Scott Birchall, Dairying for Tomorrow Coordinator, Murray Dairy
Murray Dairy, DEPI and the North East Regional Network held, two 'Watts in the dairy' field days in early May. The aim was to give farmers strategies to reduce their dairy plant's energy consumption and prioritise suitable energy saving technologies when considering future dairy equipment purchases.
Attendees were given excellent material by one of Victoria's most experienced practitioners, Gabriel Hakim from AgVet projects.
Gabriel set the scene with some general energy saving tips to ensure participants were getting the best performance from their equipment. He pointed out the bulk of electricity use is from cooling milk and heating water, so the bulk of efforts to improve efficiency should be concentrated in these areas. Plate coolers should be able to achieve a milk-out temperature within two to three degrees Celsius of the water supplied to it. If the gap is bigger, farmers need to investigate why. Start with the following questions:
- Is the flow rate for the water supplied at two to three times the maximum milk flow?
- Have the plates been cleaned to remove any build-up that might reduce heat exchange?
- Is the flow of milk and water going in the opposite direction, as it is designed to?
Using the coolest water available to supply the plate cooler is a key factor in reducing the load on the vat's refrigeration system.
Participants were reminded the heat removed from the milk by the refrigeration system can be recovered and used to pre-heat water for the hot water system. Commercial heat recovery units are available but a technician should investigate individual's specific situations before a purchase is made. Larger cow dairies have a higher potential to reclaim heat.
Gabriel then talked us through the energy assessment completed on each host farm. Energy assessments start with an audit of the plant's various electrical components and matches the expected power use to the previous year's energy bills.
David and Maree Colbert's 200 cow dairy near Corryong had an energy assessment. Typically, a third of a dairy's energy use is from milk cooling with another third from heating water. In the Colbert's case, 60 per cent was attributed to milk cooling. Among many of the assessment's findings was that the milk is leaving the plate cooler at 23 degrees whereas the water entering is 17 degrees. This six degree difference is higher than the target of two degrees. The temperature difference is easy to measure by applying strip thermometers to the water inlet pipe and to the milk outlet pipe. Gabriel suggests fixing this could potentially save the Colberts $685 a year. Fixing this problem will include inspecting the plates to determine if cleaning is required, and to check the water's flow rate is at least two times the peak milk's flow rate.
Another key finding in the water heating area could save $171 a year. The current solar system should be able to heat water to an average of 50 degrees but it is only reaching 45 degrees. This could be improved through regular cleaning and re-orientating for winter and summer sun angles. The water temperature for vat washing was set too high and could be reduced to below 70 degrees, a common problem on many farms and a waste of energy.
It was estimated $855 a year could be saved in this dairy without upgrading or installing new equipment.
Gabriel also completed an energy assessment on Bruce and Jane McNaughton's 250 cow dairy at Kergunyah South. In contrast to the Colbert's the McNaughton's heating water comprised 58 per cent of the energy consumption. The main reason is an LPG gas boost system is used to heat the water. Unfortunately the system on this farm is very energy inefficient. Almost half the energy of the gas purchased is lost through inefficiencies which means the cost of heating water is almost double that of an efficient water heating system. There is a solar system but it is suspected it is not operating properly. If this is rectified, this could amount to a saving of $2,900 a year.
The plate cooler at the McNaughton's also had a difference greater than two degrees between water in and milk out temperatures and this should be examined.
Some of the savings may not seem large in comparison to other farm expenditure, but often the suggestions are free, easy to undertake, and could still amount to saving thousands of dollars a year. It is not expected farmers should race out and buy new water heating units. However, farmers whose systems may be nearing the end of their life could do research to ensure on more efficient models. That way, when the item fails, farmers won't make a rushed decision and buy another inefficient model.
Gabriel also raised the common practice of pre-rinsing with cold water. Milk at body temperature (~38oC) moves freely but when cooled tends to be more "sticky" requiring more cleaning effort. Using warm (38oC) water as a pre-rinse does a better job and helps keep the plant warm for the next cycle. Having a warm plant at the start of the wash cycle means less energy (that's in the hot wash solution) is used to heat the plant and more is used to do the cleaning; again resulting in a better job.
Everyone attending the field day went home with a pair of adhesive strip thermometers and instructions on how to fix them on their plate coolers as their first step on the path to reducing their energy bills. Anyone who would like an information pack, including a pair of strip thermometers, is encouraged to call Murray Dairy on (03) 5833 5312.
These events were sponsored by the Future Ready Dairy Systems project with funding from the Australian Government's Climate Change Research Program and Dairy Australia.