
Solar power is also becoming more affordable. The cost of solar panels has fallen by 10% per
year for the past thirty years, while production has risen by 30% per year. If costs continue to
be reduced based on this historic rate, solar energy will be less expensive than coal by 2020[4].
The impact of wide-spread solar installations is an area of increasing interest. Regional
PLOS ONE | https://doi.org/10.1371/journal.pone.0203256 November 1, 2018 1 / 15
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OPEN ACCESS
Citation: Hassanpour Adeh E, Selker JS, Higgins
CW (2018) Remarkable agrivoltaic influence on soil
moisture, micrometeorology and water-use
efficiency. PLoS ONE 13(11): e0203256. https://
doi.org/10.1371/journal.pone.0203256
Editor: Mauro Villarini, Universita degli Studi della
Tuscia, ITALY
Received: January 18, 2017
Accepted: August 18, 2018
Published: November 1, 2018
Copyright: ©2018 Hassanpour Adeh et al. This is
an open access article distributed under the terms
of the Creative Commons Attribution License,
which permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: Data are available
from the Oregon State University library (ir.library.
oregonstate.edu) with DOI: 10.7267/N9W37T8D.
Funding: This material is based upon work that is
supported by the National Institute of Food and
Agriculture, U.S. Department of Agriculture, under
award number OREZ-FERM-852-E, and by National
Science Foundation award number EAR
1740082. The funders had no role in study design,
data collection and analysis, decision to publish, or
preparation of the manuscript.
climatology may be influenced by large scale solar installations, but simulations have provided
conflicting results: 3–4˚C increase in air temperature over solar panels compared to wildlands
at night [5], 0.1–0.5˚C decrease in air temperature [6], 26˚C increase in the shaded roof top
temperature compared with unshaded roof top [7], 1–2.5˚C increase in regional and global
temperatures in urban area [8] and a 5.2˚C increase in air temperature under solar panels [9].
Solar installations can occupy large land areas and sometimes compete with agriculture for
the land resource [10]. Agrivoltaic systems are created when solar and agricultural systems are
co-located for mutual benefit. The formal introduction of agrivoltaic systems is credited to
Dupraz in 2011 [11]. Land demand for energy production decreases profoundly when agrivol-
taics are used [10]. Not all agricultural crops are suitable, but plants with less root density and
a high net photosynthetic rate are ideal candidates [11]. Agrivoltaic systems have been shown
to increase land productivity by 60–70% [12], and increase the value of energy production sys-
tem by 30% [13]. Very limited experimental research was found on the impacts of a solar
arrays on agricultural production. Marrou et al. [14] measured soil water potential and soil
water gradient (difference between uptake and drainage) in cucumber and lettuce and revealed
lower soil water potential under the panels. This water potential led to an increase in harvested
final fresh weight. Another experiment by Marrou et el. [15] found that plants cover soil faster
under the shade of solar panels. An experimental study by Dupraz et al. demonstrated that
summer crops benefited of solar shade more than winter crops such as pea and wheat crops
[16]. Co-locating agave plant below solar panels increased yield per m
3
of water used in the
San Bernardino County in California [17]. Non-beneficial effects have also been observed in
Welch onion fields where, photovoltaics reduced the fresh and dry matter harvest weight [18].
In this paper, a field study was performed to measure the effects of a six-acre agrivoltaic
solar farm on the microclimatology, soil moisture and pasture production. The experimental
setup included microclimatological and soil moisture measurements from May to August
2015 in Rabbit Hills agrivoltaic solar arrays, located on the Oregon State University campus.
The field data for this study is accessible through Oregon State library system [19].
2 Material and methods
The field study was performed on a six acre agrivoltaic solar farm and sheep pasture near the
Oregon State University Campus (Corvallis, Oregon, US.). The PhotoVoltaic Panels (PVPs)
have been arranged in east–west orientated strips, 1.65 m wide and inclined southward with
a tilt angle of 18
o
. PVPs have been held at 1.1 meters above ground (at lowest point) and
the distance between panels is 6 meters as shown in Fig 1) e. The whole solar array system
has a capacity of 1435 kilowatts (http://fa.oregonstate.edu/sustainability/ground-mounted-
photovoltaic-arrays). As shown in Fig 1, the data were collected from localized zones (descri-
bed hereafter) including areas below solar panels and a control area outside the agrivoltaic sys-
tem. The pasture below the solar panels and the control areas were in the same paddock that
was actively grazed by sheep. Exclusionary plots, to eliminate grazing pressure, were main-
tained with fencing. The total size of the fenced areas was limited by agricultural activities. The
pasture was not irrigated, and typically experiences water stress mid-summer. The soil classifi-
cation for >70% of the pasture area (control and agrivoltaic system) is Woodburn Silt clay
[20]. The control and treatment plots were located within Woodburn Silt clay classification
areas. The intent of the field measurements was to minimize uncontrollable differences
between the treatments and control (e.g. solar forcing, soil types) and minimize impact on
agricultural activities. Thus, the distance between the treatment site and the control site was
kept minimum. The observations within the treatment site were further divided into three
sub-treatments (Fig 2): (1) Sky Fully Open area between panels (SFO), (2) Solar Partially Open
Environmental effects of solar panel on agricultural fields
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Competing interests: The authors have declared
that no competing interests exist.
Fig 1. a) Aerial photo of 35
th
Street agrivoltaic solar array, Oregon State University Corvallis campus (this photo is taken in winter and shadow pattern
is different from the measurements which held in summer) Copyright: Oregon State University, b) Solar panel set up, c) Control area set up, d) Shade
zones in solar panel, e) Schematic drawing of shade zones (H is object height and L is shadow length).
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between panels (SPO) and (3) Solar Fully Covered area under panels (SFC). SFO areas are
between the edges of installed PV panels and experienced full sun. Shadow length calculation
also confirms no shade covers the SFO zone [21]. SPO areas are in the penumbra and experi-
enced episodic shade. SFC areas are directly beneath the PV panels and experienced full shade.
Data from these sub-treatments were compared to the data collected from the control area out-
side the agrivoltaic array, where each measurement was replicated.
