Small off-grid system in Hawaii

[Logan005]

sounds like you are off to a good start, learning to live with less electricity is very hard, but worth it in the end especially if you only need a 500lbs battery as opposed to a 1200lbs battery.

[jflorey2]

Just a little update

We are now two months into our adventure, and we just graduated from the headlamps-and-solar-lights stage into the generator stage! We drove our brand new Honda EU2000i home today.

Looking back on these few weeks, I must say that roughin' it is... rough! (Short list: mold, rain, more mold, getting water, lack of regular showers/hygiene, timing perishable foods, isolation/learning how to be out in the sticks), and really, I think any of the difficulty is in the transition itself, because it gets easier every day. It is completely worth it. I also, ha, won't look at modern convenience and infrastructure the same way again! It's been a fascinating process whittling down to the bare essentials, and I'm thankful to experience this before building our own infrastructure back up with newer eyes.

Soon we'll have a bathhouse and water catchment set up... Next up in electricity land will be a battery bank!

Good to hear it's going well. In a few months, you'll be the one giving advice to the people here who buy a $500 solar kit and decide to "go off the grid."

[mia.da]

Just a little update

We are now two months into our adventure, and we just graduated from the headlamps-and-solar-lights stage into the generator stage! We drove our brand new Honda EU2000i home today.

Looking back on these few weeks, I must say that roughin' it is... rough! (Short list: mold, rain, more mold, getting water, lack of regular showers/hygiene, timing perishable foods, isolation/learning how to be out in the sticks), and really, I think any of the difficulty is in the transition itself, because it gets easier every day. It is completely worth it. I also, ha, won't look at modern convenience and infrastructure the same way again! It's been a fascinating process whittling down to the bare essentials, and I'm thankful to experience this before building our own infrastructure back up with newer eyes.

Soon we'll have a bathhouse and water catchment set up... Next up in electricity land will be a battery bank!

[zed]

My shopping list to the OP?

Allow say...US$15k

1 x Sunny Island controller
1 x Sunny Boy TL grid tie inverter
4 x AGM 200 AH batteries in 48V string

8 x 200w 24v solar panels...(.add more later if the Sunny Boy is big enough)

Then get one of the new Samsung Fridges with inverter compressor technology (40 watts on full sing)

problem solved and scaleble

[inetdog]

Stacking kids is the same as paralleling any controller. each controller has to have it's own PV array, and the outputs go to the battery bank.

In theory two MPPT CCs could exchange information for the MPPT algorithm, which would let them share the same array too. But I have not seen that feature advertised yet.

I take that back. I have now. From the Midnite manual for The Kid:

Can be input paralleled for a true 60 Amp single controller

Twin Mode: is true paralleling where the inputs and outputs are paralleled. You are allowed only two KIDS in Twin mode. This is a Master/Slave configuration. The Master Twin tells the second Kid what to do.

Sync Mode is where the outputs are paralleled, but each input has its own PV array. Twin mode only works when two kids are connected. Sync Mode: When any one of the KIDs change state, Absorb, Time, Float or Equalize it sends a signal downstream to the next one to follow and change state. Then the second one sends the same message downstream and so on until it finally comes back around the communications circle and all units are in the new state. There is no limit to how many controllers can be connected in Sync mode. Both Sync and Twin mode are MidNite Solar exclusive methods of applying multiple controllers.

The sync cable is actually a serial data/networking cable, so it can enable anything that the firmware was written for.

[mia.da]

Logan- GC2's are FLA, 208ah. $85 here. T-105's are closer to $200.

Mike- Oh, duh! That's true. I must have been more enamored with Midnite's approachability/marketing- one part art deco, two parts 70's magazine print ads!
I guess that you can sync the Kid via cable (must be like other cc's), but I must say I haven't surveyed the field for all the possible charge controllers that would be good for me. More research.

[Mike90250]

Hello everyone! Many spreadsheets later...

Up top, I'm very enamored of Midnite Solar's Kid. Obviously their Classics are incredibly nice, but the ability to stack Kids will be helpful to me in starting out small ....

Stacking kids is the same as paralleling any controller. each controller has to have it's own PV array, and the outputs go to the battery bank.

[Logan005]

Sounds like a well though out plan. hope to see some future pic's of wiring and battery bank. maybe a pic of your vista. are the GC2's sealed? or FLA?

