Author Topic: the Pareto principle and solar power  (Read 2811 times)

Offline Alan Georges

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the Pareto principle and solar power
« on: January 19, 2019, 11:25:04 AM »
We’re all probably familiar with the Pareto principle: you get about 80% of the results from the first 20% of effort.  Sometimes it’s called the 80/20 rule, and probably a few other things besides.  A while back a friend pointed out that not only does the Pareto principle hold, but that powers of this ratio work as well.  For example, Pareto squared would give 64% of the results from the first 4% of effort.  Since then I’ve been mulling this idea over in regard to solar power.

Taking this even further, I put calculator to paper and made a table.  Starting with a $100 per month electric bill, it shows about what you can expect for each power of 0.8 and 0.2 down to some ridiculous level.  Now, all of these numbers are rough-and-ready, but as the currently fashionable phrase goes, they’re directionally correct.  Anyway, here we go:

Start with a $100 electric bill at $0.13 per KW-H, and in round numbers it's 25 KW-H per day.  Figure on 5 hours per day of sun; that’s the average in a lot of the U.S., though it will vary.  Look up “insolation chart” and you’ll find what you need.  So to make 25 KW-H over 5 hours, it’d take a 5 KW system.  The “P” column is the “Pareto to the power” column.

W-H/day   P   %lifestyle  %pwr  size solar    comment

      25K    0      100       100        5 KW         baseline, normal living
      5K      1      80          20         1 KW         still a pretty big system
      1K      2      64            4       200 W         easy, cabin-sized system
      200    3       51           0.8       40 W        pretty small
      40      4       41           0.16      8 W         dinky, portable

Don’t get hung up if something’s 20% or even 50% off, the idea is to examine the Pareto-to-some-power principle and look at a few directionally correct round numbers.

The first system, 25 KW-H per day, is doable with a professional solar install.  Get your checkbook out.  But you know, for some rich geezer who wants to get off-grid and not worry about hurricane season, it’s not a bad way to go.  I’d admire the system and want to be the guy’s neighbor.

The second line is a pretty big and it too might mean a professional install.  You’re not going to run an electric water heater or heat pump on this one, and even running a stove for very long is not doable.  But you can run a refrigerator, the control electronics and fan on a gas furnace, and pretty much everything else within reason on this system.  No central AC, deal with it, but you might run a window unit a little.  Honestly, this is about the level of power consumption I grew up on.  Like the Pareto principle says, it’s 80% of the base standard of living.

The next line, “Pareto squared,” is where things get interesting.  This is at the DIY system level and lots of us here have something like this.  You might get by with a small 12v refrigerator, a laptop computer, LED lights, 100 watt ham radios for hours, CB, etc. off this with no problem, and with some budgeting you can watch a movie in the evening.  Even running a microwave oven for 5 minutes here and there isn’t out of the question.  Pretty useful, it’s right at about 64% of a “normal” modern lifestyle, and seems nice compared to other extended outage options.  Also, if you have a generator, you can run a few larger items, say refrigerator or room AC, recharge batteries, and be pretty much back at the 5 KW-H/day lifestyle — as long as the gasoline lasts.

The next line, “Pareto cubed,” is where things get tight.  This is about the size of one of those Harbor Freight systems.  You can do a lot with it though: lights, recharge cell phones and AA batteries, talk at 100 watts on ham during half-hour comm windows or use a CB all day long.  Couldn’t really watch a movie, but it’d be no problem to run a battery radio for entertainment and news.  You could run a laptop and a cell phone wi-fi some on this.  Yeah, you’d have to really watch your power usage, but with lights and all it’s an OK life, and right on 51% of the baseline.

The last line, “Pareto to the fourth,” is getting down to a minimum, but compared to zero power it’s still really good.  This is about the size of one of those Goal Zero notebook systems that uses a 4x AA pack for its battery “bank.”  Look at what it can do: a reading light at night, recharge a cell phone, charge batteries for an AM/FM/SW radio.  What’s more, it’s portable.  It’s a lot better than most of the poorer first-worlders had it a century ago.  Right in keeping with Pareto, you could call it 41% of the modern life.

OK, that ran long.  I haven’t put out a good mega-post in a while though, and this Pareto-to-some-power has been rattling around in my brain for a while.  Thoughts?

Online David in MN

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Re: the Pareto principle and solar power
« Reply #1 on: January 19, 2019, 12:52:01 PM »
The Freakonomics guys did a show about solar power where they did a breakdown that solar panels were more closely tied to political ideology than effectiveness. Thhey compared solar panel usage in San Francisco to more conservative inland California. The long and short is that people aren't using them where they would be effective but using them in foggy San Fran where they are not. In other words it's a way of signaling how virtuous one is.

