DESC0025039

To reach the federal governmentĺs goals of eliminating electric utility carbon emissions by 2035 and transitioning to a carbon-free economy by 2050, buildings will need to become grid-interactive energy assets. To enable this dynamic flexibility within buildings, new technologies are needed so that essential building services are maintained. Heating and cooling loads represent the most significant individual end use in buildings. Technologies that store thermal energy and provide a buffer for a homeĺs HVAC equipment could have a tremendous impact in lowering peak demand and shifting energy use to match the output of renewable electricity sources, while improving building resiliency to electrical outages and disasters. Thermal Energy Storage is one such solution. Conventional thermal energy storage, which is most frequently implemented in commercial buildings, uses equipment that is capital-intensive and takes up significant floor area. This kind of system is difficult to justify in light commercial and residential buildings. For this reason, residential buildings have not seen a significant adoption of thermal energy storage technologies due in part to the upfront cost, as well as a lack of a clear value proposition. This unclear value is in part due to limited roll-out of time of use utility rates, which is required for a reasonable payback period, and lack of knowledge among homebuyers, homebuilders, contractors, and design professionals. Electrical energy storage using on-site batteries is another growing solution, however these systems also have a significant upfront cost and payback periods. To address these current market issues, this project will develop an air distribution duct with integrated phase change material to cost effectively store and release thermal energy. This technology offers greater ease of installation and provides more efficient utilization of space than current HVAC thermal storage systems that occupy valuable floor area. By being modular, and in duct form, the amount of storage can be easily scaled up or down to meet the thermal loads of a particular building, at a lower cost than existing ôboxö type thermal energy storage appliances. With this proposed technology, heated or cooled air is routed from the central space conditioning equipment through the enhanced ducts to ôchargeö the phase change material. Once this material has completed a phase transition, the enhanced ducts are shut off by means of automated dampers. During peak load hours, when the stored thermal energy is needed, the central compressor or heating elements can be switched offŚlowering power demandŚand airflow is directed from the air handling equipment through the thermal storage ducts so that the stored energy is transferred to the occupied spaces. This unique approach can expand the duration of demand response ôeventsö from 1-2 hours to 4-6 hours for individual homes, while maintaining occupant comfort.