Story by Vivienne Wells
Climate variability will pose significant challenges to Australian farmers in the coming decades, with temperature rises since 2000 estimated to have reduced average farm profits by approximately 22% across the broadacre industry . Broadacre cropping is affected most, with an average profit loss of $70,900 per year (35%) for a typical farm .
In order to increase the resilience of Australian farmers, diversified income streams must be investigated to bolster farming income during extreme weather years. With an abundance of land and increasing demand for electricity, solar electricity generation is a potential cost-reduction and revenue source for farmers. However, traditional solar farms occupy all of the land they are installed on, with farming potential reduced to low-impact, small-animal farming due to low levels of photosynthetically active radiation (PAR) on pastures beneath the arrays, with potential damage from large animals preventing them grazing on the land. Agrivoltaics represents the combination of traditional farming being undertaken on the same land as solar PV arrays, providing both benefits to agricultural yields and renewable energy generation.
Agrivoltaic systems are designed around existing farming operations to maximise the potential land yield of areas and are installed in a range of configurations. Depending on the existing farming operations, a range of construction methods for the solar PV arrays can be used. This includes overhead trellis systems, vertical bifacial arrays, fixed tilt and tracking arrays, and, less commonly, tubular solar and solar glass on greenhouses.
Overhead trellis systems can improve the growing conditions for climate-vulnerable plants such as grapevines to improve their climate resistance by creating cooler microclimates and reducing water loss through evaporation. These systems can be installed with automated tracking technology that will change the degree of angle of the panels depending on the weather conditions to optimise the light conditions under the arrays. Whilst these systems have shown great results for certain production systems, especially viticulture in regions of rapidly-changing climate, they do limit the access of machinery to the area and so are not relevant for large-scale broadacre cropping where large machinery is needed to undertake essential operations such as harvest.
Vertical bifacial systems consist of double-sided solar panels installed upright in rows with a horizontal footprint of about 100 mm, meaning a small percentage of a paddock’s space is taken up by the rows, which can be spaced at distances that fit with farming practices. The solar yield of vertical bifacial panel arrays is reduced to around 80% of traditional fixed-tilt solar arrays, however the farming potential for the land is maintained at close to 100% of normal yield, meaning that the total land use of agrivoltaic systems may be up to 180%. Additionally, the peak electricity production periods for vertical bifacial are in the morning and evening, so the wholesale value of electricity can be equal to that of fixed tilt by avoiding the solar glut in the middle of the day when prices are very low to feed back into the grid. However, there is also very little shading of plants during the middle of the day when radiation is strongest, meaning that crops and pasture between the arrays still suffer from excess sun. Additionally, the paddocks would not be able to be used for cattle grazing because of the risk of breaking panels when they rub against them.
Fixed tilt and tracking arrays may be elevated to increase access for agricultural machinery compared to traditional solar farms, but this can be limited to small machinery only. However, new agrivoltaic systems are integrating ecosystem services into production, encouraging native species and pollinators essentially for agricultural production.
Tubular solar is less developed than the other forms of agrivoltaics, which use known technologies in novel applications. In this form, solar cells are enclosed between glass plates in lightweight tubes, which can be installed aboveground to allow farming operations underneath. The incident light reaching the ground underneath varies depending on the density of the tubes above, meaning it can be optimised for the location and production system of the farm.
In greenhouse production, solar cells can be integrated into the structure to balance production and electrical generation. This can be in the form of traditional solar cells being installed on the glass, blocking out patches of incident light, or in solar glass. Whilst solar glass is expensive compared to normal greenhouse materials, it can also be manufactured with various transmissivity, meaning that the greenhouse can be optimised for location and production.
There is currently close to 2.8 GW of installed agrivoltaics globally. The majority of this is located in China in horticultural production systems, where the panels provide electricity for the farming operations and protect the fruit and vegetable crops underneath . The agronomical effects of agrivoltaic arrays varies greatly between the type of system installed, the crops grown and the climate. However, it has been found that the use of agrivoltaics can increase drought resilience of certain crops, and reduce yield variability between different climatic conditions.
The environmental benefits of the improved drought resistance from agrivoltaics is also paired with increased profitability for farmers as the electricity produced can either be used on farm, or fed back into the grid for profit. This would decrease farmer’s vulnerability to commodity price volatility, either through reduced variable costs or diversified income streams. The availability of electricity on-farm would also provide impetus for electrification of production systems, decreasing the carbon footprint of agriculture.
Agrivoltaics have great potential to increase the economic and environmental sustainability of farming, and allows solar to be installed close to population centres and electricity users without compromising prime farming land. This will be crucial to meet the needs of a growing population as we move into a future with higher energy and food demands.
 N. Hughes, D. Galeano, and S. Hatfield-Dodds, “The effects of drought and climate variability on Australian farms,” 2019.
 M. Trommsdorff et al., “Agrivoltaics: Opportunities for Agriculture and the Energy Transition. A Guideline for Germany,” Fraunhofer Institute for Solar Energy Systems ISE, Freiburg, 2020. [Online]. Available: https://www.ise.fraunhofer.de/content/dam/ise/en/documents/publications/studies/APV-Guideline.pdf