Project Info ACTIVE Project Title
Field Evaluation of Ultra-Efficient, Compressor-less, Packaged Rooftop Unit with Integral Energy StorageProject Number ET23SWE0071 Organization SWE (Statewide Electric ETP) End-use HVAC Sector Commercial Project Year(s) 2023 - 2025
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.