Debunking the Debunker by Revisiting Photovoltaic Yield Calculations & Feasibility

Our original intention is posting “Stossel’s Myths” about global warming was to agree with him in principle, but question one of his outlandish claims. In his ABC News post of April 20th entitled “Global Warming Myths,” citing sources, Stossel believes it would take 1,000 acres of photovoltaic array to power the daily operations at Epcot Center at Disneyland Florida, when if fact it would only require 100 acres of photovotaic arrays, even at a paltry output of 10 watts per square foot and an average 8 hour (full sun equivalent) day. Florida is sunnier than average, last time I checked.

Stossel based his PV bashing on calculations that we find completely valid except for the fact he dropped a digit somewhere, therefore decreasing the cost-effectiveness of photovoltaics by one order of magnitude. Certainly an order of magnitude is worth revisiting data on photovoltaic output, wouldn’t you say?

Here’s an inconvenient question:
Stossel says the 395,000 kilowatt-hours consumed each day by the 300 acre center would require 1,000 acres of land. This understates photovoltaic output by about 10x.

Here’s why:
At a mere 10 watts per square foot of output in full time, at a mere 8 hours of full sun (or full sun equivalent) solar input, you will get 80 watt hours per day from every square foot of PV array.

That is a safe assumption. If there are 44,000 square feet in an acre then an acre can produce 3,520,000 watt-hours per acre per day, or 3,520 kilowatt-hours. This means it would only take 112 acres of photovoltaics to power Epcot, not 1,000.

One big assumption we make is that the photovolataic output can be saved. But by using concentrator technology and battery or thermal storage, 100 acres of solar array is probably plenty to power Epcot through the night.

So every claim and counterclaim should be debunked if it is debunkable. It is excessive to suggest any free thinking American would be expected to turn their thinking apparatus off in a selective manner, whether they are alarmed or skeptical. And without verifying the numerical logic of any scientifically or financially based claims, any consumer or regurgitator of vital information is only repeating plausible sounding arguments that may lack all sense of proportion.

Why isn’t anyone who is interested in photovolaic returns on investment develop an IRR analysis based on this: one cubic meter of fresh, desalinated seawater only requires 2.0 kilowatt-hours of energy input. That a mere 1.0 gigawatts of power could provide – from the ocean – residential drinking water for 20 million people is an astonishing statistic. Build desalinization plants using photovoltaic and thermalvoltaic solar arrays. Here is where an investment in massive fresh water production and transfer infrastructure would transform and green the lands from California to Burkina Faso.

Reference: Revisiting Desalinization, Photovoltaic Desalinization

2 Responses to “Debunking the Debunker by Revisiting Photovoltaic Yield Calculations & Feasibility”
  1. Jimmy says:

    Concentrators are mentioned briefly, but it should be pointed out that a solar install of this size SHOULD be done with solar concentrators. PV is so inefficient in comparison. Trough or tower systems can be 30+% efficient compared to the 10-13% of a typical PV, which would bring you down to ~40 acres instead of 112. PV is really best for small distributed installs, not for megawatt systems. If we want solar technologies to take off, we need to focus on using the right system for the given application.

  2. Ed Ring says:

    Thermal concentrators do achieve higher efficiencies at the collector surface, but due to space required for the balance of plant and the greater necessary distances between the collectors, probably have a somewhat lower energy output per area, overall. But I agree with you that concentrators are a good choice at a utility scale – they are far closer to being cost competitive with, for example, coal, than photovoltaics are at this point. And in any case, the space required to power the world with photovoltaic or thermalvoltaic arrays is not significant – Stossel is dead wrong about that.


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