Optimizing Heating Costs in Grower-Finisher

by 5m Editor
26 November 2004, at 12:00am

By S.P. Lemay and L. Chénard and published by the Prairie Swine Center - Livestock production under cold climate requires control systems that provide a healthy environment for animals and workers without wasting energy. Most of the control systems that have been and are being used in swine facilities are controlled by temperature, relying on a constant minimum ventilation rate (MVR) for relative humidity (RH) and contaminant control during the cold season.

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In winter, heating costs are directly related to the room temperature setpoint, the weather conditions and the MVR setting. Based on the current knowledge, 25 kg pigs will be comfortable at an ambient temperature of 21 to 22°C and the temperature setpoint can be reduced to 15°C when they reach 75 kg. Some producers will maintain a higher temperature setpoint throughout the whole growing cycle (ex: from 22-24°C to 18-19°C for the same weight range) which will increase heating costs. The MVR must be determined according to building characteristics, local weather conditions and the growth stage of animals in the barn. An underestimated MVR will result in high RH and contaminant concentrations while an overestimated MVR results in higher energy costs for ventilation and supplemental heating.

A computer program has been developed to simulate the impact of the temperature setpoint and the MVR on building heating costs according to weather conditions. Calculations have been made for two temperature setpoint curves (a warm setpoint [WS, 24°C at 25 kg reduced to 18°C when pigs are 75 kg and heavier] and a cool setpoint [CS, 22°C at 25 kg reduced to 15°C when pigs are 75 kg and heavier], two settings of the MVR (winter design settings for RH control, 20% above winter design settings) and two locations (Winnipeg and Montréal).

Table 1 shows that maintaining a WS will cost $0.40 to $0.48/pig sold more than when a CS is followed. Making a 20% overestimation on the MVR required for RH control will increase heating costs by a factor of 2 or 3 depending on the temperature setpoint and the location. Such a mistake in MVR setting can be easily done in practice and would increase the cost difference between a WS and a CS.

To optimize building heating costs, it is critical to maintain a temperature setpoint that is ensuring the well-being of the pig without being to high. The MVR should also be set to keep RH between 70 and 75% and adequate contaminant concentrations. A too high temperature setpoint or MVR will increase heating costs without improving pig performance.

Table 1. Heating cost for a grower-finisher room depending on temperature setpoint, the minimum ventilation rate and the location.
Heating Cost ($/pig sold)
Minimum Ventilation Setting Montreal Winnipeg
*WS *CS *Diff SW CS Diff
Winter design setting for RH control 0.65 0.25 0.40 1.09 0.62 0.48
20% above winter design settings 1.63 0.83 0.81 2.08 1.37 0.72
*WS warm setpoint; CS cool setpoint; Diff.: cost difference between Ws and CS

Source: Prairie Swine Centre - October 2004
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