Water Heating

The cost of water heating in dairy operations can be reduced in many ways:

A refrigeration heat recovery (RHR) unit captures heat collected by the refrigeration system to pre-heat well water before it enters the water heater. This can provide up to 50 percent of the energy required for water heating. It is usually economical to install an RHR unit when and electric water heater is used. These units are available from all major brands of dairy equipment manufacturers.

Illustration3: Refrigeration heat recovery unit next to a water heater. source: Scott Sanford

Illustration3: Refrigeration heat recovery unit next to a water heater. Source: Scott Sanford

Water conservation is a low-cost way to reduce water heating expenses. For example, sometimes more water then necessary is used to wash milking systems. Having your dairy equipment dealer fine-tune your pipeline washing system can help reduce the amount of water needed to wash the milking system [7].

Using water directly from the refrigeration heat recovery unit in situations when warm water will do and the precise temperature is not critical is another way to reduce water heating costs. This avoids heating the water up only to dilute it with cold water.

Do your homework when choosing a new water heater. Their thermal efficiency, i.e. the percent of energy transferred to the water, varies greatly. Electric water heaters have a thermal efficiency of nearly 100 percent. Gas and oil water heaters have a thermal efficiency of about 80 percent unless they are of the condensing type, which have thermal efficiencies in the 95 percent range. Water heaters also differ widely in standby loss, which is an indication of how well insulated the tank is. Standby loss is the heat lost over time when the water sits unused in the tank. Electric water heaters are typically the best insulated, with standby losses of about 1 percent per hour and some as low as 0.5 percent per hour This would mean 12 to 24 percent daily standby heat loss. A typical gas or oil water heater can have a standby loss of 2.5 percent per hour, which equates to a daily loss of 60 percent. When shopping for a new water heater, the more insulation the better. The overall efficiency or energy factor of a water heater can range from 50 percent to 88 percent. [8]

Heat loss through pipe walls can be substantial depending on the length of run. Covering the pipes with foam pipe insulation will reduce heat loss and result in higher water temperatures at outlets. In new construction insulating all pipes both in walls and exposed pipes is highly recommend.

Solar water Heating – generally on dairy farms there is ample waste heat from the refrigeration system to replace at least 50% of the water heating needs using a refrigeration heat recovery unit. Solar water heating systems are efficiency at heating water from well water temperature up to about 120°F but then the efficiency decreases rapidly. The payback on solar water systems is typically longer than other energy efficiency options that a dairy could invest in so they are seldom the best investment for a dairy but often a good investment for a residential home.