Shadow length (L) is calculated [20]based on the sun latitude, solar panel height, day and
time of the year the and it changes from 1.1 meters to 1.4 meters for May, June, July and
August of 2015 which makes the SFO no shadow zone.Data were collected continuously in all
areas from May-August 2015. Air temperature, relative humidity, wind speed and wind direc-
tion measurements were collected on 1 minute intervals. Soil moisture profiles were collected
three times each week, and biomass samples were collected at the end of the observation
period. Details associated with each set of measurements are explained in the following sub-
sections.
2.1 Microclimatological measurements
Two atmospheric profiling stations were installed 70 meters apart: one in the control area and
one near the center of the solar panel area. Micrometeorological variables were collected at
four levels (0.5, 1.2, 2.0 and 2.7 m aboveground) in 1 minute intervals. The gathered variables
were (1) air temperature (VP-3 Decagon Devices), (2) wind speed and directions (DS-2 Deca-
gon Devices), (3) relative humidity (VP-3 Decagon Devices) and (4) net radiation (PYR
Fig 2. Plan view of experimental setup in solar array area showing locations of towers and neutron probe access
tubes for: Solar Fully Covered (SFC), Solar partially open (SPO), Sky Fully Open (SFO), solar measurements are
almost 70 meters apart from control area.
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Decagon Devices). Data were logged on EM50 data loggers (Decagon Devices). Temperature
and humidity devices were calibrated in a chamber, and wind sensors were calibrated in a
wind tunnel prior to installation. A Kolmogorov Smirnov test was used to detect differences in
distributions of temperature, humidity, wind speed, wind direction, and down welling radia-
tion between the solar array area and the control area. A two tailed t-test was used to detect dif-
ferences in the mean temperature, humidity, wind speed, wind direction, and down welling
radiation between the solar array area and the control area and standard deviation results was
measured to quantify the amount of dispersion of a set of data values.
2.2 Soil moisture measurement
The soil moisture was obtained using a neutron probe device (503 DR hydro-probe Campbell
Pacific Nuclear International Inc. BoartLongyear Corporation (CPN), Concord, California,
USA). These data were gathered at six depths for each sampling location (0.1 m to 0.6 m in 0.1
m intervals). Fig 2 shows a plan view where nine neutron probe access tubes for soil moisture
measurements were installed in the solar area. Three access tubes were installed in each sub-
treatment: SFO, SPO, and SFC respectively. Three access tubes were also installed in the con-
trol area. Neutron Probe readings were taken approximately every three days. A standard
count was taken prior to sampling each day to calibrate data readings. Three neutron counts
were averaged for each individual measurement (a single depth in a single tube). This count
was normalized by the standard count, and the normalized count was calibrated to soil mois-
ture. Within each sub-treatment, data at the same depths are averaged to determine the soil
moisture profile and error-bars. The result is a soil moisture profile with measurements at 0.1,
0.2, 0.3, 0.4, 0.5, and 0.6 m for each sub-treatment and the control every three days. Neutron
probe readings at the 0.1m depth for all sub-treatments and the control were adjusted to
account for possible neutron losses to the atmosphere [22]. Two-way ANOVA was used to test
the independence of the soil moisture measurements with respect to zoning (the control, SFO,
SPO, and SFC) and depth.
2.3 Biomass measurements
Above-ground biomass was collected on the 28
th
of August. Six 1m by 1m quadrants were col-
lected from within the fenced areas for each sub-treatment and the control. Harvested biomass
was dried for 48 hours in a 105
o
C oven and weighed. The Daubenmire method [11] was used
to study grass species diversity at the end of July. Six transects in the control and one transect
in the solar array were performed. For each transect, a random number was drawn (from
1–10) to determine the final location of each 1m x1m quadrant. Six quadrants were collected
in each transect resulting in a total of 42 samples. In each quadrant, the coverage, by species,
was determined visually.
3 Results and discussions
3.1 Micrometeorological variables
Using a Kolmogorov Smirnov test, a two tailed t-test, standard deviation and William Watson
test[23] for wind direction showed subtle but statistically significant differences. Significant
differences in mean temperature were found in readings taken closest to the PV panel surfaces
at the 1.2 m and 2.0 m elevations. No significant differences were observed at the lowest (0.5
m) or highest (2.7 m) elevations. Note that the magnitude of these mean temperature differ-
ences are smaller than those reported from simulation studies [59]. Significant differences in
mean relative humidity and wind speed were found for all measurement heights. Solar
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radiation below the solar panel installation height was significantly reduced (as expected) and
the incoming solar radiation measured at a height above the solar panels was found to be sta-
tistically significant (unexpected) but the difference relatively small. The distribution of wind
direction was significantly altered at all heights, and the mean wind speed was significantly dif-
ferent at all heights. A summary of the p-values from all statistical tests is shown in Table 1.
Standard deviation values were big due to diurnal changes of micro climate variables during
the day.
Wind direction data at 2.7 m above ground level is shown in Fig 3 to illustrate the alter-
ations in the wind direction. For the sake of brevity, only one height is presented in this manu-
script, but all heights are shown in Supporting Information (Figure A in S1 Appendix). Fig 3
shows a histogram of incident wind direction plotted as a function of direction. Longer spokes
indicate that that particular direction is more probable. Each spoke is divided and colored
according to the strength of the wind (wind speed). For example, a long blue spoke would indi-
cate that light winds from that direction are common. We can conclude from Fig 3 that the
wind direction in the control area is distributed among many incident angles, while the wind
direction within the treatment is oriented predominantly from the south. That is, the wind
direction within the treatment area reorients with solar panels such that the wind is from
south to north. The panels do not act as ‘canyons’ and orient the wind along their rows (a com-
mon occurrence in urban flows for example)[24]. Rather, the wind is reoriented perpendicular
to the solar array’s rows. The authors believe that the local increase in temperature near the
solar panel surface results in a buoyant force that causes local anabatic flow up the panel sur-
faces. Each anabatic flow on each PV row has a vector component perpendicular to the solar
panel row orientation, and the entire solar farm acts like a ‘Fresnel slope’ that reorients the
flow. The total buoyant force is enough to accelerate the flow directionally, and contributes the
increase in wind speed above the panels. Flow acceleration around a bluff body (PV panel)
also contributes to increased wind speed above the solar panels. Increased drag due to the
Table 1. Mean/Std and p-values from solar panel and control area Two-sample Kolmogorov-Smirnov, t tests and William Watson test.
