Abstract

This thesis presents a simulation study of an active energy storage device, intended to enhance building operation, and which is designed to be installed in the ceiling plenum of an office space, a mechanical room or in other convenient locations. This device, consisting of an arrangement of several panels of a phase-change material, may be charged or discharged as required with an air stream passing through the gaps between the panels, thus operating as a PCM-air heat exchanger (PCM-HX).
The first part of the thesis focuses on the design of the PCM-HX. Several design configurations are evaluated; investigated parameters include the PCM-HX dimensions, the number of air channels, and airflow rates. The Thesis also includes an experimental validation of the PCM model. Design criteria that were considered in the parametric study include the amount of stored heat, the time needed to charge/discharge the PCM storage and the overall energy density of the device.
The second part of the thesis evaluates different control strategies targeting reductions in peak demand and HVAC system sizing during winter. The effect of a linear ramp of room temperature setpoint and PCM-HX on peak load reduction is investigated. It was found that implementing a two hour linear ramp in temperature setpoint –together with a PCM-HX configuration with six air channels– can reduce the heating peak load by 41%, relative to a benchmark case without the PCM-HX.
The third part of the thesis presents a simulation case study of The PCM-HX for free-cooling purposes. Results show that in the present case-study, 14% reduction in energy consumption and 24 % reduction in cooling power fluctuation (W) during daytime could be achieved using the PCM heat exchanger (PCM-HX) for free cooling.
The last section of the thesis evaluates effect of the PCM-HX on energy flexibility in building. The potential of shifting the energy use from high to low price periods is investigated. Results show that such a PCM HX along with appropriate control strategies could provide flexibility to the grid, reduce mean power load during daytime and peak power demand. It was found that the PCM-HX could enhance energy flexibility by 10 % in winter day and 20% in summer day.