The physics of practical storage have been fully understood and well internalized in civil engineering for centuries: E = Fx. All that remains unclear is which

The physics of practical storage have been fully understood and well internalized in civil engineering for centuries: E = Fx. All that remains unclear is which forms will turn out to be cheapest at the time when they need to be built. What is known now is that costs are falling even faster than did solar and wind, and are already of similar order.