I'm so glad I found this forum!

System

My family and I just decided we are moving off the grid. We have forty acres in northern Arizona, at this time we have a rather small system consisting of four deep cells, one small panel and a propane generator. It's worked fine for the past 12 years! But that was as a vacation home, staying no more than a few weeks at a time. However, we will be moving there full time in the very near future. Can anyone help with a few suggestion as to what we need to live (comfortably) full time. Power requirements would be an evaporative cooler (in the summer, 1/8 hp motor and 15gph pump), washer and dryer(servicing three people), Sat. DVR, and TV (4hrs a day active DVR would be a phantom load) and a lap top (4 hr a day), this should be worst case power usage, and no they won't be all running at the same time.:D

BB.

Re: I'm so glad I found this forum!

First, you really need to characterize your loads... A Kill-A-Watt meter would be a great investment for the the AC loads (~$30 or less).

Kill-A-Watt AC Power Monitor Meter
P4400 Cumulative Killowatt-Hour Monitor

If you have substantial DC loads--a DC cumulative Amp*Hour / Watt*Hour meter would be useful. A Watts Up or a Doc Wattson look very interesting (I have not used either product or the vendor).


Once you know your loads (and, typically, work to find low power devices and work on conservation)--Then knowing your Peak Watts (i.e., well pump starting load, etc.) and your average daily kWhrs / Watt*Hours / Amp*Hours (at a particular voltage) -- the the rest pretty much falls out (battery size, panel size, etc.). Just need to know here your home is located based on the Solar PV Watts calculator webstite to predict solar production. If you want to do your own calculations--use a derating factor of 0.52 [fixed decimal point to 52%] for an Off-Grid system (less efficient because of battery and inverter losses).

For very small systems, people try to stay with 12 volt DC systems. For larger systems (and year round living)--people tend towards 120 VAC (sometimes 240 VAC too) systems. The losses associated with inverters (80+% efficiency) is made up for less problems, issues, and costs with distributing 120 VAC to appliances vs trying to make 12 VDC distribution (10x the current, a couple volt drop and DC appliances fail, DC appliances that don't like the 15+ volts required to properly charge a deep cycle battery, etc.).

Once you choose to go with an AC Inverter--you may end up with a 24 or 48 volt battery bank. This makes it easier keep battery cables smaller gauge and fused/breakers smaller less expensive. Also, the larger Solar Charge Controllers are based on output current rating--so at 48 volts, the can handle 4x the solar panel wattage vs a 12 volt system.

-Bill

niel

Re: I'm so glad I found this forum!

kingazjay,
you always forget something and there are always future needs to plan for too. i can tell you straight up that you did not mention lighting. really sit down and analize your needs as bill said and go further because of things forgotten and could possibly be needed later. you don't want to just barely squeek by and be worried or having to run a genny all the time to make up for the shortfall of the system.
do some reading here on the forum too to get yourself further in tune with what you may want and/or need. comfortable is something you need to define for yourself and go for it. we can give our opinions too, but get a better handle on your comfort needs that you need to design for.

System2

Re: I'm so glad I found this forum!

Thanks for the info.

We have the place set up now as a two system set up (a lot like an RV) all the lights and heater run on DC with their own batt bank (four deep cells) and solar panel. Then the AC side of things are driven by the generator. What I want to do convert the generator as a back up by adding a bank of batteries, solar panels, and a converter. This will power a water cooler in the summer, tv, sat. and computer, washer, and dryer, and a few outside lights for emergencies (will be CFL's) The fridge runs on propane as does the water heater. The beauty of what we are doing is that every thing is built and wired to be separate, power is not needed nor available throughout all the time. It's only available when you needed it.

BB.

Re: I'm so glad I found this forum!

PS: Fixed my previous post regarding using the PV Watt website... The derating factor is 0.52 -- not .052 ...

-Bill

niel

Re: I'm so glad I found this forum!

bill,
i already mentioned this to tony, but i'd like to hear how you came up with this one size fits all derating factor.

AntronX

Re: I'm so glad I found this forum!

What is your budget for this priject? Are you handy with tools and building stuff? Do you have good basic electrical knowlege?

