绝热条件下固体氧化物燃料电池的瞬态电化学特性

doi:10.3969/j.issn.1674-1951.2021.07.005

摘要/Abstract

摘要：

在能源系统内耦合储能设备,可有效提升可再生能源的利用效率和技术水平。为获得固体氧化物燃料电池（SOFC）在电解与发电模式切换瞬态过程中内部的热电耦合特性,基于热力学、电化学机理,建立了SOFC电堆动态模型;基于动态模型,获得了SOFC电堆在绝热环境中从电解向发电模式切换时,电堆温度、电池能斯特电动势、电池活化极化电压损失、电池欧姆电压损失、电池浓差极化电压损失和电池输出电压的变化趋势,对比分析了电堆在定温和绝热环境下电化学特性的差异。结果表明：电堆在绝热环境下先电解后发电,每个模式各运行20 000 s,采用阶跃及斜坡方式改变电流密度时,电堆温度变化幅度分别为45.8 K和101.1 K;电流密度相同的情况下,电堆分别在绝热和定温环境运行时,单电池输出电压最大相差0.015 V。

关键词: 可再生能源, 储能, 固体氧化物燃料电池, 热电耦合特性, 模式切换, 瞬态过程, 动态模型

Abstract:

Coupling energy storage equipment into energy systems can effectively improve the utilization efficiency and technical level of renewable energy.To obtain the internal thermoelectric coupling characteristics of a solid oxide fuel cell （SOFC） during the transient process switching from electrolysis mode to power generation mode, we established a dynamic model for the SOFC stack based on thermodynamics and electrochemical mechanisms. Based on the dynamic model, the stack temperature, the Nernst EMF, activation polarization voltage loss, ohmic voltage loss, the concentration polarization voltage loss and the output voltage of the cell during the switching from electrolysis mode to power generation mode were calculated. The electrochemical performances of the SOFC under isothermal and adiabatic conditions are compared. The results show if the stack operates in electrolysis mode and then in power-supply mode for 20 000 seconds each, the stack temperature will vary by 45.8 K and 101.1 K by modifying current density in step and ramp format, respectively. When the current density is identical, the maximum output voltage difference of a single cell is 0.015 V if the stack operates in adiabatic and isothermal environment.

Key words: renewable energy, energy storage, SOFC, thermoelectric coupling characteristics, mode switching, transient process, dynamic model

中图分类号:

TK91

王朝阳, 刘明, 赵永亮, 种道彤, 严俊杰. 绝热条件下固体氧化物燃料电池的瞬态电化学特性[J]. 华电技术, 2021, 43(7): 30-36.

WANG Chaoyang, LIU Ming, ZHAO Yongliang, CHONG Daotong, YAN Junjie. Transient electrochemical characteristics of solid oxide fuel cells under adiabatic conditions[J]. Huadian Technology, 2021, 43(7): 30-36.

图/表 17

图1

表1

电堆动态模型控制方程

名称	表达式
质量守恒	$d M i d t = q ˙ n, i, in - q ˙ n, i, out + ϕ q ˙ n, i, react$
动量守恒	$R r q ˙ n, i, total 2 = p in - p out$
动量守恒	$q ˙ n, i, total = ∑ q ˙ n, i, out$
能量守恒	$c s m s d T s d t = ∑ q ˙ n, i, in h i, in - q ˙ n, i, out h i, out - W ˙ s + Q ˙ s, react + P ˙ ext + P ˙ s, int W ˙ s = N V cell J A cell$ $Q ˙ s, react = JN A cell 2 F Q ˙ react$ $P ˙ ext = σ T f 4 - T s 4 A sur$ $P ˙ s, int = J V act + V ohm A cell - J A cell T s Δ S 0 2 F$ $Δ S 0 = Δ S H 2 O 0 - (Δ S H 2 0 + 0.5 Δ S O 2 0)$
电化学控制	$V cell = E Nernst - V act - V ohm - V conc$ $V s = N V cell$ $E Nernst = - Δ G 0 2 F + - R T s 2 F ln p O 2 p H 2 p H 2 O$ $V act = R T s 2 αnF sin h - 1 J 2 J 0$ $V ohm = J R as$ $V conc, fuel = R T s 2 F ln p H 2 O, tpb p H 2 p H 2 O p H 2, tpb$ $V conc, oxygen = R T s 2 F ln p O 2 p O 2, tpb$ $V conc = V conc, fuel + V conc, oxygen$

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参考文献 16

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项目	参数
单电池有效面积/cm²	87.7
单电池个数N	8
工质	H₂/H₂O/O₂
工作压力/MPa	0.1
H₂/H₂O摩尔流量/(mol·s^-1)	0.006 50
O₂摩尔流量/(mol·s^-1)	0.002 98
工质入口温度/K	1 073.0