Empirical Equation을 이용한 고분자전해질 연료전지의 전압 손실에 대한 연구

Study of Voltage Loss on Polymer Electrolyte Membrane Fuel Cell Using Empirical Equation

Abstract

고분자전해질 연료전지(PEMFC)의 성능을 예측할 수 있는 empirical equation의 역할이 중요하게 대두되고 있다. 본 연구에서는 polarization curve에서 activation loss, ohmic loss, mass transfer loss 영역을 분리하였고, 현재까지 개발된 model 중 Kim의 model과 Hao의 model을 선정하여 각 영역의 fitting을 시행하였다. 온도, 압력, 산소 농도 및 막 두께를 운전변수로 설정하여 조건 변화에 대한 각 loss의 변화를 비교하였다. 기존 model은 전반적으로 좋은 fitting 정확도를 보였지만, 분리된 loss 영역에서는 부정확한 fitting 결과를 보이기도 하였다. 연료전지 성능 예측의 정확도를 개선하기 위하여 converge coefficient를 도입한 새로운 model을 제안하였다. 본 연구에서 제안한 model을 연료전지 성능 예측에 적용한 경우에 신뢰도 평가에서 개선된 결과를 얻을 수 있었다.

The role of empirical equation to predict the performance of polymer electrolyte membrane fuel cell is important. The activation, ohmic and mass transfer losses were separated in a polarization curve, and the curve fitting according to each region was performed using Kim's model and Hao's model. Changes of each loss were compared according to operation variables of the temperature, pressure, oxygen concentration and membrane thickness. The existing model showed a good fitting convergence, but less fitting accuracy in the separated loss region. A new model using the convergence coefficient was suggested to improve the accuracy of performance prediction of fuel cells of which results were demonstrated.

Figure 1. Cells used in the experiment (a) FCT Cell (b) K Cell.

Figure 2. Polarization curve at different temperatures.

Figure 3. Loss Separation at different temperatures (a) activation loss of Hao’s model (b) activation loss of Kim’s model (c) ohmic loss of Hao’s model (d) ohmic loss of Kim’s model (e) mass transfer loss of Hao’s model (f) mass transfer loss of Kim’s model.

Figure 4. Polarization curve at different pressures.

Figure 5. Loss Separation at different pressures (a) activation loss of Hao’s model (b) activation loss of Kim’s model (c) ohmic loss of Hao’s model (d) ohmic loss of Kim’s model (e) mass transfer loss of Hao’s model (f) mass transfer loss of Kim’s model.

Figure 6. Polarization curve of different oxygen concentrations.

Figure 7. Loss separation at different oxygen concentrations (a) activation loss of Hao’s model (b) activation loss of Kim’s model (c) ohmic loss of Hao’s model (d) ohmic loss of Kim’s model (e) mass transfer loss of Hao’s model (f) mass transfer loss of Kim’s model.

Figure 8. Polarization curve at different membrane thicknesses.

Figure 9. Loss separation at different membrane thicknesses (a) activation loss of Hao’s model (b) activation loss of Kim’s model (c) ohmic loss of Hao’s model (d) ohmic loss of Kim’s model (e) mass transfer loss of Hao’s model (f) mass transfer loss of Kim’s model.

Figure 10. Data fitting of Hao’s model (a) activation loss (b) ohmic loss (c) mass transfer loss.

Figure 11. Percentage of current density parameter i_loss.

Figure 12. Data fitting results by changing converge coefficient c (a) activation loss (b) polarization curves.

Figure 13. Data fitting results by Hao’s model and New model (a) activation loss (b) ohmic loss (c) mass transfer loss.

Table 1. Standard Operation Conditions of Fuel Cell Performance Test

Table 2. Fitting Parameters and Losses at Different Temperatures (1,500 mA/cm²)

Table 3. Fitting Parameters and Losses at Different Pressures (1,500 mA/cm²)

Table 4. Fitting Parameters and Losses at Different Oxygen Concentrations (1,500 mA/cm²)

Table 5. Fitting Parameters and Losses at Different Membrane Thicknesses (1,500 mA/cm²)