Implications for vegetation growth when large opaque objects such as solar collectors are placed between the sun and ground-level vegetation across large portions of earth surface have received little attention to date. The present study seeks to address this void, advancing the state of knowledge of how constructed PV arrays affect ground-level environments, and to what degree plant cover, having acceptable characteristics within engineering constraints, can be re-established and thrive.
Tag Archive for: soil health
Worldwide, water is becoming scarcer and more expensive due to the effects of climate change. Significant adaptation will be necessary to ensure adequate supply and efficient use of a diminishing resource. This reduction in the supply of water will affect agriculture and will require a change in focus from increasing productivity of land to increasing productivity per unit of water consumed.
Community-based Stormwater Strategies and Vegetation Management for Sustainable Solar PV Development
Solar photovoltaic (PV) technology is being deployed at an unprecedented rate. To this end, we investigated critical soil physical and chemical parameters at a revegetated photovoltaic array and an adjacent reference grassland in Colorado, United States.
This study, performed by a research group that includes AgriSolar Clearinghouse partners Greg-Barron Gafford and Jordan Macknick, describes an integrative approach for the investigation of the co-location of solar photovoltaics and crops, and the potential for co-located agrivoltaic crops in drylands as a solution for the food-energy-water nexus impacts from climate change.
The research focused on three common agricultural species that represent different adaptive niches for dryland environments: chiltepin pepper, jalapeño, and cherry tomato. The researchers created an agrivoltaic system by planting these species under a PV array—3.3m off the ground at the lowest end and at a tilt of 32°—to capture the physical and biological impacts of this approach. Throughout the average three-month summer growing season, researchers monitored incoming light levels, air temperature and relative humidity continuously using sensors mounted 2.5m above the soil surface, and soil surface temperature and moisture at 5-cm depth. Both the traditional planting area (control) and agrivoltaic system received equal irrigation rates, with two irrigation scenarios—daily irrigation and irrigation every 2ays.
The researchers found that shading from the PV panels can provide multiple additive and synergistic benefits, including reduced plant drought stress, greater food production and reduced PV panel heat stress. The agrivoltaic system conditions impacted every aspect of plant activity, though results and significance varied by species. The total fruit production was twice as great under the PV panels of the agrivoltaic system than in the traditional growing environment
Cumulative CO2 uptake was 65% greater in the agrivoltaic installation than in the traditional growing area. Water use efficiency was also 65% greater, indicating that water loss to transpiration was equal between the treatment areas. The increased productivity in the agrivoltaic system is probably due to an alleviation of multiple stress interactions from heat and atmospheric drought.
Because PV panels are sensitive to temperature, the cooling of panels below daytime temperatures of 30 °C positively impacts their efficiency. In this study, researchers found that the PV panels in a traditional ground-mounted array were significantly warmer during the day and experienced greater within-day variation than those over an agrivoltaic understory. Researchers attribute these lower daytime temperatures in the PV panels in the agrivoltaic system to a greater balance of latent heat energy exchange from plant transpiration relative to sensible heat exchange from radiation from bare soil. Across the core growing season, PV panels in an agrivoltaic system were ~8.9+0.2 °C cooler in daylight hours. This reduction in temperature can lead to an increase in PV system performance. Using the system advisor model (SAM) for a traditional and a colocation PV system in Tucson, AZ, researchers calculated that impact from temperature reductions from the agrivoltaic system would lead to a 3% increase in generation over summer months and a 1% increase in generation annually.
These results show the additive benefits of agrivoltaics, to both crop production and energy production, as well as the impacts to ecosystem services such as local climate regulation, water conservation, and drought resiliency.
Recent research conducted on a Minnesota agrisolar operation showed that grazing sheep at ground-mounted solar projects improves the health and quality of the soil and that consecutive annual grazing treatments to land under solar panels realized more benefits than intermittently grazed land.
The MNL Conservation Grazing Program’s flock of sheep has been grazing under the solar panels of Enel’s 150 MWdc Aurora Solar operation since 2017. The research studied the impacts of sheep grazing on six separate solar PV sites compared to undisturbed control sites.
Soil samples taken in 2020 from six locations were compared to soil samples taken in 2021, revealing a variety of benefits in soil health related to micro and macro nutrients and soil grain size distribution. Managed sheep grazing significantly increased the total carbon storage (10 to 80%) and available nutrients of the soil.
MNL’s solar grazing manger stated that,” More solar means more opportunities for new farmers to get started in the industry. We consult with solar projects throughout the Midwest and the concept of grazing sheep on a solar projects opens the door for new shepherds who may lack easy access to grazing land to get started,” according to a media report by Solar Power World.
The research was made possible through the partnership of MNL, Enel Energy, Temple University, and the National Renewable Energy Laboratory (NREL), which also highlighted other potential benefits aside from things like macro and micronutrients in the soil, such as water quality, stormwater control, and healthy pollinator habitat.
Read more about the research here.
The vulnerabilities of food, energy and water systems to projected climatic change make building resilience in renewable energy and food production a fundamental challenge. Researchers investigate a novel approach to solve this problem by creating a hybrid of collocated agriculture and solar photovoltaic (PV) infrastructure. They took an integrative approach—monitoring microclimatic conditions, PV panel temperature, soil moisture and irrigation water use, plant ecophysiological function and plant biomass production within this ‘agrivoltaics’ ecosystem and in traditional PV installations and agricultural settings to quantify trade-offs. They found that shading by the PV panels provides multiple additive and synergistic benefits, including reduced plant drought stress, greater food production and reduced PV panel heat stress. This study represents the first experimental and empirical examination of the potential for an agrivoltaic system to positively impact each component of the food–energy–water nexus. The results from a dryland system indicate a reduction in daytime temperatures of the solar panels (energy) and microclimate under the panels (food), and a dampening in the diurnal fluctuations of each and day-to-day fluctuations in soil moisture in irrigated agriculture (water). Together, our findings suggest that a dryland agrivoltaic system may be a resilient energy and food system that has reduced vulnerabilities to future climate variability. However, there are probable barriers to wider adoption, which include challenges associated with some forms of mechanized farming and harvest and the additional costs associated with elevating PV arrays to allow for food production in the understorey. An integrated approach to the physical and social dimensions of our food and energy systems is key in supporting decision making regarding PV development and sustainable food and energy production in a changing world
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