Combining solar photovoltaic panels and food crops for optimising land use: towards new agrivoltaic schemes.

In order to meet global energy demands with clean renewable energy such as with solar photovoltaic (PV) systems, large surface areas are needed because of the relatively diffuse nature of solar energy. Much of this demand can be matched with aggressive building integrated PV and rooftop PV, but the remainder can be met with land-based PV farms. Using large tracts of land for solar farms will increase competition for land resources as food production demand and energy demand are both growing and vie for the limited land resources. This land competition is exacerbated by the increasing population. These coupled land challenges can be ameliorated using the concept of agrivoltaics or co-developing the same area of land for both solar PV power as well as for conventional agriculture. In this paper, the agrivoltaic experiments to date are reviewed and summarized. A coupled simulation model is developed for both PV production (PVSyst) and agricultural production (Simulateur mulTIdisciplinaire les Cultures Standard (STICS) crop model), to gauge the technical potential of scaling agrivoltaic systems. The results showed that the value of solar generated electricity coupled to shade-tolerant crop production created an over 30% increase in economic value from farms deploying agrivoltaic systems instead of conventional agriculture. Utilizing shade tolerant crops enables crop yield losses to be minimized and thus maintain crop price stability. In addition, this dual use of agricultural land can have a significant effect on national PV production. The results showed an increase in PV power between over 40 and 70 GW if lettuce cultivation alone is converted to agrivoltaic systems in the U.S. It is clear, further work is warranted in this area and that the outputs for different crops and geographic areas should be explored to ascertain the potential of agrivoltaic farming throughout the globe.

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The potential of agrivoltaic systems

The vulnerabilities of our food, energy and water systems to projected climatic change make building resilience in renewable energy and food production a fundamental challenge. We investigate a novel approach to solve this problem by creating a hybrid of colocated agriculture and solar photovoltaic (PV) infrastructure. We take 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. We find 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. The results presented here provide a foundation and motivation for future explorations towards the resilience of food and energy systems under the future projected increased environmental stress involving heat and drought. Agrivoltaics can achieve synergistic benefits by growing agricultural plants under raised solar panels. In this article, the authors showed that growth under solar panels reduced tomato and pepper drought stress and increased production, while simultaneously reducing photovoltaic panel heat stress.

Agrivoltaics provide mutual benefits across the food–energy–water nexus in drylands

https://hal.archives-ouvertes.fr/hal-01137075/document

Productivity and radiation use efficiency of lettuces grown in the partial shade of photovoltaic panels

The expansion of renewable energies aims at meeting the global energy demand while replacing fossil fuels. However, it requires large areas of land. At the same time, food security is threatened by the impacts of climate change and a growing world population. This has led to increasing competition for limited land resources. In this context, the combination of photovoltaics and plant production — often referred to as agrophotovoltaic (APV) or agrivoltaic systems — has been suggested as an opportunity for the synergistic combination of renewable energy and food production. Although this technology has already been applied in various commercial projects, its practicability and impact on crop production have hardly been investigated. In this review, we give a short summary of the current state of the art and prospective opportunities for the application of APV systems. In addition, we discuss microclimatic alterations and the resulting impacts of APV on crop production. Our main findings are that (1) crop cultivation underneath APV can lead to declining crop yields as solar radiation is expected to be reduced by about one third underneath the panels. However, microclimatic heterogeneities and their impact on crop yields are missing reference and thus, remain uncertain. (2) Through combined energy and crop production, APV can increase land productivity by up to 70%. (3) Given the impacts of climate change and conditions in arid climates, potential benefits are likely for crop production through additional shading and observed improvements of water productivity. (4) In addition, APV enhances the economic value of farming and can contribute to decentralized, off-grid electrification in developing and rural areas, thus further improving agricultural productivity. As such, APV can be a valuable technical approach for more sustainable agriculture, helping to meet current and prospective needs of energy and food production and simultaneously sparing land resources.

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Agrophotovoltaic systems: applications, challenges, and opportunities. A review

In this paper we propose a configuration of a solar, e.g., photovoltaic, power plant, which allows for additional agricultural use of the land involved, although the collectors are optimized for solar-energy conversion. If the collectors are not installed directly on the ground, but are elevated by about 2m above the ground with the periodic distance between collector rows of about three times the height of the collectors, one achieves nearly uniform radiation, (integrated over the day), on the ground of a value of about two-thirds of the global radiation without solar collectors. The mathematical relations allowing calculation of the fraction of light reaching the ground under the collector field are derived. Numerical calculations for both the direct and diffuse part of solar radiation are carried out yielding the seasonal and local dependence of this fraction. In addition, we give an outline of the various advantages offered by this configuration.

A. Goetzberger

Papers

On the Coexistence of Solar-Energy Conversion and Plant Cultivation