Elevation (m) 0.5 1.2 2.0 2.7
Temperature
(˚C)
Mean/Std (solar panel area) 18.34/7.87 18.03/8.06 18.30/7.39 18.37/7.65
Mean/Std (control area) 18.27/7.85 18.32/8.31 18.36/7.47 18.11/7.64
p-values (KS test) 0.9964 0.9964 1.0000 1.0000
p-values (t test) 0.1527 0.0000 0.0000 0.5996
Relative humidity
(%)
Mean/Std (solar panel area) 65.62/0.226 64.17/0.252 64.29/0.209 64.92/0.230
Mean/Std (control area) 66.23/0.234 66.38/0.242 64.89/0.222 65.37/0.223
p-values (KS test) 0.0004 0.3611 0.7014 0.6703
p-values (t test) 0.0000 0.0000 0.0000 0.0118
Wind speed
(m/s)
Mean/Std (solar panel area) 0.5471/0.506 0.4880/0.427 1.3777/1.083 1.0889/0.909
Mean/Std (control area) 0.8752/0.665 0.6384/0.520 1.1313/0.859 0.9726/0.757
p-values (KS test) 0.9579 1.0000 0.8497 0.9964
p-values (t test) 0.0000 0.0000 0.0000 0.0000
Solar radiation (W/m2) Mean/Std (solar panel area) - 59.53/96.65 - 275.72/322.59
Mean/Std (control area) - 328.26/407.93 - 271.58/323.34
p-values (KS test) - 0.0099 - 0.9597
p-values (t test) - 0.0000 - 0.0054
Wind direction
(˚)
Mean/Std (solar panel area) 196.29/107.71 220.96/102.32 211.83/101.68 206.11/96.65
Mean/Std (control area) 210.54/102.29 196.82/121.16 211.87/95.91 182.13/115.97
p-values (WW test) 0.0000 0.0000 0.0000 0.0000
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‘solar canopy’ is likely the cause of the reduced speed below the solar panels. Note that the
most common wind speeds are weak (<2m/s), and it is unclear if this wind direction shift
would be a robust result for windy locations. Higher wind speeds are also observed to reorient
in Fig 3; however, the number of occurrences are limited.
3.2 Soil moisture data comparisons
The horizontal axis shows the Day of Year (DoY) of the data collection in 2015 and vertical
axis is the volumetric soil moisture in vol/vol. Independence was determined with a p-value of
less than 0.01 for all depths and zones by two-way ANOVA test. The soil moisture is near satu-
ration for all depths and all treatments at the start of observation. That is, all areas had nearly
identical initial soil moistures. The differing rates of soil water depletion in the three sub-treat-
ments and the control led to dramatic differences in late season soil moisture.
The soil moisture in the SFO area is depleted more rapidly than the SPO, SFC or control
areas. This result is intriguing since the SFO area and the control experience similar incident
solar radiation. Thus, the SFO must have a different energetic balance despite similar exposure
to direct solar energy. We hypothesize that this difference in rate of soil moisture loss is a result
of the longwave radiation transfer. The SFO will experience incident long wave radiation from
the adjacent PV panels. These PV panels would also reduce the sky view factor of the SFO
area. In contrast, the sky view in the control area is unobstructed. Thus, we infer that the total
net long wave and net shortwave radiation both play an important role in the energetics and
evaporation in the SFO area. The complete long and short wave radiation budgets within an
agrivoltaic system will be explored in future study.
Time series of the soil moisture at 0.2 m, 0.4 m and 0.6 m are presented in Fig 4 in subpan-
els a-c. Time series of soil moisture at 0.1 m, 0.3 m and 0.5 m can be found in Supporting
Information (Figure A in S2 Appendix). Soil moisture is most persistent in the SFC area and
remains available for a larger portion of the growing season. The soil moisture at 0.6 m depth
remained close to saturation (0.3 vol/vol) for the entire season which implies that water is
available at the bottom of the root zone over the period of observation Fig 4C. Overall the SFC
area remained wetter than all other areas, including the control. This water availability is in
stark contrast to the SFO area which was near saturation at the start of observation (~0.3 vol/
vol) and depleted to ~0.2 vol/vol at the end of the season. This stark contrast in the moisture
availability between the SFO and SFC creates an undesirable variability across the field and
hints that shade uniformity may be an important consideration for the design of future agri-
voltaic systems. The SPO area dries at a rate slower than the SFO but faster than the SFC and
the control.
In other words, for most times and soil depths, the SFC had that highest soil moisture fol-
lowed by the SPO, control and SFO respectively. It should be noted that the mean soil moisture
across the SPO, SFO and SFC regions is similar to the control. But, the solar panels increase
the local heterogeneity of soil water conditions, which results in some areas (SFC) having
more persistent stores of soil water throughout the growing season.
The soil profiles at the beginning and end of the observation period are shown in Fig 5 All
areas were near saturation for all depths initially. By the end of the observation period, the soil
moisture in the SFC zone was nearly twice the SFO. These measurements are separated by less
than two meters spatially. All measured soil moisture profiles are available in Supporting
Information (Figure A in S3 Appendix).
Fig 3. Wind rose plots for control (upper) and solar areas (lower) for May-August average winddirections. The data are
for elevation 2.7 m.
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Fig 4. Soil moisture time series (a) 0.2m, (b) 0.4m and (c) 0.6m. For more information: there was 40 mm precipitation
over the observation period, i.e. May-Aug 2015.
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3.3 Vegetation
Eight grass types were identified in the control pasture and five were identified in the solar
farm area. A summary of the results is presented in Table 2. The most common species in the
solar panel area was Alopecurus, a long-lived perennial that thrives in moist conditions. Alope-
curus provides a “succulent and palatable forage” [25]. The most prevalent grass type in con-
trol area is Hordeum that has spikelet clusters that can enter nostrils and ear canals in
mammals. Three types of grasses Calamagrostis, Cirsium and Dactylis were observed only in
the control area. These grasses are only favored by sheep and cattle in the early stage of the
grass before spine develops [26]. The causal factor for the diversity change between control
and treatment requires further investigation.
