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Cooler, more energy-efficient dairy cows possible through heat exchangers, finds report

POSTED September 27, 2011 9:58 p.m.

A new, energy-efficient technology to keep dairy cows cool in summer heat has real-world potential, according to a study funded by the Turlock Irrigation District.

Currently, cows are cooled through evaporation with high-speed, low-volume fans and water misters providing relief from the heat. But those fans take a lot of electricity to run – as much as 188,257 megawatt-hours in California each year – during times of peak electric demand.

That electricity doesn’t come cheap to California dairies, which spend nearly $17 million annually just on fan operation.

Instead, the new system, developed by Arizona-based AgriAire, looks to cool cows by piping naturally cold well water through heat exchangers installed under cows’ bedding areas.

“Using the cooling capacity of the normal operational water supply of the dairy, there is a large potential to reduce both electricity consumption and water usage by diverting a significant portion of the required animal cooling to a conduction method of cooling,” explained Jim Bruer, AgriAire general manager.

The technique is similar to one employed by dogs on warm days, which often gravitate toward colder tile floors. The cold floor acts like a radiator, absorbing heat from the animal’s body and reducing the animal’s temperature.

Proof of concept tests were successfully completed on the technology at the University of Arizona’s agricultural research center in June and July 2010, drawing the attention of the Turlock Irrigation District. In August 2010, the district contributed $49,000 in public benefit funds, specifically reserved for such energy-efficiency projects, to fund a larger-scale test run in Tulare.

The district’s interest in the project traces back to the preponderance of dairies in the TID service area. Nearly 25 percent of statewide milk production occurs locally, according to AgriAire.

The 30-day trial, spanning the month of September 2010, saw AgriAire convert 52 beds of a 202-cow pen to their conductive cooling technology. The dairy cows’ condition – temperature, milk output and general health – were then measured by University of California, Davis and University of Arizona scientists.

Over the trial, average temperatures were found to be identical between the AgriAire-cooled cows and the control group. Respiratory rates, milk production and white blood cell counts were found to be near-identical.

But in the last week of the trial, when temperatures climbed to the 100s, scientists noted that some of the conductively cooled cows showed greater signs of heat stress.

According to Bruer, the findings point to the possibility of a joint cooling solution, one which uses conductive cooling until the temperature reaches 90 degrees, then switches on fans and misters to aid in cooling.

A 3,600 cow dairy could save $26,000 of a $40,000 annual utility bill by turning on fans at 90 degrees rather than the industry-standard 75 degrees. Statewide, the practice could save nearly $13 million.

Cutting back on the use of misters would also save water – nearly 32 million gallons of a 3,600 cow dairy’s typical 42 million gallon usage. Statewide, 43,759 acre-feet of water could remain in the ground, providing a potential boon to valley cities’ groundwater-based drinking system.

But AgriAire believes their system can do better.

“We know we can do better,” Bruer said. “In fact, we did better.”

A 2011 test in Ohio illustrated some issues with the Tulare test. Due to the short-term test and quick installation, the system was piped into the existing mister water source, rather than installing dedicated underground, insulated piping from the well to the heat exchangers.

That lack of insulation saw water temperatures increase by 10 degrees, reducing the system’s effectiveness.

“That’s the big difference between installing it right and taking shortcuts,” Bruer said.

To contact Alex Cantatore, e-mail acantatore@turlockjournal.com or call 634-9141 ext. 2005.

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