Double harvest: Solar panels on farms

Fabian Karthaus is one of the first farmers in Germany to grow raspberries and blueberries under photovoltaic panels. His solar field near the city of Paderborn in northwestern Germany is 0.4 hectares (about 1 acre), but he would like to expand it to 10. He could then generate enough electricity for around 4,000 households — and provide more berries for supermarkets.

Up until now, many farmers have grown delicate fruits and vegetables under plastic film. But that lasts only a few years, costs money and produces a lot of plastic waste. This is one reason why ever more farmers in the Netherlands are planting under glass panels, as here in Groenleven. These protect the harvests, last for at least 30 years. And there's additional income from electricity sales.

China is massively expanding photovoltaics and has also been relying on agricultural photovoltaics (agri-PVs) for several years. This plant in the northern Chinese province of Hebei has an area of more than 10 hectares, with grain growing beneath. The solar modules are manufactured nearby. This also creates jobs and helps fight poverty.

Some of the largest solar parks in the world are located in the Chinese Gobi Desert, where there is plenty of space. In some places, crops are grown in the shade of the modules. This helps to stop desertification and allow soils to become arable again.

This small solar roof in a field near Santiago in Chile is one of the first agri-PV systems in Latin America. Researchers are using broccoli and cauliflower to test how the system works best. The region is very sunny, and has been suffering from declining rainfall and increasing drought. Initial experience with solar shade in this field has been positive.

This farmer in Rwanda earns her money with a mobile solar water pump. She pulls her panel to other farmers' fields and irrigates them from nearby water sources for a small fee. Across Africa, there is substantial potential for solar modules in agriculture.

This novel arrangement is in eastern China, 150 kilometers south of Shanghai. On this lake, solar panels float on pontoons, and beneath that is a fish farm. The panels were positioned to make sure the fish get enough light. The 300 hectares of panels produce electricity for 100,000 households.

Placing solar panels vertically in a field allows them to receive light from both sides. In Germany, such structures can produce as much electricity per module as roof systems. At the same time, these "solar fences" provide wind protection and leave plenty of space for harvesting equipment.

Cultivation of corn, wheat and sugarcane for biogas and biofuel account for about 4% of global arable land use. Generating the corresponding energy with solar modules would be much cheaper — and would only need one-tenth of the arable land currently used for that.