Viability of an partly unattended system?

BJW · February 2017

We are exploring the possibilities of building on a Bahamas family island and before I dive really deep into living off-grid I wanted to get some advice on whether it's viable or advisable to have an installed solar system that could be off or in "sleep mode"? for perhaps half the year. This would be a Winter place and so we would probably be there January through May. We haven't purchased any land but I was wondering if we would be tied to areas where the grid exists given our part time situation. BEC is a notoriously unreliable electrical source and uses very dirty fuel to generate. We'd love to not be a part of that. But before I go any further I'd love to hear your thoughts!

Thanks in advance
Ben

Marc Kurth · February 2017

That is a very broad question, but yes - unattended systems are installed on a regular basis. Just be sure to work with a competent designer who is familiar with doing it!

BJW · February 2017

Thanks Marc that's very encouraging! I've been reading as much as I can about battery maintenance and thought it might be untenable to leave an install, with no remote access, and come back after months away and just hit the start button. This would be another hobby for me

littleharbor2 · February 2017

We have a beach house in Baja, totally off-grid. During the summer when it's too hot for comfort I shut down the main system and maintain the battery bank with a couple panels mounted flat on the roof running through a small charge controller. There are no loads at all and the 2 panels keep the bank topped off without needing the big charge controller ($$$) to operate in the summer heat which gets into the 110's regularly, in July, August and September.

Estragon · February 2017

My cabin is mainly summer use at present. It wouldn't be a big problem to leave it unattended from Oct to May except for a problem with snow. That obviously shouldn't be a problem for you.

You sort of have an opposite issue. Heat shortens the life of batteries and electronics. Making a partly below grade space if possible to avoid high daytime temps, for example, may help. Having a small backup system to maintain batteries in case of a problem with the main system could avoid the fast self-discharge of batteries in warm temps.

I don't currently have a way of remotely monitoring the system, but it's on the to-do list.

littleharbor2 · February 2017

I have discussed underground battery vaults with neighbors. Some people have them down there. Only had the place 2 years now. lets say it's on the project list. I'm very curious how long my AGM battery bank is going to last as it sits now.

Your theoretical temporary setup would likely benefit from your panels sitting vertically and high enough above horizontal surface as not to hold built up snow.

BJW · February 2017

Thank you both and again it's encouraging to hear that it could be done. Baja? and here I thought you were part of the Abaco Little Harbour crowd. Your solution sounds simple and enough to keep a battery bank alive. Estragon we are in the opposite scenario aren't we? When you mentioned a "small backup system" did you mean one similar to what Little Harbor uses or an automatic generator backup system? I would probably need a generator on site regardless so perhaps I could utilize that but it certainly sounds more involved. All of this is obviously VERY involved but I'm starting to learn. The daunting part in my scenario will be learning all the necessary things then adding the island living with it's salt, storms and scarcity to the mix. This space is really an outstanding resource so thank you to all who contribute!

littleharbor2 · February 2017

The Little harbor handle comes from my home in the states. Little Harbor is a beautiful cove on the Backside of Catalina Island where I live. Spend a lot of time camping there.

Dave Angelini · February 2017

It will always be much easier to use an unreliable grid with some back-up as you will have many more options in a place like you describe.

You need some load data also. Theft in that part of the world is always there and by having the grid there would be less to steal.
Running an unattended generator is worse in my mind than the other challenges you listed. Good Luck!

BB. · February 2017

If you have no (or very low loads) when the system is unattended--Not too much of an issue.

If the system will be running significant loads while unattended (refrigerator, irrigation, etc.) while unattended--That can be a bigger issue (what happens if you have a stretch of bad weather, charge controller failure, etc.).

In the end, you should design the system to be safe no matter what--In general, that would usually mean that the battery bank be in a location that if the batteries leaked acid or over heated, that the main building would not be at risk of fire (and obviously, follow code/best practices for wiring, etc.).

Stuff fails... Charge controller stop charging (kill batteries). Or worse yet, allow uncontrolled charging (batteries over charge, boil off water, and risk of fire). Remote monitoring/weekly on site check and a local contact to check/repair system when you are not there would be a possible solution. The more stuff you add for backup/redundancy adds more points of failure. Simple vs complex/redundant--Not always clear which is the "better" choice.

Keeping the system (and your loads) relatively small--So if something fails, the cost to replace batteries/etc. is not the end of the world.

-Bill

Estragon · February 2017

By "small backup system" I was thinking separate small panel and controller. Some use an auto-start generator for this, but in my mind there is just too much to go wrong with nobody around to take corrective action. As Bill suggests, this assumes no loads other than controller self-consumption, battery self-discharge, and maybe some low power monitoring.

