The main technical objective of this project is to perform an independent evaluation of the High Efficiency Dehumidification System (HEDS) in two different climates to collect data on design and integration costs and system performance. One building will be located in a high humidity, high temperature climate to evaluate HEDS performance under extreme conditions. The other building will be located in a more moderate climate with lower peak temperatures and humidity. Additional objectives are to develop and calibrate an energy model that can be used to perform analyses to determine conditions and scenarios under which HEDS should be considered.
The performance objective of the project is to quantify the energy savings for cooling and heating plants associated with the installation of a HEDS unit in comparison to a “normal” dehumidification/reheat air handling unit. The cooling energy used to cool and dehumidify the supply air will be measured, as well as the amount of reheat energy (BTUH) that is avoided, and the amount of cooling plant load and heating plant load reduction that is actually experienced through the use of the reclaimed waste heat from the cooling process. Additional objectives are to determine the extent to which the systems are able to be downsized, determine the level of improved efficiency of the HVAC systems, determine the ability of the systems to handle added loads without adding equipment, and determine the extent to which expensive upgrades can be reduced.
The HEDS technology is comprised of a standard air handling unit (AHU) built with a pair of deep, low face velocity heat transfer coils: a cooling coil and a cooling recovery coil. The first coil does the cooling and dehumidifying, the second coil uses the warm water leaving the cooling coil and does the reheating for RH control and cuts the loads on the chiller and boiler plants by using the low-quality recovered cooling energy to meet reheat loads. The result is a dehumidification system that is energy efficient, maintainable, and resilient.
Instrumentation will be installed on the HEDS units to measure the effectiveness and efficiency gains associated with the HEDS installation and help to determine what limitations there may be associated with the HEDS unit. The chilled water supply and return temperatures into and out of the cooling coil and cooling recovery coils (CRC) combined with the differential pressure across the chilled waterside of the coils will be used to calculate flow and temperature differential and thus the cooling load in BTUH and the CRC energy recovery in BTUH. Fan speeds and fan kilowatts, return air temperatures, mixed air temperatures, cooling supply air temperatures and CRC supply air temperatures, return air, mixed air and supply air dew points will be used to calculate relative humidity, unit static pressure and chilled water and CRC valve positions will all be monitored to evaluate system performance.
The HEDS technology was demonstrated previously at Fort Bragg and Tinker AFB. The results from these demonstrations are promising and additional test and evaluation is necessary to develop sufficient data and run-time experience to inform future investments. Base on the previous results and assuming that HEDS units can be applied to a large portion of Department of Defense buildings, the savings from reduced energy cost and facility maintenance is significant.