Energy-saving mechanical systems are popping up everywhere — even cows are feeling the benefits. After decades of energy-saving applications for industrial openings and more recently for commercial building entrances such as hospitals, hotels and schools, air curtains now have been proven successful at preventing milking parlor equipment freeze-ups on dairy farms.

Milk productivity setbacks were frequent challenges from November through March during subfreezing days for Griesen’s Family Dairy located 60 miles northwest of Madison, WI, in Prairie du Sac, WI. The medium-sized, 680-cow farm suffered product losses and production delays from automatic milking equipment freeze-ups nearest the parlor entrances, and potential injury issues from slippery floors and poor indoor air comfort for employees.

Materials handling equipment dealer Bernie’s Equipment Co. recommended air curtains by Berner International to retain heat in the milking parlor.

On ambient temperature days above 32°F, the floor’s radiant system supplied by a 400,000-Btu, stainless steel, 95.1% efficient Munchkin boiler combined with each cow’s inherent 4,000-Btu/hr heat output, adequately maintains the milking parlor’s target temperature range of 38°F to 40°F. The heating system was adequate despite the fact co-owner Hans Griesen prefers the two 16-ft by 8-ft entryways to remain open through three daily shifts for optimum productivity and animal movement in and out of the 24-stall herringbone-style milking parlor. On subfreezing days, however, the heating system couldn’t maintain set point temperatures near the entryway.

Griesen first tried portable salamander forced-air heaters. The entrances were warmer. However, the $100 per day cost for fuel, kerosene emission odors, and potential fire hazard sent Griesen looking elsewhere. 

An employee dedicated to opening and closing the two doorways all day was considered cost prohibitive, even at minimum wage rates, according to Griesen.

Griesen also considered both strip curtains and air curtain technology so the entry doors could stay open. Strip curtains were too obstructive to the animals. His first review of an air curtain at a nearby farm wasn’t a positive experience, either. The farm used an inexpensive foreign air curtain brand with short lengths bolted in tandem to span the wide doorway. The air curtain was noisy, its modular construction vibrated, and it didn’t provide the proper volume, velocity, or uniformity of air stream to prevent outdoor air infiltration.

Finally, Clyde Conger, Bernie’s general sales manager, and Berner manufacturer’s representative, Tim Spreda, vice president-sales for MII Equipment, worked with factory sales engineers to specify two 16-ft long, one-piece air curtains from the Berner’s VSA model product line. The air curtains are mounted above the milking parlor’s open doorways and retain up to 80% of the facility’s energy even during wind loads of up to 5 mph. Each air curtain features a corrosion-resistant powder-coated finish, five high-efficiency 1/2-hp motors, and a welded aluminized steel frame that retains a strong structural integrity as they span across the opening. Consequently, there are no gaps in the 7,631-cfm, 1,635-fpm air stream it provides across the 16-ft-wide entryways.  

“Hans had already educated and sold himself on the air curtain concept before we got involved; therefore he knew exactly what he wanted and had designed the application in his head,” said Conger.

According to Griesen, some of the dairy workers had their doubts about the air curtains, but changed their tune.

“Some of our co-workers were skeptical as to whether air curtains would solve the problem, but they’re believers now since we haven’t had any more frozen equipment issues,” he said. “One employee took infrared color temperature readings and there was a big difference in temperature inside the doorway with the air curtains on and off.”

Air curtains consist of fan motors, blowers, nozzles and directional vanes, and a control package. When properly engineered for the proper horsepower, nozzle discharge and airstream angle, an air curtain essentially “seals” a doorway from outdoor elements, flying insects, and dust. The airstream must strategically “break” at the threshold of the doorway for ultimate performance. While air curtains are typically activated by a plunger switch after a door opens, the milking parlor air curtains are activated by a thermostat located near the entrance. Gas-fired hot water or steam, and electric heating coil options were considered, however Griesen felt the milking parlor’s heat radiant heat system was sufficient if cold air infiltration could be curtailed.

Although Griesen’s main concern was subfreezing air infiltration, the air curtains are also saving the facility energy because the radiant floor system’s boiler cycles on less to maintain the set point temperature.

The air curtains supplement the overall energy efficiency design and construction conception when the Griesen family relocated from the Netherlands to build the 40-acre farm from the ground-up in 2005. Other technologies on the farm include energy efficient metal halide fixtures with lamps, a VFD on the milking vacuum pump, four scroll compressors for milk refrigeration, and two heat exchangers by DeLaval/Germania for compressor heat recovery.

Griesen said all the efficiency equipment combined saves the farm an estimated $35,000 annually in energy costs.