For cooling, the award was given for the Danfoss ApexxTM VSH compressor, the first high-capacity (12 to 40 TR) R-410A variable speed scroll compressor for air conditioning and heat pumps. The Apexx solution offers continuous matching of cooling capacity to cooling load, resulting in high energy efficiency and enhanced cooling comfort. In each application range, a high efficiency scroll compressor and a variable speed drive are designed specifically for operation with each other and optimized for efficient performance.
“The Apexx solution results in significantly higher energy efficiency because the entire evaporator is used, even at the part load conditions that exist most of the time in air conditioning applications,” said Mogens H. Rasmussen, business development manager for the Apexx VSH project. “High isentropic efficiency is maintained throughout the speed range. At lower speeds, below 50 Hz, oil injection to the scroll eliminates both leakage and high discharge temperature. Comfort is enhanced in two ways: First, because Apexx capacity always matches the cooling demand, tighter temperature control is possible; also, new controlling strategies for dehumidification are made feasible,” Rasmussen continued.
The AKD 102 Variable Frequency Drive series, which took the Innovation Award for Refrigeration, also matches capacity to load, but is specifically designed for supermarket applications.
In response to continual load determination computed by its internal electronics, the AKC drive is used to vary the speed of a compressor, condenser fan motor, or HVAC fan motor. In all three applications, operating efficiencies and significant energy savings result, as well as improved motor life and reduced maintenance cost.
A welcome feature for the installer and service technician is the ease of setup of these drives. Refrigeration terminology is used, rather than electronic and computer terms that would likely be unfamiliar to the technician. David Hebel, business development manager for supermarket electronics, said, “The AKD 102 speaks in the supermarket technician’s language; it was designed at every step to make installation, commissioning, and service a comfortable, efficient, and straightforward procedure.” The drive also has a setup “Wizard” to guide the technician through setup and common tasks.
With compressors, when networked to a Danfoss AK-SC 255 rack controller, an AKD drive can act to offer a virtually infinite range of capacities from a properly sized rack that includes one inverter-rated compressor. This means that rack capacity can be controlled to exactly match the load on the refrigeration system with considerably less on-off cycling of compressors. Without the use of a variable frequency drive, the only way to vary the rack’s capacity is to turn compressors on in different combinations, and each time a compressor is turned on, considerable energy is expended in inrush current to overcome inertia and bring the motor up to speed. With the AKD drive installed on one of the rack’s compressors, the speed variation on that one compressor will provide all the capacity change needed to meet 90% of the load variations the rack has to deal with. With less cycling, compressor wear is lessened, extending useful life and reducing service calls.
When applied to condenser fans, the AKD 102 can raise and lower fan speed to regulate airflow through the condenser and maintain a constant temperature differential (delta-T) between outside air and the outlet of the condenser. This allows system head pressure to float between limits in order to provide greatest efficiency at any heat load.