Solar power's biggest problem is land. It takes too much potentially arable land away from the food system to generate enough energy to make it worthwhile. However, agrivoltaics (APV) combines agriculture and photovoltaics (solar panels) on a single piece of land. Some experiments suggest that the two can act synergistically, improving the productivity of each and helping us lower the strain on our food and energy systems. This article examines how APV works and what benefits it may confer.
Traditional Solar Power Is Tremendously Land-Hungry
Rural solar parks have been popping up all over the US for over two decades. The primary issue with this form of solar installation is that the ground underneath the panels is not suitable for any concurrent purpose, owing to the narrow intervals between the rows of panels. These lanes are insufficient for agricultural equipment to pass through, and dual-use solar land is limited to small-scale operations.
Spacing Out Panels and Small Livestock Are Imperfect Solutions
When a standard solar park is designated as grazing space for small animals such as chickens, geese, and sheep, it can reap some benefits of dual land use. The small livestock enjoys the shade afforded by the panels and benefits owners by lowering the expense of vegetation management while posing no harm to the panels themselves. Unfortunately, larger animals are not appropriate in this context and can damage solar panels.
While crops may be grown in the gaps between the solar panel rows, especially if they are spaced further apart, the area underneath the panels remains unreachable by farming equipment. Moreover, this does not alleviate the large land footprint of solar power or agriculture. Therefore, scientists and farmers have experimented with new technologies and configurations to develop more efficient designs.
New Configurations Perfect the Dual-Use Land Format
Vertically placed bifacial panels can free up arable land. These models can gather solar energy from both sides of the panel. Bifacial panels can produce more electricity per square meter than standard, single-faced panels and do not have any moving components. This construction could be instrumental in locations prone to wind erosion since the panels limit wind speeds. This effect shields the crops and topsoil, preserving soil health and improving yields.
Perhaps the most common configuration of APV is panels raised on stilts. This arrangement limits productive agricultural land the least, as farming equipment can pass under the solar panels. The only loss is the land area where the stilts meet the soil.
Operators can install panels with actuators instead of permanent fixtures, enabling the panels to tilt in one or two directions. This allows farmers to micro-manage (and even automate) solar energy collection and plant development. As a result, they can adapt to evolving weather and plant life cycle conditions.
The Science: Getting the Right Amount of Light to the Right Crops
Most people probably assume that the shade cast on crops by a solar panel may stunt the plant's growth. However, those with modest gardens know that different plants require different amounts of sunlight. Put scientifically, each plant has a light saturation point, beyond which there will be no corresponding increase in photosynthesis. So instead, the plants throw off that excess energy by excreting water, which evaporates – they dry out.
Research from the German Fraunhofer Institute for Solar Energy asserts that all crops may be grown using solar panels. However, yield loss may occur during less bright seasons for sun-loving plants. Therefore, although nearly every plant will suffer from too much sunlight, crops with lower light saturation points work best in APV setups.
The 2016-2018 project near Lake Constance in Germany showed the same result. It demonstrated that APV-crop yields were 25% lower than a standard field during a relatively' wet and cold' year. However, in a 'dry and hot' year, APV-crop growth surpassed typical yields. The results suggest that APV may be a boon for hotter, dryer climates.
The Best APV Models Produce an Exciting Synergy
While it was encouraging to discover that APV is a practical dual-use proposition, some synergies between crops and solar panels were unexpected and exciting. For example, solar panels can protect plants and artificial structures (trellises, etc.) from hail and excessive wind, saving labor and (potentially) entire crops.
Furthermore, other research shows that temperatures under the solar panels remained cooler and more stable than in the control fields. The workers found this much more pleasant, but the irrigation water usage dropped by half – with enormous implications for water conservation.
Finally, the water that DID evaporate off the plants lowered the temperature of the solar panels, which lose their efficiency in high heat. Therefore, solar panels on stilts over crops convert more sunlight to electricity than ones over barren land. Some companies have even developed a gel that absorbs more water evaporated from the plants during the day (cooling the panels more) and discharges the water at night (re-watering the plants below).
Agrivoltaics Is Young but Offers Encouraging Results
Agrivoltaics is a young science. However, it has met limited success in several notable installations worldwide. The most encouraging results come from crops with low light saturation points, like spinach, potatoes, tomatoes, and lettuce. What's more, new technologies may further increase the efficiency of PV tech and crop optimization, helping us meet our food, energy, and water challenges as we approach mid-century.
Dual-Use – How efficiently do you manage your land? While you might not be able to incorporate agrivoltaics at home, get the most out of your land by gardening, composting, and even using small livestock (like chickens) to help you around the yard. You will never have better tomatoes than the ones you grow in your own natural garden.
Collaborate – There are solar power collaboratives in many cities and suburbs. Do some research to find out if there is one in your area. It could lower your carbon footprint and maybe even reduce your energy bill.
Use Shade – If you have a home garden, you know how tough it can be to get each plant the right amount of sun. Try looking for space-saving vertical gardening arrangements on the internet. Some of them are designed to protect lower plants from getting too much sun.