Someone quoted the following article at me: Did Germany Really Surpass 100% Renewable Power? They claimed this as evidence that its possible for the US to move to 100% wind and solar energy. But, if you look in this very article, you find this quote:
We still only have 20% wind and solar on the German grid
The report was merely that there was a peak in solar/wind generation that reached 100% of the load that the grid can carry. While this is a great achievement, and offers hope that, with buffering (e.g. giant battery farms), solar and wind may one day be able to sustain 100% of the German grid, it does not mean that 100% is anywhere close.
Another little hurdle to overcome: Germany is densely populated. One of the biggest loads on grids in North America is transmission. Sending power from places that have plenty of generation capacity (e.g. the Arizona desert) to places that need the power and can’t easily generate it (e.g. rainy Seattle) is not feasible without huge losses. So how will wind and solar ever power a place that isn’t windy or sunny? They probably won’t. Instead, hydro and geothermal (if available), natural gas and coal (for now), or nuclear will be used.
The best way to reduce greenhouse gas emissions and minimize the number of nuclear power plants that will be built (and river valleys flooded for hydro) is to reduce power consumption. If Germany could become 80% more energy efficient (unlikely, but imagine), the entire grid really could be run with solar and wind power. Now suppose that they were to become 40% more efficient (seems possible), doubled the amount of solar and wind power generation, and made generation 50% more efficient with better technology. They’d be done.