Capturing at least some of the heat from stale or “old” air being exhausted from poultry and hog barns is one more step in developing intensive livestock operations with net zero energy barns. The net zero term means a barn is producing as much energy as it is using.
Two poultry barns in Alberta, for example, have installed heat recovery systems that capture heat from air being exhausted from broiler and layer barns and use it to warm cold fresh air that’s being vented into the barn.
The heat recovery ventilators (HRV), used primarily in winter months, take some of the cold edge off the fresh incoming air, helping to reduce heating costs inside the barn. It’s not so dramatic as being able to feel hot air going out, and then being replaced inside the heat exchanger with hot fresh air coming in, but the system can warm up cold winter air by 15 to 20 degrees.
“It is just one aspect of the overall energy efficiency program,” says Kelly Lund, an agricultural research engineer with Alberta Agriculture in Edmonton. She’s working with two poultry producers to monitor the efficiency of the HRV systems that were recently installed in respective barns. Next year she is planning to expand the program further and monitor the energy efficiency when an HRV system is installed at a hog operation.
The Brant Hutterite Colony, about an hour south of Calgary, is one of the poultry operations that has installed the HRV system as it works toward having a Net Zero energy barn. When the Brant Colony built the new barn in 2015 it was designed with energy efficiency in mind, says Darrel Mandel, poultry manager.
The barn was outfitted with 100 solar panels on the roof to produce energy. Inside the barn some of the energy conservation measures included natural gas boilers for a hot water heating system — the boilers are 94 per cent energy efficient. The barn also has an energy efficient lighting system.
The HRV system replaces conventional ventilation that simply exhausted old or so-called dirty air out of the barn and drew in cold fresh air that would fan out along the ceiling of the barn before dropping down as it warmed.
With HRV system both the dirty air and new fresh air pass through a heat exchange system inside a chamber, that in the Brant farm case, is located on the outside of the barn. Air flow has to be properly controlled, says Lund. The dirty and fresh air are contained within their respective duct work and don’t mix. But the duct work has to be designed so heat from the dirty air can be transferred to fresh air without the two air streams mixing.
At the layer barn at the Brant Colony which houses about 15,000 birds in one large open concept design barn, the ambient temperature of the barn is kept at a constant 24 C. The HRV system is most useful in winter months, says Lund with optimum operation at temperatures above -20 C (if much colder then that condensation and freezing can be a problem inside the chamber). As the warm dirty air is drawn out of the barn and passes next to the cold air entering the barn the heat is transferred. “If the temperature of the outside air was about -15 C, for example,” says Lund. “The HRV unit is probably able to pre-heat the cold air to about +5 C or perhaps +10 C.” From the HRV chamber the warmed fresh air is carried into the barn through a large duct and distributed along the ceiling of the barn before dropping down and being warmed further.
Looking at return on investment, Lund says the capital cost of the HRV unit is quite high and as of early 2018 the cost of natural gas is relatively low — so it will take a while for the HRV to provide a payback. “Preliminary estimates on energy savings suggest at current costs it will take about 12 to 15 years to see a return on investment,” says Lund.