ET23SWE0071 - Field Evaluation of Ultra-Efficient Dedicated Outdoor Air System with Integral Energy Storage
This project is an Emerging Technology Field Demonstration to evaluate the efficiency, cooling performance, and load shifting/demand flexibility, of a liquid desiccant- enhanced commercial packaged rooftop unit with integral energy storage. This tests a new class of equipment referred to by the US Department of Energy as a Separate Sensible and Latent Cooling (SSLC) air conditioning (AC) system on a commercial building. This technology uniquely brings high performance under extreme conditions. The project includes independent evaluation, measurement, and verification services.
The equipment is designed for use as a sustainable replacement for the ubiquitous compressor-based, direct expansion, packaged rooftop equipment, found on most commercial buildings under 300,000 square feet. For this project, the packaged rooftop design is sized to deliver 2,000 CFM of conditioned air with at least 30%, and up to 100% fresh air in the supply air stream. The unit can be used in dedicated outdoor air supply (DOAS) and/or return air unit applications.
One of the key differentiators is independent control of latent and sensible cooling. A novel conditioner core uses a low flow of non-corrosive liquid desiccant to dehumidify the mixed outdoor and indoor return air streams in combination with a dew-point-style indirect evaporative cooler that provides sensible cooling. The unit is designed to operate in all combinations of indoor and outdoor air, ranging from hot/humid through hot/dry. Integral thermal energy storage provides load flexibility with 6 hours of peak load shifting. The packaged unit includes a novel, electrically-driven, low global warming potential (GWP) refrigerant heat pump with small refrigerant charge to produce low grade heat which is used to regenerate the liquid desiccant. System cooling capacity and energy efficiency increases as ambient temperature increases, eliminating the negative impact of air conditioning load during heat waves and eliminating the need for equipment oversizing to meet design day cooling loads. The technology has a high turndown ratio, eliminating partial cooling load inefficiency.
The Project will install one unit on an existing commercial building and independently measure and evaluate the performance throughout the summer cooling season.
Commercial building energy performance has improved significantly over the past two decades through evolving codes, technology innovations, and building standards. Heating, ventilation, and air-conditioning systems remain the largest energy consumer in buildings and represent the greatest opportunity for energy and carbon emission reductions. As Title 24 standards evolve to include dedicated outdoor air systems (DOAS), it is important to evaluate how the operational efficiency of DOAS contributes to energy and carbon emission savings.
This project demonstrated and validated a novel emerging technology that has the potential to achieve high cooling efficiency using a desiccant-enhanced, indirect evaporative cooling approach with integrated storage for providing load flexibility. This field evaluation project measured the energy performance and peak load-shifting capability of this emerging DOAS technology. The technology combines liquid desiccant with indirect evaporative cooling and thermochemical energy storage to fundamentally reimagine how buildings are cooled, dehumidified, and interact with the grid.
The field test results showed that the DOAS with integral energy storage has the potential to increase distribution grid resilience during periods of extreme heat, futureproof buildings against the frequency and duration of heat waves with rising dew points. This technology advances building decarbonization by providing improvements in energy efficiency and load flexibility. Furthermore, operating costs can be reduced by lowering total electricity use and by shifting electricity consumption to take advantage of time-of-use rates and utility-sponsored load management tariffs and incentives.
This CalNEXT project aims to reduce risk and accelerate adoption of advanced DOAS systems for the benefit of ratepayers and society at large. Future efforts should both inform the development of new code requirements and identify potential barriers to broader adoption and codification of these advanced systems. It is recommended that additional field evaluation of the final commercial product be conducted to validate the energy savings determined in this project and provide additional data for measure development.
