Performance Evaluation of a Nanomaterial-Based Thermoelectric Generator with Tapered Legs

A thermoelectric generator (TEG) converts thermal energy to electricity using thermoelectric effects. The amount of electrical energy produced is dependent on the thermoelectric material properties. Researchers have applied nanomaterials to TEG systems to further improve the device’s efficiency. Furthermore, the geometry of the thermoelectric legs has been varied from rectangular to trapezoidal and even X-cross sections to improve TEG’s performance further. However, up to date, a nanomaterial TEG that uses tapered thermoelectric legs has not been developed before. The most efficient nanomaterial TEGs still make use of the conventional rectangular leg geometry. Hence, for the first time since the conception of nanostructured thermoelectrics, we introduce a trapezoidal shape configuration in the device design. The leg geometries were simulated using ANSYS software and the results were post-processed in the MATLAB environment. The results show that the power density of the nanoparticle X-leg TEG was 10 times greater than that of the traditional bulk material semiconductor X-leg TEG. In addition, the optimum leg geometry configuration in a nanomaterial-based TEG is dependent on the operating solar radiation intensity.

Exergy and Environmental Assessment of a Steam Power Plant

Many electricity generating stations are concerned with the reduction of environmental pollution associated with the thermodynamic activities of power plants. Such environmental pollution includes emissions from exhaust gases, cooling tower blowdown, boiler blowdown and demineralization. In this paper, an exergo-environmental analysis was conducted using design data from the Egbin power plant for a 220MW steam power plant. Enhancement was carried out on the plant under varying pressure and temperature conditions to assess the plant’s performance improvements that would lead to more reduction in environmental pollution. The exergy destruction efficiency value indicates that the boiler sub- system gave the highest exergy destruction in the power plant. Also, sustainability indicators such as environmental effect factor, waste exergy ratio and sustainability index factors have been performed and results presented with respect to the plant. The improvement options considered were: (i) increasing the inlet temperature of the high-pressure turbine at constant boiler pressure, and (ii) the second approach, simultaneous increase in inlet temperature of high-pressure turbine and boiler pressure. The result showed that the second improvement approach gave a better improvement approach than the former by reducing the environmental effect factor by 17.32% and increasing the sustainability index factor by 21.54%. These effects ultimately reduced the steam power plant emissions and improved efficient fuel utilization by the plant for sustainable development and for more power production.