# In case you were wondering, solar PV is now a net good for the earth...



## woodgeek (Jan 1, 2017)

Apologies for a slightly technical and wonky post about a recent paper I came across....

It addresses a major solar 'naysayer' issue....the (supposed) low EROEI of solar PV, and its (supposed) resulting inability to support modern civilization.

Many here have a current or former 'energy doomer' bent.....this is a story for you. FYI...I do not intend 'doomer' as a prejorative, no offense intended....I am a recovering doomer myself.

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The good news:  future projections of current (exponential) growth rates of solar PV production would result in all global electricity and all primary energy needs being satisfied by solar PV in 2-3 decades.

Major roadblocks for this 'clean energy eco-utopia' are not obvious:
--solar PV kWh are already cheaper than fossil kWh in many locations in the world (mostly sunny developing countries, and the US SW).  Many of these locations are now driving global PV capacity growth with minimal or no subsidies.
--falling costs (due to tech learning curve) mean that the regions for which the above is true will expand to cover most global population in a decade or so
--the available energy resource (global sunshine) is more than sufficient for anticipated needs.
--the materials required, silicon, oxygen, aluminum are all earth abundant (being what the earth is primarily made of) and ubiquitous.

The hypothetical problem:

There are still energy doomers out there.  They will cite a couple related issues.  Some say that the EROEI of solar is too low to support civilization.  Recent studies have determined that the 'energy payback time' for solar PV is 1-2 years; it takes that long for the panel to generate as much energy as it took to manufacture.  A similar figure for greenhouse gas emissions (from initial manufacturing versus saved) comes up with a similar payback time 1-2 years.

On its face, this seems ok...the panels last 20-30 years...so we get an EROEI (energy return on energy invested) of 15-30 or so.

Some current doomers will cherrypick studies that have higher payback times, so EROEI is less than 10. These same folks often say that the EROEI of 10 is a magic number that if a technology is below it, then civilization collapses.  Or climate doomers say that energy payback is ok, but that manufacturing PV requires fossil fuels, so 'you can't make PV with PV', so it won't work (this latter point is silly...PV is often made with electric furnaces).

I never understood the above doomer math/logic, so I won't say anything else about it.  I think its weak.

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This post is about another, subtler issue.  Imagine that solar PV payback (energy or GHG) takes 3 years.  And imagine that the amount installed doubles every 2 years.  The math says that installing PV would then be a net loss for both energy production and GHG avoidance **forever**...no savings are realized until a couple years after we stop the exponential growth curve.  In fact the 'bad' grows exponentially in proportion to the installed capacity!

This is cited as a concern by some (more sophisticated) doomers...that the installed amount of PV will always deliver less than the amount of energy needed to make next years (larger) amount of installed PV.

A (free access) peer reviewed study in _Nature Communications_ addresses this very issue:

http://www.nature.com/articles/ncomms13728

The bottom line is that, while obviously 'doubling time' needs to be less than 'payback time' to see a benefit, the payback times (for energy and GHG emissions) are also falling due to learning curve, just like the prices have been.  And should continue to fall.

In their extensive analysis it appears that solar PV may have been a net negative for global energy supply and GHG emissions as recently as _a few years ago_.  But even the most pessimistic estimates for energy and GHG payback show PV pulling into the black no later than this year, despite solar's current amazing rate of growth.

IOW, solar PV is a net good for the global energy supply and GHG emissions, at current growth rates, and the good will grow exponentially going forward.

Happy New Year


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## velvetfoot (Jan 1, 2017)

Good.  Then no more subsidies needed.


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## woodgeek (Jan 1, 2017)

US subsidies get us the benefits (e.g. healthier air, etc) earlier.  The US is getting left behind....most of the biggest solar projects these days are overseas.


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## begreen (Jan 1, 2017)

If we're dropping subsidies be sure to include the fossil fuel sector too.


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## Treacherous (Jan 1, 2017)

I put in a small hobby array this year.  Just a small 12V 400 watt system, 4 batteries 1500/3000 inverter and utilizing a linear tracker with horizontal & vertical sensors.  I plan to add vertical actuator in the spring.  I was surprised how much the panel prices had fallen.  I mainly use it for a small amount of emergency power and charging stuff right now.  I'm gonna put in a similar unit at my cabin next year.  I can manage everything about it from the web.


