Nano-Micro Materials Enabled Thermoelectricity From Window Glasses

Abstract

With growing world population and decreasing fossil fuel reserves we need to explore and utilize variety of renewable and clean energy sources to meet the imminent challenge of energy crisis. Solar energy is considered as the leading promising alternate energy source with the pertinent challenge of off sunshine period and uneven worldwide distribution of usable sun light. Although thermoelectricity is considered as a reasonable energy harvester from wasted heat, its mass scale usage is yet to be developed. By transforming window glasses into generators of thermoelectricity, this doctoral work explores engineering aspects of using the temperature gradient between the hot outdoor heated by the sun and the relatively cold indoor of a building for mass scale energy generation. In order to utilize the two counter temperature environments simultaneously, variety of techniques, including: a) insertion of basic metals like copper and nickel wire, b) sputtering of thermoelectric films on side walls of individual glass strips to form the thickness depth of the glass on subsequent curing of the strips, and c) embedding nano-manufactured thermoelectric pillars, have been implemented for innovative integration of thermoelectric materials into window glasses. The practical demonstration of thermoelectric windows has been validated using a finite element model to predict the behavior of thermoelectric window under variety of varying conditions. MEMS based characterization platform has been

fabricated for thermoelectric characterization of thin films employing van der Pauw and four probe modules. Enhancement of thermoelectric properties of the nano- manufactured pillars due to nano-structuring, achieved through mechanical alloying of micro-sized thermoelectric powders, has been explored. Modulation of thermoelectric properties of the nano-structured thermoelectric pillars by addition of sulfur to nano-powder matrix has also been investigated in detail. Using the best possible p and n type thermoelectric materials, this novel energy generation technique promises 304 watts of thermoelectricity from a 9 m2 glass window utilizing temperature difference of 20 OC. In addition to be useful even during off sunshine hours of the day, these energy harvesting windows will be capable of power generation even in the absence of a cooling systems inside the building as long as a natural temperature gradient exists between the two counter environments. With an increasing trend of having the exterior of buildings and high rises entirely made up of glass, this work offers an innovative transformation of these building exteriors into mass scale energy harvesters capable of running average lighting loads inside the building hence providing a complimentary source of electricity to the main power grid.