Soil quality deteriorates due to solar parks. What can we do? You see it more and more often: a landscape full of solar panels. Such a solar park is a relatively cheap way to generate green electricity, but this is often at the expense of soil quality. This can also be done differently, according to researchers from TNO Netherlands. In a new study, they show that better design for solar parks improves soil quality and biodiversity. Solar parks are an important link in the energy transition from gray to green energy. Nevertheless, there has been discussion for a long time about the negative effects of solar parks, such as the appearance of the landscape, biodiversity and soil quality. Because a large part of the Dutch solar parks are equipped with east-west oriented solar panels: a roof made of panels that stand against each other, so that about 90 percent of the ground surface is covered. This concerns the space between and under the rows of panels, and not the space in the edge around the solar park. No more growth “You see that nothing at all grows in those places anymore,” says TNO researcher Kay Cesar. “Plants grow through photosynthesis and you need sunlight for that. If that cannot happen, the supply of food and carbon in the soil will stop. The entire ecosystem of fungi, bacteria, worms and moles is getting out of balance,” explains Cesar. “The natural strength of the soil is lost.” When a solar park is cleaned up after 25 years, there is a good chance that the soil will no longer be usable: the first fertile soil will lose value. And that is a shame, according to the TNO researchers, because restoring the soil quality costs much more time and money than adjusting the design of the solar parks. Semi-transparent and two-sided That is why the TNO researchers are making a suggestion. Previous field measurements by Wageningen University and Research (WUR) showed that under south-facing solar panels with a lower cover ratio, many more plants grow than under east-west panels. TNO mimicked those conditions with an advanced computer program: BIGEYE. The best solution appears to be the use of semi-transparent and two-sided solar panels. They provide the same return and ensure a good soil. The so-called bifacial solar panels compensate for the loss of transmitted light because they also convert the reflected light from the bottom through the back of the panel into electricity. “They are already being produced on a large scale: about 15 percent of solar panels worldwide are already bifacial. It is expected that by 2030 half of all panels will be two-sided,” says Cesar. In terms of costs, according to the experienced TNO researcher, it is not much different from existing solar cells. “They already have the same price as high-efficiency panels and the bifacial panels also deliver an even higher return.” TNO had previously tested the two-sided solar panels, and they indeed proved to work excellently. Don't convert but improve future plans plannen According to Cesar, it is not the intention to convert the existing solar parks. “The energy transition cannot wait, but we can improve the process for the coming solar parks.” Current east-west oriented solar panels are much more common in the Netherlands than in other European countries. According to Cesar, this is due to the subsidy legislation, the high land costs and the grid connection. “If you optimally orient solar panels, not the entire yield is subsidized. The ground here is also expensive, so people want to put as many panels together as possible,” explains Cesar. The semi-transparent two-sided panels can change that. “We are arguing for a new standard that takes into account soil quality and biodiversity.” The TNO report, commissioned by the Central Government Real Estate Agency, is in line with WUR's previously published research into the effects of solar parks on biodiversity. The WUR examined 25 solar farms to determine which types of parks have which effects on soil, vegetation and species richness, among other things. The east-west oriented parks in particular performed poorly there.