The solar bell curve

With fixed solar panels, for example rooftop panels, the amount of power produced describes a bell, or perhaps better, a sine wave, rising steeply, then more slowly, then achieving a brief peak before falling slowly then faster.  There's a very brief "lip" at dawn and sunset, hence the "bell curve".

Single-axis tracking solar panels follow the sun, so they produce a much "squarer" generation profile.  Compare the two in the chart below (from Australian company, Carnegie Clean Energy):

This has important implications for the usefulness of solar to the grid.  Output rises sharply to its peak and stays there (unless it gets cloudy).  This is very useful for the morning demand ramp.

“The additional generation gained due to the single axis tracking system selected for the project has been evident with the system’s output quickly ramping up in the morning,” Carnegie said in a statement.

It also means that it's easier to project how much storage will be needed to approximate the output from a baseload plant.  Assuming nighttime demand is 2/3rd of daytime demand (as in California, for example), we would need 66% of maximum output for the 12 hours of darkness (on average; it would be different by season).  That means 2/3*12, or 8 hours of storage.  That leaves no safety margin for cloudy days, but if many geographically separated solar farms are attached to the grid, and there are other generation sources in the grid (wind/offshore wind/hydro) then it would be enough.  We will ultimately need more storage as renewables increase their penetration in the grid, but by then, battery costs will also have fallen--they should halve over the next 6 years.