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Solar Panels at the Cincinnati Zoo & Botanical Gardens

March 23, 2013

Zoo pic

Per an article in the Cincinnati Enquirer by Mike Boyer and presented by USA Today “Solar canopy energizes Cincinnati Zoo

“Billed as one of the largest public urban solar displays in the country, the $11 million solar “canopy” will do much more than help control the zoo’s utility bills and shelter visitors from the elements when it’s turned on in mid-April, developers say……….

……….According to Melink, the project consists of 6,400 photovoltaic solar collection panels assembled on more than 100 metal arrays, 15 to 18 feet high. They cover about 800 of the 1,000 parking spaces at the zoo’s main entrance. The project is designed to produce 1.56 megawatts of electricity, about 20% of the zoo’s annual need and enough to power 200 homes.”

Additional current data can be found at the website for the zoo,, which indicates a measured return of about 1,913 MWh per year. This would be a dollar value return of $191,300 per year if you allow $100 per MWh (which is an over-statement).


For performance evaluation the capacity factor (CF) is calculated as follows:

CF = [1913 MWh/year] ÷ [1.56 MW x 8760 hrs/year)] x 100% = 14 %

This return would lead to a payback of the $11 million “investment” in slightly over 57 years.  Unfortunately the life of the solar panels is probably more like 20 years, and their performance will actually degrade at least 1% per year with age, so we will never see a payback on the $11 million. 


Investing $11 million in CCGT generation could have bought roughly 10 MW of CCGT capacity, capable of generating about 75,000 MWh per year, assuming:

  • CCGT costs roughly  $1.1 million per MW
  • The Capacity Factor (CF) for CCGT generation is 85%

This means we could have gotten 39 times the electricity, and about 20 times the reduction in CO2 emissions, had we invested in CCGT rather than solar panels, assuming that the electricity produced would be directly replacing coal fired generation.


It is possible that the “car port” portion of this project might have accounted for 50% of the investment; an assumption that is very generous to the solar panels.

If this is the case, then payback for the 50% that was invested for the solar panels would still be 28+ years (still longer than the life of the panels) and we might only get 20 times the electricity and 10 times the CO2 reduction from CCGT.


There is no doubt that we in the USA need to alter our energy strategy.  The question of how we will change it, however, needs to be determined by scientific evaluation of fact and logical analysis of performance and economics; not by emotion, political considerations, and “feel good” methodologies.

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