The harvested dry biomass at the end of the observation period is shown in Fig 6 Results
show 126% more dry biomass in the SFC zone relative to the SFO zone and 90% more dry bio-
mass in the SFC zone relative to the control. Although the sample size is small, difference
between the SFC and the control were found to be significant, (p-value = 0.007). In addition,
the difference between the SFC and the SFO were found to be significant, (p-value = 0.007).
3.4 Water usage
Water usage was calculated based on difference in depth averaged soil moisture between the
beginning (Fig 5(A) and end (Fig 5(B)) of the observation period. Averages are calculated by
integrating soil moisture over soil depth from 10cm to 60cm. Water Use Efficiency (WUE) is
then calculated as the biomass produced per unit of water used. Water use efficiencies in kg
biomass/m
3
of water against the biomass weight in control and SFO and SFC treatments are
presented in Fig 7 (WUE SFCWUE Control area
WUE Control area ). The higher producing SFC treatment was also signifi-
cantly more water efficient (328%).
The seasonal climate pattern at the site produces an initially saturated pasture and a a dry
growing season. Initial water stores are depleted, through evapotranspiration (ET), and water
scarcity occurs in the control and SFO areas. The shaded treatments (SFC and SPO) experi-
ence lower potential evapotranspiration (PET) due to decreased solar radiation throughout the
observation period which resulted in a slower dry-down of the stored soil water. The decreased
rate of dry-down in the SFC and SPO areas left soil water stores available throughout the
observation period and allowed pasture grasses in the SFC and SPO to accumulate a signifi-
cantly greater biomass. The reduced PET in the SFC and SPO treatments also contributed to
Fig 5. Selected normalized soil moisture profiles from data sampling to show the change in soil moisture through growing season, (a)
May 06–2015 and (b) August 27–2015.
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Table 2. The results of biomass monitoring for different grass types in solar and control area.
Grass scientific name (common name) Solar area (%) Control area (%)
Hordeum (Foxtail barely) 10 25
Agrostis (Redtop bentgrass) 30 20
Alopecurus (Meadow foxtail) 50 7
Schedonorus (Tall rye grass) 5 9
Bromus (Foxtailbrome) 5 22
Calamagrostis (Reed grass) 0 6
Cirsium (Thistle) 0 10.5
Dactylis (Orchard grass) 0 0.5
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Fig 6. Dry biomass comparison in three places Solar Fully Covered (SFC), Sky Fully Open (SFO) and control area.
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Fig 7. Biomass productivity in kg/ m
3
of water.
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an increase in water use efficiency of the pasture grasses. That is, a ‘water limited’ area, in a
Budyiko [27] sense, could be considered as an area of ‘solar excess.’ By harvesting this solar
excess with solar panels, PET is reduced. Taken to an extreme it is possible to shift the aridity
such that the shaded area becomes energy limited. Thus there must exist a shading level, for a
water limited area, where PET and AET would be in balance. We would not expect a similar
outcome in ‘energy limited’ areas (Budyko sense) as observed by Armstrong et al. [8]. In this
case, there is no solar excess and the PET is already equal to the AET. If solar arrays were
placed above growing plants in ‘energy limited’ conditions we would expect that the total bio-
mass production would decrease, consistent with the findings of Armstrong et al. [16].
4 Conclusion
Typical agricultural operations manage multiple on-farm resources including soil, nutrients
and water. This study suggests that the on-farm solar resource management could also be
implemented for productive benefits. Water limited areas are most likely to benefit as solar
management reduces PET and consequently the water demand. Not all crops will be amenable
to solar management, and the economics of active solar management with PV panels needs
further study. But, semi-arid pastures with wet winters may be ideal candidates for agrivoltaic
systems as supported by the dramatic gains in productivity (90%) observed over the May-Aug
2015 observation period at the Rabbit Hills agrivoltaic solar array. These net benefits were
largely achieved through an increased water use efficiency in the shaded areas of the field
which left water stored in the soil column available throughout the entire observation period.
Extreme heterogeneity and spatial gradients in biomass production and soil moisture were
observed as a result of the heterogeneous shade pattern of the PV array. Future agrivoltaic
designs should eliminate this heterogeneity by optimizing PV panel placement to create a spa-
tially uniform shadow pattern. A spatially uniform shadow pattern would foster uniform bio-
mass accumulation benefits. The agricultural benefits of energy and pasture co-location could
reduce land competition and conflict between renewable energy and agricultural production.
Reduced or eliminated land completion would open new areas for PV installation. Local cli-
matic effects of agrivoltaic installations were statistically significant but subtle, however the
regional climatic impacts (e.g. rainfall patterns) of large scale agrivoltaic instillations are still
unclear and should be the subject of further study.
Supporting information
S1 Appendix. Figure A: Wind rose plots for four level heights.
(DOCX)
S2 Appendix. Figure A: Soil moisture time series (a) 0.1m, (b) 0.3m and (c) 0.5m. For more
information: there was 40 mm precipitation over the observation period, i.e. May-Aug 2015.
(DOCX)
S3 Appendix. Figure A: Selected normalized soil moisture profiles from data sampling to
show the change in soil moisture through growing season: May 06–2015 to August 27–2015.
The dates are mentioned on top of each figure with mmddyy format.
(DOCX)
Acknowledgments
Sincere acknowledgment is addressed to Dr. Ziru Liu (Postdoc in NewAg lab) for field
assistance.
Environmental effects of solar panel on agricultural fields
PLOS ONE | https://doi.org/10.1371/journal.pone.0203256 November 1, 2018 13 / 15
Author Contributions
Conceptualization: John S. Selker, Chad W. Higgins.
Data curation: Elnaz Hassanpour Adeh.
Formal analysis: Elnaz Hassanpour Adeh.
Funding acquisition: Chad W. Higgins.
Investigation: Elnaz Hassanpour Adeh.
Methodology: Chad W. Higgins.
Project administration: Chad W. Higgins.
Supervision: Chad W. Higgins.
Writing original draft: Elnaz Hassanpour Adeh.
Writing review & editing: John S. Selker, Chad W. Higgins.
