﻿ 高输出功率温差发电系统的研究

# 高输出功率温差发电系统的研究Studies on the High Output Thermoelectric Power Generation Systems

Abstract: An alternative energy technology based on thermoelectricity generation is investigated and its power is systematically investigated under various work conditions in thermoelectric applications. In addition, authors have modelled, designed, and constructed the thermoelectric power system. Moreover, they have invented a state-of-the-art table-top instrument that may evaluate several critical thermoelectric characters in situ. Several aspects of the thermoelectric features are characterized in situ that include the efficiency, force response curve, current-voltage (i.e., I-V) curve, power-voltage (P-V) curve, and the power versus temperature (P-T) responses. Furthermore, they have successfully built a high-power heat harvester and have applied to the automotive case study in details. Finally, they have obtained the multi-stack thermoelectric devices that have improved characters; e.g., both the power output and the thermoelectric efficiency have improved in comparison to the devices commercially available. The investigation leads to 19% efficiency in triple stack devices and 10.6% in the dual-stack one.

1. 引言

2. 热电模块原理说明

$ZT={s}^{2}T/\rho k$ (1)

$ZT={\left({s}_{P}-{s}_{N}\right)}^{2}T/{\left[\sqrt{{\rho }_{N}{k}_{N}}-\sqrt{{\rho }_{P}{k}_{P}}\right]}^{2}$ (2)

$\Delta V={S}_{NP}\ast \Delta T$ (3)

$\eta =P/{Q}_{h}$(4a)

$\eta =\frac{{T}_{h}-{T}_{c}}{{T}_{m}}\ast \left[\frac{{\left(1+Z{T}_{m}\right)}^{\frac{1}{2}}-1}{{\left(1+Z{T}_{m}\right)}^{\frac{1}{2}}+\left(\frac{{T}_{c}}{{T}_{h}}\right)}\right]$(4b)

3. 试验

3.1. 试验原理

Figure 1. The operating principle diagram of a TEPG: (a) schematic diagram of a TE device composed of P- and N-type TE legs; (b) a typical TEM integrates a large number of TE devices; (c) the physical diagram of TEPG with an output power of more than 100-Watt

3.2. 热电模块原位测试仪

Figure 2. Structural diagram of In-situ characterization station of TEM (ICSTEM)

${Q}_{c}={S}_{PN}I{T}_{c}-\frac{1}{2}{I}^{2}R-k\left({T}_{h}-{T}_{c}\right)$ (5)

ICSTEM具有很好的热管理系统。热电模块应平放，并与冷板附近热流传感器的两个边缘相对平行。隔热层是由金属薄层和玻璃纤维片的复合材料制成的多层交替隔热结构。它的多层交替的隔热效果比空气要好，隔热热导率小于0.01 W/M∙K。保温层从12层到20层不等，工作性能比石棉材料好很多，原因如下。一方面，金属箔具有很高的红外反射能力，根据计算，多层膜可以将红外辐射热泄漏的影响降低到可以忽略的程度。另一方面，纤维玻璃导热系数较低，中间有一定的空气，可以显著降低热量泄漏的影响。此时，由z方向热损失引起的误差估计在1%以下。

3.3. 余热回收温差发电系统设计

Figure 3. Design, development and test flow chart of the TEPG unit

Figure 4. Automobile exhaust TEPG device: (a) dual stack in sandwich structure; (b) a batch of TEMs configuration; (c) energy harvest unit

4. 结果和讨论

4.1. 数据和分析

4.2. 热量采集方法的研究

Figure 5. Test result diagram: (a) I-V curve; (b) P-V curve; (c) P-F curve; (d) the TE efficiency shows dependence on the temperature differential

Figure 6. Temperature distribution of thermoelectric modules (3 × 9)

Figure 7. P-T diagram

4.3. 多级联的温差发电

Figure 8. The diagram of P-type and N-type material efficiency and length ratio: (a) the P-type efficiency shows dependence on x; (b) the N-type efficiency depends on x.

Table 1. The variation law of ZT value of different materials with temperature. (P1-PbTe: Pb0.94Sr0.04Na0.02Te, N1-PbTe: Pb0.94Ag0.01 La0.05Te, P2-BiTe: Bi0.5Sb1.5Te3, N2-BiTe: Bi2Te3)

ZT值与材料的电导率、导热系数、塞贝克系数等性能有关。分段热电偶所采用的热电材料的ZT值列于表1中。基于PbTe的热电材料的高温度工作区间为573 K到873 K，此时P型的热电优值系数范围约为1.5~2.1，N型为0.9~1.4。基于BiTe的热电材料的低温工作区间为室温到573 K，此时P型的热电优值范围约为0.7~0.9，N型为0.8~1.1。提高ZT值来改进热电材料已经引起广泛深入的研究 [15] [20] [26] [28]。

5. 总结

NOTES

*通讯作者。

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