I think you may have to choose clothes line instead of a dryer (I assumed it's electric). Go with MPPT chrage controller (Outback FM-60 or Xantrex equivalent) because it offers flexibility at choosing solar panel voltage, so you can shop for a panel with lowest $ per Watt ratio. Multicrystalline Silicon panels are best ones right now, look for a price between $2.5 - $3.7 per Watt. I don't think you will need UL rated panels (more expensive) in far away offgrid. In this case non-UL Evergreen B stock (blemished) panels will be best value. They can be had for $2.5 per Watt from some sources.

BB.

Re: I'm so glad I found this forum!

I used the 0.77 from the PV Watts Website (derating factor explained) -- And, I trusted it because the PV Watts did a very good job of predicting my GT Array's output (probably too close--random weather would dictate that PV Watts should only be within ~10% of my yearly numbers).

Then I used 80% for flooded cell batteries (includes losses due to equalization) and I used 85% for Inverter Efficiency (assumed that Charge Controller eff~GT Inverter eff):

0.77 * 0.80 * 0.85 = 0.5236

When I first started posting here (you can find those posts if they made it through the couple of forum migrations)--I used to go into the agonizing details of every point of my derivations... I got tired of typing them and, for the most part, I don't think new users (or probably anyone) cared about the details when trying to do a quick and dirty system capabilities estimate...

Also, since even the sunshine (watts/sq.unit) can vary over the year by +/-10% (more in coastal areas with fog/clouds, less in deserts with lots of sun). I have seen my winter numbers over the last three years vary by almost 2:1.

Add the the mix that 80% is probably the bottom end of flooded cell battery efficiency (old bank + equalization + 1-2% per day self discharge + differences in battery design/chemistry), or somebody may be using AGMs with >90-98% efficiency.

That 85% inverter efficiency -- may be well over 90% efficient (at medium loads), or much less at light loads (large inverter for well pump + on many hours to power smaller loads like computer + lighting).

Or an MSW inverter that may waste 20% power when running a fridge/freezer/other AC Motor loads. But not "waste" energy when powering power factor corrected computers and some other loads (some CLF's, LED's, filament bulbs, some other PFC electronics, etc.).

And given that a person would find it almost impossible to use 100% of an Off-Grid sytem's power every day (unless using programmed dump load like electric heater, well pump, or desalinator)--there is another cushion there.

In the end, the rules of thumb will give a workable system that will operatate well for 80% or so of the users out there. If we were to ask the detailed questions (measure Watts, Watt*Hours, VA, PF, etc.)--nobody would know all of those answers. And if we knew those detailed answers--would the recommendations change that much anyway (could we predict how every inverter/load/wiring/battery/charge controller/solar panel/weather/genset/external chargers/etc.)?

Yes, my recommendations/back of the envelope calculations tend to be conservative. Designing an Off-Grid system to operate on the ragged edge will probably not make for a happy user (assuming optimum efficiencies, cool clear weather, optimum load usage, cheap MSW vs costly TSW inverters, differences between PWM/MPPT controllers, bird poop based on 1 Sigma distribution on panels, etc.).

Lastly, perhaps, anyone with systems out there can relate their experiences with how much useful power they get from their On-Grid and Off-Grid systems.

So far, the few and far between reports back (my GT system, Tony/Icarus' 50% derating, a poster in LA CA a few years ago that said my "predictions" for his RV were exactly equal to what our rules of thumb suggested)--I am always open to better/more accurate ways of doing it.

For example, I keep getting banged on from both sides on costs... Solar Guppy saying I estimate 2x too high--to an installer from Washington state who says that he could not pay his installers on my costs estimates. No doubt about it--costing on an Internet forum is really just guesses.

I know that there is only so much accuracy we can provide when trying to answer questions from around the US (and around the world).

-Bill

mike95490

Re: I'm so glad I found this forum!

BB. wrote: »

I used the 0.77 from the PV Watts Website (derating factor explained) -- And, I trusted it because the PV Watts did a very good job of predicting my GT Array's output (probably too close--random weather would dictate that PV Watts should only be within ~10% of my yearly numbers).

Yet another case where the government screws up, again. A blatant example of PV Watts using next years weather (so it fits better), and then getting caught. Really folks, this is all planned out a couple years in advance, the planes are loaded up with chems, and HARRP is tuned, and they all work together.

