Abstract
The energy consumption of sheep milk cooling systems (MCSs) was quantified in this study to provide original information filling a literature gap on the impact of sheep milk cooling on the energy and economic balance in dairy farms. Performance and energy monitoring tests were conducted simultaneously on 22 MCSs in Sardinia (Italy). The results determined the cooling time as a function of the performance class and number of milkings. The Energy Utilization Index (EUI) was applied to measure the energy required to cool down the milk and estimate the incidence on its price. The average EUI was 1.76 kWh 100 L−1 for two-milkings and 2.43 kWh 100 L−1 for four-milkings MCSs, whereas the CO2 emissions ranged from 998 to 1378 g CO2 100 L−1 for two- and four-milkings MCSs, respectively. The estimated energy consumption for the storage of refrigerated sheep milk was 0.12 kWh 100 L−1. The malfunctioning MCSs averagely consumed 31% more energy than regular systems. The energy cost for cooling accounted for 0.61% on the current sheep milk price in Italy. Based on the analysis, the reported EUI values can be used as a preliminary indicator of the regular operation of MCSs.
Highlights
The progress of dairy farming has been accompanied by increases in the energy demand and application of different energy sources that change depending on the structural characteristics of the farm [1]
The milk cooling systems (MCSs) sample showed a predominance of the BII class MCSs in Sardinia, which is positive in Mediterranean area, where the average ambient temperature rarely exceeds 32 ◦ C during the milking the Mediterranean area, where the average ambient temperature rarely exceeds 32 °C during the season and it is the best compromise between the need for a good cooling rate and the purchase cost, milking season and it is the best compromise between the need for a good cooling rate and the compared to the expensive I class MCSs
The results showed that the Energy Utilization Index (EUI) for sheep milk cooling was systematically higher than those for cow milk; while the average EUI under ST conditions (EUIS) for sheep milk was 1.76 kWh 100 L−1 for 2BII MCSs (Table 4), the cow milk cooling with the same performance class ranged from 0.90 to 1.10 kWh 100 L−1 [9,14], approximately 95% higher
Summary
The progress of dairy farming has been accompanied by increases in the energy demand and application of different energy sources that change depending on the structural characteristics of the farm [1]. Rationalizing energy consumption and applying renewable energy sources, especially in remote areas where grid power is not available, reduce farming costs and improve the competitiveness of dairy farms [2]. In dairy farms the largest impact is the milk cooling system (MCS), accounting for 31–43% of the total energy consumed in the milking parlour, followed by the electric boiler for hot water used for washing (23–27%), and the vacuum pump for milking (15–20%), whereas other users have less influence on the energy balance [4,5].
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