Innovations in Materials and Devices for Efficient Solar and Thermal Energy Utilization
Carl Richard Soderberg Professor of Power Engineering
Department Head / Mechanical Engineering
MIT Department of Mechanical Engineering
Human history has very much depended on how we used heat from the sun and terrestrial sources. Over 90% of human society?s energy input is used by first converting it into heat, and yet only 40% of the total energy input is utilized, significantly lower than what the second law of thermodynamics allows. Understanding of basic heat carrier transport and energy conversion at nanoscale can lead to new materials and devices to improve the efficiency of heat utilization. This talk will present some of our work on developing advanced materials and devices to improve the efficiency of solar and thermal energy conversion devices and systems. To lower the cost of solar energy to electricity conversion, we use nanostructures to reduce the thickness of crystalline silicon thin-film solar cells and optically-transparent and thermally-insulating aerogels to replace the vacuum-tube solar collectors in concentrated solar thermal systems. We improve thermoelectric materials via nanostructuring and demonstrate significant improvements in the efficiency of solar thermoelectric energy conversion devices. We also demonstrate the ability of boiling water under unconcentrated sunlight using spectrally selective surfaces. For terrestrial thermal systems, we show that by reflecting infrared radiation back to its emitting heat source, we can significantly improve the efficiency of converting thermally-radiated photons into electricity via thermophotovoltaic devices and the luminous efficiency of incandescent light bulbs. We can turn a battery into an efficient thermal-to-electrical energy converter by cycling it between high and low temperatures. Although polymers are usually thermal insulators, we show that they can be made as thermally conductive as metals by aligning molecular orientations. With properly chosen polymer fiber diameters, we design fabrics so that they are opaque to visible light and yet allow thermal radiation from human body to escape to environment for passively cooling. Nanoscience foundations behind these diverse innovations will be explained along the way.