Energy savings from indirect evaporative pre-cooling: Control strategies and commissioning

Conference · Wed Jul 01 04:00:00 EDT 1998

OSTI ID:20006322

Felts, D; Jump, D A

Package rooftop air conditioning units (RTU) with evaporative pre-cooling systems were installed at an Agricultural History Museum and conference center in the northern Sacramento Valley in California, a hot and dry summer climate region. The evaporative pre-coolers serve to extend the economizer range of the RTU's. A commissioning team monitored the performance of the RTU evaporative pre-coolers. The purpose of the monitoring was to determine if changes were warranted to optimize the system's energy efficiency. The commissioning process revealed that the RTU evaporative pre-coolers were being controlled by the economizer control cycle. With this control cycle, the evaporative pre-cooler operates when the outdoor air temperature is falling below the space return air temperature. This means that the pre-cooler will never operate at peak load conditions. The conference center is an assembly occupancy. Building codes require significant levels of outdoor air for ventilation. The evaporative pre-cooler system provides the means to significantly offset the energy requirements for cooling down and heating up this ventilation air. A DOE2 energy simulation analysis indicated that the evaporative pre-cooler could cut energy use by over 50% if it were working correctly. Investigation concludes that in buildings with high outdoor air requirements, evaporative pre-cooling, using building exhaust air as the indirect evaporative cooling source, significantly reduce building energy consumption. This evaporative pre-cooling technology works in any climate, regardless of outdoor conditions, since the return air stream exhausted from the building provides a relatively constant temperature and humidity source for evaporative cooling. An added benefit is that the evaporative pre-cooler heat exchanger recovers heat from the exhausted air stream in cold weather.

• Research Organization: Pacific Gas and Electric Co., San Francisco, CA (US)
• OSTI ID: 20006322
• Report Number(s): CONF-980815--
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
CALIFORNIA
ENERGY EFFICIENCY
EVAPORATIVE COOLING
HEAT RECOVERY
OPERATION
PUBLIC BUILDINGS
SPACE HVAC SYSTEMS