Packaged Roof Top Unit with Integrated Heat Pump and Indirect/Direct Evaporative Cooling

The emerging technology assessed in this study is a packaged RTU that integrates a heat pump with an indirect-direct evaporative cooling (IDEC) system that is designed as a direct replacement for a traditional RTU. This project evaluates a Hybrid system in a field study and compares its performance to a baseline packaged RTU.

The Hybrid technology demonstrated was able to maintain thermal comfort, increase outside air for human health and performance, eliminate natural gas combustion for heating, and save electricity, even when including the electricity used for heating. A simplified model based on field test data showed that the expected energy savings in four California cities is a 4-33% reduction in electricity and elimination of natural gas for heating. Peak demand for cooling was similar between the baseline and Hybrid systems and peak demand for heating was increased due to the use of a heat pump instead of gas for heating. The Hybrid was estimated to consume 3,600-5,700 gallons of water annually to achieve this electricity savings, which equates to an average of 8.5 gallons consumed per kWh saved for cooling. The analysis also showed an expected increase in ventilation air of 25-59% above the baseline, which is an important finding expected to result in reduced probability of long-range airborne transmission of infectious disease and improved student performance.

Keyword Search:

HVAC, evaporative cooling, electrification, all-electric, RTU