## 3 Results
### Power Output Related with Atmospheric Stability  
Based on the above atmospheric stability analysis results, we want to confirm the change in power generation according to atmospheric stability. In more detail, we examine how the error between the expected generation and actual generation based on REWS and HHWS changes, depending on atmospheric stability.  
First, the wind shear-based wind power generation error rate for each atmospheric stability was calculated (Figure 21). When the atmosphere is unstable, neutral, or stable, HHWS sometimes has a smaller error rate, and there are turbines where REWS simulates the actual generation more closely. In particular, in the case of the A01 turbine with the widest free stream sector, it is the first turbine to receive wind from the upwind side, without the influence of wakes. Rather, in this case, it was shown that the simple HHWS simulates the actual power generation more closely than the REWS when the atmosphere is unstable, neutral, and stable. This is because when unstable, neutral, or stable, the vertical wind velocity profile is moderately inclined in the positive direction. On the other hand, when the atmosphere is strongly unstable or in a strong stable state, it can be seen that REWS significantly reduces the error with actual power generation compared to HHWS. In particular, when the atmosphere is strong and stable, the error rate with the actual power generation can be reduced by more than 5%.  
Figure 21: Comparison of error rate with actual power output by wind shear-based atmospheric stability classification. Green bar indicates the error rate between the REWS-based simulated power output and the actual power output, while gray indicates the error rate between the HHWS-based simulated and the actual power output. From (**a**–**e**), Turbine A01, Turbine A02, Turbine A03, Turbine B01 and Turbine C01 are indicated, respectively.  
Second, the error rate of wind power generation by atmospheric stability was calculated based on the intensity of turbulence (Figure 22). This confirmed that when the atmosphere was strongly unstable or somewhat unstable, that is, when the turbulence intensity was high, both HHWS and REWS did not properly simulate the actual power generation. However, when the atmosphere was strongly unstable, unstable, or neutral, it could be confirmed that REWS improves the error rate with the actual power generation, compared to HHWS. On the other hand, when classifying atmospheric stability based on turbulence intensity, it was confirmed that when the atmosphere is strongly stable, that is, when turbulence hardly occurs, the simulated power generation based on HHWS is relatively closer to the actual power generation.  
Figure 22: Comparison of error rate with actual power output by turbulence intensity-based atmospheric stability classification. Green bar indicates the error rate between the REWS-based simulated power output and the actual power output, while gray indicates the error rate between the HHWS-based simulated and the actual power output. From (**a**–**e**), Turbine A01, Turbine A02, Turbine A03, Turbine B01 and Turbine C01 are indicated, respectively.  
Finally, the error rate of wind power generation by atmospheric stability was calculated based on the Richardson number (Figure 23). What is interesting here is that REWS only gives good results when the atmosphere is very unstable, i.e., within the atmospheric boundary layer, where free convection over mechanical convection dominates. Table 9 summarizes the error rates for each atmospheric stability index and the actual power generation.  
Figure 23: Comparison of error rate with actual power output by [PERSON] number-based atmospheric stability classification. Green bar indicates the error rate between the REWS-based simulated power output and the actual power output, while gray indicates the error rate between the HHWS-based simulated and the actual power output. From (**a**–**e**), Turbine A01, Turbine A02, Turbine A03, Turbine B01 and Turbine C01 are indicated, respectively.