# Intermitt FOCV Using an I-V Curve Tracer for Minimizing Energy Loss
## 5 Experimental Results  
The proposed FOCV MPPT circuit was in a 0.18-\(\upmu\)m CMOS process. Figure 16 shows a microphotograph of the fabricated chip. The proposed FOCV MPPT circuit occupies an area of 750 \(\times\) 300 \(\upmu\)m\({}^{2}\). Figure 17 shows the experimental setup. A 5-W LED lamp (Power Stand-X1) and the neutral density filter (Kenko ND) was used for the varying illuminance condition instead of solar irradiance. A PV cell was attached on the Peltier module for the varying temperature condition. The specifications of the PV cell (AM-1815) were \(V_{\text{OC}}=4.9\) V, \(V_{\text{MPP}}=3.0\) V, and \(I_{\text{SC}}=47\)\(\upmu\)A under the condition of 200 lx and 25 \({}^{\circ}\)C. Under the experimental conditions, the specifications were \(V_{\text{OC}}=4.16\) V, \(V_{\text{MPP}}=3.50\) V, and \(I_{\text{SC}}=40\)\(\upmu\)A, respectively. Figure 18 shows the measured I-V curves and the \(\alpha\) valuesat 25 \({}^{\circ}\)C and 65 \({}^{\circ}\)C. As the temperature varied from 25 \({}^{\circ}\)C to 65 \({}^{\circ}\)C, not only did \(V_{\text{OC}}\) and \(V_{\text{MPP}}\) change, from 4.20 V to 3.40 V and from 3.50 V to 2.30 V, respectively, but \(\alpha\) also changes significantly from 0.84 to 0.69, a 17.86% difference. Figure 16: Chip micrograph. Figure 17: Experimental setup for the proposed FOCV MPPT. Figure 18: Measured I-V curves and \(\alpha\) of PV cell under various temperature: (**a**) 25 \({}^{\circ}\)C, (**b**) 65 \({}^{\circ}\)C.  
The measured MPP tracking waveforms and the operating voltages (\(V_{PV}\), \(V_{MPP}\), \(P_{max}\), and \(P_{PV\_PWM}\)) are shown in Figure 19. In Figure 19, the operating points of the PV cell track the MPP according to the proposed FOCV MPPT algorithm. Figure 20 shows the measured varying P-V characteristics and \(\alpha\) of the PV cell under various temperature conditions, from 25 \({}^{\circ}\)C to 65 \({}^{\circ}\)C. Even in the single PV cell, \(\alpha\) varied significantly depending on temperature variation from 0.85 to 0.69. Comparison of the energy loss caused by wrong \(\alpha\) between the conventional FOCV and the proposed FOCV MPPT with the refreshing frequency \(f_{0}\) for 13 h under varying temperature conditions is shown in Figures 21 and 22. Each temperature daily profile was measured at Death Valley, California, USA on 30 April, 2021 [34] (Scenario I), and Seoul, South Korea on 30 July 2021 [35] (Scenario II), respectively. According to Figure 21, the energy loss of the conventional FOCV and the proposed FOCV MPPT were 441.12 mWs and 0.25 mWs, respectively while the temperature varied from 25 \({}^{\circ}\)C at 06:00 to 42 \({}^{\circ}\)C at 18:00. The energy loss by the proposed FOCV decreased by 99.94% of that of the conventional FOCV per hour. In Figure 22, the energy loss of the conventional and the proposed FOCV are 521.71 mWs and 0.36 mWs, respectively; the proposed FOCV reduced the energy loss by 99.93% compared the conventional FOCV. Figure 19: Measured power tracking waveforms with the proposed FOCV MPPT under 25 \({}^{\circ}\)C.  
Figure 20: Experimental results for (**a**) power versus voltage characteristics a PV cell and (**b**) \(\alpha\) under various temperatures: 25, 35, 45, 55, and 65 \({}^{\circ}\)C.  
Figure 23 shows the measured varying P-V characteristics and \(\alpha\) of the PV cell under varying illuminance conditions, from the normalized illuminance 1 to 1/16. Each illuminance step is quantized by the distance and the neutral-density filter and normalized by the Illuminance-1 that was measured under a 0.3-m distance between the PV cell and the LED lamp. As shown in Figure 23b, \(\alpha\) varies significantly from 0.69 to 0.79 depending on illuminance. Figure 24 illustrates comparison of the energy loss between the conventional and the proposed FOCV with the refreshing frequency, \(f_{0}\), under varying illuminance over 13 h (Scenario III). In Figure 24, the energy loss caused by the conventional and the proposed FOCV are 585.58 mWs and 0.35 mWs, respectively.