Water Heating Case studies

The following case studies show the hot water savings that could be achieved by installing either a de-superheater or a Mahana Blue™ heat recovery system. The table uses the input data from three different-sized dairy farms audited by Genesis Energy.

Farm Description Small Medium Large
Location Taranaki Taranaki Manawatu
Number of cows 170 480 1,000
Shed type Herring Bone Rotary Rotary
Milking days per year 290 290 290
Time for morning milk (minutes) 150 240 270
Time for evening milk (minutes) 120 210 210
 
Hot Water Inputs
Equipment wash hot water volume (litres/wash) 240 500 800
Number of equipment washes per week 7 8 8
Vat wash hot water volume (litres/wash) 240 500 400
Number of vat washes per week 7 3.5 7
Hot water temperature (°C) 85 85 90
Average water supply temperature to cylinders (°C) 16 17 16
Refrigerant in milk chiller R12 R22 R22
Output water temperature from pre-cooler (°C) 22 22 22
Milk cooling refrigeration motor size (KW) 2 3 8
 
Hot Water Requirements
Litres per year 139,200 238,214 381,143
Electricity used to heat water (kWh) 12,825 21,630 37,661
Electricity cost to heat water ($) $1,599 $3,872 $3,201
 
De-superheater - Dairy Technology Services Ltd
Installed cost $2,400 $2,100 $2,100
Reduction in cost per year $166 $1,239 $1,216
Simple payback (years) 14.4 1.7 1.7
Electricity Usage Savings (%) 10% 32% 38%
 
Mahana Blue™
Installed cost $8,200 $8,200 $8,200
Reduction in cost per year $831 $2,185 $1,280
Simple payback (years) 9.9 3.8 6.4
Electricity Usage Savings (%) 52% 56% 40%

To estimate your own hot water energy savings and to evaluate which heat recovery system is most appropriate for your farm, complete the water-heating section of our Dairy Efficiency Calculator.

Genesis Energy trialed a Mahana Blue™ on a medium and large farm and a de-superheater on a small farm. The other results are based on theoretical calculations and estimates of installed costs. The installed costs for the Mahana Blue™ can vary between farms and the cost will vary depending on your farm size. To compare suitable products for your farm, validate your estimated savings or obtain a firm quote contact the product suppliers.