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– David Munson Jr

Real Solar Output History

Solar output history

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The solar industry loves to talk about nameplate power output based on a benchmark solar radiation of 1000 watts per square meter.  Yet the industry is promoting solar farms in areas that will not see anywhere near that level of solar radiation. Years back, FOI Group LLC of Dallas, Texas worked on a solar energy patent that offered a way to have more reliable power. Part of the project included measuring solar radiation minute by minute in the Dallas area for over a year.

Here is a week’s worth of data from late December:

Solar input data from 2006

Note that peak output was over 600 watts for a very short time on one day but very low on three days.  Even the best day is marred by many wild dips in solar output shown by the many vertical lines on the graph.  There is only one unblemished day in this week.  Intermittent clouds only affect a small area at a time. If solar farms or arrays were widely dispersed, the short-term fluctuations would cancel out as a cloud would only pass over one solar array at a time in an area of many.  Unfortunately, solar farms tend to be large and concentrated. In such a layout, an intermittent cloud can cause loss of power to a large percentage of total solar output in the area.  Notice on the graph that there is no power most of the time, and power output is only at a peak for a short time. Much is made of the lower prices for solar based on peak output. Yet the ideal conditions for peak output are fleeting.  The data from this winter week shows only a small fraction of peak total output with three days of almost no output.  Counting on a solar energy system as a primary source without backup would mean large power blackouts.

Here is a summer week:

Solar input data from 2007

There is clearly a much higher peak output than the winter week, but the wild fluctuations in power would be a disaster as a major or sole energy supplier for a home.  The swings would be even wider farther north or in higher rainfall areas.  FOI Group LLC’s solar thermal power system would have been equipped to deal with the wide swings, but it is difficult to size a mirror array to produce high temperatures that are needed with such wide variance.  The patent can be seen at,  but material limitations made FOI discontinue development in conjunction with these discouraging graphs.  

It is hoped that these graphs, which are not specially selected for bad results but are representative, will make it clear that we need backup power with equal capabilities to the installed solar power.  Ideally, the backup power system would consist of natural gas power plants on standby to quickly step in when needed, along with flywheel storage to fill the short term disruptions that would make a computer crash if solar power alone were a big part of the power supply of the electric grid.  

Proponents of batteries vastly underestimate the amount of batteries and charging solar arrays needed to provide continuous power.  To meet a megawatt of load full-time would take an extra 3 megawatts of actual solar power output at the average solar radiation over a six hour period. This is a multiple of the nameplate power output that is used for cost calculations.  And this only provides power for nighttime needs.  One would need four more megawatts of solar panels to charge the batteries to provide power for a cloudy day.  The costs would be large even if there were enough raw materials to make all those batteries.  

So while the nameplate power output of a solar panel results in a competitive cost with a natural gas powerplant, the actual produced power is up to three times more expensive in winter at peak times and sharply higher over the course of a day.  Adding full-time battery backup drives the cost through the roof.

It is time to Get Real about solar energy before we mandate its use by law.  See www.getrealalliance/book .org for how to order the thorough book on climate and renewable energy.