The Mahana Blue heat-pump type heat recovery system works by taking wasted heat from the refrigeration system and converting it to 85 degree hot water at a very low cost, typically 60% less than that used to heat the hot water electrically. In addition they improve the efficiency of the refrigeration unit and at times we can reduce the capacity of refrigeration due to this effect. In most cases we would recommend retaining the recommended capacity as this efficiency gain is only present when the hot water cylinders are not full plus there is the inevitability tightening of the milk cooling legislation.
While we have access to other systems, we have consistently recommended the Mahana Blue as they have been in service for about 10 years now and proven themselves in the industry whereas other systems have only recently been put on the market and the reliability and energy savings are unproven. The Mahana Blue is also manufactured by the same company as the majority of our refrigeration units and we can buy them as a tidy combination package.
The desuperheater is designed to heat hot water directly utilising a heat exchanger and typically will heat hot water to 40 to 45 degrees entering the hot water cylinders. Testing has shown this can save up to 30% on hot water heating costs although this is variable depending on milk collection times and 20 to 25% savings are more typical, with no tangible savings to the refrigeration running costs.
Generally we advise farms milking under 500 cows to install a desuperheater due to the lower capital cost and the larger farms to look at a Mahana Blue as the payback times are generally between 2 and 4 seasons depending on the hot water usage at the shed.
The most economical cow numbers are about 800 to 1000 as this will usually utilise the heatpump to its fullest potential.