References
1. Lewis NS, Nocera DG. Powering the planet: Chemical challenges in solar energy utilization. Proc Natl
Acad Sci. 2006; 103: 15729–15735. https://doi.org/10.1073/pnas.0603395103 PMID: 17043226
2. Rodman LC, Meentemeyer RK. A geographic analysis of wind turbine placement in Northern California.
Energy Policy. 2006; 34: 2137–2149.
3. Rogner HH, others. inGlobal Energy Assessment—Towards a Sustainable FutureCh. 7, 423–512.
Cambridge University Press; 2012.
4. Trancik JE. Renewable energy: Back the renewables boom. Nature. 2014; 507: 300–302. https://doi.
org/10.1038/507300a PMID: 24654279
5. Barron-Gafford GA, Minor RL, Allen NA, Cronin AD, Brooks AE, Pavao-Zuckerman MA. The Photovol-
taic Heat Island Effect: Larger solar power plants increase local temperatures. Sci Rep. 2016; 6:
srep35070. https://doi.org/10.1038/srep35070 PMID: 27733772
6. Millstein D, Menon S. Regional climate consequences of large-scale cool roof and photovoltaic array
deployment. Environ Res Lett. 2011; 6: 034001.
7. Scherba A, Sailor DJ, Rosenstiel TN, Wamser CC. Modeling impacts of roof reflectivity, integrated pho-
tovoltaic panels and green roof systems on sensible heat flux into the urban environment. Build Environ.
2011; 46: 2542–2551. https://doi.org/10.1016/j.buildenv.2011.06.012
8. Hu A, Levis S, Meehl GA, Han W, Washington WM, Oleson KW, et al. Impact of solar panels on global
climate. Nat Clim Change. 2016; 6: 290–294. https://doi.org/10.1038/NCLIMATE2843
9. Armstrong A, Ostle NJ, Whitaker J. Solar park microclimate and vegetation management effects on
grassland carbon cycling. Environ Res Lett. 2016; 11: 074016.
10. Nonhebel S. Renewable energy and food supply: will there be enough land? Renew Sustain Energy
Rev. 2005; 9: 191–201.
11. Seidlova L, Verlinden M, Gloser J, Milbau A, Nijs I. Which plant traits promote growth in the low-light
regimes of vegetation gaps? Plant Ecol. 2009; 200: 303–318. https://doi.org/10.1007/s11258-008-
9454-6
12. Dupraz C, Marrou H, Talbot G, Dufour L, Nogier A, Ferard Y. Combining solar photovoltaic panels and
food crops for optimising land use: Towards new agrivoltaic schemes. Renew Energy. 2011; 36: 2725–
2732. https://doi.org/10.1016/j.renene.2011.03.005
13. Dinesh H, Pearce JM. The potential of agrivoltaic systems. Renew Sustain Energy Rev. 2016; 54: 299–
308. https://doi.org/10.1016/j.rser.2015.10.024
14. Marrou H, Dufour L, Wery J. How does a shelter of solar panels influence water flows in a soil–crop sys-
tem? Eur J Agron. 2013; 50: 38–51. https://doi.org/10.1016/j.eja.2013.05.004
15. Marrou H, We
´ry J, Dufour L, Dupraz C. Productivity and radiation use efficiency of lettuces grown in the
partial shade of photovoltaic panels. Eur J Agron. 2013; 44: 54–66.
16. Dupraz C, Talbot G, Marrou H, Wery J, Roux S, Liagre F, et al. To Mix or Not to Mix: Evidences for the
Unexpected High Productivity of New Complex Agrivoltaic and Agroforestry Systems. 2011. Available
Environmental effects of solar panel on agricultural fields
PLOS ONE | https://doi.org/10.1371/journal.pone.0203256 November 1, 2018 14 / 15
Onlin E Httpswww Res Netpublication230675951To Mix Andagroforestrysystems Accessed 9 Dec
2015.: 202–203.
17. Ravi S, Lobell DB, Field CB. Tradeoffs and Synergies between Biofuel Production and Large Solar
Infrastructure in Deserts. Environ Sci Technol. 2014; 48: 3021–3030. https://doi.org/10.1021/
es404950n PMID: 24467248
18. Kadowaki M, Yano A, Ishizu F, Tanaka T, Noda S. Effects of greenhouse photovoltaic array shading on
Welsh onion growth. Biosyst Eng. 2012; 111: 290–297. https://doi.org/10.1016/j.biosystemseng.2011.
12.006
19. Hassanpour Adeh E, Higgins CW, Selker JS. Remarkable solar panels Influence on soil moisture,
micrometeorology and water-use efficiency. 2017; Available: https://ir.library.oregonstate.edu/xmlui/
handle/1957/60846
20. Web Soil Survey—Home [Internet]. [cited 5 Jun 2017]. Available: https://websoilsurvey.sc.egov.usda.
gov/App/HomePage.htm
21. Appelbaum J, Bany J. Shadow effect of adjacent solar collectors in large scale systems. Sol Energy.
1979; 23: 497–507.
22. Parkes ME, Siam N. Error associated with measurement of soil moisture change by neutron probe. J
Agric Eng Res. 1979; 24: 87–93.
23. Berens P. CircStat: a MATLAB toolbox for circular statistics. J Stat Softw. 2009; 31: 1–21.
24. Pavageau M, Schatzmann M. Wind tunnel measurements of concentration fluctuations in an urban
street canyon. Atmos Environ. 1999; 33: 3961–3971.
25. W.M. Murphy M. J. Grass varieties for central Oregon. 1976 Nov. Report No.: Special Report 468.
26. De Bruijn SL, Bork EW. Biological control of Canada thistle in temperate pastures using high density
rotational cattle grazing. Biol Control. 2006; 36: 305–315.
27. Budyko MI (Mikhail I. Climate and life. 1971; Available: http://agris.fao.org/agris-search/search.do?
recordID=US201300494263
Environmental effects of solar panel on agricultural fields
PLOS ONE | https://doi.org/10.1371/journal.pone.0203256 November 1, 2018 15 / 15

Supplementary resources (3)

... Efforts are being made to optimize agrivoltaic system design to manage trade-offs between energy production, crop productivity, and water consumption (Warmann, 2024). Research has also focused on assessing the economic feasibility and microclimatic impacts of agrivoltaic systems, emphasizing the need for even lighting to maximize comprehensive economic benefits (Adeh;Selker;Higgins, 2018;Zheng et al., 2021). Additionally, comparative analyses of different photovoltaic configurations for agrivoltaic systems have been conducted to enhance system performance (Niazi;Victoria, 2023). ...
