Dairy farms today face challenges and opportunities fuelled by rapidly rising energy costs and concerns about environmental impacts. Dairy farms use more energy than almost any other agricultural operation.
Why be energy efficient?
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.
This is especially true for the south west, which is home to half a million dairy cows, and there is massive scope for the region’s dairy farmers to become more competitive and lower the overhead costs of the milking operation.
How can I save energy on my farm?
- Record the amount of electricity being used on the farm at regular intervals.
- Compare energy use of similar operations to your output and to previous consumption and investigate any large variations.
- Compare your tariff to other options and remember to look at the notice period required to terminate your current contract.
- Use cheaper night time electricity, especially for water heating.
- Insulate water heaters and pipework to minimise losing heat that you are paying for.
- Consider investigating in energy saving devices for example heat recovery devices, variable speed motors or a heat exchanger.
- Install a plate cooler if there is not one already present in the parlour set up.
- Switch off any equipment and lighting whenever possible and make all staff aware of efforts to save energy costs.
- If equipment is due to be replaced consider replacing it with energy efficient models.
- Consider using radiant heating rather than space heating systems.
Source: Dairy Co: Energy Efficiency on farm, The Carbon Trust: Agriculture and Horticulture, Energy Saving Opportunities for farmers and growers
Where can I save energy
Variable speed motors
These can have a range of applications, most commonly as vacuum pumps, but can also be applied to milk pumps irrigation, and ventilation systems.
Variable speed vacuum pumps
Current vacuum pumps operate at a constant speed to provide the vacuum requirements for milking. Variable speed vacuum pumps are designed to meet capacity required when it is needed.
The addition of a variable speed drive pump eliminates the need for a conventional regulator because less energy is delivered to the motor, and operating speeds are reduced.
By maintaining a constant vacuum level and only producing necessary amounts of air flow, energy cost savings of up to 60% can be made. The noise level is also greatly reduced allowing for a gentler parlour environment.
There are also reduced maintenance costs and less wear – leading to an extended life compared with a conventional oil vane pump.
Cooling milk accounts for the highest energy cost associated with the milking process. Milk needs to be cooled from its harvested temperature of 35-37°C to 3°C to maintain high milk quality and low bacterial counts. There are various options to help cool the milk, including heat exchangers and variable speed milk pumps.
These are used for pre-cooling raw milk – transferring the heat from the milk to an intermediary cooling fluid (usually water). Installing a heat exchanger to pre-cool milk prior to entry to the bulk tank can reduce energy consumption by 60%.
Variable speed milk pumps
The use of a variable speed milk pump allows the milk to be pumped through the plate cooler at a more consistent speed, allowing the plate coolers to operate more efficiently and resulting in greater milk cooling. It also allows more heat to be extracted by the plate cooler, and reduces the energy demand on the bulk tank. Milk can be cooled by an extra 15 – 20 degrees by installing a variable speed milk pump.
Heat recovery units
During the process of cooling milk, heat is rejected from the condenser coil of the refrigeration system. It is possible to recover this by passing the hot refrigeration gas through a heat exchanger which is immersed in water. Water temperatures of over 50 °C can be achieved by using this technique.
The water heating system needs to be carefully configured so that the heat recovery can deliver the maximum benefit without compromising the operation of the milk cooling system. Depending on the number of cows being milked, the water storage tank should be sized to provide enough hot water for one milking.