phase change materials, building energy efficiency, simulation
The building sector accounts for about 41% of the primary energy consumption, 71% of the electricity usage and 38% of the CO2 emissions in the U.S. Therefore, it is critical to develop efficient solutions to reduce its energy consumption and environmental impact. Building envelope plays an important role in energy use of buildings: it separates the indoor from the outdoor environment, regulates the heat flux entering the inside of buildings and ensures comfort for the occupants. Carefully designed high performance building envelope can reduce total energy consumption by a big portion. Among the several effective envelope techniques, incorporation of phase change materials (PCMs) have received considerable attention during the past decades. PCMs are substances change phase at a certain temperature range with capabilities of storing and releasing large amounts of energy. Being an integrated component of envelope, they absorb heat when outdoor temperature rises and solar energy strikes the building until complete phase change occurred. When surrounding temperature is lower than their phase-change temperature, heat will then flow out of PCMs and reverse phase change occurs. Previous researches have shown that PCMs integrated building envelopes can mitigate indoor air temperature swings, decrease cooling loads and greatly reduce or shift the building peak loads. Most PCMs evaluated for envelope integration change phase from solid to liquid at a temperature around acceptable comfort range of 21 oC to 27 oC. For locations with moderate climate, a reduction in annual residential cooling energy consumption about 10% can be expected. Nevertheless, the effectiveness of PCMs in envelope is strongly influenced by several factors including climate, location of PCM in the wall, amount of PCM, PCM melting and freezing temperatures, wall orientation, etc. Texas is a highly populated and energy-intensive state with long and hot summer. Residential buildings in the state typically have light constructions â€“ favorable for PCMs integration in envelope â€“ and present low energy efficiency. Therefore, a comprehensive study of PCMs integrated residential building envelope is needed for the location. This paper investigates the impact of PCMs integrated building envelope on energy consumption and thermal comfort of residential buildings in south Texas. A prototype single-family building is used as case study. Annual simulation is performed in EnergyPlus to obtain yearly total energy consumption, yearly energy consumption on space heating and cooling. Results for cases with and without PCMs integrated envelope will be compared to analyze the feasibility and energy savings performance of this technique, taking the type of PCM, PCM location in the wall, amount of PCM and application orientation into consideration. Additionally, improvement of indoor thermal comfort will also be presented by evaluating the mean radiant temperature.