... Efforts are being made to optimize agrivoltaic system design to manage trade-offs between energy production, crop productivity, and water consumption (Warmann, 2024). Research has also focused on assessing the economic feasibility and microclimatic impacts of agrivoltaic systems, emphasizing the need for even lighting to maximize comprehensive economic benefits (Adeh;Selker;Higgins, 2018;Zheng et al., 2021). Additionally, comparative analyses of different photovoltaic configurations for agrivoltaic systems have been conducted to enhance system performance (Niazi;Victoria, 2023). ...
... Efforts are being made to optimize agrivoltaic system design to manage trade-offs between energy production, crop productivity, and water consumption (Warmann, 2024). Research has also focused on assessing the economic feasibility and microclimatic impacts of agrivoltaic systems, emphasizing the need for even lighting to maximize comprehensive economic benefits (Adeh;Selker;Higgins, 2018;Zheng et al., 2021). Additionally, comparative analyses of different photovoltaic configurations for agrivoltaic systems have been conducted to enhance system performance (Niazi;Victoria, 2023). ...
Article
Agrivoltaic is a system that integrates agricultural activities with the production of solar photovoltaic electricity on the same piece of land. Agrivoltaic systems are gaining popularity in Indonesia since they enable farmers to generate renewable energy while making efficient use of agricultural land. This research technique employs the analytical descriptive approach, which aims to offer a comprehensive description or overview of the topic of study using acquired data or samples without undertaking further analysis to draw generalizable conclusions. An instance of agrivoltaic in Indonesia involves the placement of solar panels above crops to provide shade and minimize water evaporation. Simultaneously, these solar panels generate energy to operate irrigation systems or other agricultural machinery. Nevertheless, the use of agrivoltaic in Indonesia remains restricted and need further investment and assistance from both the government and private sector to enhance the acceptance of this technology in the agricultural industry.
... Die Umweltwirkungen der Agri-PV werden national wie international erforscht, insbesondere mit Blick auf die Kompatibilität und Optimierung der Nutzungskombination. Im Vordergrund stehen dabei die Auswirkungen der Anlagen auf das pflanzenverfügbare Licht sowie den Wasserhaushalt (Hassanpour Adeh et al. 2018;Parkinson und Hunt 2020). Agri-PV-FFA könnten dabei, z. ...
... The environmental impacts of Agri-PV are being researched upon both nationally and internationally, particularly with regards to compatibility and optimization of crop-use combinations. The focus lays on the impact of plants depending on the plant-available light as well as water balance (Hassanpour Adeh et al. 2018, Parkinson und Hunt 2020. Agri-PV FFAs could thereby enable productive agriculture in the first place in arid and semiarid areas, for example, due to reduced solar radiation or reduced soil water losses. ...
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Im Zuge des Umbaus des Energiesystems auf erneuerbare Energieträger muss die Photovoltaik (PV) stärker ausgebaut werden als bisher gedacht. Der Energiebedarf vieler Anwendungen im Bereich der Wärme und der Mobilität, der bisher durch z. B. fossile Energieträger oder teilweise Biomasse bereitgestellt wurde, soll künftig durch Strom gedeckt werden (Prognos et al. 2021a). So hat die Bundesregierung im Juli 2021 die Prognose für den künftigen Strombedarf in 2030 von 580 Terrawattstunden (TWh) auf 655 TWh pro Jahr erhöht (Bundes-ministerium für Wirtschaft und Energie 2021b). Diese Erhöhung der Stromproduktion aus Pho-tovoltaik wird nicht ohne die Nutzung von Freiflächen möglich sein, wie auch das Umweltbundesamt in der RESCUE Studie berechnet (Purr et al. 2019). Im Bereich der Freiflächen-Photovoltaik ist dabei aktuell zu beobachten, dass landwirtschaftliche Flächen erneut bevorzugt für eine Inanspruchnahme in den Fokus geraten, u. a. aufgrund der zunehmenden und teils umfänglichen Öffnung von landwirtschaftlichen Flächen in „benachteiligten Gebieten“ in aktuell sieben Bundesländern (BW, BY, HE, NI, RP, SR, SN). Auch die Projektierungsaktivitäten außerhalb des EEG fokussieren sehr ausgeprägt auf derzeit landwirtschaftlich genutzte potenzielle Anlagenstandorte. Forschungsgegenstand und Projektziel Die Anlage- und Nutzungskonzepte klassischer Photovoltaik-Freiflächenanlagen (kPV-FFA) sind vielfältig und werden derzeit durch zwei spezielle Ausprägungen ergänzt. Die Agri-Photovoltaik (APV), als erste Ausprägung, kombiniert die landwirtschaftliche mit der solarenergetischen Nutzung auf der gleichen Fläche. Untersuchungsergebnisse zu den gelegentlich als Biodiversitäts- oder Biotop-PV bezeichnete zweiten Ausprägung zeigen auf, dass sich Solarparks bei extensiver Pflege der Fläche im Laufe der Zeit intensiv besiedeln und somit einer Reihe von gefährdeten Arten Lebensraum bieten können. Ziel des vorliegenden Projektes ist die Analyse der naturschutzfachlichen Relevanz dieser beiden Anlagenkonzepte sowie eine Schärfung der Position des Naturschutzes in diesem Themenfeld. Agri-Photovoltaik Die Bandbreite derzeit verfügbarer Agri-PV-FFA reicht von vertikal aufgestellten bifacialen Modulen bis hin zu hoch aufgeständerten Konstruktionen. In Deutschland existiert inzwischen eine Vornorm, die DIN SPEC 91434 „Agri-Photovoltaik-Anlagen – Anforderungen an die landwirtschaftliche Hauptnutzung“ (DIN Deutsches Institut für Normung 2021). Um die APV von der klassischen Photovoltaik abzugrenzen, sind dort als Kriterien unter anderem ein Flächenanteil der verbleibenden landwirtschaftlichen Nutzung von mindestens 90 Prozent für hoch aufgeständerte PV-Anlagen und 85 Prozent für