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off-the-grid solar-based electrical generation system
Old 01-03-2017, 07:27 AM   #1
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off-the-grid solar-based electrical generation system

Does anyone here have any experience and/or knowledge about off-the-grid electrical system using solar cells?

Seems quite expensive.

How much capacity does a typical household need?

What is a "good" brand?
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Old 01-03-2017, 08:12 AM   #2
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If you are interested in doing this for yourself, the 'typical' household capacity is meaningless. You need to find out what your capacity needs are.

There are two parts of a 'capacity' number. First is what you use on average each day (Kilo-Watt-Hours). Then second is what you use peak (Kilo-Watts), at a time when a lot of things are running.

Being off-grid, you need to supply all this yourself. And then you need some idea of how many days you might have low sunshine. You need to design for worst case, or be flexible and be able to deal with outages or reduce your usage for days at a time, or have a back up generator.

For anything near what a 'typical' US household uses, it will be expensive. Very expensive. Lots of batteries that will need regular replacement and/or maintenance. Lots of panels.

Tell us more about your situation. Do you have to go off-grid, or do you want to?

-ERD50
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Old 01-03-2017, 10:06 AM   #3
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For anything near what a 'typical' US household uses, it will be expensive. Very expensive. Lots of batteries that will need regular replacement and/or maintenance. Lots of panels.
+1. Reducing demand (compared to a "typical" home) will be worth doing, once we've considered the price of the panels and (especially) the price for storage. Going off grid and relying entirely on solar can be extremely expensive in most areas unless you are very flexible in your power requirements, this is because you'll need a >lot< of battery capacity to get through an extended period of lack of good sunlight. But, incorporating even a small backup generator (fueled by propane, natural gas, diesel, or gasoline) for occasional use can significantly reduce the expense of the system by reducing the size of the battery capacity needed, and maybe the size of the array needed to keep things going during marginal production periods.

In nearly all cases, if AC grid power is available, using that as the "backup power" is much more cost effective than trying to be truly off-grid and independent.
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Old 01-03-2017, 10:07 AM   #4
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Not for me.

I am trying to understand what material I should read to learn more about this and whether all systems on the market are the same or whether one is better than the other.
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Old 01-03-2017, 10:19 AM   #5
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Not for me.

I am trying to understand what material I should read to learn more about this and whether all systems on the market are the same or whether one is better than the other.
If you are not looking for specific advice for your own case, then a search engine will bring up lots of info.

here's one link:

So You Want to Go Off-Grid... | Home Power Magazine

It's not simple. Are you totally off grid? Need to pump well water, no natural gas, propane or fuel oil for heat? Many considerations.

Do a little research, I think you will quickly find that as we said, it is expensive. Probably not even a good environmental decision - I'd bet a common existing grid has less environmental impact than a lifetime of batteries and all the other stuff needed.

Quick example - a 'typical' home in the US uses 1,000 kWh a month ( @ ~ 10 cents/kWh, that would be $100/month). So ~ 33 kWh per day. To just get through the late afternoon, and overnight until strong sunshine late the next AM, you'd need to store a good portion of that 33 kWh. The batteries in a Tesla are ~ 55 kWh, so that might get through a single day of low sunshine. But those batteries could not stand daily recharging.

Check out the prices of the Tesla wall units, but check the ones that can be cycled daily (they make one for occasional backup duty). Lots of $$$$$$$$$$$$.

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Old 01-03-2017, 10:23 AM   #6
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Not for me.

I am trying to understand what material I should read to learn more about this and whether all systems on the market are the same or whether one is better than the other.
This stuff is pretty standardized. While there are differences across suppliers, installers, etc, in general they are all pretty much using similar designs from a handful of manufacturers.

Solar panels, inverters, batteries - fairly generic pricing on all this.

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Old 01-03-2017, 10:34 AM   #7
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Quick back-of-the envelope calculation (wooops, too quick, I forgot to allow for 24 hours in a day):

To supply an average of 33kWh per day, you need ~ 5x that in nameplate capacity for your solar panels. Basically, you get ~ 15%~20% of their power rating on average, since the sun doesn't shine all day.