Uh oh, the black van just drove up so I &*%#NO CARRIER

AntronX

Re: I'm so glad I found this forum!

I have actual data from FM-60 and Kill-a-Watt during 18 day span. FM-60 logged 18.8 KWh DC produced and KaW logged 13.22 KWh AC used.

13.22 / 18.8 = 0.703 = 70.3% efficiency (+/- 5%) from AGM battery to inverter AC outlet.

At peak sun my FM-60 runs at 97% efficiency, data derived with separate DMM voltage meter measuring input and output voltages and FM-60s built in Amp meter. I understand accuracy would be higher using indentical external current shunts. That's my future project.

70.3% * 0.97 = 68.2%

70 feet of 10 AWG wire from the panels is 97.3% efficent at peak power.

68.2% * 0.973 = 66.36%

So here it is, 33.6% of solar panel generated electricity gest stuck on it's way to my AC outlet. My gear when tested: 2x Evergreen 170W panels, Outback FM-60, 24V 100Ah Fullriver AGM, 24V exeltech 600W sine wave.

BB.

Re: I'm so glad I found this forum!

I figured it out--I am using Government Estimates--which only have a loose connection with reality.

-Bill

niel

Re: I'm so glad I found this forum!

sorry bill, but imho there are too many variables to use one figure for all, whether you're tired of typing it or not.

BB.

Re: I'm so glad I found this forum!

But, the differences, if people ask, I will use different numbers... But even a change from flooded cell to AGM and we use 80% to 90% is not a huge change to get tripped up over:

0.77 * 0.85 * 0.80 = 0.52 with flooded cell
0.77 * 0.85 * 0.90 = 0.59 with AGM

7% point change... May be a big deal to somebody--but not a huge change (barely 10% at the "derated value).

And closer to 7% of the "Panel Rating"--again not a make or break issue normally.

And given that AGM's cost (very roughly) 2x as much--those costs (I always) list out when I type about the differences between using flooded cell and AGM batteries.

-Bill

nigtomdaw

Re: I'm so glad I found this forum!

My motto to people over here in sunny Spain is there s no such thing as too many solar panels .

I take the average off grid couple who are energy saving savvy they need about 800 /1000 watt of PV for a Gas Fridge Equipped house and 1200/1600 watt for a A+ FridgeFreezer Combi equipped house. Includes a small booster pump for there cisterna. My calculations allow for one laundry wash a day.

4 hours a sun a day sees them self sufficient in energy , any extra sun can be used with standard household battery extender appliances such as extra washing,ironing, hoovering. slow cooker ect.

I encourage more panels with my motto "There no such thing as too much Solar" and they usually opt for my upper figure or even more, once I have explained the use of battery extender appliances,and the rule of use it or loose it

Its my KISS approach and yes I factor in variables like kids and other stuff.
Remember my formula works for my area, weather and geographical use of energy European v American with so many variables across the board it would be nice to know if other installers on this forum use a similar rule of thumb.

Next somebody is going to say what is your definition of an off grid couple, which I answer as
My model for my area and adjust to fit, after three years of off grid living.:p

It takes as standard

2 Bed House, Energy Savvy Couple, One Laundry Wash a day (no heated water)
Sat TV 4 hours a day, 1000w booster water pump with tank, 24 hour radio link internet, laptop 4 hours, CFL and LED Lighting, assumption of cooking and water heating via LPG. solid fuel stove/fire usually wood in Spain

I have one couple who elected for extra solar 1500 watts with a VFX3048E MX60 400 ah agm and a gas fridge and dont even run a genny as if the sun hasnt been good they dont switch the TV on in the evening they read a book, AGM batteries never dropped below 49 volts. They claim this only happens once or twice a month in winter time. Never such a thing as too much solar:cool:

Ralph Day

Re: I'm so glad I found this forum!

A 1000w booster pump? My Grundfos submersible at 1000w delivers 10gallons per minute, my Dankoff booster pump for cistern uses less than 150w for 2.5gpm. What and why such a lot of water delivery for 2 adults etc? Just curious.

Ralph

nigtomdaw

Re: I'm so glad I found this forum!

Its what most people have from 500/1000w pump and small pressurised tank usually the type with a large orange globe tank on top of the pump motor assembly allows a small amount of stored water pressure. So i allow for that.

