Hybrid RTU Measure Development

This project will leverage the findings from the following two (2) recent emerging technology (“ET”) projects: "Packaged Roof Top Unit with Integrated Heat Pump and Indirect/Direct Evaporative Cooling": a field test of prototype equipment in an unoccupied classroom (emerging technology project number: ET21PGE1902); and  "Heat Pump and Indirect Evaporative Cooling Packaged Unit (Hybrid RTU) – Lab Test”: a laboratory test of equipment in climate control chambers (emerging technology project number: ET22SWE0034).   This project will take the next steps toward a measure package for hybrid rooftop packaged units (“RTUs”) (the “Technology”) by either developing a new measure or updating an existing measure to include this Technology as a subset. UC Davis will calculate energy savings for the required matrix of building types, vintages, and California climate zones with “EnergyPlus” simulations and gather cost data for the measure package.  The 2022 California Commercial End-Use Survey reports that RTUs provide heating, ventilation, and air conditioning (“HVAC”) for approximately 65 percent (65%) of commercial building floor area in California. RTUs use refrigerant vapor compression cycles to provide cooling and typically use integrated natural gas fired furnaces to provide heating, although heat-pump RTUs are becoming increasingly more common in California.  This hybrid HVAC Technology eliminates on-site natural gas consumption and reduces electric energy consumption while improving indoor air quality through increased outside air ventilation used for cooling. By packaging the high performance indirect evaporative cooling with a heat pump, this Technology reduces the design, equipment, and installation costs compared to existing separate heat pump and evaporative cooling products. This makes the Technology accessible to small and medium commercial buildings. Current indirect evaporative cooling products are typically used as direct outdoor air systems for providing ventilation alongside RTUs for providing space conditioning. These existing products require custom design to size both the evaporative equipment and the RTUs. The separate evaporative system requires additional controls and commissioning. The existing designs using separate systems increase the additional weight of the equipment on the roof and can trigger structural review requirements. These custom design and controls steps and requirement for structural review add upfront cost and increase the retrofit time. Higher cost, longer time, and the requirement for designers to have specialized knowledge reduce the likelihood that these energy saving options are selected. This Technology removes these barriers by providing a fully integrated packaged hybrid system that has a rated capacity for the climate zone so that it can be specified and selected much more easily without the need for sophisticated design to specify sizing. This hybrid packaged system is also expected to reduce the weight on the roof compared to existing separate systems.