Pretty easy to solve. We know that electricity can go around the Earth 7 times in a second. Now, if Germany has excess electricity during the day, they can simply pospone that electricity by wrapping a long cable 302 400 times around the globe (12h * 3600s/h * 7/s = 302 400). During the day they feed the excess electricity into one end of the cable, and then 12 hours later at night, electricity comes out the other end at just the right time, when they need it!