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Solar Energy – Do the math

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  • Sun, Dec 14, 2014 - 09:12pm



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    Solar Energy – Do the math

Can anyone help me out?  I have a debate running on facebook about limits to growth and a relative of mine just landed this gem: “As far as fulfilling our energy needs, our entire energy needs could be met by using a relatively small portion of the globe for solar power infrastructure alone. Add wind, hydro, etc. and we have all the energy we will ever need. Fossil fuels will die out as their use becomes economically disadvantageous, we’re already seeing it happen.

At one point I read an article on Do The Math ( that pretty well debunks the renewable as a replacement argument.  I can’t find the article, but would love to reference it if anyone can find it since the person I am discussing this with values education and the author, Tom Murphy, is an associate professor of physics at UC San Diego.  I have plenty of other references I could use, but I want to head off the credibility attacks by picking my source carefully to satisfy my audiences concept of qualification.



Tom Murphy is an associate professor of physics at the University of California, San Diego – See more at:….

Tom Murphy is an associate professor of physics at the University of California, San Diego – See more at:


  • Wed, Dec 17, 2014 - 08:14pm


    Mike Dill

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    Solar panels and EROEI

A few years ago, solar panels were expensive, and all of them were built using rare minerals. While most solar cells are still built using these older and well know processes, there are new cell types out there that are using organics (carbon) and common minerals.

If I recall correctly, the EROEI for PV solar on a residential rooftop now is about 8 to 1, assuming a twenty year lifespan. My panels have a twenty year warranty, and I expect them to last forty years, as there are currently PV systems that are still running at that age.

The new technologies are increasing the EROEI, and this will continue to improve for the foreseeable future, as there are announcements on new breakthroughs almost daily.

So, the current BAU situation probably needs an EROEI of 10 or 12 to 1 in order to continue. This is not happening YET. Battery powered cars have an EROEI of less than that currently, and we do not yet have planes and trains that will work with renewables. The website is probably correct for the CURRENT situation, but fails to foresee the improvements that are coming.

I am waiting for another year or two before buying battery storage to back up my grid tied power system, as the prices there are dropping rapidly, which also implies that the EROEI is improving there.

  • Fri, Dec 19, 2014 - 01:27am



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    You’re both right

As far as fulfilling our energy needs, our entire energy needs could be met by using a relatively small portion of the globe for solar power infrastructure alone.


Your relative is correct and you are correct and so is Mike Dill. Your relative's statement, of course, is over-simplistic, because he seems to be saying 'let's harness the sun because of all the power that is there,' without taking into account the EROEI as discussed by Mike Dill above or James H. Kunstler in The Long Emergency. If we'd started on solar 30 years ago and stuck with it, his hopes might be realistic. As it is, we'll have to adjust to a world with less energy.

  • Fri, Dec 19, 2014 - 05:16pm


    Mike Dill

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    Solar can power the world – BUT

I did miss a part of the argument here, as I did not mention that solar PV and wind currently only accounts for less than one percent of all energy consumed. If there is a crash right now we are not going to do well as a global community.

If the current growth rates of those two and other renewables continue at the present rate, we should be able to be completely renewable by 2050 or so (exponential growth curves). Reducing our energy footprint is required if the energy system fails to change before that time. Either that, or we have to fall back to the  systems that existed before the 1850's.

  • Tue, Dec 23, 2014 - 04:45pm



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    Try this out…

This site has a very good numbers based breakdown of why solar/wind can't make it up:

This analysis just asks and answers the the question "how much energy would be required to install the concrete bases for enough wind turbines to supply 50% of the world's energy needs by 2030?"

The answer is stunning…

  • Wed, Dec 24, 2014 - 01:49pm



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    Is the scale wrong?

What I mean is,

It appears that large wind and solar collectors are more energy intensive and hold a greater investment and therefore a greater risk of loss if/when the device fails. Not to mention that the paradigm is still that of a "centralized" production of electricity and then distribution. 

What about smaller, individualized units providing "de-centralized" production using the existing distribution network? 

I don't know, but I think the answer is in smaller, not larger units.

