*3.5. Impact on Annual Cost and CO*<sup>2</sup> *Generation*

Figure 16 shows the CO2 emissions generated due to the fuel consumed by coal and LNG generators.The combination of solar and LNG electricity generation could cut the CO2 emissions by half when comparing the "No solar + 10 TWh LNG" and "20 GW Solar + 28 TWh LNG" scenarios. The impact of solar power is also readily seen by comparing the values in each LNG quota scenario, which should be attributed to its capability to reduce coal generation even beyond 12 GW.

**Figure 16.** Range of CO2 emissions for various scenarios in Kyushu.

As seen in Figure 17, since solar power has a higher generation cost than using LNG, its impact on the annual generation cost is more significant. The weather conditions greatly influence the annual generation cost: 2014 and 2013 represented the lowest and highest costs, respectively. The variations in the cost attributed to the LNG scenarios were more evident in 2013 followed by 2018 and 2016 caused by higher coal production during the extreme and severe summers. In the least costly year, the cost ranged from 1.22 to 1.36 trillion JPY (11.48% increase), and in the most costly year, the cost ranged from 1.26 to 1.41 (12% increase) trillion JPY (April 2021: 100 JPY = 0.92 USD = 0.77 EUR).

**Figure 17.** Annual generation costs for various scenarios in Kyushu.

Using 2016 as the representative, Figure 18 shows the impact of the installed solar capacity and the LNG quota on the levelized cost of generation and levelized CO2 emissions. Currently, the Kyushu region already has 10 GW of installed solar capacity and generates around 10 TWh from LNG. This reference scenario is annotated as scenario 0 (*S*0) in Figure 18 and values for the levelized cost and CO2 emissions for the various weather conditions are shown in Table 9.

From this reference scenario, the company could further decrease their CO2 emissions by having more LNG generation, adding more solar capacity, or both, but at the expense of increasing their generation cost. Five potential scenarios are annotated as *S*<sup>1</sup> to *S*<sup>5</sup> in Figure 18 and the impacts are tabulated in Tables 10 and 11. Initially, the LNG generation could be ramped up to 20 TWh to complement the solar capacity increase, as seen in *S*1. This increased the generation cost by an average of 0.63% and decreased the CO2 emissions by an average of 12.80% to 0.3226 kgCO2/kWh. From *S*1, solar capacity could continuously increase, as seen in *S*<sup>2</sup> and *S*3, or LNG could increase further as seen in *S*3. The impact of *S*<sup>2</sup> and *S*<sup>4</sup> in reducing CO2 emissions was the same, but the increase in cost was lower for *S*4. *S*<sup>5</sup> represents the greenest yet feasible scenario that reduces the CO2 emissions by an average of 37.31% but increases the cost by 5.60%.



As of April 2021: 100 JPY = 0.92 USD = 0.77 EUR.

**Figure 18.** Levelized generation cost and CO2 emissions for the warmer year (16SM) scenario. The CO2 emissions (abscissa) are formatted in decreasing order to emphasize the trend. *S*<sup>0</sup> reflects the current situation, and *S*1–*S*<sup>5</sup> are the potential future scenarios.

**Table 10.** Cost increase from the reference scenario.


**Table 11.** CO2 emission decrease from the reference scenario.

