Local Sunshine Meets Local Needs with Global Impact — Key Is Cogenerating Electricity Alongside Farming
Life teems on earth in vast variety and across a wide geographic distribution, just as it did eons ago with ancient plants and organisms. Fossil fuel energy sources formed from the decay of that primeval life, and just as it was spread unevenly across the planet then, the natural availability of these fossil resources is limited to certain regions of the world today as well. This has led to an economic order where most countries — constituting a major fraction of the human population — rely on oil, coal and natural gas that must be imported over long distances.
This has made energy expensive for large swaths of the global population and has limited their economic growth. As we wean off fossil resources and embrace renewable solar energy, we have a transformative opportunity to meet our daily needs for food, electricity, heat, purified water, transportation and chemicals with locally available solar energy — by installing photovoltaic (PV) modules on agricultural land, to cogenerate electricity alongside farming.
Our computer modeling at Purdue has revealed that — for the most densely populated regions, using PV modules to collect solar energy as electricity — there will not be enough rooftop and other conventional land areas available locally to supply the solar energy for most of the daily needs of the local inhabitants. This means more national and global interdependencies for energy and solar-energy-related products, just as with fossil fuels.
The way out of this land constraint in a solar economy is to put the PV modules on farmland and cogenerate electricity alongside crops. The snag is that PV module installations cast deep shadows on the land underneath, depriving plants of sunshine and reducing yields by more than 20% in major food crops such as wheat, potato, soybeans, etc. This competition for land between food and energy is a deal-breaker for meeting local needs with local sunshine.
At Purdue, a team of engineers, agronomists and economists at the Center for Sustainable Food, Energy and Water Systems (SFEWS), supported by the National Science Foundation, has developed novel PV module designs. Their installation and operation minimizes shadow duration and intensity on the land underneath, allowing uninhibited growth of plants. Some of the new designs use currently available silicon solar cells in new patterns; others employ new materials and innovative concepts to allow unimpeded transmission of the portion of sunlight that plants need for their growth while using the remaining sunlight to generate electricity.
The SFEWS team has installed these PV module structures at Purdue’s Agronomy Center for Research and Education (ACRE) farm and has begun its first set of experiments to study plant growth and crop yield to get insights into how plants thrive while electricity is cogenerated from the same land. In subsequent harvesting seasons, we will be trying different PV panel ideas as well as different crops.
The success of these trials would mean we could eliminate competition for land between food and energy. It would enable local availability of energy alongside unhindered crop yields to fulfill local needs in all corners of the world. Farmers will be able to grow major crops such as corn, wheat, soybeans, rice, potato, etc. without any loss in yield while cogenerating electricity.
We have named farming while cogenerating electricity as “Aglectric” farming and the one using PV modules for electricity generation as PV-aglectric farming. We envision that PV-aglectric farming will lead to higher farmer earnings. Where crops can be grown only during summer months, farmers will have electricity as a source of revenue throughout the year. Using local electricity, farmers will be able to treat farmland water to reduce or eliminate pollution caused by water runoff to adjoining aquifers.
We will see microgrids at the county level connecting to adjoining counties, then to neighboring states, generating a national and global impact. Parts of the world with acute energy shortages caused by insufficient fossil resources will be able to prosper by harvesting electricity from local sunlight, even using the cogenerated electricity to increase crop yields and pure water supplies.
The opportunities for meeting local needs with local sunshine are limitless.
By Rakesh Agrawal and Mitch Tuinstra, director and co-director of the Center for Sustainable Food, Energy and Water Systems at Purdue University: engineering.purdue.edu/NRT
Caleb K. Miskin, Yiru Li, Allison Perna, Ryan G. Ellis, Elizabeth K. Grubbs, Peter Bermel & Rakesh Agrawal. “Sustainable co-production of food and solar power to relax land-use constraints.” Nature Sustainability Vol. 2 (October 7, 2019) pps. 972–980. DOI: 10.1038/s41893–019–0388-x