For thousands of years, farmers have been the most direct users of solar energy, using sunlight to grow food that sustains the human population. From that perspective, it seems obvious that solar photovoltaic technology could be so beneficial for farming - so much so that it has earned its own name - ‘Agrisolar’.
Agrisolar is the application of solar PV tech to the farming industry. It is sometimes also known as agrivoltaics, or by the more tongue-twisting name ‘Agrophotovoltaics’ (APV). Let us go ahead and learn a bit more about agrisolar and its feasibility in New Zealand.
What is Agrisolar?
Agrisolar combines agriculture and solar power (as is evident from the name), in a way that both technologies mutually benefit each other. It was first proposed in Germany in 1981. Over the next 40 years, numerous studies have shown that solar power and farming can be highly compatible as well as significantly beneficial to each other.
Agrisolar is a somewhat broad term that includes several ways of combining solar and agriculture. While the fundamental principles of both technologies always remain the same, multiple innovations have found ways in which the two areas boost each other’s benefits. Let us take a look at the types of agrisolar techniques and their advantages.
Types of Agrisolar and Their Benefits
1. Regular Ground-Mounted Solar Panels
Ground-mounted solar panels are the best option when a farm has enough extra space for a solar power system. These systems are similar to any other ground-mounted solar plant, with the only exception being that their power is used locally for farm-related applications.
Ground-mounted agrisolar project visualisation (Source: RNZ)
Benefits of ground-mounted solar panels
When not mounted on a rooftop, ground-mounted panels are the basic form of solar power plants. Their simplicity means there are a lot of available options in racking and other components.
The solar panels installed over vegetation are also cooler, leading to better efficiency and higher power generation. A study conducted in the USA found that solar panels over vegetation were significantly cooler (on average, 8.9°C cooler) during daylight hours compared to panels above bare land.
On farms, ground-mounted panels work great for solar grazing (more on that later), horticulture, and beekeeping.
2. Elevated Ground-Mounted Solar Panels
Elevated solar panels are installed with taller mounting structures with the intention of leaving sufficient space below the solar panels.
Crop plantation under elevated solar panels (source: NREL)
Benefits of elevated ground-mounted solar panels
Elevated panels save space by allowing farmers to directly plant crops below the panels. Additionally, the shade created by the panels also reduces evaporation from the soil, lowers soil temperature, and also protects the plants from heat in arid areas. For example, one study in Arizona found temperatures under the panels were around 1.2°C lower during the day and around 0.5°C warmer at night.
Planting native and flowering vegetation on a solar farm also has provided excellent habitat for bees and other pollinators in some countries. This is beneficial for both beekeepers and regular farmers - bees get more food throughout the year, producing more honey, and also help pollination, improving crop yield.
A ground-mounted agrisolar system combined with a beekeeping facility (source: Lakewinds)
3. Rooftop Solar Panels
Most farms have one or more buildings, so the solar panels don’t necessarily have to be mounted on the ground. They can be mounted on a barn, processing or storage units, and even greenhouses.
A patented French solar greenhouse growing asparagus (source: Tenergie)
Benefits of rooftop-mounted solar panels
Unlike ground-mounted panels, rooftop-mounted panels do not require creating a new supporting structure - the roof itself acts as a support. This saves cost since there is no need for concrete foundations and large, strong racking. A basic, low-profile racking often does the job well. Rooftop-mounted panels also free up ground space for other operations on the farm.
4. Solar Grazing
Yes, we mentioned solar grazing before. But the concept is so interesting, that we had to put it in a separate section. Solar grazing uses solar panels to grow – you guessed it right – pastures where farm animals can graze. This seemingly simple application has a number of benefits.
Sheep grazing under solar panels (source: Bloomberg)
Benefits of Solar Grazing
Installing solar panels on pastures provides shade for the livestock. This can be important in hotter climates or summers in general, when animals typically don’t fancy bathing in the sun. Where solar grazing is employed, studies have found an increased level of health and well-being in sheep due to protection from the elements.
In drier regions, the shade from the panels can prevent the pastures from drying off. That’s not all, the water running off from the solar panels results in higher vegetation growth, creating more food for the livestock. A team of scientists at Auckland’s Massey University found that the strips between solar panels produced nearly 40% more grass compared to farms without agrisolar projects.
On the other hand, in areas with higher precipitation, solar panels can control the growth of vegetation by blocking some sunshine. They also reduce the risk of fire by keeping the pasture down. Moreover, this reduces the need for applying herbicides or mowing regularly.
