AGRI-PHOTOVOLTAICS

The aforementioned agronomic advantages (fulfilling the requirements for increased yields through shading and yield protection) are particularly evident in our efficiently designed systems, which create ideal growing conditions for vegetables, arable crops, and berries, as well as improving the crops' adaptability to adverse weather events. Pome and stone fruit crops, such as strawberries, are generally unsuitable for agri-PV systems, primarily due to high construction costs and low electricity production, as they require sunlight for their own use. The primary function of agri-PV systems is to provide stable, partially covered weather protection for agricultural crops. This protection has a positive ecological impact against severe weather events such as late spring frosts, heavy rain and prolonged rainfall, sunburn, heat stress, water scarcity, droughts, wind erosion, hail (including scattered hail), and strong gusts of wind. Secondarily, agri-PV systems serve the purpose of long-term and profitable energy production. At suitable locations and when ideally coordinated, both functions form a highly interesting synergy.

Depending on the constellation of project participants, various actors and areas of responsibility with different functions are involved in the implementation. Technically well-planned agri-PV plants, especially with regard to the structural arrangement functions (system design and orientation, external loads and statics, substructures, mounting, module arrangement, land use rate, planting density, soil compaction, cultivation and management, landscape aesthetics, system parameters, etc.) as well as the crucial agronomic analysis (biocenosis and ecophysiology, plant growth modeling, light compensation and saturation point, phenotyping and shade avoidance strategies of the plants, convective air cooling and microclimate, soil quality improvement measures, biodiversity and environmental influences, etc.), enable resource-efficient cultivation in vegetable, arable farming and berry crops from an interdisciplinary and agricultural science perspective and promote biodiversity. For crop development, methods such as regenerative agriculture (strengthening soil life through minimal tillage, undersowing and organic fertilization for humus enrichment), permaculture (closed nutrient cycles, use of crop residues, mulch material and shade for moisture retention and weed suppression), precise fertilization and drip irrigation (system-integrated) as well as plant protection (mechanical weed control instead of herbicide use) are integrated to optimize microclimate, soil, water (-evaporation) and nutrients.

Key measures for improved soil quality include stronger and more homogeneous direct soil irradiation (thanks to adjusted tilt angles of the PV modules and a reduction in ground cover), less year-round vegetation, humus build-up, avoidance of pesticides, use of drip irrigation, and mechanical weed control. High qualitative benefits for valuable plants and animals (including biodiversity, small animals, ground-nesting birds, soil fungi, protozoa, nematodes, arthropods, archaea, bacteria, microorganisms, and soil ecology) can always be expected in our plants. Benefits from reduced risks of water contamination (nitrate leaching and denitrification, pesticide residues [also on solar modules], drainage, slurry issues, etc.) are also present.

Crops that benefit from or even require partial shading and prefer a specific microclimate are particularly suitable for protected cultivation under agrivoltaic systems. In addition to traditional arable crops (cereals, root crops, oilseeds, legumes, fiber crops, and forage crops), vegetables (cabbage, leafy greens, bulbs, flowering vegetables, tubers, and root vegetables), most herbs and spices, aggregate fruits (raspberries, blackberries, and cloudberries), true berries (red and black currants, blueberries, jostaberries, elderberries, aronia berries, and cranberries), and certain pome and stone fruits (e.g., certain apple and cherry varieties) are also ideal.

In production, the aforementioned plant genera require and tolerate a certain amount of shading. This shade is optimally and homogeneously generated under a properly designed agri-photovoltaic system, thus enabling the desired yields to be maintained even under exceptionally unfavorable weather conditions (including appearance, freshness, cleanliness, ripeness, taste, nutrient content, health, and shelf life). The climatic conditions in spring, which are crucial for the growth of young plants, are undergoing fundamental changes (precipitation, uncompensable moisture deficits, early warm and cold fluctuations, direct and diffuse radiation, etc.). The combination of decreasing precipitation and increasing global solar radiation further enhances the suitability of agri-PV systems. However, robust varieties remain the recommended choice for agri-PV systems. Flowering and light management of the entire system are also two important success factors that must be considered on a case-by-case basis and always optimally coordinated during the planning of agri-PV plants.

Plug-in plants and cuttings (young plants after propagation) require a specific amount of light to develop lateral buds at the desired time and to bear fruit on schedule. Flowering (the transition from the vegetative to the reproductive phase) occurs either autonomously upon reaching a certain stage of plant development (flowering maturity) or can be induced by day length (photoperiodism), and in many plants also as a reaction to stress factors (fungal or parasitic infestation). This latter method is now widely used in the propagation of, for example, various long cane raspberry varieties (autumn and summer varieties) and is primarily employed to produce healthy and vigorous plants.

In addition to the aforementioned berry cultivation, agrivoltaic systems are also conceivable for pome fruit and espalier fruit orchards. Since these belong to the category of ground-based perennial crops and have proven to be somewhat sensitive in terms of light management, we consider long-term research results from existing systems desirable before constructing agri-photovoltaic plants above such growing areas. The height of the system under pome fruit trees could also be a limiting factor, as height translates to higher costs, and these costs – along with the often lower density of solar cells above pome fruit orchards – are crucial for the financial viability of such an agri-PV project. It is quite conceivable that the advantages of agri-PV systems above pome fruit and espalier fruit orchards could lie in reducing the need for frost protection irrigation and chemical thinning (fruit set).

Precision farming is also becoming increasingly important in our agri-PV plants; for example, integrated water management, plant support and decision support systems, compatibility with LaserGuide guidance systems or automatic steering assistance systems, as well as autopilots, drones, and automated tractor concepts (ATC) are ideally suited for our agri-PV systems. GPS position signals and real-time kinematic corrections are replaced in our systems by laser sensor data acquisition, which is based on the system design and no longer depends on rovers, satellites, and base stations. This allows farmers to use tow vehicles and machines that can drive much more precisely and autonomously (which could mean less work) and to have an ATC that would be available at a lower cost than conventional systems on the market. Precision farming methods also increasingly focus on the resource-efficient production of crops (photosynthesis), which is achieved in our agri-photovoltaic systems, as explained in detail above.

Solar module surfaces installed in agrivoltaic plants in arid regions can become heavily soiled by dust (possibly generated during soil cultivation or harvesting), which would impair their performance. Particularly during extended periods of dry weather, dust can accumulate on the module surfaces and thus slightly reduce power production. Furthermore, pesticides, especially fungicides – which are often formulated to provide high wetting, good adhesion, and sometimes even a form of sun protection for the leaves – can deposit on the panels (including the back glass) and lead to further performance losses. Therefore, our PV modules can be optionally equipped with a long-lasting nanocoating to repel these dust particles and chemical substances, thus achieving the desired self-cleaning properties.

FOOD & ENERGY NATURE