Using energy-recovery systems to increase building efficiency
"Energy efficiency is one of the top concerns we hear about from new clients across different market sectors. Whether we’re working on a health care or an industrial project, maximizing efficiency is a big priority," said RTM Project Engineer Andrew McMahon. "As increasing utility costs are driving innovations within our industry, there are many opportunities to employ creative solutions in terms of energy recovery."
Well-designed heating, cooling and ventilation energy-recovery systems are able to maintain a building’s proper temperature and air quality while minimizing energy loss. The type of system to use varies depending on the application, but the most common is ventilation energy recovery.
Ventilation energy recovery
Ventilation energy recovery is used to transfer heat from a building’s relief or exhaust air stream to the make-up air (MUA) stream. Projects in buildings that operate 24/7 are typically the best applications for this type of energy recovery, as they are continuously exhausting conditioned air and drawing in untreated outdoor air.
In winter, when the outdoor air temperature is low—such as winters in Chicago—the building predominantly is in heating mode, and an absence of heat-recovery systems means energy will be spent to heat air that eventually will be ejected to the outdoor environment. An energy-recovery system in the form of a heat exchanger would transfer the heat energy from the outgoing exhaust air to the incoming fresh air. This increases the incoming air’s temperature, thereby reducing the amount of energy necessary to heat the air to a level required for thermal comfort. Depending on the energy-recovery system used, humidity also can be recovered from the exhaust air stream.
In summer, the exhaust air stream would be cooler than the incoming outdoor air stream, and the same principles would be used to reduce the temperature of the incoming air supply. This reduces the work required by the air handling unit (AHU) processing the air.
As noted by McMahon, energy efficiency is top-of-mind for customers, and as such, increasing energy efficiency is a proven area of expertise for RTM.
McMahon cited Chicago’s 351 W. Huron as a recent example. RTM provided mechanical, electrical, plumbing, and fire protection (MEP/FP) design for a new mid-rise condominium development. Since the building consists of residential units, the space requires around-the-clock ventilation. By adding a fixed-plate heat exchanger to the MUA unit to pressurize the structure, RTM’s design allowed for the recovery of heat being exhausted from the building to the incoming fresh air stream. This is an ideal application as the MUA is 100% fresh air, which means the temperature difference between the exhaust air stream and the incoming fresh air stream is at its maximum. The building also contains high-efficiency furnaces and condensing units to condition each of the living units.
While other forms of energy-recovery systems did not come into play during the 351 W. Huron design, additional types include:
VRF heat recovery
While using VRF (Variable Refrigerant Flow) systems with heat recovery, the systems are zoned in a way to recover heat. This is especially helpful when serving multiple zones with different occupancy types. For example, if a retail space and a residential space are served using the same system, it is possible that the retail space is in cooling mode when the residential space is in heating mode. The VRF system allows the heat to be transferred from one space to another.
Water-source heat pumps
Water-source heat pumps operate in a similar manner to VRF systems, except they use a water loop for both heat rejection and absorption with backup cooling towers and boilers. Varying load profiles allow the water loop to maintain certain temperatures, aiming to reduce the amount of input energy required from the boilers or the cooling tower.
-This article originally appeared on RTM. RTM is a CFE Media content partner.