So that's ~ 6875 watts of panels @ 20% (optimistic unless you are in a very sunny location). At $2.00/ watt installed, that's $13,750 before you add batteries.

And at ~ 240 watts per panel, that is ~30 panels. That's a lot of roof space!

A big installation near us is only getting ~ 11% capacity factor.

Having fun yet?

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Old 01-03-2017, 02:01 PM   #8
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My mancave/camp has no utility connection. Would cost well over $25000 to connect utility power. It is also not useful for comparing to residential solar.

I have a total of about 230 Watt solar panels and two Golf cart beatteries for house power. Plus a small wind generator which is not in a favorable location.

Most lighting is 12 volt LED and a few 12 volt cfls. Also have a 2KW continuous 4KW peak, inverter for running toaster, coffee maker, drills atc. In winter months it requires close attention to be useable. The location seems to have several weeks no sun with a few days of sunlight for a few hours. Summer no problem, power to burn.

The mancave is wired for 220/110 service and with the inverter or gen set(s) it functions as normal AC system. Until the batteries die or run out of fuel for generators. Gen sets are very expensive electric source.

For heavy loads I have a 3KW Onan generator, and if need be a 6KW onan diesel.

About 2 or 3 weeks apart I run the smaller Onan a few hours to run a battery charger in order to top off batteries.

A separate 100 watt, 30 year old solar panel charges two tractor batteries for running an air compressor to pressurize water barrel for water to toilet.

Clearly none of this is essential, just makes roughing it a bit less rough.

At home DW would not put up with any of this. Her idea of roughing it is a first class hotel balcony on the beachfront with room service.
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Old 01-03-2017, 02:59 PM   #9
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ls99: Sounds as if you've got part time living pretty much figured out. There are many RV's with solar panels on the roof--used when they're boondocking (without electricity.)

I can see long term changes coming in home electrical usage when new technology comes into play.

$.04 KWH coal generation is still half our power in the U.S., and nuclear power is never going to be as much of our power as it is today. Natural gas is the new hot thing in electricity @ $.11 per KWH. And forget wind power @ $.26 per KWH, as they're using 10% of U.S. steel production just building those beymouths. And little of the U.S. has enough reliable wind to turn the props.

We'll see what the future holds. I'm just thankful to have medium-low electricity rates from TVA for now.
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Old 01-03-2017, 03:20 PM   #10
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Seems like we need a tech breakthrough to get off the grid to really work from an economically positive perspective. Maybe if you could forget batteries and instead use a tank:
Could 'unburning' CO2 be 'the next big thing' in energy?
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Old 01-03-2017, 04:49 PM   #11
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ls99: Sounds as if you've got part time living pretty much figured out. There are many RV's with solar panels on the roof--used when they're boondocking (without electricity.)

I can see long term changes coming in home electrical usage when new technology comes into play.

$.04 KWH coal generation is still half our power in the U.S., and nuclear power is never going to be as much of our power as it is today. Natural gas is the new hot thing in electricity @ $.11 per KWH. And forget wind power @ $.26 per KWH, as they're using 10% of U.S. steel production just building those beymouths. And little of the U.S. has enough reliable wind to turn the props.

We'll see what the future holds. I'm just thankful to have medium-low electricity rates from TVA for now.
Here on SW PA the total delivered price of utility electric is around 12 cents/KW.

