Opportunities abound for dairy farm energy efficiency
By Andy Pressman
National Center for Appropriate Technology Agriculture Specialist
Dairy farms today face challenges and opportunities fueled by rapidly rising energy costs and concerns about environmental impacts. Dairy farms use more energy than almost any other agricultural operation. Energy is used in the milking process and for cooling and storing milk, heating water, lighting, and ventilation. Determining the best energy-efficiency and energy-management opportunities for dairy farms will help reduce energy costs, enhance environmental quality, and increase productivity and profitability.
Energy efficiency in the milking process
The vacuum pump operates during the milk harvest and equipment washing and can consume 20 percent to 25 percent of all electrical energy use on a dairy farm. Sizing the vacuum pump to meet the needs of the milking and washing system can reduce capital costs for equipment, reduce energy operating costs during the life cycle of the pump, and ensure that the pump is performing properly.
A variable-speed drive, also referred to as an adjustable-speed drive or variable-frequency drive, is an energy-efficient technology used for controlling the vacuum level on sliding-vane rotary pumps and rotary-lobe pumps. Energy operating costs of a vacuum system with a VSD can be reduced by up to 60 percent.
Milk cooling systems
Cooling milk accounts for most of the electrical energy consumption on a dairy farm. Heat exchangers cooled by well water, variable-speed drives on the milk pump, refrigeration heat-recovery units, and scroll compressors are all energy-conservation technologies that can reduce the energy consumed in the cooling system.
Installing a properly sized precooler can reduce refrigeration energy consumption by about 60 percent. A properly sized well-water heat exchanger can reduce milk temperatures to within 5 to 10 degrees of the groundwater temperature.
A refrigerant heat recovery unit can recover 20 to 60 percent of the energy that is removed from the milk cooling process. It is possible for RHR units and milk precoolers to interact and compete with each other, however. For maximum energy savings, an energy audit should be conducted to determine if one or both units would be optimal.
There are several ways to reduce the amount of energy used for heating water. Whether using a direct or indirect water heater, overall efficiency is determined by the combustion efficiency of the fuel source and the amount of heat loss from the storage tank, known as standby loss. A direct water heater combines the water storage tank and the heating element. The storage tank in an indirect water heater contains a heat exchanger that is connected to a separate boiler unit. Insulating the storage tank and connecting pipes can reduce standby losses for both types of water heaters. The sides and top of an electric water heater and the sides of gas and oil water heaters can be insulated.
Replacing inefficient light sources with an appropriate and higher-efficiency light can result in better task lighting with energy savings that continue over the life of the lamp. Energy conservation opportunities involve changing incandescent lamps to compact fluorescents, upgrading to smaller diameter and more efficient fluorescent lamps, and upgrading to HID lighting.
Proper ventilation is needed in dairy barns throughout the year to help maintain animal health and productivity, the barn’s structural integrity, milk quality, and a comfortable work environment for the laborers.
Dairy ventilation systems require routine maintenance to keep fans operating at high performance levels. Poorly maintained fans and obstruction to air inlets and fan outlets can reduce fan efficiency by as much as 40 to 50 percent. Cleaning fan parts, lubricating bearings and other moving parts, checking belt tension and alignment, and removing any obstructions will keep fans performing at peak efficiency and reduce energy costs.
To learn more about implementing efficiency improvements in your dairy farm, consult the ATTRA publication Dairy Farm Energy Efficiency at https://attra.ncat.org/attra-pub/summaries/summary.php?pub=198.