Date on Master's Thesis/Doctoral Dissertation

12-2013

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Civil and Environmental Engineering

Committee Chair

McGinley, William Mark

Author's Keywords

Phase change materials; Energy efficiency; PCM; Thermal mass; Concrete masonry; Holistic building analysis

Subject

Building materials--Energy conservation; Concrete--Additives; Change of state (Physics)

Abstract

Thermal mass incorporated into the building envelope has the ability to attenuate peak interior diurnal temperature fluctuations and energy flow, provide interior thermal phase shifts, and absorb surplus energy from solar gains as well as internal gains created by occupants, lighting, appliances and electronics. Heating and cooling demands can be reduced and delayed by thermally massive building envelopes. Historically, thermal mass has been achieved using thick, dense building envelopes such as stone, adobe, and mass concrete. These massive walls absorb heat during the day keeping the interior cool, then release the stored heat during the night maintaining interior comfort. The thermal mass of a building envelope, in this case concrete, can be further increased with the incorporation of Phase Change Materials (PCMs). PCMs increase the effective thermal mass of a structure without increasing the size or significantly changing the weight of the structure. PCMs store energy as they change phase from a solid to a liquid state during a nearly isothermal process. This occurs when the material reaches the transition temperature of the PCM. Once melting of the PCM is completed, the temperature of the material can once again rise. When the material cools and returns to the transition temperature, the PCM solidifies releasing the stored thermal energy. In this research Concrete Masonry Units (CMUs) were examined for improved thermal energy performance using the enhanced thermal properties provided by PCMs. PCMs can be incorporated into concrete to form CMUs with higher energy storage capability than standard CMUs. CMUs were chosen for this application because of their extensive use in the construction industry which has the potential to contribute to commercial acceptance. The work represented in this dissertation indicates that Phase Change Materials can be successfully incorporated into concrete mixes appropriate for use in CMUs. CMUs incorporating PCM will look and function structurally like standard units while also having improved thermal storage performance. In some climates and building configurations, CMUs with improved energy storage via PCMs may have the ability to compete with mainstream insulation technologies.

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