30 Charge Charge Limit Charge Amount 20 Charge and Discharge Amount and Limit (GWh/h) Charge and Discharge Amount and Limit (GWh/h) 30 10 0 -10 1 5 9 13 17 21 -20 CL2 CL3 Charge Amount 10 0 -10 1 5 -20 -30 CL1 Charge Limit 20 Discharge -30 Charge Discharge CL4 9 120 120 Demand (GWh/h) Demand (GWh/h) 140 100 80 60 40 20 5 9 13 Curtailment 21 CL5 (b) 140 1 17 Discharge Limit Discharge Amount (a) 0 13 17 EVs 100 80 60 40 20 0 21 1 Original Load (c) 5 Net Load 9 13 17 21 Adjusted Net Load (d) figure 24. The flexibility provided by the smart charging/discharging of EVs (1 April, 10 balancing areas in Japan). (a) Charge and discharge of uncontrolled charging. (b) Charge and discharge of controlled charging and discharging in homes and offices. (c) Load and curtailment of uncontrolled charging. (d) Load and curtailment of controlled charging and discharging in homes and offices. Clusters (CLs) 1-5: The charge and discharge capacity limits of five EV clusters according to usage patterns. 8 Capacity (GW) 6 4 2 0 -2 1 3 5 7 9 11 13 15 17 19 21 23 -4 Hour of Day Oil Combined Heat and Power Gas HPWH Coal EVs Bioenergy Hydro Pumped Storage Pumped Generation Wind PV Request for Upward Flexibility Request for Downward Flexibility figure 25. An example of an optimum demand and supply analysis, including a balance of tertiary-slow flexibility against an extreme forecast error in Kyushu in April. 62 ieee power & energy magazine november/december 2020