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Air-to-air energy recovery can be used to reduce ventilation loads for small commercial buildings. Enthalpy exchangers are one approach to energy recovery that is commonly employed. An alternative technology involves the use of a heat pump that operates between the ventilation and exhaust streams. In this paper, the performance of a ventilation heat pump heat recovery unit was studied through simulation. A model of the heat pump was developed and validated using manufacturers' and laboratory test data. This component model was then incorporated within a system simulation to investigate operating cost savings for the heat pump relative to a base case that does not employ energy recovery but utilizes fixed minimum ventilation rates with an enthalpy economizer. The operating costs were found to be greater than the base case in moderate climates with relatively small savings in more extreme climates (hot or cold). The performance is not competitive with the performance of enthalpy exchangers or demand-controlled ventilation. The breakeven ambient conditions for positive savings utilizing a ventilation heat pump were also investigated. The primary performance penalties associated with the use of a heat pump are added fan and compressor power consumption, along with lost economizer savings. [ABSTRACT FROM AUTHOR]

The ventilation airstream required to maintain acceptable indoor air quality is typically a .significant contributor to the total heating and cooling load in commercial buildings. Demand-controlled ventilation (DCV) and enthalpy exchangers are two technologies that can be used to reduce ventilation loads and overall operating costs. This paper evaluates the operating cost savings and overall economics associated with these two different ventilation load reduction technologies for a variety of small commercial building types and climates. A specialized simulation tool was developed and utilized to perform the evaluations. Both demand-controlled ventilation and enthalpy exchangers were shown to result in significant operational cost savings as compared with fixed ventilation and no energy recovery in a number of small commercial buildings and locations. For both technologies, the savings potential and economic payback are better in more extreme climates. The opportunities are particularly great in cold climates because the ventilation load is a larger portion of the overall toad. For retrofit applications, demand-controlled ventilation (DCV) with an economizer was found to give the greatest savings in utility costs for all the buildings and climates considered. Air-conditioning utility cost savings for DCV of up to 52% were found for offices and restaurants. Payback ranged from about one to six years for most locations. Although utility cost savings were found to be less for enthalpy exchangers, they have the advantages of allowing smaller primary cooling and heating equipment for new applications and providing better indoor air quality. The operating cost savings for both DCV and enthalpy exchangers are dependent on assumptions concerning occupancy. The impact of occupancy schedules on cost savings for DCV and enthalpy exchanger systems should be considered in more detail in future studies. [ABSTRACT FROM AUTHOR]

This paper describes the design, simulation, building, and testing of a 10.5 kW (3-ton) residential air conditioner for hot/dry climates. The unit was optimized to field-measured indoor and outdoor conditions and duct system losses, subject to the same packaging constraints as conventional systems. A new type of microchannel flat tube plate fin evaporator and condenser were designed and fabricated for this project. The system was tested in a psychrometric room at extreme hot/dry conditions and met the project goal by reducing peak power demand by more than 25% compared to a typical SEER 12, R-410A baseline unit. Component and system performance data were compared to the results of simulation modeling conducted during the design process. Results suggest that additional performance improvements might be obtainable with minor changes in system configuration. [ABSTRACT FROM AUTHOR]