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| Fig. 1: Agrivoltaic Energy Production on a Rice Field in Kamisu, Japan. (Source: Wikimedia Commons) |
Photovoltaic (PV) energy is a renewable energy source produced when solar cells assembled into panels convert sunlight into electricity. However, panel installation often requires significant land area.
To address land constraints while sustaining energy production, dual-use PV applications such as agrivoltaics have grown in popularity. Agrivoltaic energy occurs through the coexistence of PV panels with agricultural activities. This allows crops and livestock to thrive underneath and between the panels (see Fig. 1). [1]
Both parties benefit from this dual-use interaction. The panels provide partial shade which improves irrigation efficiency for crops and reduces heat stress for livestock. The moist, humid soil associated with agricultural production cools the panels, resulting in a higher energy output compared to standard operating conditions. [1]
However, shared land use is also a double-edged sword. Certain PV configurations require wide row spacing which may result in panels casting excess shade onto nearby rows. This blocks sunlight exposure and reduces energy efficiency. Additionally, crop yields may decline if shaded plants receive insufficient sunlight for photosynthesis.
Given these constraints, agrivoltaic performance relies on optimizing panel tilt and row spacing. This balances loss of energy output due to shade against improved overall land-use efficiency compared to separate PV and agricultural systems.
We consider a published case study of an agrivoltaic, grid-connected farm in Kansas City, Missouri (Latitude: 39.0997 Longitude: 94.5783 Altitude: 311 m) to identify the most efficient dual-use system. [2] "Most efficient" in this context is defined as the system which best maximizes the dual-use objectives of agrivoltaic systems: power and agricultural activity. Additionally, data from the original study was plotted by month over a year. We summarize these results in Table 1. [2]
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| Table 1: Three-Way Annual Assessment of Agrivoltaic Energy Performance in Kansas City, MO. [2] |
In the ground-mounted agrivoltaic system, solar panels were mounted close to the ground and spaced wide enough to provide nearly full sunlight for low-growing crops. Accordingly, this system experienced the least shading loss (0.6%) when panels were placed at a fixed 25 degree angle (chosen by the study due to maximized PV output), since the wide row spacing likely prevented the panels from casting significant shadows onto adjacent rows. [2] Meanwhile, the stilt-mounted configurations represent elevated PV panels which provide adequate shade for taller crops to grow underneath, with full density (FD) configurations maximizing PV density on farmland and half density (HD) configurations achieving half this density.
Regarding energy production between the three configurations, the ground-mounted system attained the highest annual output of PV arrays (23,878 kWh) and subsequent energy injection into the grid (22,829 kWh), likely attributed to the minimal shading from the small crops beneath the panels. [2]
The stilt mounted FD configuration produced a slightly lower, yet comparable output of PV arrays (23,802 kWh) and energy injection into the grid (22,756 kWh). [2] However, the compacted row spacing between panels in the FD system may have casted larger shadows on adjacent rows, resulting in over double the shading loss than the ground-mounted system (1.3%) when placed at a 25 degree angle. [2] Even so, power output and grid injection remained stable in the FD configuration, since the elevated panel height likely minimized the impact of shadows from adjacent rows, enabling adequate sunlight exposure despite high-density row spacing.
The tradeoff is that adequate sunlight for the panels does not always equate to sufficient light for the crops beneath them. Agricultural yields may decline if stilted shading patterns restrict crops sunlight exposure for photosynthesis, creating productivity limitations for the FD configuration compared with separate PV and agricultural systems.
The same holds true if the agrivoltaic system is scaled back to an HD configuration with slightly wider spacing than the ground- mounted system (6.4 m versus 6 m) and taller stilted height than the FD system. [2] While the shading loss for this configuration was not quantified in the case study, it may actually be closer in magnitude to the FD configuration versus the ground-mounted system because the added height creates longer shadows which may cast on adjacent rows and offset the benefits of wide spacing. Perhaps this shading loss contributes partially to the significant decrease in annual energy output (14,103 kWh) and grid injection (13,477 kWh) for the HD configuration, since more inter-row shading may prevent adjacent panels from absorbing enough sunlight. [2]
In conclusion, while the scope of the comparisons are limited to the fixed 25 degree tilt angle, specific row spacing, and PV configurations examined in the case study, the FD configuration appears the most efficient of the three dual-use systems. This configuration nearly meets the energy output of the ground-mounted system while accounting for the decreased power and increased shading loss through its ability to support a variety of agricultural production underneath the elevated panels. Meanwhile, the ground-mounted system is limited to low-growing crops despite producing the highest energy output, and the HD configuration yields significantly lower energy which offsets the agricultural benefits of its elevated panels. This leaves the FD configuration as the most efficient agrivoltaic system to balance its dual-use objectives: power and agricultural activity.
