With all the installed photovoltaic solar panels, Flanders in 2020 covered only 1.2% (3958 GWh) of its total final energy consumption. Large solar parks could contribute to making Flemish energy production more sustainable, but given the limited open space available, this is by no means a given.
Abroad, a start has already been made on tapping into a new potential area under the name of agrivoltaics. This involves the smart combination of energy and food production on the same site. The first published results already show that, in addition to the sustainable energy yield, there are also possible benefits for agricultural activity: the solar panels can offer protection against hail, frost, sunburn, drought or high temperatures, etc. The increasingly frequent extreme weather conditions, the limited open space and the need for more solar energy production in Flanders make it worthwhile to investigate this technology here as well.
Solar modules can be installed in various ways in agriculture. Think of the combination of large solar parks with grazing sheep tending the fields, or panels on top of greenhouses and stables. The definition of agrivoltaics - as used on this website - refers only to the combination of solar panels with agricultural crops on the same agricultural plot. The primary activity remains agricultural production, where we consider the energy yield as added value.
In order to know which crops to consider, we must first look for shade-tolerant species. After all, the growth of crops is strongly related to the daily amount of sunlight.
As shown on the figure above, plant growth increases if more sunlight enters the plant, but at high amounts of daily irradiance this growth saturates. If the amount of sunlight increases even more, this can lead to crop damage. This optimum is different for each crop and its growth stage. Moreover, this saturation point can shift under the influence of other environmental parameters such as CO2 content and crop temperature. In our part of the world most crops are in the left-hand area, so that a reduction in light will usually result in a reduction in yield. But plant growth under reduced irradiance sometimes provides benefits. For example, research shows that some leafy greens seek out more light under those conditions and actually grow larger leaves.
So we need to think carefully about which crops we should place the solar panels above and how much light they should take away in the process. But many other factors also determine whether agrivoltaics can be applied successfully. Agricultural crops with crop rotation or plants that are worked with very large machines require a different approach than fruit trees, for example.
In agrivoltaics setups, the solar panels are installed fixed or tiltable on a support structure. In the latter case, the position of the panels can be adjusted according to the position of the sun (=tracking) or arranged so that the shading from one row to the next is limited (=backtracking) or just increased for the plants (=anti-tracking).
It is important that the construction of the agrivoltaics setup does not hinder the agricultural activities, the harvest and the soil quality. The agrivoltaics construction should:
The financial feasibility of the construction must also be monitored. The higher the installation is placed above the ground, the greater the material cost and the more expensive the anchoring will be. In addition, we must take into account the (aesthetic) integration of the construction into the landscape and limiting soil compaction during construction. The latter can be done, for example, by using driving plates.
Agrivoltaics constructions can be divided into 2 categories. In category I installations, the solar panels are placed on a high support structure so that agricultural vehicles can pass underneath to cultivate the land. The solar panels can cover all or part of the usable cultivation area. The implantation of the structure using vertical profiles ensures that the effectively available cultivation area is reduced only minimally. The demonstrators build in Bierbeek and Lovenjoel are both examples of category I installations.
Category II agrivoltaics installations are low-lying installations, with cultivation between the solar panels. This means that in many cases it is not possible to cover the entire usable cultivation area. What can no longer be used for cultivation can possibly be filled in with flower strips in a buffer zone. In Grembergen two different examples of category II installations were build.