I've also done the calculations you're looking at. Like setting up for a minimalist off-grid system. But I have a problem. My highest draws are all winter where we get cloud cover all the time. Yes, I could offset energy costs by having panels out in June when we get 16 hours of sun but it's 70 degrees, the windows are open, and I'm cooking on a grill.

But let me give the flipside. There are companies up here getting damn good results with vertical turbines and wind is probably our best bet. So I have been looking and I agree that you probably can get by 80% on 20%. At that point it becomes an engineering optimization problem. And I assume you've seen the same as us where the advent of moore efficient appliances and LED bulbs has driven down the energy use in the past decade.

It will be interesting to see if others feel similar.

Offline Alan Georges

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Re: the Pareto principle and solar power
« Reply #2 on: January 19, 2019, 01:59:08 PM »
No, of course, solar power isn't generally an economic winner for daily use.  Nor is the intent here to show how to spend $10k on a small solar power system to live like a virtue-signaling miser and save the remaining $20 electric bill per month.  That is not the point here.

The point is that when grid power is out, even a small amount of electricity is enormously useful.  Moreover, the high cost of solar power should not deter people – modern survivalists – from using it as a backup, because a small but practical system can be made for very little money.

Having a quiet, reliable backup source of electricity that does not require gas or rely on wind is a good thing.  This has nothing to do with political ideology.

Offline armymars

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Re: the Pareto principle and solar power
« Reply #3 on: January 19, 2019, 02:15:14 PM »
I think most of us agree that you don't put all your eggs in one basket.

Offline iam4liberty

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Re: the Pareto principle and solar power
« Reply #4 on: January 19, 2019, 05:11:29 PM »
A couple months ago there was a good point made in a TSP episode with Steven Harris, that solar has become cost effective for some new installations.  It is becoming more and more expensive to hook into the grid in some areas so that bends the return curve. In fact, solar + propane/natural gas generator is looking very good for property which is ultra cheap because of distance to utilities.  This 'land discount' should be included in calculations when looking at new installs.

On the return aspect, yes, even a little electricity is a remarkable thing.  And it will only get better as power consumption of devices goes down.  So maybe a 'Pareto meets Moore's Law' situation could occur.

The biggest issue is that air conditioning bumps up against thermal efficiency and that cant budge by any known technology.
« Last Edit: January 19, 2019, 05:42:45 PM by iam4liberty »

Offline fratermus

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Re: the Pareto principle and solar power
« Reply #5 on: January 22, 2019, 10:26:46 AM »
The long and short is that people aren't using them where they would be effective but using them in foggy San Fran where they are not. In other words it's a way of signaling how virtuous one is.

Germany in perpetual gray conditions (I saw direct sun maybe 3x each year) and makes a big chunk of their power through solar.  I will suggest it has as much to do with wealthy areas (SF, Germany) having capital to expend on the solar infrastructure as anything else. 

To OP's point:

Quote
1K      2      64            4       200 W         easy, cabin-sized system

Scrounging and research can help bring these estimates down radically.   The 570w system in my offgrid campervan (my home) cost:

Code: [Select]
$360  3x 190w mono panels @ $120 off eBay, picked up locally off the pallet
$200  4215bn 40A mppt controller w/remote display
$220  2x 6V golf cart batt @ $110
< $50 wire, fuses, gland, etc

The 200w example in OP's chart is $5/watt.  My actual 570w setup is $1.45/watt.  Not theoretical:  I live this way successfully and without any sense of hardship.  I have a 12v compressor fridge, the laptop I am typing on now, a Raspberry Pi, powered roof vent, phone/tablet, /etc.

I share this not to push back on OP's ;  I am suggesting that resourceful TSP folks will likely be able to get (much) more for (much) less if they are informed and patient.   BTW, I agree with OP about the usefulness of small systems.   

I've starting writing rvwiki articles on solar topics for vehicle dwellers.  Not all of it is complete, but might be useful for cabin and other prepper setups.  At least to get the juices flowing.   