[mia.da]

Hello everyone! Many spreadsheets later...

Up top, I'm very enamored of Midnite Solar's Kid. Obviously their Classics are incredibly nice, but the ability to stack Kids will be helpful to me in starting out small and increasing the system later. And, hey, MPPT.

And yes, (math saves the day) I'm looking at a 24v or 48v system. I like that it means I can have my battery bank in series, no parallel strings, and meet daily Wh needs. Wiring is better. No, I'm not an electrical engineer, but yes, I understand voltage drop, and that amps & voltage are inversely proportionate when you want to deliver the same amount of power, resulting cable size, etc.

Overall I'm aiming for that sweet spot for a good entry point, but don't want to corner myself in from future expansion. Pricing looks to be around $3000 for the system I'm planning (I'll probably throw on another $500 buffer for random nuts & bolts along the way) and I'll be able to purchase items in steps, but still have functionality along the way- first the generator & headlamps stage, then a battery bank maintained by generator, then solar panels & charge controller, then nicer/larger inverter at a future time.

Re: jflorey2 & generator reliability- the EU2000i is well suited to pairing, we'd probably look at picking up a second one at some point! Another good thing is if we're in a dire pinch before we do that, our friends nearby have portable generators as well, for now.

A challenge in Hawaii is always availability and shipping cost, which trickles down on way or another.

Batteries- Trojans/etc are higher cost here. And funny enough, almost everyone I've come across just goes to Costco for the GC2's? I know they're not as high quality as other brands, but for my first time around, it wouldn't be a bad set to try out on, will it? Easier replacements/readily obtainable stock/reliable source. My ideal would be T-105's or L-16's. Weighing it out. A friend out here has had his bank of GC2's going for 8 years now, but I don't know his specifics.

I found a Steca fridge in stock out here (5.8 cu ft, aiming to purchase 8-10 months from now) that also can run on 24 volt, and is more efficient than a not-available-out-here Sundanzer of the same size (140wh/day for Steca with average residential use at 35°C/95°F, our location will normally be between 50°-85°F, so could expect better). It's rather neat- digital controls, can be programmed as a fridge or freezer. Planning ahead.

[jflorey2]

We'll be starting out with just our generator for the first month, and then moving towards building a battery bank for that. Solar was the last part of my thought process because we are approaching our energy needs primarily through our generator, and then finding more efficient ways to complement that (diverting low power needs to battery/avoiding nighttime use), so solar would be to help us maintain our battery bank, and not our primary energy source. Please advise if you have thoughts or disagreements with that approach . . . .

I think that's a very reasonable approach. It gives you fairly reliable power and allows you to take good care of a battery bank when you are starting out. The solar you will add later can then be used to reduce generator run time; if you get bulk taken care of in the early morning (i.e start before sunrise) you can then get the best efficiency out of your generator and leave the end of absorb/float for solar.

If you need more reliability, then a second generator is a pretty good investment. That way one can be in town getting rebuilt when it dies while the second carries your loads. The EU2000i is especially nice for this since it's so portable.

The true thing is that math will save the day in the end, huh? Just need to pin down all the variables and calculate it out.

Realizing that will put you ahead of most people trying to get started with off-grid living. Good luck and let us know how it goes.

[inetdog]

One of the things that you will see discussed here is how to get the most out of your generator with the least fuel and lowest run time.
If your generator is not the inverter output type, which allows the engine speed to be reduced without affecting the output voltage or frequency, then you want to minimize the amount of time the generator is running with a low load.
Your battery bank and inverter will help do this. To make sure that your batteries get to full charge, especially when your panels are not able to completely replace the energy used each day, you need to keep the batteries on charge for longer than the time your panels are producing useful power.
The general consensus is that the way to bring in the generator for charging is to use the generator for a few hours first thing in the morning to do most or all of the bulk charging, and then turn off the generator and let your panels and CC take on the job of finishing the charge.

[mia.da]

Hey everyone- Just want to let you know that I appreciate all of the advice you are giving and that I'm crunching on all of this (and, in middle of a couple 12-hour shifts at work). Each of you have very valid points that depending on variables can take things in a variety of ways.