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## woodgeek (Jan 1, 2017)

Is the tracker like a homebrew arduino thing, or something else....??


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## Treacherous (Jan 1, 2017)

I was going to do that but ended up with one of these models you find on eBay or Aliexpress.

I still need to trim the ends of that 2" steel pipe.  I used this to build mounts.

http://www.affordablesolarmounts.com/




I built not really knowing what to expect but used panels from here:

http://www.windynation.com/

I also went with a sine wave inverter.  There are some good & expensive brands but skimming through the cheap Chinese ones this one seems to be quite reliable.  They took my offer of $151.


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## woodgeek (Jan 1, 2017)

I have a fantasy of setting up a pole-mounted heliostat mirror using arduino or raspberry pi, to get some more light into the house.


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## Treacherous (Jan 1, 2017)

That is a pretty cool idea.  I was gonna do the tracker with a Pi but got lazy I guess since there was something already out there off the shelf.


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## semipro (Jan 3, 2017)

begreen said:


> If we're dropping subsidies be sure to include the fossil fuel sector too.


I would even go further to suggest that the same subsidies historically spent on fossil fuels should be spent on renewables in the future.


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## semipro (Jan 3, 2017)

woodgeek said:


> and the good will grow exponentially going forward.


Assuming that external political interference doesn't override economic forces...


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## woodgeek (Jan 3, 2017)

semipro said:


> Assuming that external political interference doesn't override economic forces...



I am only familiar with the new admins in the US and UK and neither of them have much or anything to do with the rate of global solar PV production, innovation or installation at this point.  Can they impose trade tariffs or sanctions to punish foreign countries for installing solar with their own money?


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## semipro (Jan 3, 2017)

woodgeek said:


> I am only familiar with the new admins in the US and UK and neither of them have much or anything to do with the rate of global solar PV production, innovation or installation at this point.  Can they impose trade tariffs or sanctions to punish foreign countries for installing solar with their own money?


I was thinking of the U.S market. 
However, the U.S. is a large market for PV products produced overseas.  A change in the market here may well impact the economies of production elsewhere. 
As to whether the U.S. can use tariffs or sanctions as sticks, all bets are off.


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## woodgeek (Jan 3, 2017)

semipro said:


> I was thinking of the U.S market.
> However, the U.S. is a large market for PV products produced overseas.  A change in the market here may well impact the economies of production elsewhere.
> As to whether the U.S. can use tariffs or sanctions as sticks, all bets are off.



I looked it up.  The US installed 16 GW of solar PV in 2016, and the rest of the world installed 57 GW.  If the US took a breather, the drop in PV prices would accelerate installs elsewhere, which would likely have equivalent or greater climate benefit (displacing dirtier power).

Don't worry, there are plenty of other things to worry about!


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## semipro (Jan 3, 2017)

woodgeek said:


> I looked it up.  The US installed 16 GW of solar PV in 2016, and the rest of the world installed 57 GW.  If the US took a breather, the drop in PV prices would accelerate installs elsewhere, which would likely have equivalent or greater climate benefit (displacing dirtier power).


Good point.  Sometimes its hard to think globally with so much negativity here at home.  (and ironically, my contribution to it).


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## woodgeek (Jan 3, 2017)

Treacherous said:


> I also went with a sine wave inverter.  There are some good & expensive brands but skimming through the cheap Chinese ones this one seems to be quite reliable.  They took my offer of $151.



View attachment 191725


Looks like a fun project.  I got a similar 1500W pure sine inverter for $199 to backfeed my house from my LEAF EV during blackouts.  Works aok so far.


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## iamlucky13 (Jan 4, 2017)

velvetfoot said:


> Good.  Then no more subsidies needed.



The federal tax credit is being phased out over the next several years. The market probably could have handled starting a couple years earlier, but I don't really think accelerating the phase out now will be worthwhile.

Developing economically sustainable feed-in tariff policies will be a much more complicated question. I expect we'll still be debating that part a decade from now.



woodgeek said:


> US subsidies get us the benefits (e.g. healthier air, etc) earlier.  The US is getting left behind....most of the biggest solar projects these days are overseas.