My camp solar setup was cheap. A few years ago got the panels, the previous set of marine batteries, wind generator and regulator for $600.-, craigslist. The dude selling it could not figure out how to make it work. This fal I bought 2, 8 month old unused golf cart batteries from Autozone for $80.-. I do have a desulfator which brought them back to full capacity in a week.
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Old 01-03-2017, 05:20 PM   #12
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I do have a desulfator which brought them back to full capacity in a week.
Interesting. I'd never heard of a desulfator - did some reading (~15 minutes worth) and it seems they work. I wouldn't put a "restored" battery in DW's car but I'd sure try it in other applications.
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Old 01-03-2017, 06:43 PM   #13
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$.04 KWH coal generation is still half our power in the U.S., and nuclear power is never going to be as much of our power as it is today. Natural gas is the new hot thing in electricity @ $.11 per KWH. And forget wind power @ $.26 per KWH, as they're using 10% of U.S. steel production just building those beymouths. And little of the U.S. has enough reliable wind to turn the props.
If fossil-fuel energy is ever priced honestly (taking into account health/environmental costs) it'd be a lot more expensive. Not sure why we should forget wind power just because it uses a lot of steel - sounds kind of like a good economy-stimulating thing. And I question the "10% of US steel production" assertion: can you provide a reliable source ?
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Old 01-03-2017, 08:10 PM   #14
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Not sure why we should forget wind power just because it uses a lot of steel
You are right. A better reason to forget about it is that it is among the most expensive, least useful/practical ways to generate electricity in the US. A niche player, and an expensive one, at best.
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Old 01-04-2017, 02:49 AM   #15
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Grid solar panels don't work out for us roof angle and costwise, but it has become kind of a hobby for us to lower our energy usage and use what odds and ends solar power we can. We would like to set up RV type solar panels in the backyard for every day, supplemental grid power use. We have some solar lighting outside now plus some odds and ends solar gadgets from Amazon like flashlights, reuseable battery chargers and camping lights.
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Old 01-04-2017, 04:16 AM   #16
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You are right. A better reason to forget about it is that it is among the most expensive, least useful/practical ways to generate electricity in the US. A niche player, and an expensive one, at best.
And let's not forget all the dead birds from wind.

Another promising renewable energy source is ocean wave energy.
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Old 01-04-2017, 08:15 AM   #17
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And let's not forget all the dead birds from wind.

Another promising renewable energy source is ocean wave energy.
And bats. For a while, they couldn't figure out the dead bats, they didn't appear to have been hit by the blade. Then they learned that the low pressure area behind the blade basically sucked the lungs out of the poor little flying rodents.

Some people will say there is an offset from lower coal use, that coal has a negative effect on bird populations (air quality, habitat destruction?). I'm sure there is something to that, but I doubt wind is replacing much coal. Due to the intermittent nature of wind, I would think it is mostly the NG peaker plants that are being throttled down, and then back up as the wind changes. Coal can't be changed that fast, so it isn't a good match for wind supplementation.

Is wave energy 'promising'? I've read that some of the pilots have been shut down with no real plans to replace them.

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Old 01-04-2017, 12:12 PM   #18
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If fossil-fuel energy is ever priced honestly (taking into account health/environmental costs) it'd be a lot more expensive.
I would think that most people would agree that the benefits of fossil fuel energy far outweigh the negatives. Here's just one example:

"By the late 1800s London had over 50,000 horses moving cabs and buses every day. Each one produced 15 to 35 pounds of manure and 2 pints of urine daily. At the same time, New York had over 100,000 horses producing 2.5 million pounds of manure each day.

No one could figure out how to handle all this manure, and in 1894 the Times newspaper predicted based on the increase in population and horses at the time In 50 years, every street in London will be buried under nine feet of manure.

Automobiles burning fossil fuel solved the problem.
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Old 01-04-2017, 05:25 PM   #19
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I would think that most people would agree that the benefits of fossil fuel energy far outweigh the negatives. Here's just one example:

"By the late 1800’s London had over 50,000 horses moving cabs and buses every day. Each one produced 15 to 35 pounds of manure and 2 pints of urine daily. At the same time, New York had over 100,000 horses producing 2.5 million pounds of manure each day.

No one could figure out how to handle all this manure, and in 1894 the Times newspaper predicted based on the increase in population and horses at the time “In 50 years, every street in London will be buried under nine feet of manure.”

Automobiles burning fossil fuel solved the problem.
Yeah sure, compared to horses, fossil fuels probably better. I'm talking compared to renewables. Duh.

The things that aren't priced into fossil fuels as they should be IMHO, include first and foremost carbon in the atmosphere, health effects, and let's not forget the need to periodically send a bunch of our best young people overseas to kick Arab ass (while simultaneously inspiring terrorism).
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Old 01-04-2017, 05:49 PM   #20
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I'm not getting into a fossil fuel debate...far too much misinformation is out there, starting with the deliberately misleading word "carbon" when referring to the essential (for life to exist) and harmless trace gas CO2.

Have a nice day...
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