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23 August 2019

OSU finds 1% of farmland enough for total solar needs, however …

Researchers at Oregon State University (OSU) have published research that finds that converting 1% of the world’s croplands to solar panels would provide enough electricity to meet the world’s current needs. However, while this sounds like a simple enough task, our inability to conceptualize very large numbers is quite misleading.

The World Bank says that there is 48,632,688 km2 of land used in agriculture, and so 1% of this would be 486,327 km2 or 187,772 square-miles. For some context, London is around 1,738 km2, while Los Angeles is around 1,213 km2. Even accounting for its infamous urban sprawl, where Los Angeles covers 34,490 km2, the area needed for this 1% conversion of cropland is equivalent to just over 14 entire Los Angeles metropolitan areas.

This is before you solve a number of other problems, most prominent of which is the availability of enough solar panels to meet this requirement. Similarly, last-mile connections to local electricity networks, and then the connections to the largest distribution networks, needs to be solved, and energy storage is going to be essential in accommodating the variable generation output from the PV panels. Napkin-mathematics suggest this is equivalent to around 10bn panels.

But, humans are pretty good at breaking down large problems into smaller, more easily achievable ones. One percent is after all, 1% of 100%, but 1% of 48.6mn km2 is still an incomprehensible amount of land. Current solar panel output is around 500mn annually, and so reaching the 10bn rough estimate means that this is around a twenty-year job – plenty of time to lay the groundwork.

Climate change could actually be one of the biggest motivators. Some farms are going to find that their outputs fall due to more frequent extreme weather, drought, or higher temperatures, and for farms that begin to become unviable, switching professions to solar farms, rather than arable crop farms, could be a very tempting proposition.

Before anybody tries to chime in with the notion that turning farms into solar arrays is going to cause food shortages, it should be noted that food wastage estimates range from 20% to 50% of total food produced globally. To this end, food shortages would be best solved by properly matching supply to demand, that this is actually a distribution problem rather than a question of production.

If that is not another to persuade someone, then wasteland, deserts, and of course rooftops are excellent candidates for this same challenge. Vertical farming is also a much better solution to the concern of future food shortages, and a much better allocation of resources than trying to expand conventional arable farming footprints.

So whether 100% of farmers decide to convert 1% of their land to solar arrays, or a smaller percentage of farmers convert the equivalent amount of land to meet the OSU estimate, this is something that is certainly achievable in time. However, it is important to be able to properly visualize this sort of claim, and recognize the actual scale of the problem.

The OSU project does take a little time to properly understand. It is concerned with ‘agrivoltaics,’ or the concept of putting solar panels above active crop fields – rather than a straight swap. There is a large pile of research that suggests agrivoltaics is the best use of available land, since the concept was first introduced in the 1980s.

The principle is that the crop output you lose by placing the panels above the fields is more than offset by the electricity you produce, which can run the farm and then be exported to the grid. Similarly, running two agrivoltaic fields produces more of each resource than running one field dedicated to each. Pilots in Japan, Germany, and Chile have been successful.

The OSU team calculated that the approach could provide 28 W of electricity per square-meter, and on that basis, the global demand of 21 PWh of electricity would be met by the 1% conversion. Notably, the team recommend against deploying solar arrays in deserts, due to the loss of efficiency that occurs as temperatures rise.

“Our results indicate that there’s a huge potential for solar and agriculture to work together to provide reliable energy,” said corresponding author Chad Higgins, an associate professor in OSU’s College of Agricultural Sciences. “There’s an old adage that agriculture can overproduce anything. That’s what we found in electricity, too. It turns out that 8,000 years ago, farmers found the best places to harvest solar energy on Earth.”

The project was based on data pulled from five Tesla installations on arable land that OSU owns, and data from weather stations. A model was created that could calculate solar panel efficiency with regard to air temperature, wind speed, and relative humidity. The findings are published in Scientific Reports.