Offline Hurricane

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Re: the Pareto principle and solar power
« Reply #6 on: January 22, 2019, 03:28:12 PM »
 :popcorn:

Offline Alan Georges

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Re: the Pareto principle and solar power
« Reply #7 on: January 22, 2019, 05:56:09 PM »
The 200w example in OP's chart is $5/watt.  My actual 570w setup is $1.45/watt.  Not theoretical:  I live this way successfully and without any sense of hardship.  I have a 12v compressor fridge, the laptop I am typing on now, a Raspberry Pi, powered roof vent, phone/tablet, /etc.
Um, I didn't put in any prices.  Maybe you're mistaking that 1K in the 1st column?  That's  watt-hours per day, not dollars.  5 hours sunlight per day x 200 watts = 1KW per day.

Nice system you have there fratermus, and at a good price too.  How big is your battery bank?  What type batteries did you go with?

One more time, let me say that this thread isn't about pricing out a solar power system (or saving polar bears, or living like a eco-hermit).  It's about how even a very small and affordable system can be much better than no electricity at all in an extended outage.

Offline fratermus

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Re: the Pareto principle and solar power
« Reply #8 on: January 23, 2019, 12:17:44 PM »
Um, I didn't put in any prices.  Maybe you're mistaking that 1K in the 1st column?  That's  watt-hours per day, not dollars.  5 hours sunlight per day x 200 watts = 1KW per day.

You're right;  I overlooked the column header.  If I can edit that post I'll strike through that portion to avoid confusing others.  [uggh, looks like there is a time limit for editing]

Quote from: Alan Georges
Nice system you have there fratermus, and at a good price too.  How big is your battery bank?  What type batteries did you go with?

220Ah.  Duracell 6v (Deka relabels from batteries plus.).

Quote from: Alan Georges
It's about how even a very small and affordable system can be much better than no electricity at all in an extended outage.

Totally agreed, brother. 

For the van-curious out there, I'll add that even small solar installs (100-200w) added to alternator charging are great for keeping the "house" (living area) battery bank healthy.

Offline Alan Georges

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Re: the Pareto principle and solar power
« Reply #9 on: January 23, 2019, 05:56:04 PM »
220Ah.  Duracell 6v (Deka relabels from batteries plus.).
Veerrry nice, fratermus.  Throw in alternator charging discussed at the links you gave and that's a beautiful system.

It's a funny thing but on the whole I'm skipping generators.  (Well, apart from the option for an occasional boost-up from my truck's alternator.)  After watching the hassle people went through for gas after Katrina, it's use less power and run silent on solar for me. 

Opinions may vary however, and I'll always graciously accept a cold beer from a generator-equipped neighbor's refrigerator.  And then I'll recharge his cell phones the next week after his gas runs out.

Offline creuzerm

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Re: the Pareto principle and solar power
« Reply #10 on: March 04, 2019, 10:07:53 PM »
This concept is really resonating with me. That squared level just seems right.

I am in the process of buying some property and doing an addition on the house.  The addition I am thinking of wiring every other outlet for solar. There is no reason cell phone charging, alarm clocks,   led desk lamps,  TVs and so on shouldn't run on solar. 

Use white and ivory receptacles to tell the difference so I don't plug the vacuum into the solar.

Keep the kitchen and well off the solar and, there isn't really all that much power use.  Lots of phantom power use.

Power goes out,  you only need the generator for the well, fridge, deep freeze and Hvac. Now you aren't burning fuel all day,  just a few times a day for shorter periods.

Loving the concept!

Offline Alan Georges

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Re: the Pareto principle and solar power
« Reply #11 on: March 07, 2019, 08:04:48 PM »
Loving the concept!
Glad it's clicking for you, creuzerm.  Personally we're at the squared level here at the house, and it is an easy backup system for power outages.

Quote
Use white and ivory receptacles to tell the difference so I don't plug the vacuum into the solar.
That's a good workable plan.  One gotcha to watch for is that common grid power sockets have one 120 VAC hot leg and one ground, but many affordable inverters have two 60 VAC legs wired in push-pull fashion.  From a power delivery point of view they're equivalent, but when there's a third-prong safety ground things get complicated.  Do your research before wiring this concept up.

Offline creuzerm

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Re: the Pareto principle and solar power
« Reply #12 on: March 11, 2019, 09:41:07 AM »
Good tip on the 60/60 voltage. I shall pay attention to that now that I am aware.

Offline mountainmoma

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Re: the Pareto principle and solar power
« Reply #13 on: March 11, 2019, 02:43:04 PM »
This concept is really resonating with me. That squared level just seems right.

I am in the process of buying some property and doing an addition on the house.  The addition I am thinking of wiring every other outlet for solar. There is no reason cell phone charging, alarm clocks,   led desk lamps,  TVs and so on shouldn't run on solar. 

