Electrochromics and Thermochromics for Energy Efficient Fenestration: New Applications Based on Transparent Conducting N
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Electrochromics and Thermochromics for Energy Efficient Fenestration: New Applications Based on Transparent Conducting Nanoparticles C. G. Granqvist1, İ. Bayrak Pehlivan1, Y.-X. Ji1, S.-Y. Li1, E. Pehlivan2, R. Marsal2, and G. A. Niklasson1 1
Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, P. O. Box 534, SE-75121 Uppsala, Sweden 2
ChromoGenics AB, Märstagatan 4, SE-75323 Uppsala, Sweden
ABSTRACT This paper summarizes some recent advances for electrochromic and thermochromic fenestration. For the former application, we consider a polymer-laminated construction and show that the addition of nanoparticles to the electrolyte can enhance its ionic conductivity (with fumed silica) and quench the near-infrared transmittance which transmits solar energy but is not important for visible light (with ITO nanoparticles). Regarding thermochromics, we discuss recent experimental and theoretical work on Mg-doped VO2, where the doping lowers the luminous absorptance, and on measurements applied to Al2O3-coated VO2 with good stability with regard to high-temperature treatment. INTRODUCTION Electrochromic (EC) and thermochromic (TC) fenestration is able to control the throughput of visible light and solar radiation into buildings and can create energy efficiency as well as human comfort. This paper summarizes some very recent work and focuses on the uses of transparent conducting nanoparticles to accomplish new and improved functionality. Electrochromics and thermochromics belong to the “green nanotechnologies” [1] which are of keen interest today. We first consider why this is so and look at the world’s population and its interrelationship to our common environment. The population has grown from roughly one billion in 1800 to some 2.5 billion in 1950 and is now (2013) somewhat above seven billion; the growth is not forecast to stabilize until around the year 2100, at a level of ten billion or more [2]. This population explosion is paralleled by an improvement in the overall living standard, and people in the poorer countries rightly expect to enjoy the same qualities of life and amenities that we are used to in the more affluent countries. The result of this evolution is that the demands on the global resources are growing steeply and that there is an unsustainable demand on energy, water, minerals, etc. The energy is mainly derived from coal, oil and gas, all of which release carbon dioxide to the atmosphere leading to global warming, rising sea level, harsher weather, growing risks for the spreading of diseases, mass migrations, risks of more violent conflicts, abrupt shifts in the Earth’s biosphere, etc [3]. The effect of global warming due to greenhouse gases is aggravated by the fact that about half of the world’s population now lives in cities, and the booming of mega-cities is fast and leads to “urban heat islands” with temperatures several degrees above those of the surrounding countryside [4]. We note that there is a clear connection
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