Agrivoltaics - harnessing the sun for both food and electricity 

Posted by Robertas Tumilo
2022-03-17

As the urgency for decarbonisation increases, more land must be used for large-scale energy generation. Eventually, available unutilized land will become scarce. Attention will fall on the most land-intensive sector – agriculture. This will increase competition for land between food and energy producers, as sometimes solar parks can offer an even better return than growing crops. Agrivoltaics (agriculture + photovoltaics) came up as an answer to combine both food production and solar energy generation in a way that would not negatively impact either side.

Agrivoltaics to date

Agrivoltaics is not a brand-new concept – projects of different scope and types are undergoing for almost two decades now. In our analysis we evaluated projects based on cost, technology, and other parameters and categorised three main types of projects:

High-mount – Solar panels which are mounted 2-5 meters above agricultural land using aluminium and (or) steel construction frames. This creates a large area of shaded land which significantly impacts what type of agricultural produce can be grown on the land. However, generation is largely unaffected or even slightly increased. It is also the most expensive type of agrivoltaics as the frames are not yet mass-produced and increase the cost of the project significantly.

Jacks Solar Garden InSPIRE, Photo by Werner Slocum / NREL, (CC BY-NC-ND 2.0)
Image: Jacks Solar Garden InSPIRE, Photo by Werner Slocum / NREL, (CC BY-NC-ND 2.0)

Vertical-mount – Vertically mounted bifacial solar panels, which are mounted almost like fences in between patches of crops. This creates partially shaded areas near the panels and about 90% of the land can be used for growing hay and fodder for livestock or shade-tolerant plants with minimal effect on agricultural yield, quality, and solar generation. Usually, such projects are slightly more expensive than standard solar parks and require about twice as much land area for the same generation capacity.

Agrivoltaics Mounting system from a birds-eye perspective, Photo by Next2Sun GmbH
Image: Mounting system from a birds-eye perspective, Photo by Next2Sun GmbH

Greenhouses – Semi-transparent solar panels mounted on the roof of a greenhouse. This allows for sufficient sunlight to reach crops while still allowing for electricity generation, albeit roughly 50% lower than standard solar panels. Certain types of greenhouse crops can benefit from less sun, increasing yield or quality, and allowing for a different harvesting schedule. These projects can also positively impact the intensive use of water by greenhouses.

Image: Solar Panel on Greenhouse. Photo by Khyati Vyas. "Solar Farming with Agricultural land". Acta Scientific Agriculture 3.10 (2019).
Image: Solar Panel on Greenhouse. Photo by Khyati Vyas. "Solar Farming with Agricultural land". Acta Scientific Agriculture 3.10 (2019).

There are also more limited applications of combining agriculture with solar panels, such as using sheep or cattle to graze the land around standard solar parks. However, such activities are more of an „add-on“ to standard solar park projects rather than a true combination of agriculture and solar generation.


Potential benefits

  • More effective land use – instead of 100% agriculture or solar generation, it is possible to create combinations to reach higher than 100% efficiencies.
  • Increased generation due to natural cooling of the solar panels by crop water evaporation
  • The shade from solar panels can reduce stress caused to shade-tolerant plants by high temperatures and UV rays
  • Protection of crops against weather phenomena such as hailstorms or strong winds
  • Water savings as solar panels will reduce the temperature of the land below them.

Shortcomings

  • Higher cost per kilowatt-hour generated due to more larger capital expenditures
  • Most agricultural plants require as much sunlight as they can get, thus potential farmland is more limited
  • Can require significant changes in agricultural practices or machinery
  • Support mechanisms for such projects are largely non-existent

Lithuanian Agrivoltaics Potential

To evaluate the potential for agrivoltaics in Lithuania we looked at the amount of land used to grow hay, fodder, and shade-tolerant plants. Plants such as root and leaf vegetables are suitable for agrivoltaics applications.

About 8% of sown land in 2020 was used to grow hay and fodder, while roughly 1-2 percent was used to grow shade-tolerant crops. This amounts to an estimated 250 thousand hectares of land that could potentially employ agrivoltaics solutions.

Using vertically mounted bifacial solar panels, up to 72 GW of solar panels could be installed, while high-mount panels over shade-tolerant crops could amount up to 17 GW of solar capacity. Both numbers are extremely large and in reality, we would need only a fraction of that land for solar generation to satisfy energy needs.

An important thing to note is the legal background – currently, in Lithuania, up to 0,5 MW of solar panels are allowed on a plot of farmland, thus we require regulatory changes to adopt large-scale agrivoltaics.

Solar developers in Lithuania have made small steps towards agrivoltaics – Ignitis platform “Saulės parkai” has featured several projects from local developers that employed sheep grazing to maintain the grass and placed beehives in the park’s territory.

Summary

If possible, the focus should be on the utilization of unused space – roofs and unproductive land, as this would be the most efficient use of resources and the lowest cost per kilowatt-hour produced.

If a choice is made to invest in agrivoltaics, the integration of vertically mounted bifacial panels into agricultural activities seems to be the most attractive today, as it is the least expensive and would minimally impact current agricultural practices compared to the alternatives.

Favourable legal regulation is also a must, i.e., permits for the construction of higher-capacity power plants for such projects, and support mechanisms.

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