This project will demonstrate a new liquid desiccant based dedicated outdoor air system’s (DOAS) ability to deliver improved indoor environmental quality at half the electricity consumption of a conventional DOAS in Department of Defense facilities. A liquid desiccant DOAS has high latent capacity, thus delivering deeply dried ventilation air that offloads the remaining heating ventilation and air-conditioning (HVAC) system’s latent loads allowing the tandem system to maintain temperature and humidity at their desired setpoints. By doing this, the DOAS improves the building’s entire HVAC system’s energy efficiency, saving over 25% of its annual energy use.

The DOAS incorporates novel liquid desiccant heat exchangers (LDHX) that replace finned tube heat exchangers in air conditioning systems. These LDHXs condition air to the precise temperature and humidity in a single step instead of overcooling for dehumidification and reheating steps in a conventional HVAC system. The temperature and setpoint can be adjusted according to a building’s environment and load profile to maintain all comfort metrics within bounds. The liquid desiccant DOAS has undergone over ten years of joint product development between Emerson, 7AC Technologies, and the National Renewable Energy Laboratory, which led to the acquisition of the technology by Emerson in 2020 (An HVAC original equipment manufacturer and supplier of Copeland™ scroll compressors). As a result, the system’s efficiency, measured using the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) 920 Standard, achieves an integrated seasonal moisture removal efficiency (ISMRE) of 8.2 lbm/kWh.” This is double the current code minimum standard in ASHRAE standard 90.1, which dictates all DOAS equipment must have a minimum ISMRE of 4.0 lbm/kWh.

The system monitors a building’s indoor temperature and relative humidity and adjusts its sensible and latent cooling and building pressurization in response. This operation strategy mitigates humidity infiltration to maintain the desired indoor air environmental quality.

A dedicated outdoor air system that efficiently supplies ventilation air is the cornerstone to indoor air quality, comfort, and productivity in a building. The improved efficiency of an electric-powered desiccant system can reduce the energy consumption of DOAS systems by 50% and reduce a site’s Scope 2 green house gas emissions. Even during early adoption, the unit’s cost premium (over standard DOAS equipment) is expected to payback in less than five-years.

The Emerson system employs the latest in variable speed refrigeration technology, allowing the system to precisely control the capacity of the system, which prevents cycling and inadvertent delivery of humid air. Further, the including of advanced demand control ventilation capabilities ensures that indoor environmental quality, building pressurization and humidity is always controlled.