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Design and development of smart cool materials for the built environment

Gobakis Konstantinos

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Summary

In recent decades, a significant increase in the world’s urban population has been recorded. One of the major problems of the cities’ environment is the urban overheating. Buildings and urban construction materials play an important role in the urban overheating. Moreover buildings are responsible for 40% of the world’s primary energy consumption. Therefore, there is an urgent need to improve the buildings’ energy performance through advanced materials.The scope of the present thesis is to develop, test and integrate cool coatings into the built environment. The introduction of cool coatings leads to energy saving and better living conditions for the people.The present thesis is structured in seven chapters.In Chapter 1 an introduction into cool materials is given. Moreover, the state of the art, research objective and methodology of the thesis is presented. Chapter 2 is devoted to the experimental equipment used for the characterization, development and measurement of the cool coatings.In Chapter 3 the development and testing of the mineral based cool coating is presented. A detailed analysis for the raw materials used for the formulation of the cool coatings using X-ray diffraction is presented. Twenty two cool coatings are developed, characterised and tested. Their characterization includes the measurement of solar reflectance and infrared emittance. Finally, the cool coatings are exposed to the environment and their ability to reduce the surface temperature is measured. The best performing developed cool coating showed reduction of the surface temperature is up to 7.2K.In Chapter 4 the development and testing of the thermochromic based cool coatings is presented. Two main families of thermochromic coatings are discussed: inorganic and organic. The synthesis and characterization of the inorganic thermochromic coatings is presented. Three commercially available organic thermochromic coatings are developed. The solar reflectance and infrared emittance of all thermochromic coatings is measured. Furthermore, the surface temperature of the coatings is measured to be 5.5K compared to the conventional coating with the same colour.In Chapter 5 the ageing effect of the environment on the cool coatings is discussed. All coatings are exposed to the outdoor conditions. The initial and aged solar reflectance and infrared emittance are measured. The mineral based cool coating presented small decrease in the solar reflectance and infrared emittance. The thermochromic coatings presented mixed results. The effect on the outdoor conditions on the inorganic thermochromics is negligible. While significant degradation is observed for the organic thermochromic coatings.In Chapter 6 the changes on buildings and surrounding areas by the use of the developed cool coatings are examined. The effects of the developed coatings on a well and poor insulated building are calculated using advanced thermal modelling software. All coatings contribute to the energy efficiency of both well and poor insulated buildings by 5-14% on annual basis. Moreover, the impact of cool coatings on the urban environment is calculated. A novel method has been developed on indirect coupling of the building advanced thermal modelling and microclimatic modelling software. The importance of coupling the external and internal environment is presented. The microclimatic condition of the under investigation area can lead to difference of ±10% in power for heating/cooling needs when the local microclimatic conditions are introduced to the weather file. If the exchange of data between the 2 domains includes the exchange of the Convective Heat Transfer Coefficient, the difference in heating/cooling needs can be as high as ±50%.

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