Feasibility and Numerical Analysis of Hybrid Photovoltaic (PV) Panels with Thermoelectric Cooling (TEC) Systems

Photovoltaic-thermoelectric hybrid (PV-TE) systems combine photovoltaic (PV) cells and thermoelectric cooling (TEC) modules to improve the system performance. PV panels efficiency is undesirably influenced by temperature rise, reducing power outlet from PV cells. As a countermeasure, cooling methods have been widely suggested. In this chapter, we provide an overview of both technologies, as well as an analysis of thermoelectric cooling as a possible solution to temperature rise in PV panels. Energy and exergy balances of hybrid system are conducted to determine if the thermoelectric cooling is viable for a self-sustaining system. Our results show that copper indium gallium selenide (CIGS), crystalline silicon (c-Si), amorphous silicon (a-Si), and cadmium tellurium (CdTe) PV panels are unsuitable candidates using the TE cooling. Even though exergy losses diminish with temperature decrease in CIGS, c-Si, and a-Si, the power consumption of the TEC has shown to overcome power generation from PV panels

Performance Analysis of Composite Thermoelectric Generators

Composite thermoelectric generators (CTEGs) are thermoelectric systems composed of different modules arranged under various thermal and electrical configurations (series and/or parallel). The interest for CTEGs stems from the possibility to improve device performance by optimization of configuration and working conditions. Actual modeling of CTEGs rests on a detailed understanding of the nonequilibrium thermodynamic processes at the heart of coupled transport and thermoelectric conversion. In this chapter, we provide an overview of the linear out-of-equilibrium thermodynamics of the electron gas, which serves as the working fluid in CTEGs. The force‐flux formalism yields phenomenological linear, coupled equations at the macroscopic level, which describe the behavior of CTEGs under different configurations. The relevant equivalent quantities—figure of merit, efficiency, and output power—are formulated and calculated for two different configurations. Our results show, that system performance in each of these configurations is influenced by combination of different materials and their ordering, that is, position in the arrangement structure. The primary objective of our study is to contribute new design guidelines for development of composite thermoelectric devices that combine different materials, taking advantage of the performance of each in proper temperature range and type of configuration

Thermodynamic Analysis of Thermoelectric Legs with Different Geometric Parameters

The design of thermocouple legs is the central theme of this chapter, the methodology of reduced variables is shown, which allows the designer to obtain the dimensions of the geometric parameters, specifically the cross-sectional areas transversal An, Ap and length of the legs ln=lp. The main quantities used within this scheme calculation method are the reduced current density U, the thermoelectric potential Φ, and the thermal conductivity κ. Subsequently, the performance of the designed thermocouple is analyzed through the electrical power produced when the system is connected to an electrical resistance load. In this step, the condition of the dependence of thermoelectric properties on temperature is used. The results show specific values of the cross-sectional areas in which the maximum power value occurs. Although the main method has the advantage that it uses minimal computing and software requirements, a spreadsheet may be sufficient for the calculations. It is also important to mention that in addition to calculating the dimensional parameters, the technique allows the generation and evaluation of various designs for the same temperature range

Thermoelectric Cooling: The Thomson Effect in Hybrid Two- Stage Thermoelectric Cooler Systems with Different Leg Geometric Shapes

This chapter aims to analyse the performance of hybrid two-stage thermoelectric cooler systems [two-stage thermoelectric cooling devices (TEC)], which are composed of different thermoelectric materials in each stage with different leg geometric shapes. If we consider a temperature gradient inside a two-stage TEC, then, besides Joule heat, also Thomson heat has to be taken into account. We discuss the out-of-equilibrium thermodynamics equations of a one-dimensional model to provide the performance expressions that govern the system. TEC system performance is analysed in function of the Thomson coefficients ratio of both stages. We describe a recent geometric optimization procedure that includes leg geometry parameters such as ratio of cross-sectional area and length of legs for each stage of the two-stage TEC

Peltier Supercooling in Transient Thermoelectrics: Spatial Temperature Profile and Characteristic Cooling Length

Thermoelectric coolers (TECs) can reach temperatures below that obtained with a steady-state current by applying an electrical current pulse which enables a transitory state in a Peltier device. This effect is known as supercooling. In this paper, we study characteristics parameters, such as the minimum cooling temperature and spatial temperature profile, in a TEC operated under current pulses and a cooling load ( Q c ) . Numerical analysis for a one-dimensional thermoelectric model of the cooling system is developed, and a novel MATLAB programming code is proposed for the transient state based on finite element analysis. We also investigate the influence of the thermoelement’s length upon the cooling mechanism. A new parameter called the “characteristic cooling length„ is proposed to describe the length in which the minimum cooling temperature occurs along the elements of a TEM. Results show the transient temperature profiles along the elements of the semiconductor P-type element, and a “characteristic cooling length„ is characterized. We also propose a general principle, and the lowest cooling temperature values are obtained for a semiconductor’s small length and variable pulse cooling load under current pulse operation. The present study will serve as guidance for the geometric design of TECs under current pulse operations

Optimization of Two-Stage Peltier Modules: Structure and Exergetic Efficiency

In this paper we undertake the theoretical analysis of a two-stage semiconductor thermoelectric module (TEM) which contains an arbitrary and different number of thermocouples, <em>n<sub>1</sub> and n<sub>2</sub></em>, in each stage (pyramid-styled TEM). The analysis is based on a dimensionless entropy balance set of equations. We study the effects of <em>n<sub>1</sub> and n<sub>2</sub></em>, the flowing electric currents through each stage, the applied temperatures and the thermoelectric properties of the semiconductor materials on the exergetic efficiency. Our main result implies that the electric currents flowing in each stage must necessarily be different with a ratio about 4.3 if the best thermal performance and the highest temperature difference possible between the cold and hot side of the device are pursued. This fact had not been pointed out before for pyramid-styled two stage TEM. The ratio <em>n<sub>1</sub>/n<sub>2</sub> </em>should be about 8

Optimization of Two-Stage Peltier Modules: Structure and Exergetic Efficiency

In this paper we undertake the theoretical analysis of a two-stage semiconductor thermoelectric module (TEM) which contains an arbitrary and different number of thermocouples, n1 and n2, in each stage (pyramid-styled TEM). The analysis is based on a dimensionless entropy balance set of equations. We study the effects of n1 and n2, the flowing electric currents through each stage, the applied temperatures and the thermoelectric properties of the semiconductor materials on the exergetic efficiency. Our main result implies that the electric currents flowing in each stage must necessarily be different with a ratio about 4.3 if the best thermal performance and the highest temperature difference possible between the cold and hot side of the device are pursued. This fact had not been pointed out before for pyramid-styled two stage TEM. The ratio n1/n2 should be about 8