Given the demonstrated efficiency of the FD configuration in supporting dual-use energy production, we now assess the land-use efficiency of overall agrivoltaic production versus that of separate PV and agricultural systems through the Land Equivalent Ratio (LER), defined below: [3]
| LER | = | YcrAV Ycrref |
× (1 - LL) + | YeAV Yeref |
| YcrAV | = | crop yield from an agrivoltaic system per unit area |
| Ycrref | = | crop yield from reference case (separate agricultural production per unit area) |
| YeAV | = | electricity yield from an agrivoltaic system per unit area |
| Yeref | = | electricity yield from reference case (separate PV system per unit area) |
| LL | = | land loss from an agrivoltaic system per unit area |
offers an appropriate benchmark to evaluate this comparison. [3]
According to the equation, if the LER > 1, the agrivoltaic system has more land-use efficiency than separate PV and agricultural systems, while LER=1 equates to equal land use efficiency and LER<1 represents less land-use efficiency, respectively. [4]
For example, if the formula generates a LER of 1.6, this indicates that 100 hectares of agrivoltaics produce the same combined output (PV energy plus crop yield) as 160 hectares of land used for separate PV and agricultural systems, assuming panel configuration remains constant. In other words, the agrivoltaic system achieves 60% greater land-use efficiency than separate systems.
Conversely, if the formula generates a LER of 0.6, 60 hectares of agrivoltaics produce the same combined output as 100 hectares of land used for separate PV and agricultural activity, meaning the agrivoltaic system is more inefficient. Possible sources of inefficiency include panel orientation, shading patterns, and crop selection, all of which may negatively impact combined energy production and crop yields. In such cases, the dual-use system may be redesigned or reverted to traditional, separate PV and agricultural operations to achieve higher land output.
One major drawback of both agrivoltaic and traditional PV systems is the monetary cost associated with production and installation at scale. While commercial farms can afford to place PV infrastructure around crops, smaller-scale operations may resort to generating energy from crops by burning them as biomass.
While quantifying the cost between these systems is challenging, the monetary discrepancy can be inferred from published data on the scale of solar versus biomass energy in the United States.
According to 2022 data from Oak Ridge National Laboratory, biomass-based renewable energy as a whole (including agricultural biomass, forest and woody biomass, and waste biomass) comprised 60% of total renewable energy consumption in 2022. [5] Conversely, solar energy as a whole (including agrivoltaic energy, traditional PV systems, and other dual-use configurations) comprised only 9.4% of renewable energy consumption that year. [5]
As for the portion of biomass-based renewable energy attributed to agricultural biomass, the same laboratory noted that 162 million dry tons of agricultural biomass were consumed nationally in 2022. [5] This amount comprised roughly 47% of the total biomass used for energy and bio-based chemicals that year. [5] When placed in the context of overall renewable energy, agricultural biomass alone likely accounted for a larger share than total solar energy consumption that year, highlighting its potential as a viable and affordable energy source.
Although burning crops is water-intensive and requires additional steps for energy conversion, these demands are likely negligible compared to the significant cost savings of biomass energy production, which contributed to the overall consumption discrepancy noted above. So where does that leave agrivoltaic energy?
Looking forward, agrivoltaic energy faces a structural paradox: it must scale to reduce costs, yet current costs are too high to support widespread deployment. Perhaps long-term scaling could be implemented through additional federal incentives specifically designed for dual-use PV applications on farms, since most existing policies favor conventional PV systems and do not explicitly reward agrivoltaic energy production. In the meantime, short-term scaling could occur by pairing agrivoltaic systems with high-value cash crops, allowing high installation costs to be recouped through profitable crop production and export. Ultimately, future policy and technological advancements that reduce production and installation costs at scale will determine whether agrivoltaics can remain an effective dual-use PV application.
© Anushka Godambe. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] A. Ghosh, "Nexus Between Agriculture and Photovoltaics (Agrivoltaics, Agriphotovoltaics) for Sustainable Development Goal: A Review," Sol. Energy 266, 112146 (2023).
[2] H. Dinesh and J. M. Pearce, "The Potential of Agrivoltaic Systems," Renew. Sustain. Energy Rev. 54, 299, (2016).
[3] S. Asa'a et al., "A Multidisciplinary View on Agrivoltaics: Future of Energy and Agriculture," Renew Sustain Energy Rev. 200, 114515 (2024).
[4] C. Dupraz et al., "Combining Solar Photovoltaic Panels and Food Crops for Optimising Land Use: Towards New Agrivoltaic Schemes," Renew. Energy 36, 2725 (2011).
[5] "2023 Billion Ton Report," U.S. Office of Energy Efficiency and Renewable Energy, March 2024, Ch. 2.
