Although the actions covered in this section require more extensive implementation efforts, they can dramatically increase the efficiency of your dairy farm without compromising speed or reliability. Ask your local utility’s representative for more information about initiating such projects.
Milk cooling is an energy hog in dairy facilities. There are a couple of high-efficiency refrigeration technologies that can reduce energy consumption.
Scroll compressors. Dairy farms have traditionally used reciprocating compressors for milk-cooling systems, but in the last 10 years, they have started to utilize scroll compressors, which can reduce compressor energy costs by as much as 20 percent when compared to traditional reciprocating compressors. In addition to being more energy efficient, scroll compressors are also quieter and produce less vibration because there are no valves and only one moving part.
Refrigeration heat-recovery systems. Heat-recovery systems reduce energy costs by recovering waste heat that typically gets discarded by the milk-cooling condenser units. The recovered heat is then used for preheating water that is used for washing milking equipment. As an added bonus, heat-recovery systems also increase the refrigerator's heat-exchanger efficiency because heat-transfer rates are higher between refrigerant and water than between refrigerant and air.
Water-cooled precoolers. Using well-water heat exchangers to precool milk before it enters the refrigerated milk tank can reduce milk-cooling costs by up to 60 percent because heat exchangers can drop the milk's temperature by as much as 30°F. To ensure that plate precoolers are performing at an optimal level, check that the well-water lines are sized correctly. In addition, if you already have a refrigeration heat-recovery system in place, check that a water-cooled plate cooler will not negate the cost benefits of the heat-recovery system (plate coolers will reduce the amount of heat generated by refrigerated milk tanks). When weighing the benefits of heat-recovery systems versus water-cooled plate coolers, it is best to conduct an energy audit to analyze the cost benefits. It is often more cost-effective to install a heat-recovery system, especially on farms with smaller refrigeration loads, because it is less expensive to cool milk than it is to heat water. However, in large farm applications (150 cows or more) where refrigeration loads are larger, it might be cost-effective to use a plate cooler in addition to a heat-recovery system.
Pumping systems consume almost a fifth of all the energy on dairy farms. When purchasing pumps, be sure to size them correctly—oversized pumps will result in increased energy consumption.
VSDs for pumps. Variable-speed drives (VSDs) use integrated controls and sensors to operate the drive at the lowest possible speed to perform the required job. The savings from VSDs add up quickly because the power needed to drive a pump is proportional to the cube of the motor speed. Depending on the size and operation of the farm, purchasing VSDs for vacuum pumps and milking pumps could prove to be economical, though smaller farms—those with fewer than eight hours of milking per day—may not be able to offset the capital costs of VSDs with energy savings. In most dairy farm applications, replacing constant-speed pumps with VSD pumps can reduce pumping energy consumption by half.
Heat-recovery systems. As mentioned above, an efficient way of heating water on dairy farms is by recovering heat energy from the refrigeration condenser units. Up to 50 percent of a farm's water heating requirements can be met through heat-recovery systems.
High-efficiency water heaters. The thermal efficiency of water heaters varies greatly depending on the water heater type. Though electric water heaters can operate at nearly 100 percent efficiency, oil and gas water heaters will typically have lower operating costs because the fuel costs less than electricity. Conventional oil and gas water heaters will have a thermal efficiency of about 80 percent. When looking to save energy in water heating, consider purchasing a high-efficiency condensing oil or gas water heater, which recover more of the heat from the combustion gases. Condensing water heaters have thermal efficiencies of more than 95 percent.
Supplying air to dairy cows at the right temperature and humidity can increase the productivity of the farm—heat stress can drop cows' milk production by 20 to 30 percent. In addition, because cows can get pneumonia in cold and humid environments, humidity sensors and controls should be installed that will turn fans on when humidity levels are high and temperatures drop below freezing.
High-efficiency fans. Ventilation energy costs on dairy farms are dependent on the efficiency of the fans. When looking for new fans, be sure to pay attention to the air-circulation system design, the blade design, and the level of efficiency. One solution is to use high-volume, low-speed fans, which provide widespread air movement but consume much less energy and produce less noise than high-speed fans.
Controls. For optimal ventilation, fans should be controlled by programmable thermostats. Install the thermostat in a location that will measure air temperature and be sure to clean the thermostat regularly to prevent dust buildup.
Energy-efficient lighting is a simple solution to reducing energy costs, especially when the technique of long-day lighting—in which lights are left on for 18 hours a day to increase milk production—is implemented.
Compact fluorescent lamps (CFLs). CFLs can replace incandescent lamps in many applications, reducing energy use by 75 percent—yielding savings of up to $20 per lamp per year—and increasing lamp lifetime by 6 to 10 times.
T8 fluorescent lamps. If your dairy farm uses T12 fluorescent lamps, relamping with modern, electronically ballasted T8 lamps can reduce your lighting energy consumption by 20 percent or more. These lamps should be enclosed in water-resistant fixtures. Adding specular reflectors, occupancy sensors, or timers can more than double the savings. Paybacks of one to three years are common. For more information, see our article on fluorescent lamps.
Pulse-start metal halide lamps. If your farm uses old probe-start metal halide lamps, replacing them with pulse-start metal halide lamps can cut energy use by at least 10 percent. In addition, the lamps will last longer, maintain their light output at higher levels, and start up more quickly.
Outdoor yard lights. When selecting outdoor lights, consider fluorescent lamps, low-wattage metal halide (MH) or high-pressure sodium (HPS) lamps rather than mercury vapor lamps. These lamps are far more efficient than mercury vapor lamps, which have effectively been banned by recent federal legislation. MH lamps are less efficient than HPS lamps in conventional terms, but MH lamps put out more light in the blue part of the spectrum, which is easier for our eyes to see under low-light conditions. This allows for the use of a lower-wattage MH lamp. Fluorescent lamps can be used outdoors as long as their ballasts are rated for cold-weather starting.
Photocells and timers. Install photocells or timers on outdoor lighting. A photocell control will turn on a light at dusk and turn the light off when the photocell detects daylight. Newer photocells are able to dim lights or turn them off in the middle of the night if they are no longer needed. For more information, see our article on lighting controls.
Anaerobic digestion is a solution to managing agricultural waste from cows that can also reduce energy costs. In addition to providing a treatment route for manure with fertilizer as an end product, running a generator off the produced biogas brings in revenue for the farm. Estimates show that dairy anaerobic digesters could produce between 4 and 5 kWh per cow per day. With concentrations of more than 100,000 cows at some operations, the potential energy resource is huge. For more information on anaerobic digestion, refer to the U.S. Environmental Protection Agency's Guide to Anaerobic Digesters or the fact sheet, Anaerobic Digester—Controlled Temperature (PDF), created by the Natural Resources Conservation Service.