Design and operation of increased thermal capacitance and dual thermal storage and its effects on building energy dependence

Abstract

This research explores the design and operation of an increased thermal capacitance (ITC) and thermal storage management (TSM) system for reducing building energy consumption associated with heating, cooling, and domestic hot water (DHW) usage. Thermal capacitance is a controlling factor for phase shift and amplitude reductions of cyclical heat transfer due to weather, and control of the ITC through TSM improves upon the benefits offered by additional capacitance. Using the transient energy modeling software TRNSYS, ITC is achieved by water circulating in copper pipes embedded in the walls of a three-story residential building. Temperature and season-controlled valves divert circulation to either the building shell, ground heat exchanger, solar panel, cold storage tank or hot storage tank. A phase change material is thoroughly mixed into the water storage tanks to allow a tank volume reduction without loss of thermal storage. Proper design and operation of the ITC/TSM system are investigated through a parametric study of the water tank size, water mass flowrate, and solar panel size. These analyses are focused on reducing the overall building energy requirement associated with the heat pump and DHW usage. Results range from 24% to 35% energy savings for the evaluated parameter ranges.