Flächen mit niedrig aufgeständerten PV-Anlagen angegeben. Die Hauptnutzung der Fläche ist dabei stets die landwirtschaftliche Nutzung, die Solarnutzung wird entsprechend als Sekundärnutzung betrachtet. Die Ausgestaltung der PV-Anlage folgt dementsprechend den Anforderungen der landwirtschaftlichen Nutzung. Dies betrifft zum einen die Abmessungen, wie z. B. den Modulreihenabstand und bei hoch aufgeständerten Anlagen die lichte Höhe in Abhängigkeit von den eingesetzten Maschinen und Geräten. Zum anderen sind APV-Anlagen geeignet, v. a. Folien und Netze zum Schutz vor Witterung wie Hagel oder Starkregen bei Sonderkulturen wie Beerenobst oder bei Obstgehölzen zu ersetzen. Abgesehen von vertikalen Anlagen, zumeist auf Grünland, sind in Deutschland dabei bislang lediglich kleinflächige sowie Pilotanlagen realisiert worden. Agri-PV-FFA sind bezogen auf die installierte Leistung insgesamt aufwändiger und kostenin-tensiver als klassische PV-FFA. Während Anlagen mit vertikalen bifacialen Modulen kostenseitig noch mit üblichen Anlagenkonstellationen vergleichbar sind, sind hoch aufgeständerte Anlagen oder solche mit Nachführtechniken teurer. Die Anlagenkonfiguration beeinflusst dabei die erzielbare Leistung der Solaranlage bezogen auf die Flächeneinheit. Synergieeffekte sind auch für die Landwirtschaft vorteilhaft wirksam, z. B. durch den Ersatz sonstiger Schutzvorkehrungen durch PV-Module. Vertikale Anlagen haben sich dabei auf Grünlandflächen unter bestimmten Voraussetzungen bereits am Markt etabliert. Die Umweltwirkungen der Agri-PV werden national wie international erforscht, insbesondere mit Blick auf die Kompatibilität und Optimierung der Nutzungskombination. Im Vordergrund stehen dabei die Auswirkungen der Anlagen auf das pflanzenverfügbare Licht sowie den Was-serhaushalt (Hassanpour Adeh et al. 2018; Parkinson und Hunt 2020). Agri-PV-FFA könnten dabei, z. B. aufgrund der Reduzierung der Sonneneinstrahlung oder den geringeren Bodenwasserverlusten, in ariden und semiariden Gebieten überhaupt erst eine produktive Landwirtschaft ermöglichen. In sonstigen Gebieten steht eine gesteigerte Flächeneffizienz mit einer erhöhten Landnutzungsrate im Mittelpunkt (Trommsdorff et al. 2020). In Regionen bislang gemäßigten Klimas könnte Agri-PV zukünftig an Bedeutung zur Steigerung der Resilienz der Landwirtschaft gegenüber den Folgen der Klimakrise gewinnen (Trommsdorff et al. 2020). Zu den Wirkungszusammenhängen aus naturschutzfachlicher Perspektive liegen spezifisch zu Agri-PV-Anlagen national wie international praktisch keine Untersuchungen vor. Bei der Betrachtung der potenziellen Auswirkungen von APV-FFA auf Natur und Landschaft ist zunächst festzustellen, dass im Gegensatz zu kPV-FFA auf landwirtschaftlichen Flächen, nicht mit einer Änderung der Bewirtschaftungsintensität – also einer Extensivierung, wie diese in der Regel bei kPV-FFA auf landwirtschaftlichen Flächen, stattfindet – zu rechnen ist. Untersu-chungsergebnisse, die auf den Wirkungszusammenhang der extensivierten Bewirtschaftung zurückzuführen sind, spielen bei APV entsprechend keine oder nur eine untergeordnete Rolle. Anlagenseitig sind Abweichungen der potenziellen Auswirkungen auf Natur und Landschaft im Vergleich zu kPV-FFA zu erwarten. Dies betrifft etwa eine intensivere Beeinträchtigung des Landschaftsbildes oder ein erhöhtes Konfliktrisiko durch Scheuchwirkung für gegenüber Vertikalstrukturen sensiblen Vogelarten. In Bezug auf die Umzäunug der Anlagenfläche konnten im Vorhaben unterschiedliche Aussagen in der Spannbreite von „nicht nötig“ bis „obligatorisch“ recherchiert werden. Ist die Anlagenfläche umzäunt, tritt die damit verknüpfte Barrierewirkung ebenso wie die visuellen Effekte auf. Baubedingte Unterschiede in den Wirkfaktoren zwischen kPV- und APV-Anlagen liegen nicht vor, da die zur Anwendung kommenden Bauteile, insbesondere Aufständerung, Gründung und Kabel, mit denen der kPV vergleichbar sind. Bei APV ist davon auszugehen, dass die bodenbezogenen Bedingungen für die landwirtschaftliche Nutzung bestmöglich erhalten werden und mittel-/langfristigere Effekte auf das unbedingt erforderliche Maß reduziert sind. Darüber hinaus gilt für APV-FFA gleichermaßen, dass das Auftreten sowie die Intensität potenzieller Auswirkungen vom konkreten Einzelfall und damit sowohl von den Eigenschaften des Standortes, als auch von der Konfiguration und Ausgestaltung der Anlage abhängen. Naturverträgliche Photovoltaik und weiteres Aufwertungspotenzial Solarparks jeglicher Art sind in der Regel Bauvorhaben in der freien Landschaft, oder baurechtlich ausgedrückt, im Außenbereich. Die Standorte sind möglichst konfliktarm auszuwählen, d. h. aus Sicht der Belange von Natur und Landschaft hochwertige Gebiete sind zu meiden. Es soll zu keiner unmittelbaren Inanspruchnahme derartiger Landschaftsteile kommen, und kultur- sowie naturlandschaftlich bedeutende Landschaftsräume mit hoher Sensibilität ge-genüber technischer Überprägung sind zu schützen. Mit entsprechender Zielsetzung hat das EEG von Beginn an Anlagenstandorte vergütet, die die Vorbelastung als Standortmerkmal in den Vordergrund rückt. Über einen gewissen Zeitraum war die Nutzung von landwirtschaftlichen Flächen außerhalb des 150- bzw. 200-m-Bereichs entlang von Infrastrukturtrassen nicht vergütungsfähig. Inzwischen sind die landwirtschaftlichen Flächen innerhalb der nach EU-Vorgabe benachteiligten Gebiete, bei entsprechender Landesverordnung, wieder eine der wichtigsten Standortkategorien geworden. Klassische PV-FFA auf landwirtschaftlichen Flächen zeichnen sich insbesondere dadurch aus, dass deren Bewirtschaftung eher im Sinne einer Pflege, häufig als extensives Grünland, stattfindet. Insbesondere auf zuvor intensiv landwirtschaftlich bearbeiteten Flächen können sich positive ökologischen Effekte einstellen und klassische PV-FFA als technische Anlagen zu einer naturschutzfachlich beschreibbaren