There has been a lot of noise in the media recently about solar farms “threatening” UK farmland.
Politicians have been using these claims to tussle with their opponents, simultaneously leading the public to believe that solar energy production and farming cannot co-exist.
In this article, we introduce you to Agrivoltaics: a practice in which the land is harmoniously used for both electricity production and farming.
What are agrivoltaic farms?
As the name suggests, in agrivoltaic farms the land is utilised to produce solar energy using solar panels while simultaneously performing agricultural or animal husbandry activities.
Both practices may synergise with each other to optimally make use of sunlight which is the primary resource sought for energy production or photosynthesis.
Other names for this technology include agrophotovolatics, agri-solar or dual-use solar.
What is the origin of ‘agrivoltaics’?
Solar panel technology only became industrially available in the 1970s-1980s, and it was only when ‘solar farms’ started coming into existence that a potential conflict of land use between agriculture and energy production became apparent to academics.
On top of this, new solar panels rapidly became popular in remote farms that were often disconnected from the electricity grid, particularly during the 1980s oil crisis which hampered the popularity of traditional petrol generators.
The first mention of combining both farming and electricity production was in a 1981 paper written by Adolf Goetzberger and Armin Zastrow from the renowned Fraunhofer Institute of Solar Energy Systems.
Yet, it would be another 30 years before the term “agrivoltaic” would be first coined in this 2011 paper.
What are the different types of agrivoltaic farms?
Generally speaking, there are three major variations of agrivoltaic farms:
- Spaced: Solar PV arrays that are typically installed at a steep angle (in high/low latitudes) and leave large gaps between rows for crops or grazing.
- Stilted: Solar PV arrays that are lifted from the ground with stilts, leaving large spaces to overlie crops that require limited sunlight/temperature regulation/water retention.
- Roofed: Solar PV arrays that are placed on top of greenhouses or livestock sheds, providing insulation and electricity for heating.
These methods aren’t mutually exclusive and may be used simultaneously within different parts of a single project. The effectiveness of each method depends on the specific setting of the project and its aims.
What are the determining factors of an agrivoltaic project?
The factors affecting the design or even the viability of any agrivoltaic project depend on both human and physical factors.
Human factors
Legislation: Local land use laws may be problematic when regulating two contrasting activities in the same land area.
Public Opinion: Solar farms may be unpopular with local farmers (as may be the case in the UK, with recent political debacles against ground-based solar).
Expertise: Both agriculture and operating solar panels require expertise. A solar energy producer may need to hire a farming specialist and farmers would need to hire a solar engineer or technician capable of doing maintenance.
Existing practices: Much of the land in developed nations is already being used for farming or energy production, which means there is already a bias for one activity over the other.
Subsidies: Some governments like the Netherlands and Germany have been subsidising solar energy implementation, making agrivoltaic projects potentially very lucrative for farmers.
Feed-in-Tariffs: Each government has a different system for selling energy to the grid, which may affect the attractiveness of putting up solar panels or scaling them for this purpose.
Physical factors
Sunlight intensity: If solar panels can produce a lot of energy in your area, then this becomes a more obvious choice. As the price of solar panels keeps decreasing (it has decreased over 80% since 2010) agrivoltaics is becoming increasingly viable in areas of less solar potential (see global solar potential map) such as the UK.
Terrain: The accessibility, stability and steepness of the land determine both the type of agriculture possible as well as the viability of solar panels.
What are the advantages of agrivoltaics?
Solar panel installation on farmland brings numerous advantages both in terms of farming and risk management opportunities.
It can improve agriculture and animal husbandry by synergetically providing temperature regulation, moisture retention, shade and cheap electricity for heating.
And in business terms, installing solar panels may bring a reliable base source of income to a farm’s often unpredictable earnings, which are heavily reliant on nature and which climate change and environmental decline are making increasingly erratic.
Below we touch on each of these in more detail.
Temperature Regulation
Photovoltaic systems work optimally at cool temperatures (between 15C and 35C), and so installing them over agricultural land with temperature-regulating properties is more effective than doing so over barren land.
This is due to the higher moisture and humidity due to having plants and moisture-retaining soil.
It’s the same reason why floating solar power systems that are cooled by the underlying water bodies are becoming increasingly popular.
