One
the main components of almost any commercial or
industrial mechanical system is the central air handling unit. The air
handling unit consists of a boxed frame, a motor driven fan and a refrigerant
or chilled water coil or multiple coils. Although one of the simplest pieces of
equipment in the mechanical system, it consumes the energy. An air handler
works by using a motor driven fan to force return or outside air across a coil,
resulting in cool air. Air handlers are controlled by the building automation
system or thermostat. As cool air is required, the motor kicks on and off to
meet the buildings demand. As in many cases, air handlers are oversized and have
tendency to cycle on and off the requiring much more power than necessary. To
offset the high demand for energy and the constant need for cooling
manufacturers have introduce energy recovery ventilators.
How
it Works
Energy
recovery ventilation works by mixing preconditioned exhaust or return air, with
incoming outside air. This is typically done through what's known as a heat
wheel. The preconditioned air and incoming air is separated into different
plenum spaces, that are connected through the heat wheel. As the wheel rotates,
it traps cooled preconditioned air and mixes with outside air, which in turn is
cooled and dehumidified. Since the air is preconditioned as it enters the air
handling unit the motor does not have to work as hard to meet the cooling
demand from the building occupants. This also prevents the motor from cycling
on and off because of the constant flow of cool air being received from the
energy recovery ventilator. The more cool air transferred to the outside or
return air, the more efficient the system becomes.
Conclusion
Energy
recovery ventilators are a common sight in almost any green building. With
these advances in technology and the necessity for more efficient mechanical
systems, the demand for high efficiency equipment is greater than ever. Energy
recovery ventilators seem to be here to stay, due to their proven performance, relatively
low cost and easy maintenance. It will be interesting to see what the
mechanical market will come up with next.
Energy Recovery Ventilators are certainly more efficient when it comes down to utility bills by providing a constant cycle of mixed air for the system. It would be beneficial to owners if a long-term breakdown was given by the contractor since installation and maintenance costs tend to be higher for these more complex units. ERV's seem to be the perfect fit for mild climates where there are no drastic changes in humidity and temperature. This week in Florida would cause the system to work harder with the low at 35 degrees Sunday and the high around 70 degrees Tuesday.
ReplyDeleteMany ventilation designs are including Energy Recovery Ventilators (ERVs) to improve the system efficiency. In addition to providing controlled ventilation, ERVs are able to filter, humidify, dehumidify, heat, or cool the incoming fresh air. The most common type of ERVs utilizes a desiccant wheel to remove both heat and a significant amount of moisture and hence it reduces the load on the air-conditioning system. It is interesting that in hot humid areas, ERVs job during the summer months is mostly removing moisture from than cooling the air. For example, in Raleigh a regular home with 80 cfm of ventilation air would require 5,760,000 BTUs to remove moisture from the incoming air stream, but only 864,000 BTUs to cool it. (87% of the energy used to condition the air is spent on dehumidification)
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