Building a green dairy on the prairie
Kim Ukura, Morris Sun Tribune
Later this spring, two new wind turbines and a new solar array will be installed at the West Central Research and Outreach Center (WCROC) in Morris, part of a project to develop a dairy system that collects more energy from renewable sources than it uses.
Brad Heins, assistant professor of dairy, estimated dairy operations are one of the highest energy consuming livestock systems. In addition to electricity to run milking equipment multiple times each day, energy is needed to heat water to clean the equipment, and to cool milk to safe temperatures for consumption.
At the WCROC, scientists and engineers have been looking at ways to retrofit the existing dairy operation to make it "net zero," combining energy efficiency measures and new sources of renewable energy from the wind and the sun.
"A lot of the things we're doing here you could do on a dairy, where you'd bring in these different renewable technologies and it would fit within the system — you wouldn't have to modify much at all," said Heins.
Setting baseline measurements
The project started with an energy audit, trying to determine what systems use the most energy, then finding ways to design usable systems that address those high-energy areas, said Mike Reese, renewable energy director at the WCROC.
The energy audit of the WCROC's milking parlor, responsible for milking around 240 cows each day, began in 2013 and was overseen by Renewable Energy Scientist Eric Buchanan.
"Coming at this as an engineer, I look at the whole thing," explained Buchanan. "There's a system, there are inputs, there are outputs, there are constraints — as Brad reminds me all the time, cows have to be milked twice per day, no exceptions."
The energy use data was collected by a series of sensors installed on equipment in the dairy. The sensors log data every 10 minutes from more than 30 different locations, providing millions of data points on energy use, Buchanan explained.
"I don't think people realize how much electricity different components of their system use," said Heins. "I think this will provide good data in terms of monitoring energy use or putting in some energy efficient upgrades."
The audit showed that the dairy was using a lot of hot water for cleaning milk lines and equipment, as well as a lot of electricity to run the equipment that milks the cows and chills the collected milk.
One of the first steps, even before developing a system that relies on renewable energy, is to reduce the amount of power being used by the system.
"The easiest energy to replace is the energy you don't use — you want to minimize your use as much as you can before you start throwing solar panels on the roof or putting up wind turbines," said Buchanan.
To save energy, the WCROC installed variable frequency drive motors in the milking parlor to milk the cows more efficiently. A variable system matches the motor system to the demand — in this case, the vacuum needed to milk the cows hooked into the parlor — and reduces the total electrical load.
Using the heat you have
Through the energy auditing process, scientists observed that the heat of the milk was essentially a waste product of the system that could be used to save energy in other areas.
The central component of the new net-zero dairy will be a heat pump designed to collect the heat from the cow's milk and store it in a 2,000 gallon thermal storage tank custom built by Custom Fabrication and Repair of Morris.
Water will also be heated using solar thermal collectors already built along the east side of the dairy barn, adding another source for preheated water. This reduces the amount of energy needed to warm the water to the necessary temperature.
They've also installed three heat exchangers — devices that transfer heat between a warm substance and a cold substance — that will be used to chill the milk and help move heat into and out of the thermal storage unit. From the storage unit, the water will flow through an electric, tankless water heater system to get up to the final temperature needed for cleaning.
"We're not intending to need to add much heat, because we'll have it pre-heated with this storage tank," said Buchanan.
One of the shifts in the dairy needed to make this milking system work is moving from a natural gas heating system to an electric heating system. The dairy building will continue to be heated by natural gas, for now, but they hope to eventually convert it to electric power as well, relying on solar and wind energy to provide power.
"This is the path to a net-zero milking parlor, which has been the goal of this project — convert all the non-electric loads to electricity, then add enough renewable energy to generate as much electricity as we're using," said Buchanan.
On-site renewable energy
The final piece of project is to generate electricity on site using a 50 kilowatt solar panel array and two small-scale, 10 kilowatt wind turbines funded through a $982,000 grant from the Xcel Energy Renewable Development Fund.
Previous work on the project was supported through grants from the University of Minnesota and the Minnesota Agricultural Research Response Fund and the Legislative-Citizen Commission on Minnesota Resources Environment and Natural Resources Trust Fund.
At 80 feet tall, the two turbines will be much smaller than the WCROC's existing 365 foot, 1,650 kilowatt turbines that can be seen almost anywhere in Morris. The design is also unique — they don't need a concrete foundation for construction. Instead, they use a ballast system so they can be raised and lowered easily for construction and maintenance, said Buchanan.
"I'm interested to see how it performs because it's the kind of thing that might be really great for farmers — it's a simple design, they can do the maintenance themselves, and the tower can be put up in a day," said Buchanan.
A key, however, is to make sure whatever energy system is put in place is consistent and reliable.
"Energy systems decades ago were designed to be very robust for farms — cows need to be milked, livestock need water, farmers need to be able to go out and do the work and have energy available. We can't just have these neat concepts, they need to be robust systems that farmers will be able to implement," said Reese.
Reese emphasized that the on-site electricity won't take the dairy "off the grid" — it will still be connected to electric systems for energy when needed.
"That's one of the challenges with renewables, wind doesn't always blow and it's not always sunny," said Reese. "We're working on (electricity) storage systems, but we're not at a point where you can be an island on your own."
The dairy project is part of the WCROC's overall mission to reduce the fossil energy consumption in production agriculture to reduce the carbon footprint of agriculture products through renewable energy systems and production of crops, cows and swine.
"Agriculture is a critical industry here in western Minnesota," said Reese. "If you look 10 to 20 years down the road at the risks and opportunities, renewable energy and energy efficiency is an opportunity but it's also a risk as the processors and retailers and consumers are demanding products that are grown more sustainably and using less energy."
For video and photos about the project, visit the Morris Sun Tribune site.