We can build super-tankers and ever larger generating plants. What if that effort was redirected in making small, end user type units? I understand that would change the power (political, investing) and control to different folks.

Either way, to do nothing, yields just that – nothing.


  • Thu, Dec 25, 2014 - 02:47pm



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    Are the variables wrong?

What happens if, rather then trying to scale energy production up to the current population, we scale the population down to a level that can live with sustainable energy?  The math seems to suggest that the human population must return to a pre fossil carbon level once the fossil carbon runs out.  So if 99% of the human race dies off in the next century and the 70,000,000 survivors self select for intelligence, physical and emotional resilience, and pragmatism, the issue of only being able to generate a fraction of our current energy production solves it's self.  

The question is "How large a population does it take to maintain our current level of technology?"  It seems to me that if you have a couple of dozen population centers with a couple of million people each sprinkled around to globe, some one some were should be able to keep the ball rolling.

Sucks for the rest of us, 

John G

  • Sat, Dec 27, 2014 - 06:01am



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    I haven’t read the linked

I haven't read the linked articles except for do the math but here are some issues:

  • The renewable alternatives only provide electricity. This is much less useful than portable chemical fuel. We should have sufficient electricity long after we have widespread collapse from lack of portables fuels. Also, there is no large scale"battery" available to store the intermittent electricity from solar and wind. Good luck running a manufacturing industry on intermittent electricity… But you could get by for your house.
  • The financial collapse will make funding renewables much more difficult as interest rates rise. This will favour capital into the remaining fossil fuels as their net energy return and thus profit will be realized quickly whereas solar panels return the investment over 20 or 40 years… Tom Murphy's energy trap. 
  • our current infrastructure is nowhere near ready to run off electricity. The 40 year oil trade deficit has allocated capital into the worst places in highly distorted markets.  
  • There are a couple hopes. One is that Alberta has a lot of coal which can be turned into oil for a price. Secondly, with the right price incentives maybe someone will figure out industrial processes for artificial photosynthesis and or electricity to hydrocarbon catalysts. 
  • Sun, Dec 28, 2014 - 02:30am



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Scientific studies show it takes years to payback the energy used in solar electric devices. EROI (Energy Returned on Energy Invested) says it takes energy – mining, drilling, refining, transporting, installing, maintenance, and replacement parts – to make the devices necessary to capture solar energy.Spain’s Photovoltaic Revolution: The Energy Return on Investment by Prieto, Pedro A., Hall, Charles  2013.


and  Energy in Australia – Peak Oil, Solar Power, and Asia’s Economic Growth by Graham Palmer

Spain’s Photovoltaic Revolution presents the first complete energy analysis of a large-scale, real-world deployment of photovoltaic (PV) collection systems representing 3.5 GW of installed, grid-connected solar plants in Spain.  Prieto and Hall conclude that the EROI of solar photovoltaic is only 2.45, very low despite Spain’s ideal sunny climate.  Germany’s EROI is probably 20 to 33% less (1.6 to 2), due to less sunlight and efficient rooftop installations.

“Solar advocates can learn from this analysis . . . “  Not looking at the reality of EROI “is not good science and leads to wasted money and energy that could have been better spent preparing more wisely for declining fossil fuels in the future.”

This study does not detail the environmental destructive mining, toxic chemicals or air and water pollution necessary to get the materials for manufacturing and installing solar devices.  It is the sun not the devices that is renewable, green and sustainable.

  • Sun, Dec 28, 2014 - 06:43am



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    This “Math” is totally wrong and misleading

This is the second time peak prosperity has trumpeted this misleading "scientific studies!" Spain analysis of ERoEI as "proof" that solar electric cannot replace significant energy due to poor return on energy investment.

The report starts with lies, and then continues with trumped up math that is totally inappropriate to the future of solar electric.

Let's start with the lies:

1. this is NOT a scientific report and is not "science"  This is simple engineering with assumptions from economists (whom I do not automatically trust), and the analysis, while done by an "environmental" college professor and a telecom engineer with experience in owning and installing big installations, doesn't appear much different from that done by a financial analyst.  This is not rocket science and anyone can understand what these so-called "scientists" are saying.  No need to rely on an "expert" review of the "science" report.  Everyone should read for themselves, dont take anything for face value as we all (including me) are promoting something.

