Harvesting energy in Iowa


WAPELLO, Iowa – There are, as of 2020, 30.6 million acres of land being farmed in Iowa. That number is unchanged since 2010. With America’s demand for clean energy sources increasing, a little bit of that land is changing from green to shiny photovoltaics under glass with large solar installations starting to pop up.

Corn has been king in Iowa for decades, with 13.6 million Iowa acres planted in corn in 2020, according to the United States Department of Agriculture. With ethanol blends fueling cars and trucks across the country, about 53% of the corn grown on those acres is used to produce the fuel. As electric vehicles grow in popularity and if demand for ethanol blends drops, land use in Iowa might shift.

When we published this story in July about the early stages of construction on a solar site in Webster County, some comments questioned using Iowa farmland for solar power. This story will look at how much energy, in British Thermal Units (BTU) is produced on 700 acres of Iowa farmland. Seven hundred acres is the size of an existing 127 Megawatt solar facility near Wapello in southeast Iowa.

First, corn. On 700 acres with a harvest of 198 bushels per acre and each of those 138,600 bushels being converted to 2.9 gallons of ethanol and each of those 401,940 gallons of ethanol containing 76,330 BTUs the energy produced on 700 acres is 30,680,080,200 BTUs. Byproducts of the distillation process include over 1,000 tons of distillers grains and 55 tons of corn distillers oil, both used to feed livestock, and 76 tons of biogenic carbon dioxide, used to carbonate drinks and to produce dry ice.

Clenera is the company operating the Wapello solar site. To estimate the output of that site for a year, Clenera multiplies the total hours in a year, 8760, by their Capacity Factor of 25% and multiplies that number, 2190, by the megawatt capacity of 127. The Capacity Factor accounts for the hours of darkness, cloudy days and other below-capacity hours in a normal year. So, 278,300 megawatt hours per year. Each megawatt hour contains 3,412,141 BTUs. The total expected from this solar site annually is 949,018,776,330 BTUs.

That 949 billion BTUs is a bit over 30 times the amount of energy produced by converting the corn harvest to ethanol. Of course, this simple look at energy output doesn’t include investment in solar equipment, inputs into the corn crop and other factors. Those factors may be the subject of future stories.

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