Verbesserung der Lebensraumqualität bzw. der Biodiversität im Vergleich zur Ausgangssituation führen. Vertreter der Solarwirtschaft, aber auch Naturschutzverbände verweisen verstärkt mit Bestandsaufnahmen auf die besondere ökologische Qualität der Anlagen. Im Falle der Etablierung und Pflege von blühreichen, extensiven Grünländern, steigt die Vielfalt verschiedener Artengruppen (z. B. Avifauna, Insekten). Um die vorhandenen Möglichkeiten zu nutzen und Solarparks möglichst naturverträglich, d. h. mit positiven Wirkungen für den Naturhaushalt auszugestalten, ist die Erfüllung naturschutzfachlicher Anforderungen entscheidend. Dazu sind neben der Anwendung entsprechender Flächenkriterien bei der Standortauswahl Anforderungen an die Anlagengestaltung zu stellen. So sollte z. B. der maximale Überdeckungsgrad der Fläche mit Modulen, nicht mehr als 40 Prozent betragen und die Modulreihen möglichst große Abstände zueinander haben. Die Umsetzung solcher Maßnahmen, auch über den naturschutzrechtlichen Verpflichtungsrahmen der Eingriffsregelung und des Artenschutzes hinaus, ist als Beitrag zur dringend notwendigen Umkehr der Biodiversitätskrise in Agrarlandschaften unbedingt wünschenswert sowie notwendig. Entsprechende öffentliche Aussagen zur Selbstverpflichtung der Energieunternehmen sind vorhanden und lassen sich auch mit gängigen Verfahrensweisen und Standards des behördlichen Vorgehens in Zusammenhang bringen. Für die Umsetzung besonderer Maßnahmen über die rechtliche Verpflichtung hinaus werden im vorliegenden Bericht aber auch Anreizinstrumente besprochen, wie etwa die Möglichkeiten und Grenzen der Aufnahme und des Handels von Solarparkflächen in Flächenpools und Ökokontobestimmungen oder die ergänzende Zertfizierung solcher Flächen.
... Root presence in soils has been shown to increase porosity and water holding capacity, potentially compounding this effect [116] (Fig. 5b, CC2). Furthermore, reduced evapotranspiration has been observed in many GPVs [89,96,114], although the relative contributions of hypothesized mechanisms (e.g., transpirational cooling, evaporation reduction via surface cover, etc. [114]) for temperature moderation and moisture retention remain uncertain. ...
... Köppen-Geiger climate from Ref.[86]. Final corpus studies:[8,42,44,51,[89][90][91][92][93][94][95][96][97][98][99][100][101][102].N.Z. Krasner et al.Renewable and Sustainable Energy Reviews 208 (2025) 115032 ...
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Globally, solar energy is anticipated to be the primary source of electricity as early as 2050, and the greatest additions in capacity are currently in the form of large, ground-mounted photovoltaic solar energy facilities (GPVs). Growing interest lies in understanding and anticipating opportunities to increase soil carbon sequestration across the footprint and perimeter of both conventional and multi-use GPVs (e.g., ecovoltaics, agrivoltaics, and rangevolatics), especially as operators increasingly deputize as land managers. To date, studies on the relationship between soils and PV solar energy are limited to unique, localized sites. This study employed a systematic review to (i) identify a global corpus of 18 studies on interactions between GPVs and soils, (ii) collect and characterize 113 soil and soil-related experimental variables interacting with GPVs from this corpus, and (iii) synthesize trends among these experimental variables. Next, this study combined data from the systematic review with an iterative, knowledge co-production approach to produce a conceptual model for the study of soil and GPV interactions that applies to multiple installation types, scales, and contexts where GPVs are deployed, and identified research opportunities, threats, and priorities. This study's baseline understanding, conceptual model, and co-produced knowledge confer unique insight into the feasibility of combining soil carbon sequestration with the climate change mitigation potential of PV solar energy.
... Nonetheless, the quality of feed under the agrovoltaic system is superior, thus this drawback is mitigated. Both a decline [21] and an increase [22] in grass beneath solar panels were reported. These variances might be attributed to variations in climate and soil fertility. ...
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... Recent research has demonstrated the positive impact of photovoltaic power stations on soil evaporation and water content. The construction of these power stations has led to a reduction in soil evaporation, while the cleaning of photovoltaic panels has increased the water content of the soil located under the panels 37 . The cleaning frequency of photovoltaic panels in this study is once a month, as a result, the growth conditions for vegetation indirectly improved. ...
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... As for macroclimatic scale, agriculture has effectively to face climate change with episodes of extreme heat and violent weather becoming more and more frequent, which would have effectively led to a 21% drop in global production in the 20th century (Ortiz-Bobea et al., 2021). Similar to the effects observed in agroforestry systems on a microclimatic scale (Jacobs et al., 2022;Kanzler et al., 2019), several studies showed that panels create a buffered microclimate underneath,, with lower temperatures during the day and warmer soil temperature at night (Barron-Gafford et al., 2016), higher humidity and limited evaporation during the day (Adeh et al., 2018;Amaducci et al., 2018;Armstrong et al., 2016), which could be bene cial to crop in a context of climate change. However, this possible side effect on crops requires to be assessed as it can easily lead to competition between plants for land and light and consequently, a reduction in food production. ...
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