2. this alleged "science" report starts with the lie that the megawatt installations in Spain are the most  efficient in the world and in particular: "these large installations are far less expensive and more efficient that roof-top solar PV"    This is nonsense.  This lie, however, obscures an important and exciting development in solar electric: locally generated and used energy is CHEAPER and does not require bank and megacompany intervention or necessarily government-industry coalition racketeering, which in its benign form increases energy input by charging you with their lobbying energy, their fairs, their lawyers and their taxes and surcharges, and in a more realistic form, increases energy input by forcing an inefficient but centrally controlled big banker owned organization that is engineered to make money for a bank even if less efficient than local installed, controlled and owned.

a.  In fact, as reported by these "experts" who "do the math" themselves in the quoted report, the electric generation and modification equipment beginning with solar panels are only a small portion of the cost, and virtually all or at least most of the other costs are associated with megaplant needs, which VANISH for a DIY homeowner installation. 

2. Furthermore, the wonderful superior efficiencies of the panels themselves and electric delivery at the megawatt plant level are NOT higher and probably lower due to the need for inefficient, energy loss long transmission to get to the end user.  Some electronics engineers say that long distance transmission of AC power consumes 10% although that seems high to me, clearly the ground heats up and the energy is transmitted everywhere, including outerspace.  Such losses are NOT compared with local generated and used DC power from distributed rooftops. These plants are trying to scale up small panels.  There is no inherent advantage of building a company and doing this as a corporation far away in the desert using the same panels we can put on our roofs and then converting to various voltages and AC to feed old grids using old technology from far away, yet these dinosaur energy costs are included in the solar electric energy input costs in this "scientific studies!" report cited.

OK  lets "do" the math:
This "science" report comes up with a total energy cost of 2065 GwH of "energy inputs" to give a horrible ERoEI of 2.45
of this 2065 GwH energy input:
 608 for making modules, inverters, trackers, metallic infrastructure off site
and if only that is counted, the ERoEI would be 8, using old technology in an industry that is making rapid progress.
Tthe main point of the "scientific study" is that the other costs need to be counted, so let's look at these other energy costs:

"doing the math" they add on (to the energy costs of hardware which totals 608) :
 57 for foundations, canals, fences etc (10% as much as the generating/regulating equipment)
4.7 evacuation lines and right of way
139 security and surveillance (1/4 of total cost of generating/regulating equipment)
20 insurance
26 fairs, exhibitions, promotions, conferences
34 admin expenses
14 municipal taxes
9  land cost
16  labor of consultants, lawyers etc
6 market representative
12 equipment theft
178 electrical network/line restructuring 
198 network stabilization costs
This is a small portion of the added costs in this study but I want to make a point:
The total of this subset of MegaWatt Plant Bloatware energy alone (I ignored others) is 715, which is higher than energy costs of all the equipment needed to generate energy (which can be done locally with that same or similar equipment).
If we discard the lie that solar electric must be done by a banker/financier/government big agency at a far away location from a diffuse source, and instead follow the future of locally produced energy in a diffused form that is absorbed locally on individuals rooftops without massive concrete walls and barbed wire and security sentinels, and administraters, and marketers, and network stabilization, and fairs, and insurance, then doing this math, the 2065 GwH energy COSTS drop at least down to 1350 from these factors alone, which improves the ERoEI dramatically. 
MORE MegaPlant Bloatage energy costs that may not apply to locally generated solar electric are included but I want to point out that for a real person in a collapsing future with locally produced energy the energy input to solar electric is MUCH better than what the utiliites and their consultants/advisors/"scientific studies!" portray.  It likely could be 8 or better, because energy use in making and transporting equipment can and wil be reduced when costs rise and the technology is improving rapidly.

The electric solar energy future is much different than what these megaplant-career-industry pundits are telling you.  I dont know what Spain's future is, but the utilities in America are scrambling to get into locally produced solar electric.  They are following the money.

I am biased too.  I am very busy building innovative demonstration circuits that are more efficient than what the megapower industry provides and a self-regulating grid that can easily grow as needed, in my local community. 





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