INTRODUCTION

Conventional cooling technologies used about 14,255 GWh in Year 2000, according to Energy Commission estimates. This represents 16% of the 91,771 GWh consumed by the commercial sector in Year 2000. Element 4 research projects investigated four concepts that could potentially reduce electric use and demand in the future.

The first project extended research and development that has proceeded for more than a decade on natural gas absorption technologies and natural gas engine-driven vapor compression cycles. The goal was to develop a gas absorption heat pump based on a small, modular, high-efficiency gas absorption chiller that had been developed in a research partnership between Oak Ridge National Laboratory and Robur Corporation.

The second project assessed the application of a heat pump applied to the outside air and exhaust air streams of a conventional packaged HVAC unit. Energy recovery from the exhaust air stream could be an important source to reduce the cost and energy for conditioning outside air.

The third project initially planned to assess the energy savings potential of a relatively new residential hydronic distribution system using fan coils. Early consideration of market barriers for this system by the Program Advisory Committee led to the decision to shift the project to an assessment of a residential hydronic distribution system to store cooling and heating in a floor slab. The assessment included a field test of three cooling modes, including conventional forced air and combinations of night force-air cooling with radiant slab pre-cooling.

The fourth project focused on the role that natural ventilation could play in California. The project's objectives included developing natural ventilation design strategies and design methods for small commercial buildings, addressing the impact of outdoor air quality on natural ventilation, and developing natural ventilation software tools.

The key barriers to introducing alternative cooling technologies are unfamiliarity on the part of designers, lack of credible evidence of efficacy and criteria for their selection, lack of equipment in smaller sizes, and unknown or uncertain maintenance requirements.

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4-2. ASSESSMENT AND FIELD TESTING OF VENTILATION RECOVERY HEAT PUMPS

Purdue investigated application of a new heat pump application, called a "heat pump heat recovery" (HPHR) system. The heat pump in this case extracts heating or cooling energy from the exhaust air stream of an air handler or packaged air-conditioning unit and transfers it to pre-condition the incoming outside fresh air stream. In cooling season, it pre-cools the incoming air and in heating season it pre-heats it. The heat pump heat recovery (HPHR) system functioned properly during the field and laboratory testing. However, heating requirements are relatively low for California climates and therefore overall savings are dictated by cooling season performance.

• The HPHR system did not provide positive cost savings for most building type/climate combinations investigated using simulations.

• The HPHR system is an alternative to an economizer and so economizer savings are also lost when using this system. There are not sufficient hours of ambient temperatures above the breakeven point to yield overall positive savings with the HPHR system compared to a base case system with an economizer for the prototypical buildings in California climates.

• The HPHR system should not be considered for use in California, except in perhaps certain mountain areas with larger heating loads.

Research Team: Jim Braun and Kevin Mercer of Purdue University conducted this research. Todd Rossi and Doug Dietrich of Field Diagnostic Services, Inc. provided data collection services and field support.

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4-3. RESIDENTIAL HYDRONIC SYSTEM DEMONSTRATION

This project, led by the Oak Ridge National Laboratory, compared the performance of different modes of heating and cooling in a single house. The house is equipped with an innovative HVAC system which includes a conventional forced air ductwork system, a variable speed air handler with a hydronic coil and an outside air economizer, and a slab-embedded hydronic radiant system. Mechanical cooling is supplied by a small DX chiller, a condensing water heater is used in heating mode. Three cooling modes were tested: (1) conventional air distribution, (2) conventional air distribution augmented by hydronic pre-cooling of the slab at night, and (3) conventional air distribution augmented by pre-cooling the building mass using outside air at night and hydronic slab pre-cooling if necessary.

• The radiant hydronic cooling was very effective in shifting the cooling load into off-peak hours and greatly reduced energy use.

• Using night ventilation in conjunction with hydronic radiant pre-cooling was even more effective at shifting load into off-peak hours.

Research Team:Evelyn Baskin with Oak Ridge National Laboratory was the principal investigator. David Springer and Marc Hoeschle with Davis Energy Group provided instrumentation installation and monitoring services.

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4-4. DESIGN METHODS AND GUIDELINES FOR NATURAL VENTILATION IN CALIFORNIA

These NIST project objectives included developing natural ventilation design strategies and design methods for small commercial buildings, addressing the impact of outdoor air quality on natural ventilation, and developing natural ventilation software tools.

• A new ventilation cooling metric was described and used to demonstrate that the coastal climates of California are potentially very well suited to natural ventilation.

• The hotter, inland locations are less suited to a simple natural ventilation strategy but may be able to benefit from night cooling or hybrid system strategies.

• An eight-step design approach for natural ventilation applications was developed.

• A review of ambient air quality data indicated that much of California fails to meet the national standards for one or more contaminant. However, since ambient air quality problems may vary by season, time-of-day, and locality, natural ventilation strategies may still be considered acceptable at all times in some areas and part of the time in other areas through innovative hybrid systems.

• Natural ventilation design and analysis software, called LoopDA (for Loop Design and Analysis), was developed to aid in sizing and placement of natural ventilation devices. LoopDA is based on CONTAMW 2.0, a multi-zone airflow model.

Research Team: Andrew Persily, Steven Emmerich, and Stuart Dols with NIST conducted this research. James Axley, now at Yale University, also participated in the research.

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