I linked a paper talking about that. Losses are likely on the order of 5% per 1000km. I would think long distance transmission lines could transmit power both east and west which solves some of the time shifting issues. And south to north which solves some of the issue with low irradiance during the winter at high latitudes.

AKA Germany would probably be better off investing solar farms in southern Spain and connecting via long distance transmission lines. Only 1600km or so. Also consider sunset is an hour later in south west Spain.