Milk cooling costs energy. The energy consumption is expressed in kWh per 1000 kg of milk. During milk cooling there are two ways energy can be saved:
- 1. By reducing the required energy for cooling by pre-cooling of the milk.
- 2. By a recovery of the heat energy of the milk.
The amount of energy needed for this depends on the available equipment. Standard values for consumption are:
|Type of cooling:||kWh|
|Standard milk cooling||13 - 15|
|Milk cooling with pre-cooling||8 - 9|
|Milk cooling with heat recovery||16 - 17|
|Milk cooling with pre-cooling and heat recovery||10 - 11|
Pre-cooling of milk can, depending on the situation, save you money. When using tap water at a ratio of 2 litres of water to 1 litre of milk, about 40% energy can be saved with a pre-cooler, using well water as much as 50% can be saved.The water used for pre-cooling water can be used as rinse water for the milking parlour or as drinking water for cows. Another advantage of a pre-cooler is that the cooling unit requires less power and can be chosen smaller. This reduces the investment, the energy consumption and so the peak load.
When using a pre-cooler, a water valve should be installed, that only allows through water when the milk pump is running. So unnecessary water consumption is avoided. It is recommended that the valve after switching off the milk pump, remains open shortly (eg by a timer), so that the standing milk in the pre-cooler is cooled. In order to avoid unnecessary cooling of the cleaning water, no water should be in the pre-cooler during cleaning of the milk discharge line.
The pre-cooler is installed between the milk pump and the cooling tank. The pre-cooler exists depending on size of 31-55 plates and is made from high quality stainless steel. The plate cooler is available for a milk flow of 1900-3650 litres per hour and requires about twice amount of cooling water. The water supply can be controlled by a milk pump switched by a solenoid valve.
At a water temperature of 10-15° C, the milk temperature can be cooled from 35° C to about 20° C. The thus heated cooling water can be used for example as cattle drinking or cleaning water.
An investment in heat recovery can save a lot of money, depending on the situation.
With a heat recovery, energy costs can be saved and the environment can be protected. The heat generated at the cooling unit can be used to heat water. This water can be used not only for the udder cleaning, milking and cooling tank cleaning, but also as drinking water for cows and calves.
The systems are available in different sizes and types, starting from 100 litres. The hot water amount and the size of the recovery depends basically on the amount of milk. From 100 litres of milk to be cooled from about 35° C to about 4° C about 70 litres of water can be heated from about 12° C to 55° C.