Is your farm energy-efficient? How can you tell? If you add up all of your electricity use for a year that is used for milk harvesting or cow housing and divide by the number of milking cows, you will likely be in the range of 800 to 1,200 kilowatt-hours per cow per year.

If you are less than 800 kilowatt-hours per cow per year, you can stop reading because you are already very energy-efficient – congratulations.

For everyone else, we have some work to do and investments to make. Making your dairy an energy-efficient dairy is not a mystery and has a good return on investment. So where do we start? To answer that, we want to identify the largest energy uses.

Based on a survey of 32 farms in New York state, 13 percent of the energy is for vacuum pumps, 17 percent for ventilation, 18 percent for lighting, 19 percent for milk cooling, 6 percent for feeding, manure handling and miscellaneous – and the biggest energy user: water heating at 27 percent.

The percentage distribution didn’t vary much between tiestall and freestall farms. So let’s start with the largest energy usage and see what can be done to reduce energy use without adding to management time.

Hot water

The energy needed for heating water can usually be reduced by 50 percent with the use of a refrigeration heat recovery (RHR) unit. This equipment is basically a heat exchanger that transfers some of the heat from the bulk tank cooling system refrigerant into water. A RHR unit is installed in series with a hot water heater so the water is pre-heated before it enters the water heater.

One RHR unit can usually accommodate two refrigeration compressors. Large farms may benefit by having multiple RHR units depending on the amount of hot water required. These units will typically pay for themselves based on energy savings in three to five years and have a life of 10 to 20 years if they are flushed on a monthly basis.

Another way to save on water heating costs is to not heat it. For non-critical uses, water could be used directly from the RHR unit or cold water used instead. Often clean-in-place systems for cleaning milk lines are improperly set up and use more water than necessary. Having your dairy equipment dealer tune your clean-in-place system may reduce water use.

Reducing water temperature will also reduce costs. Cleaning the milk lines is typically the most critical task. At the end of washing, the temperature should be no lower than 120ºF. If it is higher, you may be able to reduce the temperature some.

Milk cooling

The energy for cooling milk can be reduced first by properly maintaining your equipment. The condenser unit (the fan and heat exchanger that dissipates the reject heat to the air) should be installed where it has free flow of air to it. It should also be cleaned once or twice a year.

Dust and other debris will accumulate on the surface of the heat exchanger and on the aluminum fins and reduce the ability of the heat exchanger to transfer heat. Cleaning will take about 20 to 30 minutes but saves 3 to 5 percent in energy costs.

Do not use a power sprayer to clean a condenser, as it will force dirt between the fins and copper tubing, reducing the heat transfer ability of the condenser. Purchase a condenser-coil cleaning product and read the directions. Only use condenser cleaners as they are formulated to not corrode the aluminum and copper press-fit connection important for proper heat transfer.

Cleaners are available as a concentrate or in an aerosol spray can. Make sure to shut off the power before cleaning.

If your farm is milking more than 100 cows, and you have an adequate water supply, then a well water-cooled heat exchanger or pre-cooler can reduce refrigeration requirements. The pre-cooler must be sized to the milk pump flow rate (typically 30 to 40 gallons per minute) and will typically require a 2-to-1 or 3-to-1 water-to-milk flow ratio in order to achieve the published cooling rates.

If properly sized, the milk can be cooled to an average of 3 to 4ºF above the well water temperature. If the water flow isn’t adequate to achieve a 2-to-1 or 3-to-1 ratio, a variable-speed milk pump controller can be used to “meter” the milk through the pre-cooler, so a higher water-to-milk flow is achieved. Savings of 40 to 60 percent on refrigeration energy use are typical with a properly sized and installed pre-cooler.

Ventilation

Fans are often a necessity to provide cooling or maintain air quality. If you are purchasing new fans, refer to the University of Illinois – BESS Lab fan database (bess.illinois.edu) to see how the fan you are thinking of buying stacks up to the competition. Ventilation fans (those evacuating air from a building) are rated in cubic feet per minute of air moved per watt of energy expended (cfm per watt).

The higher the number, the more energy-efficient the fan is. For 36-inch and larger fans, the recommended minimum efficiency is 20 cfm per watt at a static pressure of 0.05 inches of water. Circulating or mixing fans use a different rating system – thrust efficiency ratio – pounds force per kilowatt (1.34 horsepower = 1 kilowatt).

The amount of air a fan moves is proportional to the force a fan exerts. A higher ratio indicates a more energy-efficient fan. Larger fans are usually more efficient for both ventilation and circulating fans.

A large portion of a fan’s efficiency is due to the motor’s efficiency. If you are replacing a fan motor, make sure you are replacing it with a motor of equal or higher efficiency. High-efficiency motors cost more but, remember, the motor cost is only 10 percent of the lifetime cost; the rest is electricity.

Vacuum pumps

Variable-speed vacuum pumps can typically save 50 to 65 percent in energy costs over constant-speed vacuum pumps. They are typically economical when milking six to eight hours per day or more. The payback will vary with the motor size and the number of hours of use.

Variable-speed drives are best used on blower-type vacuum pumps. They can be used on rotary vane pumps but cannot be slowed down as much due to the centrifugal force required to keep the vanes in contact with the pump housing – and therefore result in a lower amount of savings.

Lighting

Lighting is low-hanging fruit because the return on investment is often less than two years. If you are still using incandescent bulbs, you are basically doing the equivalent of hand milking.

Lighting technology has made great strides in the last 10 years, with new lamps being more efficient, having longer lamp life and excellent light quality: “more for less money.” It’s possible to save 50 to 80 percent on lighting energy costs. It is recommended you switch to light-emitting diode lamps.

They don’t contain mercury, are up to six times (600 percent) more energy-efficient than incandescent bulbs and last 25 times longer or more.

You may not be able to make all the energy efficiency investment at once, so make a plan so you can boast being an energy-efficient dairy. There are incentives in many states and federal incentives to help defray the cost for installing high-efficiency appliances. You can find what incentives are available in your area online (Policies and Incentives by State).  

Scott Sanford is a distinguish outreach specialist for the Rural Energy Program in the department of biological systems engineering, University of Wisconsin – Madison.