Changing land use rules for renewable energy

The renewable energy revolution faces a major land use problem that could seriously hamper the growth of the clean energy sector. Massive renewable energy infrastructure, such as wind and solar farms, covers a much larger area than traditional fossil fuel plants, and the sector increasingly competes for land with other major industries, including agriculture. In the future, the renewable energy sector will need to be creative in using land more efficiently and in a more collaborative way with other major land users.

Late last year, global consulting firm McKinsey & Company released an analytical report that identified land scarcity as one of the three key challenges facing the renewable energy revolution, along with miles of bureaucratic red tape and woefully underprepared power grids. Solar and wind farms require huge tracts of land to operate at scale, and there is often fierce competition for plots of that scale, driving up prices for renewable energy developers. “Utility-scale solar and wind farms require at least ten times more space per unit of power than coal- or natural-gas-fired plants, including land used to produce and transport fossil fuels,” McKinsey reports, adding that “wind turbines are often remote half a mile apart, while large solar farms cover thousands of acres.”

One of the most promising solutions to this key issue is agricultural photovoltaics (AV), also called agrivoltaics, a practice in which crops and renewable energy production take place in the same area, working in symbiosis. Plants benefit from the shade of solar panels, while plants release water through transpiration, cooling the air around the panels and effectively increasing their efficiency.

However, AV is not a new concept. So why hasn’t it evolved since it was developed in the 1980s? Although optimizing the system to meet the needs of both systems – solar energy production and agriculture – seems simple on paper, in reality it is not so simple. Both plants and solar panels need a lot of sun, and making sure everything gets what it needs can be a bit complicated. “An urgent question is how AV technology can maximize crop productivity and energy production while minimizing plant water loss and irrigation needs,” recently reported. “That’s a lot to ask for a piece of land.”

Scientists are looking hard at how to design efficient audiovisual systems that can achieve this kind of balance on a large scale. One potential solution proposed by researchers at the University of California, Davis is to split the light into different wavelengths, directing different parts of the light to different applications, such as red light for photosynthesizing crops and blue light for solar panels. The study, published late last year in the scientific journal Earth’s Future, used a mathematical framework to quantify how different types of plants use different wavelengths of light in their photosynthetic processes.

Modeled plant typologies included variables such as shade tolerance and leaf area, and findings indicate that ideal AV candidate plants are those that are shade tolerant and have large aboveground leaf area. Shade tolerance allows for life under a solar panel, while the large leaf area allows for greater use of sunlight. Additionally, larger overall plant size was associated with greater respiration costs, another key element of the study, which also looked at water efficiency. The results suggest that great candidates for AV are larger plants with lots of leaves, such as arugula, kale and tomatoes.

Although AV has not yet been deployed on a large scale, some AV pilot projects are already being implemented around the world. In Germany, farmers grow hay in furrows between rows of standing solar panels. In France, vines grow in the shade of solar panels, and in Japan, tea leaves benefit from the shade produced by the panels. There are also other related innovations in shared-use systems, including sheep sharing pastures with solar panels in Canada and Australia, and apiaries that allow endangered honey bees to share space on solar farms in the United States.

The potential benefits of developing and scaling AVs are enormous and can positively transform agriculture as well as the renewable energy industry. “We cannot feed 2 billion more people in 30 years by reducing water consumption and continuing with business as usual,” said corresponding author Majdi Abou Najm. “We need something transformative, not incremental. If we treat the sun as a resource, we can work in the shade and generate electricity while producing crops underneath. The kilowatt-hours become a secondary crop that can be harvested.”

Author: Haley Zaremba for

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