Solar Cells Are Not Able to Supply Daily Power Demand Alone


Our nation’s electricity is produced mainly by fossil fuels and nuclear energy.  The role played by renewables is relatively small, even though the public seems to believe it is greater.  This is probably because the media apparently wants the public to believe it is so.  The Chart 1 below is from the Energy Information Administration (eia), an arm of the Department of Energy:

                                                   CHART 1 

Wind and solar represent 9.1% of the sources of US electricity generation in 2019. 

The sources noted in the picture above feed their power output into systems called the grids.  These grids distribute the power to the users in their area. The grids do their utmost to be a source of uninterruptable electricity at a specific frequency.  This they do reliably. 

All of us have experienced a power loss at our home or business and you know how disruptive that is.  But most power losses we have experienced are almost always local disruptions, e.g.  wind, snow, lightning, power pole meets vehicle, transformer failure, etc. But not a grid failure.

The grids fine tunes their delivery of power, matching the increases and decreases of demand.  The grid operators dictate to the suppliers what is needed.  For example, the operators can use Nuclear and Coal based plants as a base load.  These two sources are predictable and steady suppliers but may not be able to quickly react to changes in demand.  The grid operator’s natural gas plants can adjust quickly to changes to prevent supply disruptions. Most businesses need electricity to be uninterrupted as downtime is costly.

Wind and solar are non-dispatchable because they are neither predictable nor steady suppliers of electricity. The wind driving the wind turbines can go from near gale force to calm very quickly.   Solar can do the same as cloud banks appear overhead.  The grid operator has no control over how much or how little the renewables are producing.  If renewables are supplying the grid, the operator must have backup capacity to prevent shutdown of the grid. By the way, grids are not capable of storage of electricity.

The following is from a posting by American Experiment titled “No State Imports More Electricity Than California” by Isaac Orr:

“The Chart 2 below is from Electricity Map, and it shows electricity generation by source on April 3, 2019 in California. The orange section represents solar, the blue hydroelectric, light blue, wind, green, nuclear, red natural gas, and the brown section is imported electricity.

                                                   Chart 2

As you can see, imports fall when it is sunny out, and increase again when the sun goes down. It just so happens that the sun was not shining when the demand for electricity in California was highest. California’s policies promoting renewables at the expense of dispatchable generation place it in an odd predicament, it must pay other states to take the excess electricity generated by renewables when their generation is high, and it must also pay other states for their power when renewable generation is low.”

From Chart 2, you can see solar cells negatives. 

 Solar cell production is not at its maximum at sunrise nor sunset.  It peaks around noon when the sun is directly overhead. The eia Chart 3 below shows typical electricity production in Los Angeles.   Using the gold curve, that assumes that the solar cell has tracking, at 3pm, the watts are about 550 Watts and at 7pm it is at zero.  At the peak demand midpoint, say 5 pm, it can only produce about 250 watts.  (This would be the output of a single solar cell.  However, it represents the rest of the solar cells.  The change in watts is equivalent to the percent reduction the entire solar cell farm would experience.)

                                             Chart 3

The energy production Chart3 would suggest that a solar cell is not a major contributor during peak demand.  That matches the illustrated Chart 2.

  • The greens imagine pairing solar cells and wind turbines producing energy for a grid.  In this case, regardless of the capacity of the solar cells, the wind must be able to produce all the power to satisfy the capacity rating of the location. Every day, after the sun sets, the wind turbines would have to match demand.  Solar cells can never support the daily capacity rating of the location. So why have them?

I am not a proponent of either wind turbines or solar cells.  Earlier in this posting I outlined the fact that they are not dispatchable.   Industry could not function with an unreliable energy supply.  Nor would the public accept it.  Brown outs and black outs are inevitable without a backup. 

Power Engineering posted “Study Says Renewable Power Still Reliant on Backup from Natural Gas” by Wayne Barber.   In this posting he covers a study by the Massachusetts-based National Bureau of Economic Research that stated:

“We show that a 1 percent increase in the share of fast-reacting fossil generation capacity is associated with a 0.88% percent increase in renewable in the long run,” the NBER authors say in the report.


One response to “Solar Cells Are Not Able to Supply Daily Power Demand Alone

  1. You are very generous when you say solar cannot ‘function’ more than half a day. [12 hours ]. Actually, power outside of 10 to 4 is a small percent of the total; solar thus, on cloud-free day, contributes meaningful amounts for 6 hours a day.
    That is 1/4 of a day, not 1/2.

    Art Krugler

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