‘Aglectric’ Farming: A New Land-Sharing Strategy to Boost the Solar Economy

Solar power is poised to become the world’s primary energy source, but a land shortage in most regions of the world will be the next hurdle blocking progress. Purdue researchers have found a novel way to knock down the barrier.

The race for energy production from renewable resources is in full swing. The good news: The cost of solar energy production has decreased so significantly that it is now viably competing against natural gas. Unfortunately, there is bad news, too, which is that the world doesn’t have sufficient unused land for solar production. Our research at Purdue develops a workaround to solve this challenge.

We are fortunate that solar radiation is not too intense, which allows us to directly enjoy sunshine without being burned, but there’s a downside as well. Only a very small amount of solar energy can be generated from a unit land area, and it takes many solar panels to generate enough usable electricity. This means that to ramp up solar energy production, we need large, utility-scale photovoltaic (PV) — or, as they’re more commonly referred to as, solar — panel parks, which will create a demand for more land.

Detailed modeling shows that for the world to transition to a primarily solar economy, most regions will need additional non-agricultural land for PV farms. Regions that are densely populated and/or have low levels of solar intensity face the greatest shortages.

The question then arises: Can we set up PV parks on agricultural lands just as windmills are placed today? The conventional answer has been no. The shadow cast by PV modules obstructs sunlight, decreasing photosynthetically active radiation available to plants. This reduces the yield of major crops, such as wheat, potatoes and soybeans, by more than 20 percent.

So, do we have to choose between food and electricity from a given plot of land? Is there a way to double up land use by growing major crops while also co-generating electricity? Indeed, for the unimpeded growth of the human race, there is an urgent need to remove any foreseeable land constraint for harvesting electricity using PV panels.

To achieve these outcomes, engineers, agronomists and economists at the National Science Foundation-supported Center for Sustainable Food, Energy and Water Systems (SFEWS) at Purdue are working together to create and enable a novel concept: an “aglectric” farm.

This “full-earth” scenarios proposes simultaneously using different parts of sunlight’s spectrum to produce crops, generate electricity, collect heat and purify water on the same piece of land. (Purdue University image/Rakesh Agrawal, Pamela Burroff-Murr)

We are developing innovative concepts, designs and operating methods for PV modules that can be installed on farmlands with no drop in crop yields. For example, for currently available silicon solar cells, we have devised modules and installation processes to minimize the duration and intensity of the panel shadow on the land underneath.

We are also exploring new kinds of solar cells that will split the solar spectrum to benefit both agriculture and solar energy production, diverting required radiation to plants and dispatching the rest for electricity generation. These new PV systems are being installed at Purdue’s Agronomy Center for Research and Education (ACRE) farm for capturing plant growth data this summer. Experiments have been designed through extensive modeling, and verification through ACRE farming will provide much-needed knowledge to make aglectric farming a reality.

Because the largest fraction of land in most countries is used for agriculture, successful aglectric farming will permanently eliminate the competition for land, providing viable renewable energy solutions for human needs throughout the world.

Dr. Rakesh Agrawal

by Professor Rakesh Agrawal, Director, Center for Sustainable Food, Energy and Water Systems (SFEWS), Purdue University, and Professor Mitch Tuinstra, Co-Director, SFEWS

Rakesh Agrawal is a National Medal of Technology and Innovation Laureate, as well as the Winthrop E. Stone Distinguished Professor of Chemical Engineering at Purdue University.

Notable awards:
National Medal of Technology and Innovation (2011)
IRI Achievement Award (2007)

Related links:

YouTube: Rakesh Agrawal — 2010 National Medal of Technology & Innovation

Forbes: Local Farmers Will Replace Oil And Electric Companies, If A Purdue Prof Gets His Way

NSF announces funding for Purdue food, energy program
NSF Research Traineeship (NRT)



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