Use white and ivory receptacles to tell the difference so I don't plug the vacuum into the solar.

Keep the kitchen and well off the solar and, there isn't really all that much power use.  Lots of phantom power use.

Power goes out,  you only need the generator for the well, fridge, deep freeze and Hvac. Now you aren't burning fuel all day,  just a few times a day for shorter periods.

Loving the concept!

I have solar and battery back up for power outages.  I guess you could wire that way, but another way is to just back up most or all of it and not use what you shouldn't.  I usually leave my fridge on backup power, but I can unplug it if I think we are going to be extensive.  The pressure pump for house water is on a backup circuit but  I actually ran out of power on the last 3 day outage we had ( this may not be the battery bank, it may be that I now have a rental unit also using water off of my batteries -- and I DID use the stereo alot, the full stereo system, playing records for many hours. Watched a movie or two...Was a good test of back up capacity I guess, and my batteries can be run all the way down with no degradation) anyways, I now as a default flip that pressure pump breaker off when the power is out, and calm down my recreational usages with this years storms !

Generally, when power is out, I run refrigerator ( it is a under 500kW/year refrigerator, I do not own or use a seperte freezer), lights(generally just one room at once, and all ceiling lights are LED) ( the way my house was already wired I get all ceiling lights except the downstairs bathroom), charging of laptop etc.... most house outlets are on the backup circuit, I use my electric kettle for hot water, the toaster, the breadmaker the handheld HAM, internet box ( for a while until their repeater runs out of juice), etc.. and I am now reminded to minimize the entertainment if it looks like it will be out for a while.  I can forgo most of those and by hand switch the wirenuts on a couple wires and have the actual well pump and not the pressure pump on battery, but that would be some emergency as I do have a 2500gallon water tank.  Anyway, I do agree that it makes life so much better to have some power.  I brought much appreciated (instant) coffee out to the workers clearing the power lines last month with that electric kettle.  I can deal with a cold, isolated day much better with some hot tea and toast while I get the fire going, it is nice to read at night.  And, much of this can be done with way less battery back up than my system.  As has been said here, a LED reading light, cell phone charging and small radio do not take much power and realy would make it alot better. 

Offline Alan Georges

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Re: the Pareto principle and solar power
« Reply #14 on: March 11, 2019, 05:48:49 PM »
Good tip on the 60/60 voltage. I shall pay attention to that now that I am aware.
Funny, but this same thing came up over at another thread over the weekend:
http://thesurvivalpodcast.com/forum/index.php?topic=63891.0
More details over there, including a link to a circuit drawing showing why this can lead to tears, but why it's usually safe.

Offline Alan Georges

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Re: the Pareto principle and solar power
« Reply #15 on: March 17, 2019, 09:02:05 AM »
As has been said here, a LED reading light, cell phone charging and small radio do not take much power and realy would make it alot better.
Exactly right, MM.  It makes all the difference.  Even a 7 watt Goal Zero system will give this.  It's useable by most people and will be a lot of help when the power's off.

Offline ttubravesrock

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Re: the Pareto principle and solar power
« Reply #16 on: March 19, 2019, 11:16:30 AM »
This is really interesting. I currently live off-grid with a generator. It's not a super-sustainable system, and I was saving up for a 100% solar setup (doesn't have to be big because I heat with wood and refrigerate + cook with propane). However, if I look at the 80% setup then I could just use the generator as backup for that other 20%.

Offline Smurf Hunter

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Re: the Pareto principle and solar power
« Reply #17 on: March 19, 2019, 12:07:25 PM »
This may have been a TSPAZ item of the day at some point.

https://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU


I highly recommend everyone interested in backup energy get one, so that they have accurate data regarding their power needs. 

When you have accurate data for your consumption, you can plan accordingly.  There is a huge difference between keeping phones charged and LED lights running, compared with a freezer or other major appliances.

Offline Alan Georges

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Re: the Pareto principle and solar power
« Reply #18 on: March 19, 2019, 08:20:17 PM »
Exactly right, Smurf.  Good data if vital to properly sizing a solar power system.

Offline Smurf Hunter

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Re: the Pareto principle and solar power
« Reply #19 on: March 20, 2019, 10:31:54 AM »
Exactly right, Smurf.  Good data if vital to properly sizing a solar power system.

Yes, or you may decide a big old gasoline generator is appropriate for a few specific cases. My wife didn't understand why her hair dryer, coffee maker or instantPot wouldn't work off the little inverter until I plugged them into the kill-a-watt. Of course the practical conclusion is to learn to avoid using such things during an emergency :)