By Cameron Chai
Department of Energy at Oak Ridge National Laboratory under Scott Hunter, the team lead, is in the process of developing a technology that can convert the waste heat generated from various industrial processes into electric power.
The study from the Laboratory indicates that in the USA alone over 50% of the energy produced from all sources goes unused as waste heat. The process if successful will bring in savings in the form of reduced level of fuel usage and increased level of efficiency in the processes while cutting down the level of carbon dioxide releases.
In the beginning, the team is looking forward to utilize the technology to cool down the heat generated by high level computer chips thus solving the problem faced by the producers of petaflop-scale computers. The computers produce enormous amount of heat, which requires faster removal for efficient functioning of the machines. For this purpose, the team introduced 1 millimeter square in sized cantilever type of structures that can be fixed to the 1-inch sized surfaces of computer chip, concentrated PV cell or other devices that produce heat. Though each such device generated only 1 to 10 mill watts of power, the use of number of such devices is expected to generate substantial power to activate a remote sensor system or to support the quicker cooling of a heat producing device thus reducing the level of cooling requirements.
The device introduced by them utilizes an energy reaping system that includes a micro-electro-mechanical, or MEMS, and a pyroelectric capacitor structure that induces generation of current in alternate directions when heated or cooled. The cantilevers are tied to an anchor that is fixed to a waste heat producing substrate. When the heat producing substrate gets heated it heats the cantilever and makes it bend utilizing bi-material effect as in the case of thermostats and comes into touch with a cold surface known as the heat sink and looses the collected heat quickly and move back again to contact the hot surface. The oscillation of the cantilever is continued till such time the difference in temperature level is continued between the cold and hot surfaces.
The team took the idea of pyroelectricity by utilizing pyroelectric materials, which on earlier occasions have shown only 1 to 5% power conversion efficiency. But by the use of a number of cantilevered energy converters with quicker response and cycle times the team is looking forward to reach 10 to 30% efficiency by utilizing a low-cost platform, which can be made utilizing normal semiconductor production technology.