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.
Sustainable energy is gradually becoming the norm today due to greenhouse warming effects; as a result, the quests for different renewable energy sources such as photovoltaic cells as well as energy efficient electrical appliances are becoming popular. Therefore, this article explores the alternative energy case for thermoelectricity with focus on the steadystate mathematics, mixed modelings and simulations of multiple TEGs and TECs modules to study their performance dynamics and to establish their optimal operation points using Matlab and Simulink. The research substantiates that the output current from TEGs or input current to TECs, initially respectively increases the output power of TEGs and the cooling power of TECs, until the current reaches a certain maximum optimal point, after which any further increase in the current, decreases the TEGs' and or TECs' respective output and cooling powers as well as efficiencies, due to Ohmic heating and or entropy change caused by the increasing current. The research main contributions are elaborate easy to understand TEGs/TECs theoretical formulations as well as static and dynamic simulated models in Matlab/Simulink, that can be used initially to dynamically investigate an infinite quantity of TEG and TEC modules connections, be it in series and or in parallel. This is to assist system designers grasp TEGs and TECs theoretical operations better and their limits, when designing energy efficient waste heat recovery (using TEGs)/cooling (using TECs) systems for industrial, residential, commercial and vehicular applications.
As the basis for the study, this manuscript was written at a time when the energy crisis is affecting most parts of the world and most especially the prevailing and rampant electricity crisis in most developing countries. As a result, 50 combined cooling, heating and power (CCHP) systems studies were reviewed, which included the internal combustion engine (ICE), Stirling engine, biomass, micro turbine, solar and biogas, photovoltaic (PV) and gas turbine, wind turbine, PV and micro-turbine, solid-oxide and phosphoric-acid fuel cells (FCs), ICE and thermoelectric generator, low-temperature (LT) polymer electrolyte membrane (PEM), inlet air throttling gas turbine, ground source heat pump (GSHP) micro gas turbine and PV, ICE and GSHP, ICE with dehumidification and refrigeration, 5-kW PEM FC, thermoelectric cooler and LT-PEM FC, Stirling engine and molten carbonate FC, thermo-acoustic organic Rankine cycle, solar-thermal, geothermal, integrated energy systems, power- and heat-storage systems, energy-conversion systems, thermodynamic and thermo-economic optimization strategies, working fluids based on hydrogen, helium as well as ammonia, H2O, CO2 etc. Of these reviewed CCHP systems, FC-based CCHP systems were of the greatest interest, particularly the PEM FC. Consequently, FCs were further investigated, whereby the seven popular types of FCs identified and classified were summarily compared with each other, from which the PEM FC was preferred due to its practical popularity. However, PEM FCs, like all FCs, are susceptible to the fuel-starvation phenomenon; therefore, six FC-assisted schemes were examined, from which the FC assisted with the supercapacitor and battery technique was the most widely applied. In sum, the significance of the study entails assorted CCHP systems, FCs, their highlights, their applications and their pros and cons in a single reference document that anyone can easily use to holistically understand the characteristics of the CCHP systems. The study concludes with our perspective, by which we formulate and propose an alternative innovative unique CCHP system model under research, which is based exclusively on green technologies: FCs, lithium-ion battery, ultracapacitor, thermoelectricity and an energy-management system using MATLAB®.
<abstract> <p>Renewable energy technologies such as solar, thermal, wind, hydro, bio-fuels, fuel cells etc. are becoming trendy and being commissioned in large-scales, due to their environmental friendliness and energy sustainability. This manuscript focuses on alternative energy based-on thermoelectricity, particularly thermoelectric generators (TEGs). From the literature review, there is less emphasis on how multiple TEGs can be best configured electrically for optimum operations. In light of this, Matlab/Simulink were employed to institute a unique theoretical framework, that can easily be comprehensively used to simulate thermoelectricity parameters, with focus to determine TEG modules (of any quantity/configuration) optimal resistance matching and performance. The principal findings of the study are; 1) the effects of TEGs internal resistance, which proportionally causes output voltage drop and power loss as well as efficiency loss and 2) TEG modules may not be connected anyhow in series and or in parallel, but in a setup that gives a total electrical resistance that matches the load electrical resistance. Thus, TEGs should be a) of the same model with the same or approximate internal resistance, b) in a configuration whereby the TEGs total resistance equals the load resistance, as doing so ensures maximum power is transferred between the source (TEGs) and the electrical load and c) preferably be in a symmetrical electrical configuration. A symmetrical electrical configuration ensures ⅰ) the TEG modules total output resistance, irrespective of the quantity used, approximates that of a single TEG, with the overall TEG modules simply becoming now one large powerful TEG having an equivalent resistance of a single TEG and ⅱ) the TEGs power, voltage and current operations are optimal.</p> </abstract>
<abstract> <p>Energy sustainability is becoming paramount today with the focus being on renewable and alternative energy. This manuscript therefore embarks on clean alternative energy rooted in thermoelectricity with focus on thermoelectric generator (TEG). However, a TEG do practically needs heat-exchangers or heatsinks to properly and reliably work but heatsinks present another problem—thermal resistance, which affects a TEG power output and efficiency and thus, must be addressed. Consequently, we investigate a TEG with heatsinks model based-on dimensional analysis using Matlab and Simulink. Our research has three unique contributions. Firstly, we derived the analytical formulas for direct calculations of TEG dimensionless hot and cold sides temperature and by introducing and applying a new dimensionless parameter, the dimensionless temperature difference (<italic>DT<sub>s</sub></italic>). Secondly, we simplified further the new TEG dimensionless hot and cold sides temperature analytical formulas to obtain simpler and simplest forms. Thirdly, we implemented a TEG with heatsinks Matlab/Simulink theoretical model, that employs the simplified dimensional analysis, in which a TEG with heatsinks parameters of interest can be simulated to variously determine the analytical, numerical and graphical results with various optimal options to opt for, before doing a practical design.</p> </abstract>
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