Influence of the type of phase change materials microcapsules on the properties of lime-gypsum thermal mortars

In a society with a high growth rate and increased standards of comfort arises the need to minimize the currently high energy consumption by taking advantage of renewable energy sources. The mortars with incorporation of phase change materials (PCM) have the ability to regulate the temperature inside buildings, contributing to the thermal comfort and reduction of the use of heating and cooling equipment, using only the energy supplied by the sun. However, the incorporation of phase change materials in mortars modifies its characteristics. The main purpose of this study was the production and characterization of mortars with incorporation of two different phase change materials. Specific properties of two phase change materials, such as particle size, shape and enthalpy, were determined, as well as the properties of the fresh and hardened state of the mortars. The proportion of PCM was 0%, 10%, 20% and 30% of the total mass of the solid particles. In order to minimize some problems associated with shrinkage and consequent cracking of the mortars, the incorporation of polyamide fibers and superplasticizer was tested. It was possible to observe that the incorporation of phase change materials in mortars caused differences in properties such as compressive strength, flexural strength and shrinkage. Even though the incorporation of PCM microcapsules resulted in an increase in the shrinkage, it was possible observe a significant improvement in mechanical properties.The authors wish to express their thanks to the Portuguese Foundation for Science and Technology, for funding the project PTDC/ECM/102154/2008, Contribution of Thermal Active Mortars for Building Energy Efficiency

Active thermal mass enhancement using phase change materials

Buildings account for around 40% of energy consumption in the UK. For over twenty years active thermal mass systems have been a feature in low-energy buildings in northern Europe. By passing ventilation air, and utilising night ventilation, through the hollow core structures efficient heating and cooling has been achieved. Despite the success, such systems suffer from space overheating and efficiency losses during extended hot periods. Control strategies have largely mitigated this effect however low cost retrofit solutions that enhance the system are of interest. This research therefore investigates the benefit of using innovative phase change material (PCM) solutions to enhance thermal comfort and reduced energy usage of traditional active thermal mass systems. A prototype PCM enhancement was constructed, with energy saving and comfort benefits investigated under controlled laboratory conditions. In absolute terms the PCM solution offered an additional 12.5% energy storage capacity and a 29% increase in active surface area, coupled with the existing sensible thermal mass. Under laboratory conditions the PCM addition saved an additional 0.1 kWh per day, delayed AC onset by 1.2 h and offered an average 1.0 °C reduction in room temperature during 8 h of fixed internal heat gain, contrasted against the original active thermal mass system

Numerical and experimental studies of a capillary-tube embedded PCM component for improving indoor thermal environment

This paper aims to analyse the thermal characteristics of a novel system of Capillary Tubes embedded in a Phase Change Material (CT-PCM) as part of active building environmental design for energy conservation and the improvement of indoor thermal environment. The CT-PCM system is proposed based on the concept that low-grade energy utilisation potential could be harnessed and maximised by buildings’ radiant heating/cooling systems and phase change material. The CT-PCM component is first built in the laboratory, and the thermal characteristics of the CT-PCM are investigated through a set of thermal response experiments. In addition, a simplified model is developed to assess the long-term thermal performance of the CT-PCM system for its application during a strategical system design stage. To ensure the robustness of the numerical model in the assessment of the thermal performance of the system, the developed model is evaluated against the experiments under a set of dynamic thermal boundary conditions. The evaluation process revealed that when the flow rate of thermal fluids in the CT-PCM system is more than 800 ml/min, the simulation results of the proposed simplified model is in a good agreement with the experiment. When the flow rate in the capillary tube is smaller than 800 ml/min, the correction factors are derived to address the non-uniformity of temperature distribution

New method for the design of radiant floor cooling systems with solar radiation

Impacts of solar shortwave radiation are not taken into account in the standardized design methods in the current radiant system design guidelines. Therefore, the current methods are not applicable for cases where incident solar is significant. The goals of this study are to: 1) use dynamic simulation tools to investigate the impacts of solar radiation on floor cooling capacity, and 2) develop a new simplified method to calculate radiant floor cooling capacity when direct solar radiation is present. We used EnergyPlus to assess the impacts of solar for different design conditions. The simulation results showed that the actual cooling capacities are in average 1.44 times higher than the values calculated with the ISO 11855 method, and 1.2 times higher than the ASHRAE method. A simplified regression model is developed to improve the predictability of ISO methods. The new model calculates the increased capacity as a function of the zone transmitted solar and the characteristic temperature difference between the hydronic loop and room operative temperature