Water Heating – is typically the largest energy use on a dairy farm. The cost of water heating can be reduced in many ways.
- A refrigeration heat recovery (RHR) unit will capture reject heat from the refrigeration system to pre-heat the well water before it enters the water heater. Up to 50% of the energy required for water heating can be recovered from the heat rejected by the refrigeration system. It is usually economical to install a RHR unit when water is heated with an electric energy source. These units are available from all major brands of dairy equipment manufacturers.
- Refer to UW Extension bulletin A3784-04: “Energy Conservation in Agriculture: Refrigeration Systems“.
- Natural gas, LP gas or heating oil may be a more cost effective energy source for heating hot water because they are usually a lower cost energy source. Often, the cost of replacing an electric water heater with a gas water heater will payback in a few years.
- Water conservation is low cost way to reduce water heating costs. This might include having your dairy equipment dealer tune your pipeline washing system to reduce the amount of water needed to wash the milking system. Often too much water is being used to wash milking systems because of poor adjustment.
- Refer to the UW Milking Research and Instruction Lab website for more information (http://www.uwex.edu/uwmril/milking_machine/cleaning.htm)
- Another way to reduce water heating costs is to use water directly from the refrigeration heat recovery unit when warm will do and the precise temperature is not critical. That avoids heating the water up only to dilute it with cold water for cleaning equipment
- Purchasing a water heater? The energy efficiency of water heaters very greatly. An electric water heater converts electricity into water at nearly 100% while gas and oil water heaters have a thermal efficiency of about 80% unless they are of the condensing type which has thermal efficiency in the 95% range. This is the percent of energy that is transferred to the water. Where water heaters differ widely is the standby losses which is an indication of how well insulated the tank is. Electric water heaters are typically insulated the best with standby losses of less than 1% per hour with some water heaters as low as 0.5% hourly losses. This would add up to between 12 and 24% daily standby heat losses. A typical gas or oil water heater can have standby losses of 2.5% per hour which equates to a daily loss of 60%. When shopping for a new water heater, the more insulation the better. Ratings for water heaters are available at the Air-Conditioning, Heating and Refrigeration Institute (AHRI) website (www.ahridirectory.org). Water heaters can be found under both the residential and commercial headings. Dairies should be using commercial water heaters because of temperature limitations of residential water heaters.
- Refer to UW Extension bulletin A3784-02: “Energy Conservation in Agriculture: Water Heating on Dairy Farms“.
If you have questions about the information on this site, please contact
Scott Sanford, Distinguished Outreach Specialist, University of Wisconsin, email@example.com.