A Structural Review of Thermoelectricity for Fuel Cell CCHP Applications

Abstract

This article starts by introducing the ongoing South Africa electricity crisis followed by thermoelectricity, in which eighteen miscellaneous applicable case studies are structurally analysed in detail. The aim is to establish best practices for the R&D of an efficient thermoelectric (TE) and fuel cell (FC) CCHP system. The examined literature reviews covered studies that focused on the thermoelectricity principle, highlighting TE devices’ basic constructions, TEGs and TECs as well as investigations on the applications of thermoelectricity with FCs, whereby thermoelectricity was applied to recover waste heat from FCs to boost the power generation capability by ~7–10%. Furthermore, nonstationary TEGs whose generated power can be increased by pulsing the DC-DC power converter showed that an output power efficiency of 8.4% is achievable and that thicker TEGs with good area coverage can efficiently harvest waste heat energy in dynamic applications. TEG and TEC exhibit duality and the higher the TEG temperature difference, the more the generated power—which can be stabilised using the MPPT technique with a 1.1% tracking error. A comparison study of TEG and solar energy demonstrated that TEG generates more power compared to solar cells of the same size, though more expensively. TEG output power and efficiency in a thermal environment can be maximised simultaneously if its heat flux is stable but not the case if its temperature difference is stable. The review concluded with a TEC LT-PEM-FC hybrid CCHP system capable of generating 2.79 kW of electricity, 3.04 kW of heat, and 26.8 W of cooling with a total efficiency of ~77% and fuel saving of 43.25%. The presented research is the contribution brought forward, as it heuristically highlights miscellaneous thermoelectricity studies/parameters of interests in a single manuscript, which further established that practical applications of thermoelectricity are possible and can be innovatively applied together with FC for efficient CCHP applications.

Thermoelectric Generators (TEGs) and Thermoelectric Coolers (TECs) Modeling and Optimal Operation Points Investigation

“…Qcmax is the maximum absorbable heat or cooling power in watt, at Iin = Imax and ∆T = 0°C. Qcmax = (nS) 2…”

“…In this regards, we investigated thermoelectricity as a potential alternative energy for sustainable energy source and loads − that is, as a clean DC power source for low energy lighting/applications and as well to provide clean cooling/heating in various human habitats. Thermoelectricity as reviewed in [2], practically focuses on the Seebeck and Peltier effects. Seebeck effect is basically converting heat to DC electricity and the device that does this is a thermoelectric generator (TEG).…”

“…As already examined in [2], thermoelectricity lends itself to various applications with focus on how TEGs and TECs can be used respectively as a power source and as a load. Furthermore, studied in [3], is a re-configurable TEG DC-DC converter for maximum TEG energy harvesting in a battery-powered wireless sensors network (WSN).…”

Thermoelectric Power Generators: State-of-the-Art, Heat Recovery Method, and Challenges

“…As shown in Figure 11, TEG has been well-known in various fields, especially combined with renewable energy and electronics and buildings and vehicles that have a high share in the studied papers. In addition, TEG installed with other heat recovery methods, such as phase change material (PCM) [86], heat pipe (HP) [87], proton exchange membrane (PEM) [88] started to grow noticeably; which means that it is worthwhile to investigate it, even more especially with other heat recovery methods. Among the investigated papers, it is noticed that TEG with HE is well known and employed in different applications, which leads to the introduction of TEG with other HE technologies.…”