Dairy farms consume a surprising amount of energy. Electricity is needed to run milking machines, to heat water to clean the equipment and to cool milk to safe temperatures for storage and consumption.
The West Central Research and Outreach Center in Morris, Minn., is developing a dairy system that collects more energy from renewable sources than it uses. The key components: two wind turbines, a solar thermal array, a heat pump, three heat exchangers and a 2,000-gallon water tank. The Morris Sun Tribune describes the system:
"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."
In an interview with Phase Change Matters, renewable energy scientist Eric Buchanan shared more details on the tank: "The tank is partitioned into three sections in such a way to promote temperature stratification. The inlets and outlets on the cold and hot sides of the tank also incorporate radial diffusers designed to slow the flow and minimize vertical mixing. The tank will be insulated with spray foam to about R-80."