That's actually not true. The only country (China) that exceeded the amount of solar capacity installed in the US has four times our population and higher long term energy demand growth, yet installed less than twice as much as the US (based on mid-year 2016 projections).

Germany, the poster child for renewable energy, has 1/4 the population of the US, but was expected to install about 1/8 as much solar. Admittedly, that's a slowdown compared to their past rate, and their existing installed capacity is somewhere close to what the US currently has.

Either way though, despite occasional high profile commercial solar farms getting a lot of news in other countries, the US has proportionately the strongest demand at the moment.

Projecting the current exponential growth 20-30 years is not useful, but the state of solar in the US is pretty solid at the moment. EROI hasn't been a serious question in probably a decade or so.


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## velvetfoot (Jan 4, 2017)

iamlucky13 said:


> The federal tax credit is being phased out over the next several years. The market probably could have handled starting a couple years earlier, but I don't really think accelerating the phase out now will be worthwhile.


State subsidies via tax breaks and utility bill assessments still big, here in NY anyway.  But hey, our gov. is proposing  free public college.


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## woodgeek (Jan 4, 2017)

iamlucky13 said:


> That's actually not true. The only country (China) that exceeded the amount of solar capacity installed in the US has four times our population and higher long term energy demand growth, yet installed less than twice as much as the US (based on mid-year 2016 projections).
> 
> Germany, the poster child for renewable energy, has 1/4 the population of the US, but was expected to install about 1/8 as much solar. Admittedly, that's a slowdown compared to their past rate, and their existing installed capacity is somewhere close to what the US currently has.
> 
> ...



Let's see.  We can debate whether the glass is half full or half empty....

The world installed 73 GW of solar PV capacity in 2016 (by one estimate), and the US installed 16 GW.  Both numbers were records. The US figure is 22% of the world figure.  I think that 1-0.22 = 78% can be described as 'most'.

By kwH, the US uses about 19% of total world electrical energy, so maybe 22% of PV looks 'ok'.

By GDP, the US was 24.5% of world GDP, yet only could afford to install 22%?  Are we leading?

By accumulated wealth, the US holds ~25% or the worlds total wealth, but only did 22% PV?

By CO2, the US emits 15% of global human derived CO2 per year, currently, and 22% > 15%, so maybe we are doing 'our share'.  Of course, if we add in 20th century emissions (without which we would not be worried about AGW now), the US historically emitted about 35% of the human derived CO2 emitted since 1900. Since 35 > 22, perhaps we should be doing more?

I would also agree that the US is doing well compared to the EU countries, including Germany, who appear (collectively, on different schedules) to have tired of paying expensive subsidies, esp in locations with crummy solar resources.  But if we are being critical, most of the US capacity installation is in California, despite there being a LOT of high solar resource states with $$ and people that are not doing much in PV.

But the point was, that unless the Feds make PV _illegal_ here and overseas, global PV will do just fine without US Fed subsidies.  The vast majority of PV is installed overseas OR in California (which has its own incentives).


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## iamlucky13 (Jan 4, 2017)

woodgeek said:


> But the point was, that unless the Feds make PV _illegal_ here and overseas, global PV will do just fine without US Fed subsidies. The vast majority of PV is installed overseas OR in California (which has its own incentives).



I was responding there to one of the tangential points in the ensuing discussion. I've got no debate that the global market is not dependent on the US propping up demand.

With regards to California, I think they've been running at about half the total US market, which still leaves a major market outside of California. Interestingly, from what I've been able to find / heard from relatives down there who have purchased systems, California's local incentives are pretty modest. The market is mostly driven by relatively high electricity prices (especially once you exceed the bottom price tier usage) paired with good insolation. Annualized net metering doesn't seem to be under strong challenge there either, because of the good seasonal match between solar supply and cooling demand.


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## woodgeek (Jan 4, 2017)

I would argue that the modest incentives plus tiered rates IS a smart incentive system.  Along with a strong RPS.  And a great resource.  And not too many trees.

The net metering is safe because the PUCs there have been writing green power into the rules all over the state for decades, and its a liberal fortress politically.  My buddy was explaining that the major impediments to expanding utility solar are other renewable energy interests!  He said that the geothermal energy plant has rules in place that it cannot be curtailed by external forces.  Its completely throttleable technically, but not legally.  So instead of complementing PV, it prevents it.


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