And this works synergetically in reverse, as the cover provided by solar panels helps crops and soil retain moisture and, therefore a more stable temperature less prone to deadly shocks, particularly during anomalous heat waves.
Water Management
One of the consequences of climate change is the higher frequency and intensity of droughts, with even temperate countries like the UK at risk.
Solar panels can help retain water in at-risk agricultural land by reducing exposure to sunlight and providing an impermeable barrier to retain humidity.
This is particularly effective with stilted solar panels, which may act as shade during the day and capture moisture that condenses on its rapidly cooling surface at night, and drips back into the fields, forming a closed water loop.
On top of this, moisture-absorbing hydrogels can enhance this moisture-retaining cycle by absorbing the condensed water, which can be collected and used for targetted irrigation (while making the panels even more efficient by keeping them cool while they retain water).
Pilot projects using stilted panels in California have successfully grown shade-resistant crops such as cucumbers, lettuce, kale, and broccoli (i.e. plants that evolved near the ground in covered forests) with reduced water use compared to existing methods.
And the large-scale Solar Garden installed in Colorado is also successfully doing agriculture and producing solar energy while experiencing record revenue. Experiments in Arizona have also shown that these systems can save up to 50% of water in arid climates.
Shade
The shade and protection from the elements provided by solar panels may be a valuable resource for grazing animals during heat waves and inclement weather.
In return, grazing animals like sheep can keep tall grasses from interfering with the panel’s sun exposure by grazing, reducing the need for additional maintenance costs.
Plants also have a maximum amount of photons they can absorb for photosynthesis which means that much of the sunlight in agricultural land is actually surplus to requirements.
Dynamic agrivoltaics, developed in Japan by Akira Nagashima leverages this concept by using a system of portable solar PVs that are rotated to cover different crops at different times of the year and maximize yields based on their optimal sunlight exposure.
Additionally, this project in Canada has been using the panel’s shade to grow flowers to support pollinator populations and for beekeeping.
Dual revenue for farmers
Farms that combine their activities with solar arrays effectively diversify their income and hedge against the risk of drought, floods, disease and soil loss which leads to bad harvests or animal population reductions.
This is increasingly relevant as climate change is making global weather more extreme and unpredictable, making farming revenue equally volatile.
Also, solar energy production is relatively stable on a year-on-year basis, giving a base income that farms can rely on.
Dual revenue for solar energy producers
Existing land-based solar farms are introducing agriculture and animal husbandry to give more utility to their land, while hedging against changes to the energy market, energy legislation, sabotage, etc.
Also as discussed earlier, the thermal properties of moisture may ultimately improve the yields of solar panels.
This is especially the case in areas where expanding is not an option due to land unavailability (i.e. UK and Europe) or new legislation.
Are agrivolatic farms the best use for solar panels?
The cost, adaptability and modularity of solar panels have made them a popular solution for decarbonising electricity production.
However, solar panel production is limited and has a carbon and water footprint, so some argue that they should be placed where they make the highest impact.
Some would argue that solar panels are best suited to the unused parts of the built infrastructure to produce energy in proximity to where it is most needed and without causing any visual pollution or interference with productive land.
Others argue that floating solar power is an overall more efficient use of panels as the underlying water body regulates temperature while the panels help retain the reservoir’s water which is used for drinking, agriculture, hydropower, etc.
However, it is clear from this article that there is also much utility within agriculture, particularly in regions of high solar irradiance and water management issues.
Also, some governments make this practice easier by means of government subsidies and feed-in-tariff schemes (Also known as smart export guarantees in the UK) and legislative conditions.
Also, the development of transparent PV glass may shift the debate as it enables tailored use of the incoming solar frequencies not needed for photosynthesis to produce energy and make energy-producing greenhouses.
Are there agrivoltaic farms in the UK?
An extensive google search suggests that, at present, there are no purpose-built agrivoltaic farms in the UK.
However, solar panels are certainly ubiquitous in UK farmland, particularly on greenhouses, to power electrical heating in winter or mounted on barns/stables to power lighting and heating.
Also, the University of Greenwich is developing agrivoltaic greenhouses that use transparent PV glass to produce electricity while letting photosynthesising radiation through.
