Heating Things Up on the Farm: Crop Drying with Solar Air Heat in Central Minnesota


by Kathleen McCarthy • August 2011
RREAL solar furnaces used in a series for commercial heating

Since 2000, the Rural Renewable Energy Alliance (RREAL) has been serving low income communities in Central Minnesota by developing, manufacturing, and installing solar hot water and air heaters to help families reduce their heating fuel dependence and lower their energy bills. Now, RREAL is exploring other applications for sustainable energy.

Traditionally, agricultural crop drying uses a lot of electricity to run high heated fans. Crop drying is one of the most energy intensive operations of grain farming. RREAL believes that using solar thermal for air heating could significantly reduce the amount of electricity needed for this process. Farmers in Minnesota are feeling the cost of crop drying and are looking for alternatives that are less energy intensive and more cost effective.

“Having changed dramatically in the past century, crop drying today is an energy intensive process, heavily dependent on fossil fuels. Our state’s food and energy security are somewhat vulnerable to the vagaries of fuel supply and expense,” explains Jason Edens, one of RREAL’s researchers for this project.

In 2008, RREAL decided to research solar air heat as a crop drying method and “outline the benefits of using this appropriate technology in an application that has great potential to significantly contribute to Minnesota’s goals of reduced fossil fuel dependency and resulting improved environment,” explains Edens.

The project was spearheaded by Edens and then RREAL’s research coordinator, Sarah Hayden. They were motivated to find the appropriate role for solar hot air technology in the crop drying process. “Although it would certainly benefit us if we discovered our technology were appropriate for crop drying, our motivation was to determine the applicability and appropriateness for the technology as a whole, not just our collector in particular.”

To begin, the team consulted with both the University of Minnesota Extension Service and the North Dakota State University Extension Service because both institutions had literature and resources regarding agricultural crop drying and solar crop drying, in particular. “Dr. Kenneth Hellevang, of NDSU, was particularly helpful in guiding us to relevant documentation,” said Edens.

“The literature revealed that a great many farmers throughout the world have been, are and will continue to utilize solar air heat as part of their agricultural processing. In addition to agricultural crops, there are a great many folks in Minnesota who are using solar heat for
silvicultural crop drying processes,” explains Edens. Yet because the upfront cost of installing a solar air heat panel is often higher than a traditional crop drying machine, many farmers see the cost as prohibitive and are not willing to give it a try.

Despite the upfront costs, many long term economic, environmental, and social benefits can arise from utilizing a solar crop drying method, Edens argues. “Farmers employing solar crop drying methods would experience economic savings, with a specific payback period to be determined by the end of this project. Should we discover crop drying to be an appropriate application for solar, as we suspect, this project would have significant economic impact in central Minnesota through sales of locally manufactured solar collectors specifically designed for that application.”

Additionally, reducing the amount of electricity needed to crop drying by incorporating solar air heat to the process will significantly decrease the amount of unsustainable fossil fuels being burned.

Edens also identifies social benefits of renewable crop drying. “It will also make small agricultural communities and farmers more resilient against the impact of rising fossil fuel costs. Energy crises will make crop drying financially challenging. At a time when small farmers are struggling to maintain their way of life, renewable and sustainable farming methods make sense for the individual farmer and state.”

With the help of a CERTs grant, RREAL was able to dedicate staff time to investigating solar thermal crop drying and ways to engage farms with the technology. The conclusion of the literature review revealed that “generally, the literature is positive about the use of solar heat in crop drying applications in diverse settings throughout the world. In Minnesota, solar crop drying was determined to be technically feasible in a supplemental setting when excluding the costs and benefits of externalities. In summary, supplemental solar crop
drying in Minnesota can be an economically and technically feasible technology when used in combination with a low temperature crop dryer.”

The research team plans to continue this project by developing ways to implement the practice in Minnesota.

Project Snapshot:

  • Project: Research on the use of solar air heating for crop drying
  • Benefits of Solar Air Heating: Decrease use of fossil fuels, reduce emissions, build resilience against rising fuel prices, economic savings
  • Conclusions: Supplemental solar crop drying in Minnesota can be an economically and technically feasible technology
  • Partners: University of Minnesota Extension Service and the North Dakota State University Extension Service
  • Grant: $5,000 from Central CERT

For more information about the report, please contact Jason Edens at info@rreal.org or by calling 218-587-4753.

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    CERTs Partners:

Minnesota Department of Commerce University of Minnesota Regional Sustainable Development Partnerships and Extension Great Plains Institute Southwest Regional Development Commission