Phase change material in floor tiles for thermal energy storage

Abstract

Traditional passive solar systems have relied on sensible heat storage for energy savings. Recent research has investigated taking advantage of latent heat storage for additional energy savings. This is accomplished by the incorporation of phase change material into building materials used in traditional passive applications. Trombe walls, ceilings and floors can all be enhanced with phase change materials. Research to date has yet to produce a viable commercial product. This research introduces a new flooring material that incorporates a phase change material ready for commercial manufacture. An agglomerate floor tile containing 20% by mass of encapsulated octadecane has been manufactured. Flexural and compressive strength of 7.4 MPa and 24.5 MPa respectively, were measured for the tile. Peak melting transition temperature was determined to be 27.2°C with a latent heat of 33.9 J/g of tile. Structural and thermal performance of the tile surpassed that of a typical ceramic tile. Each tile was composed of quartz, resin and phase change material. Statistical modeling was performed to analyze the response of flexural and compressive strength on varying amounts of quartz, resin and phase change material. Resulting polynomials described the effect of adding phase change material into the tile. With as little as 10% by mass of phase change material, the strength was reduced to less than 50% of tile without phase change material. It was determined that the maximum phase change material content to attain structural integrity greater than ceramic tile was 20% by mass. The importance of resin compared to quartz content was also established. The statistical analysis used for this research was based on mixture experiments. A procedure was developed to simplify the selection of data points used in the fit of the polynomials to describe the response of flexural and compressive strengths. This procedure could be easily adapted to other four component mixture problems. Analysis of energy savings using this floor tile containing 20% by mass of phase change material was performed as an addendum to this research. A known static simulation method, SLR (solar load ratio), was adapted to include latent heat storage. In addition a dynamic simulation was also performed using BLAST. The program had to be modified to simulate latent heat storage. Annual heating consumptions from both methods were estimated to be reduced by approximately 5%. Using this value it was concluded that if the price of $0.60 per pound of phase change material could be obtained, a five year payback could be achieved for the product.