Photos courtesy of Miller Milling.
Over the years, a number of mills around the world have used water as an energy source to power their plants. In recent years, several flour mills have begun using wind as an energy source to help power their plants, and now a flour mill in Fresno, California, U.S., is harnessing the sun’s energy to partially power its facility that produces 9,500 cwts of flour per day.
Miller Milling Co.’s solar power system was built in 11 months and became operational toward the end of 2017, Damon Sidles, plant manager, said during a recent presentation on the project at the 2018 International Association of Operative Millers (IAOM) Conference in Atlanta, Georgia, U.S.
Sidles noted that solar energy systems reap the benefits in climates that have abundant sunshine. The southwestern United States, including the states of Arizona, Nevada and California, which accounts for over one-third of installed solar power in the United States, fits that profile.
After taking time to explore the resumes of several companies in the solar power industry, Miller Milling chose Richmond, California, U.S.-based SunPower Corp., which has been in business for more than 30 years and brings in more than $2 billion in revenue annually.
Panel installation
Sidles, who noted that this was one of SunPower’s smaller-scale projects, said Miller Milling decided to install the 2,340 solar panels required for the project on 5 acres located adjacent to the mill.
He said since it was a relatively flat section of land, very little grading of the ground was required, and there was minimal use of concrete.
“The solar foundation piles that were driven into the ground required no concrete at all,” said Sidles, adding that the piles are driven 7 to 8 feet deep, providing a sturdy foundation for the solar panel system.
While it takes 2 to 5 kilowatts of solar energy per day to power a home, the system generates 1,018 kilowatts of solar energy per hour, Sidles said.
Miller Milling purchased SunPower’s latest technology, a system called Oasis 3, in which each solar panel is rated for 435 watts. Sidles explained that a tracking system, aided by sensors, helps move the panels throughout the day so they are always receiving a direct path of sun rays.
“It uses a DC (direct current) motor that is powered by the panels and tracks the sun from east to west during roughly a 12-hour period,” Sidles said.
When the sun sets, the solar panels return to their stowed, horizontal position parallel to the ground, and then move to an angle facing east toward the sun at sunrise, he said.
Sidles described the process as “harvesting the sun’s rays or photons and converting them into electrons, or electrical energy. When the sun hits the panel, protons are converted to electrons and direct current electricity that flows to the inverter; that’s when it is transformed into AC (alternating current) power.”
Total cost of the project was just under $2.5 million dollars, Sidles said.
“For the amount of money we put into this project, we wanted to make sure it was secure, so we added security cameras around the perimeter and also surround it with chain link fences with barbed wire around the top of it,” he added.
In addition to installing the equipment, SunPower provides data summarizing yearly, monthly, weekly and daily solar energy production as well as production trends over different periods of time. The software includes data kilowatts, which involves the rate of energy use, and kilowatt hours, which measures the total amount of energy used.
Sidles used an analogy to explain this concept.
“The kilowatts, in our case, are like a speedometer while kilowatt hours are like an odometer,” he said.
Sidles said in 2017 the Miller Milling facility in Fresno used about 12 million kilowatts of electrical energy. The solar energy system is rated at 2 million kilowatts per year, which means it is producing about one-sixth, or approximately 17%, of the plant’s energy.
Environmental impact
The environmental impact of drawing 17% of the mill’s power from the sun was significant, he said. The 2.14 megawatts of solar energy produced at the mill is the equivalent of:
- 318 passenger vehicles driven for one year
- 3.6 million miles driven by an average passenger vehicle
- 478 tons of waste recycled instead of being placed in a landfill
- 68 garbage trucks full of waste being recycled instead of put in landfills.
In terms of reducing carbon dioxide emissions, the solar energy system for the year offsets the equivalent of 170,000 gallons of gasoline consumed and 1.6 million pounds of coal burned.
Sidles said the only mill shutdown that was required during the installation of the solar energy system lasted for 8 to 9 hours.
“There was really very minimal downtime with this project,” he said.
During the mill’s regularly scheduled downtimes, such as on Easter Sunday when the facility underwent fumigation, Miller Milling sends generated solar power back to that grid and receives a credit.
Sidles said the solar panels, which must be cleaned periodically to ensure optimal performance, are under warranty for 25 years and at age 25 they are guaranteed to perform at 85% efficiency.
“Solar power is not perfect, but overall it provides a positive net impact for the environment and for our long-term financials,” Sidles said. “The energy required to create a solar panel will be recouped in 3 to 4 years. Even considering the manufacturing and processing stages of solar, the emissions generated are 3 to 10 times less than generating the same amount with fossil fuels. Naturally this will vary depending on the energy generation and solar irradiance at your location, but overall solar panels provide a positive net impact.”
About the mill
Miller Milling’s Fresno plant processes hard and durum wheat into tortilla flour, all-purpose flour, wheat tortilla and whole wheat all-purpose flour, semolina, durum flours, and whole wheat durum products.
The mill is strategically located in the heart of the San Joaquin Valley growing region, which is where most of its wheat is sourced. The facility has production capacity of 9,500 cwts of flour and wheat storage capacity of 3.3 million bushels.
“High quality winter wheat and durum varieties can be grown in California due to its climate and irrigation, so we can provide customers higher protein, higher absorption winter wheat at a competitive price,” the company said.
