Fonterra is a New Zealand-founded global dairy company with a global milk distribution of 22 billion litres of milk annually. The company’s site at Wagga Wagga is the Riverina’s only milk processor, with itsRiverina Fresh brand providing white and flavoured milk, yoghurt and dairy desserts.
Refrigeration: critical process
Many of the processes at the Wagga Wagga site require refrigeration. The refrigeration plant is responsible for most of the site’s energy consumption. Minus40 found opportunities for significant energy savings with this equipment through improved efficiency.
A study done by Minus40 in 2010-11 found that the existing refrigeration plant design was ad-hoc, consisting of an ammonia chiller, an R22 chiller and also multiple individual Freon circuits. Many opportunities for improvement were identified, but the R22 chiller was found to be the most energy-intensive component.
R22 Chiller Replacement
The Wagga Wagga site was scheduled for increased production, but the existing refrigeration plant did not have capacity to support the increase. A chiller upgrade was inevitable, so it provided a compelling opportunity for efficiency improvement as well as capacity increase.
The existing R22 chiller was required to act as an “ice bank” – a practice in which the chiller produces ice during periods of low load, so that it can use this stored energy during peak load. This is a particularly inefficient practice – it is preferable to operate a chiller with capacity for peak load.
Replacing the R22 chiller also presented an opportunity for a much better environmental outcome. R22 is a type of HCFC (Hydro-chlorofluorocarbon) which is a substance with powerful ozone-depleting characteristics. It also has an extremely high Global Warming Potential (GWP) of 1780, indicating that the global warming effect of R22 is 1780 times larger than that of carbon dioxide. These two properties of R22 refrigerant are the reason for its phase-out.
These considerations led to a solution with a new chiller run on ammonia. Although the unit is larger than the original unit, it is more efficient and has a far smaller environmental footprint.