ET22SWE0034 - Hybrid Heat Pump and Indirect Evaporative Cooling Packaged Unit (Hybrid RTU)
Indirect evaporative cooling can provide cooling at much higher efficiency in California climates compared to the vapor compression cooling systems currently used in most buildings. In the past, these indirect evaporative cooling systems have been add-ons to roof top packaged units, have required mechanical system designers to be familiar with the systems to correctly design and size the equipment, have required additional controls design, and were more cost-effective only for larger systems. This Hybrid Heat Pump and Indirect Evaporative Cooling Packaged Unit is a single piece of equipment packaged retrofit for typical roof top packaged units in the most common size ranges for small commercial buildings with simple installation and no custom design work required for sizing or controls. This Hybrid RTU equipment is designed to have similar weight and size as typical high efficiency RTU equipment reducing barriers to adoption. This project will laboratory test the production-ready prototype version and produce performance curves that can be used to model and estimate energy savings across many different climates and building types. This technology is not yet commercially available, it is in the advanced prototype stage and getting ready to be mass produced by a large manufacturer. The heat pump is sized to meet the heating requirements for the packaged unit rated capacity and has the typical electric resistance heaters for defrost and to provide supplemental heat if outdoor temperatures are extremely low.
Rooftop packaged units (RTUs) provide heating, ventilation, and air conditioning for approximately 75 percent of commercial building floor area in California. This project laboratory tested a commercially available Hybrid RTU that includes a heat pump and Indirect-Direct Evaporative Cooling across a range of outdoor conditions that match California climate zones. This Hybrid RTU can replace conventional RTUs on commercial buildings.
For common California outdoor conditions of 95°F dry bulb, 50°F dew point humidity, the Hybrid RTU has a room (system) cooling capacity of 4.60 (4.85) tons and coefficient of performance (COP) 4.19 (4.42) with 56% outdoor air ventilation fraction.
The measured results were used to develop performance curves and lookup tables that will be used by future projects to estimate energy savings using Energy-Plus and CBECC-Com.