First thing, I have time. We'll be starting out with just our generator for the first month, and then moving towards building a battery bank for that. Solar was the last part of my thought process because we are approaching our energy needs primarily through our generator, and then finding more efficient ways to complement that (diverting low power needs to battery/avoiding nighttime use), so solar would be to help us maintain our battery bank, and not our primary energy source. Please advise if you have thoughts or disagreements with that approach, since it's still in an early phase. More brains looking at something = better right? Not just thoughts rattling around in my head

We plan on running our generator almost daily, so in reference to how many days of back up I should plan for, there will be opportunity to charge batteries at those times as well. I understand that our generator lifespan will be different than expected use, but there's many people out there that use it in a similar way that we can reference. I definitely plan on a good maintenance schedule (oil changes every 25-50 hours, spark plugs, etc). It will be great to aim for 20% DOD on batteries, thank you for that advice, Sunking.

Going back to LETitROLL's post, I had been thinking on using some type of a pressure tank, but you're right, in combination with timing it with our generator use and maybe a larger tank, that could be a great solution to get through nighttime/early morning needs!

Littleharbor, thank you for that quick suggestion of how to help propane fridges be more efficient.

jflorey2, that helps thinking about timing battery charging along with other needs. I imagine we'll find a sweet spot in our daily schedule, but for example if we're in absorb by afternoon/early evening, there's a gazillion things we can use the generator for at that time too.

The true thing is that math will save the day in the end, huh? Just need to pin down all the variables and calculate it out.

Thank you guys!

[Sunking]

Err you missed the point again. No DC power anything. 240/120 VAC on a 48 volt Inverter.

[jflorey2]

Lots of 12 volt gizmos are made for that market right?
Many are high powered right?
Most are cheaply made, over priced, and inefficient right?

Most inverters made for that market are overpriced, cheaply made and inefficient. She will not be using an inverter for any significant part of her load. (And If she does later, there are inverters like the SureSine 300 which are excellent, rugged, appropriately rated devices.)

Most other 12 volt products are made for either the RV, marine or automotive market. And while there is cheap crap anywhere you look, there are also plenty of high quality products made for those markets.

What does is take to overcome all the power losses using 12 volts in a home where cable distances get long.
How many extra circuits have to be ran because of low voltage?

If your loads are like those of a large traditional house - lots.
If all your loads add up to less than 180 watts in a small home - none. If she uses four circuits (lighting, water, device charging, pump) then each load is going to be well below 15 amps, thus removing the need for additional circuits.

When you ignore the details of the load, and assume every system is going to end up powering traditional American loads in a large home, going 24/48 volts as a general rule makes sense. When you look at the details, often a better solution emerges. In this case, maximum loads are quite low, overall energy need is low, the structure is small, no grid power is available, and she will rely on a generator for early operation. Under those conditions, 12 volts makes sense.

[LETitROLL]

Jeff I do not disagree with anything you have said here. However you do appear to me to be glossing over something, or perhaps ignoring some facts about 12 volt systems. 12 Volts works great in RV's and boats no doubt.

Lots of 12 volt gizmos are made for that market right?
Many are high powered right?
Most are cheaply made, over priced, and inefficient right?
RV's are small footprints with respect square footage and cable distance right?
Batteries are stowed centrally in an RV which helps keep cable distances smaller and shorter right?
You know where I am going with this, and the OP has no clue what any of that means in the end right?
What does is take to overcome all the power losses using 12 volts in a home where cable distances get long.
How many extra circuits have to be ran because of low voltage?

ANSWER: A lot of money and exposing yourself to high fire risk on cheap equipment not made to last or use energy efficiently. When you look at the big picture in color things change.

It is all about AMPS, that is why with 12v it is better to stay with a strict "NO APPLIANCES, or POWER TOOLS" policy. Although best reserved for RV's, etc., Home use can be okay if for a few lights and/or electronics (low draw stuff) only. At around 2 amps losses are not unreasonable clear out to 65 feet (with common affordable wire). I am sure that it is a very small group of people that are disciplined enough to regulate their behavior and not cheat with a home 12v system and eventually cause themselves financial trouble (or worse), so in general I agree it is best to not even recommend 12v to most people, but i think it was worth mentioning to this OP, since they are truly not going to be building a house for a couple of years, and they have stated that they are already conditioned for substantial conservation in more of a camping situation.