A 3.2 MW agrisolar project in Queensland, Australia found that the farm saved approximately $100,000 each year after installing water access and partition fencing. Additionally, preliminary results from a wool analysis of the sheep at the Parkes Solar Farm in NSW, Australia indicated that the wool quality was high, even during drought conditions.
5. Floating Solar Power Systems
Plenty of farms have a pond or lake on or beside the farm. While the land space on the farm is valuable and often limited, the surface area of a water body is typically unused – unless you go canoeing on every square foot of it.
Floating solar systems use buoyant mounting structures that stay afloat on water, creating entire solar power systems that remain on the water’s surface. Plus, it also has a cool new name - ‘Floatovoltaics’!
A floating solar plant on a winery (source: Agrisolar Clearinghouse)
Benefits of floating solar power systems
The most important benefit of a floating PV system is its ability to save land space. Secondly, it reduces the evaporation of water by reducing its contact with direct sunlight - this is particularly important in drought-prone areas.
Lastly, by being placed on a water body, floating solar panels are generally cooler than ground or rooftop-mounted panels. This reduces the thermal degradation of the panels, improving the output significantly.
6. Solar Pumps
Solar pumps are exactly what the name tells us - they are water pumps powered by solar panels. In such an arrangement, the panels are typically mounted right beside the water source.
Solar pump in operation (source: Mahindra Susten)
Benefits of solar pumps
Typically, the pumps used in solar pumping systems are DC pumps, which have higher efficiency. As compared to a traditional AC pump, these require a smaller system size and thus save on cost. Solar pumps work best in places where the water source is located away from a power source, saving money on transmission costs.
7. Solar Fencing
A solar fence is like a regular fence, except that it uses electrical cables with high-voltage current flowing through them. These are designed primarily with security in mind.
A solar-powered fence (source: Gallagher)
Benefits of solar fencing
Solar fences protect livestock from predators as well as farm property from theft. While electrical fencing using grid power is also possible, a solar fence uses free energy and does not need the transmission of power from one location to another.
Agrisolar Feasibility in New Zealand
Even though detailed agrisolar studies haven’t been conducted in New Zealand, we can borrow a lot of conclusions from the dozens of studies conducted in many parts of the world. In general, an agrisolar project can benefit farmers in multiple ways - from increased crop production to reduced operational costs and improved well-being of their livestock.
But more recently, scientists at Massey University studied an agrisolar project to analyze the technology’s suitability for New Zealand. The researchers found that pasture growth slowed below the panels but improved between two rows of panels. However, the team also noticed that the solar array reduced moisture loss from the soil caused by wind.
Overall, the scientists seem positive about the study. Professor Danny Donaghy, who is co-leading the study, was quoted saying, ‘This would be a win-win for solar farming coexisting with pastoral systems, or even horticultural crops.’
Agrisolar Projects in New Zealand
Several energy and farming businesses in Aotearoa are opening up to the idea of agrisolar. New Zealand government-owned Genesis Energy and renewables partner FRV Australia are building a massive 52 MW agrivoltaic solar project on the South Island, where they plan on grazing sheep around the solar array. The project is set to finish in 2024. It will have 80,000 solar panels spread over 90 hectares, and generate around 80 GWh of energy each year.
Another agrisolar project, the Hauraki solar farm, has been given the green light by the EPA (Environmental Protection Agency). Harmony Energy will be building a 65 MW solar farm with 330,000 solar panels on 182 hectares of the 260-hectare site. The land will remain under the ownership of the farming company, Tuahei Farms Ltd. The farm will use the area where the system is installed for grazing its sheep.
But it's not just one-off agrisolar projects that are popping up in the country. A new start-up named Solagri has raised $4 million in its latest investment round. Based in Christchurch, the company installs solar and batteries on dairy farms at no upfront cost to the customer.
Summing It Up
In the initial decades after its invention, solar panels were limited to space-based applications, as it was crazy expensive to use for anything else. Over time, solar panels have powered businesses and homes, and are now finding popularity in the farming community as well.
There are a multitude of ways to combine solar power with farming - from solar grazing to floating solar panels. Each agrisolar application offers its own unique set of benefits.
As far as New Zealand is concerned, agrivoltaics may have just begun, but its future looks promising, with projects coming up in multiple places, as well as solar companies offering agrisolar tech as a specialization.