Case Study #4: Energy Efficiency for a Poultry Barn—Winter Heating
A farmer near Danville is contemplating improving the energy efficiency of her poultry barn so that her winter heating bills are not so high.
Her main concern is the heating required when the chicks are 1 day old to two weeks old. During this time, she tries to maintain the barn at an average temperature of 85 F (when they are 1 day old it is 90 F, but as they grow older she lowers the temperature to 75 F). This two week critical period is one-third of the 6 week rearing cycle.
During the other 4 weeks of the rearing cycle, her heating requirements are very low because the 20,000 birds in the barn generate so much body heat. A chick might generate 4 Watts of heat and a 4 week old bird might generate 11 Watts of heat (including the latent heat of the exhaled moisture).
During the coldest times of the year, 8000 CFM of ventilation is required; this ventilation rate is much lower than that required for larger birds during warmer weather.
Her barn is 500 feet long by 40 feet wide by 10 feet high. It is oriented with the long wall running east west. It has a dirt floor with a 2 foot high cinder block footing wall supporting the wall. It has a flat drop-down ceiling. The lighting generates 0.036 W of heat for every square foot of floor area and is on 24 hours per day for the chicks.
The efficiency measures she is contemplating are the following:
|Base Case||Proposed Case||Cost of measure|
|Wall insulation||R 1.5 (1.5 ft2-F/(BTU/h))||R 10||$1 per ft2 of wall|
|Ceiling insulation||R 3||R 15||$6000|
|Footing wall insulation||R 2||R 5||$5000|
|Reduced air infiltration||1.2 air changes/hour||0.3 ac/h||$10,000|
|Ventilation heat recovery||0 %||40%||$6000|
The barn is heated with a fairly new, 70% efficient propane system. Propane costs around $1.50 per gallon on average. Normally the farmer has to turn on heating for the chicks whenever the outside air temperature is below 55 F.
The farmer would like to achieve a 2 year simple payback, but also achieve a good profit over the next ten years.
1) Which of these measures would you recommend that the farmer implement?
2) If you have time, examine how much additional savings would accrue to these measures during the period when the chickens are 2 to 4 weeks old and the barn need only be maintained at 72 F.
- The chickens are an important source of heat, but RETScreen doesn’t have a line for the heat generated by occupants. Include them as an “Other” load, treating them as an electric load with impacts on space heating. Make sure that the price of electricity is 0.
- You can include each efficiency measure in a separate form. This allows you to see the influence of each.
- Since the chicks need heat only during 2 weeks of the 6 week rearing cycling, you will have to multiply fuel costs in the base case and the proposed case by 1/3.
- Check all unit switches! Make sure you have used R-values and not U-values.
- The figures on the right hand side of the facility characteristics can be confusing, so it may be easier to look at the “Summary” data. But make use of the check boxes to indicate which measures to include the proposed case (when unchecked, the base case is assumed).