Using natural ground cover such as grass or crops is not only better for the environment but has other benefits as well.
Solar Frontier and the University of Tokyo are testing a concept called ‘solar sharing’ amid growing interest for more natural ground maintenance strategies in PV. The solar sharing pilot unveiled this month involves placing PV panels high enough off the ground for farmers to grow crops underneath.
“‘Solar sharing’ in Japan refers to the practice of using the same plot of land to simultaneously grow crops and generate solar power,” said Solar Frontier. “In such cases, solar panels are installed high above the crops and spaced further apart than usual, enabling sufficient sunlight to pass through and farmers to work below.” The solar sharing business model “has been gradually spreading across Japan, helping farmers earn additional income by selling electricity,” Solar Frontier said.
"Similar initiatives are underway in other solar markets as asset owners realise land-sharing techniques can help reduce costs and potentially smooth the planning process by addressing environmental concerns."
In the UK, for example, solar operations and maintenance providers are increasingly using sheep instead of mechanical methods for vegetation control on PV plants, according to a non-public report from Bloomberg New Energy Finance.
“UK-based developer Lightsource designs PV projects to facilitate grazing, raising the panels off the ground by at least 0.8m, so the majority of the land is still accessible,” it said.
James Huff, chief executive of Abakus Solar USA, which has carried out detailed research into different ground maintenance strategies, warns that asset owners choosing to allow grazing should be careful of the animals on site, though. While sheep generally do a good job of keeping vegetation down and do not interfere with PV operations, goats have a habit of breaking panels by jumping on them, and chewing through electrical cables.
Larger animals, such as cattle or horses, may damage PV arrays by using the supports as scratching posts, he said. In some parts of the US, however, attention is shifting to the benefits that PV plants could afford a much smaller animal: the honey bee.
"With increasing concern that a condition called colony collapse disorder could affect bee populations and hence crop pollination, the State of Minnesota has passed a bill allowing PV plants to be declared beneficial habitat for birds and pollinating insects."
The beneficial habitat status does not come with any specific financial incentive but is likely to help with project consenting, said Rob Davis, director of non-profit advocacy body Fresh Energy.
“In Minnesota, solar developers have used the promise of pollinator-friendly solar as a way to gain more local support for their projects, speeding the permitting process and building stronger long-term support,” he said.
“Short-growing prairie grasses and flowers have also shown to reduce operating costs over the life of a project.”
Huff supports this view. His research shows the cheapest ground maintenance strategy is to plant low-growing grass. “Gravel costs USD$1,000 for five tons and that doesn’t go very far,” he said. “You can seed an entire acre for $1,000, versus the tenth of an acre you could cover with the same investment in gravel.”