Lighting and ventilation should be prime targets for dairy producers looking to cut electrical use on their farms, a University of Wisconsin-Madison study has shown.

Farm energy use makes up a larger percentage of Wisconsin”s peak electrical load than its average electrical consumption. Results of this study point out the first places to look for energy savings on the farm, and also show how dairy farm electric load affects Wisconsin”s statewide electric demand and peak loads, according to Doug Reinemann and Ross Peebles of the Department of Biological Systems Engineering.

The researchers ran computer simulations for 30-, 60-, 200- and 400-cow dairy farms, looking at an efficient or inefficient system for each farm size. They calculated daily energy use for both January and July days to show seasonal effects. The simulations focused on the milking system”s vacuum pump, lighting, ventilation, and the chiller unit for the bulk tank. These are the biggest electricity users on Wisconsin”s 22,000 dairy farms.

The inefficient system included a direct expansion milk cooler, electric water heater, standard size vacuum pump, medium-efficiency fans, and incandescent lighting at 60 percent of recommended levels (to reflect lighting levels typically found on farms). The efficient system included heat recovery (and precooling on the two largest farms), an energy-conserving vacuum pump, high-efficiency fans, and fluorescent lighting at 100 percent of recommended levels.

Lighting and ventilation were potentially the largest energy users in the simulations, assuming that recommended levels are achieved. Current lighting and ventilation levels are well below suggested levels on many farms, Reinemann notes, and improvements in lighting and ventilation are common renovations on existing facilities.

For any size farm, changing to fluorescent lighting at 100 percent of recommended levels offered significant savings over incandescent lighting at 60 percent of recommended levels, according to Reinemann. “Efficient lighting offers large potential savings and should be installed whenever upgrading lighting or building new facilities,” he says. “Even if recommended illumination levels are not presently met in a facility, significant energy savings are still possible by replacing incandescent lighting with fluorescent lighting meeting suggested light levels.”

Ventilation is the largest electrical load on 30- and 60-cow farms. In recent years, mechanical ventilation in large freestall barns has become the largest peak energy user on dairy farms, Reinemann says. Switching to efficient fans can produce savings of 12 to 15 percent in both smaller barns and large freestall barns. Ventilation requirements are about the same for any given stall barn or parlor, regardless of the number of cows, Reinemann notes. Energy use per cow decreases as herd size increases, so fan energy use per cow on a 30-cow farm will be twice that of a 60-cow farm.

Savings from other improvements varied by farm size, the simulations showed.

On a 30-cow farm, changing the water-heating system to heat-recovery without precooling saved 4,900 kilowatt hours per year, cutting cooling costs in half and heating costs by 25 percent. Changing to an efficient lighting system saved 3,000 KwH/year.

On a 60-cow farm with a 2-inch milking pipeline, using heat recovery without precooling saved 7,800 KwH/hear on water heating. Lighting changes saved 5,800 KwH/year, and improvements in milk cooling saved 3,800 KwH/year.

For a 200-cow farm with a milking parlor, lighting improvements saved more than 43,000 KwH/year, since lighting was the largest single user of electricity. Improvements in milk cooling saved 12,000 KwH/year, and improvements in water heating and adjustable-speed vacuum pumps each saved more than 7,000 KwH/year.

Results were similar (and savings greater) on the 400-cow farm. Lighting improvements saved 81,000 KwH/year, milk cooling saved 23,500 KwH/year, and adjustable-speed vacuum pumps saved 17,000 KwH/year.

The maximum demand reduction ranged from 38 percent on the 30-cow farm to 58 percent on the 400-cow farm. Most of these energy-saving technologies should pay for themselves in two to three years, according to Reinemann.