@littleharbor2 - unfortunately my racks are already at max tilt (~70°). First winter snow normally arrives in Nov., and the wet sticky snow melts off before the sun gets too low. Cold, dry snow falls off. Last 2 years though, the early sticky snow came in mid-Dec then froze on. Later dry snow won't slide off the already covered panels. I cleared about 8-10" off panels in mid-Jan.

For next year I'm planning to add small backup systems mounted high and vertically. At some point I may try adding 6x6 sleepers to the back legs of the racks to increase winter angle, but that may just increase drifting snow buildup.

BJW · February 2017

Little Harbor...very nice! Great place Catalina.
Thank you all for the reality check. It's greatly appreciated!
I definitely see the benefits to having grid power access even if it's unreliable it just limits my location choices. I've heard it can take years for power to be extended along the line if it's over 100 yards. But we are willing to do what would work best. Who doesn't want to plop themselves down near a secluded beach and call it home though? Many of these same issues would have to be addressed in a gridded set up as well since I'd want to add some battery backup to smooth out for outages and brown outs that I have heard can kill your electronics pretty fast down there.

When we shut down for the season I envision that there would be minimal loads that would be associated in some way in keeping the batteries alive. I don't think there is any local expertise on island and I haven't seen many panels in my travels there. It's about 30 years behind as far as solar goes I think. I'd probably look into sending someone local for technical training perhaps.

So it's really all about the batteries and can I assume that the critical factor in any battery decision I make is the fact that they would be unattended? They would be in their own safe space somewhere but during the unattended time it could get hot for sure. I'm not sure whether going underground (or mounded?) to keep them cooler would be viable but I will research it.

I'm sorry I haven't reached the point where I can really discuss loads in any detail but I could safely say that we would have a cistern water pump, solar hot water and a generator (probably diesel) for bigger loads like wash day. There is access to propane.

It's still very broad stuff here. Thanks for the patience and your input.
Ben

littleharbor2 · February 2017

Good luck in your endeavors . You're taking the right approach in educating yourself in the beginning. Knowing your system and how to operate/maintain it is vital in an off grid scenario.
Here's a view of our deserted beach.

BJW · February 2017

Well Ok then, now I'm officially jealous.

westbranch · February 2017

Try a PM to user Dapdan .... he is sort of close to you ...Breezy Hill, St. Philip, Barbados

westbranch · February 2017

BJW said:

Well OK then, now I'm officially jealous.

PFFFFT! before icing over

09:17

Image: https://us.v-cdn.net/6024911/uploads/editor/ax/m0x8jfblbkiq.jpg

now where did those fish go?

09:35

Image: https://us.v-cdn.net/6024911/uploads/editor/cm/4p064epg2kvw.jpg

BJW · February 2017

Beautiful WB! Who could possibly have better views than off-gridders?

I wish I could find someone on site to help monitor the system during the Summer then I could be here in the Winter...

Image: https://us.v-cdn.net/6024911/uploads/editor/2w/0bebmgy6xuym.jpg

softdown · February 2017

Dave Angelini chimed in. You should listen to him since he designs and maintains solar systems all over the world since the Civil War...or something.

My current thoughts lean towards using a genset for high usage periods and 2-4 golf cart batteries for low usage periods. At least until you figure a few things out from spending some real time there. Unattended buildings attract the low lifes. I would figure out a way to hide the genset and batteries if possible...with the bonus of keeping the batteries cooler.

Have you considered Cuba? Relations have thawed. I don't know how easy that would be either. Asking because I have an interest in trading a Florida shack for a Cuban shack on the beach. Its all about the beach.

BJW · February 2017

If I get to the point of real design I will certainly contact David and both of your comments about theft I've taken to heart. In general this spot is ...I won't say crime-free but it's a small place, scarcely populated, and everybody knows if there's a bad actor about and who it is.

I envisioned a reconditioned military tactical diesel genset for backup and high usage and hoped I could be grid free and still leave it for a few months. Would a PowerWall2 be an alternative since I have time to wait?

I am intrigued by Cuba and it's pristine ecological environment and would love to check it out! And for us it's all about the beach too...in the dark of Winter at least. Summers will be NEK VT for us.

Dave Angelini · February 2017

Or contact the store here ! They are very good!
On the Tesla, I have looked at several of their systems to date. I think there is hope there but for a real world system that actually could be done (mostly) at this time, completely in a few months check my thread out.

http://forum.solar-electric.com/discussion/351297/conext-bridge-for-xw-li-ions-from-lg-and-hoppecke-announced-for-2nd-half-2017#latest

Thanks for the kind words Softdown

Cuba was fantastic and I spent quite a few years on my sailboat there and all thru the Caribbean.
I did like the boat at night and the beach for the day. Too many bugs at the beach during the night in the tropics.... Enjoy!

tabbycat · February 2017

Don't install a system that you can't afford to lose to a hurricane. The Bahamas are constantly getting clobbered by them.

Viability of an partly unattended system?

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