System2

Re: I'm so glad I found this forum!

AntronX wrote: »

What is your budget for this priject? Are you handy with tools and building stuff? Do you have good basic electrical knowlege?

I think you may have to choose clothes line instead of a dryer (I assumed it's electric).

Very handy, with just about any and every tool at my disposal! We will be using a clothes line most of the year, however during the winter and the monsoon season it's just not practical so the Dryer will be converted to Propane, just need enough juice for the motor. And actually since I've been thinking about this, I think the washer and dryer both will be housed in a separate building and running off of a cheap generator. Keeping that draw from the solar system.

The budget for this project will be whatever it needs to be to live comfortably. I know I won't be able to afford everything at once, but if give up Starbucks and McDonald's for the next year, I hope to be able to start installing this time next year.

BB.

Re: I'm so glad I found this forum!

kingazjay,

Make all of your power sources and appliances "justify their usage/existences"...

For example, the average gasoline genset will get around 6kWhrs per gallon of gas. At $3.00 per gallon, that is $0.50 per kWhr.

However, once the genset load falls (very roughly) below 50%--its fuel flow remains (gph)...

Example, say you have a 5kW genset that uses:

5kW/6kWh per gallon = 0.83 gallons per hour

And assume at below 50% usage it runs at 1/2 fuel flow:

0.83 gph * 1/2 = 0.4 gph

Now, lets say you run your washer and drier at the same time and average 400 watt load --- Which is less than the ~2,000-2,500 watt rating of the genset, so--you are running on minimum fuel flow:

400watts / 0.4 gph = 1,000 WattHours per gallon (1kWhr per gallon).

At $3.00 per gallon, you are now spending $3.00 per kWhr (excluding generator cost, oil, maintenance, etc.).

Very roughly, the average solar RE system will cost you ~$1.00-$2.00 per kWhr... So, if you design your system large enough to power your washer/drier -- It may be cheaper to run solar PV than a cheap genset.

Or go Tony's/Icarus' route and get a gasoline powered washer... It will use much less fuel than running an over sized genset into an electric washer.

An example of sizing the genset to the load... A Honda eu2000i (1,600 watt) inverter generator costs 2x the 5kW noise makers... But its fuel flow is proportional to load down to 1/4 load (400 watts in this case).

So... Take the same above loads on an eu2000i. 15 hours @ 400 watts on 1.1 gallons of fuel.

15 hours * 400 watts / 1.1 gallons of fuel = 5,454 Watt*hours per gallon...

Or it will use:

1.1 gallons / 15 hours = 0.073 gallons per hour

0.073 gallons per hour * $3.00 per gallon = $0.22 per hour to run the washer/drier (assuming propane powered drier).

There are lots of options to consider (smaller generator, use the generator to charge the batteries and run the wash at the same time--when needed on cloudy/dark/short days, etc.)... But do the simple math and see how things look.

The above numbers are very approximate and use information I have measured or have seen in mfg. specifications.

In the end, if you have the ability--before you go off-grid, measure your loads and fuel consumption of your genset (plus a kWhr meter) so you can get a handle on your needs and costs before you need to setup the home.

-Bill

System2

Re: I'm so glad I found this forum!

Thanks Bill that's a line of thought I haven't had.

joeaksa

Re: I'm so glad I found this forum!

Jay,

Couple of suggestions. We have a place just South of Wickenburg, so not that far from you.

First off, look around for a diesel generator if you do not already have one. Lasts a lot longer and easier to work with than gasoline. Also you can do bio-diesel and cut your fuel costs by half. We have both types and use the diesel 95% of the time as we make our own bio-diesel.

Also agree on the use of propane on the clothes dryer but please be very careful. Am in the process of buying some used solar stuff (controller and panels) from a gent in N. Arizona who lost his entire house due to a propane fire from the clothes dryer. He lost EVERYTHING when it burned up, so this is not to be taken lightly. Might want to entertain putting the washer and dryer in an outbuilding a ways away from the house "just in case" the worst happens.

Where you are in Kingman you might look into wind power as a suppliment. We are just in the process of putting an AIR-X up on our place and very happy with the results so far.

As others have said, would really increase the size of your solar panel system and battery bank. Gives you more "cushion" for the 15 days a year when its cloudy in AZ!

Joe