Off Grid Beach Lot System

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System
System Posts: 2,511 admin
in Solar Beginners Corner #1
Hi Guys,

I am a newbie and hope that some of you can give me some much needed guidance and advice for a new solar system .

I am currently in Dubai but will be moving to Philippines soon to set up home on an isolated beachfront lot, on an even more isolated island.
:roll:
There is no grid, so the Solar Option is a necessity rather than a preference.

Apart from the normal electric home appliances, I will also require to cover Split A/C for a few hours a day, desalination pump/motor occasionally and also wastewater treatment pump for effluent sometimes.

I reckon that we are talking 12kW-15kW/day requirement, (probably less).

I am considering using 12kW Sunpower PV System with SMA Inverter(s).

I need some assistance as to the quantity and size of the Battery Bank allowing for maximum of 50% discharge, to help see me over a couple of cloudy days.

I know very little about Solar and even less about electrics so some assistance from much more qualified people would be much appreciated.

Any recommended specifications are welcome.

Thanks in advance

David
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Off Grid Beach Lot System

    Welcome to the forum.

    That's some pretty big off grid power need! Do you have a number for maximum draw at any given time? Would a 6 kW Xantrex unit handle it? In other words, everything that will be running at once draws no more than 6000 Watts. This can be dicey with AC and water handling pumps, all of which have big start-up surge draws and can come on whenever they need to.

    As far as I know, SMA doesn't make battery-based inverters. Therefor the only way to use them is with the SunnyIsland option. Nice, but an expensive way to go for off grid only power. If we had that max power figure there's probably some other suggestions that might help keep the costs down. Assuming you want to keep the costs down. Haven't met anyone yet who didn't! :D

    One example system for your needs (not a specific recommendation):
    XW 6048
    Parallel banks of eight L16's (320 Amp hours, 6 Volts) for 640 Amp hours @ 48 Volts
    4 kW - 5 kW of array (could be problematic in the tropical heat - requires more panels)
    Two charge controllers (to handle a peak charge current of over 60 Amps using Xantrex system)

    That would meet the 15 kW hour demand using up to 50% of the battery capacity. You'll need some type of generator for a back up charge source too, because even in paradise the sun doesn't shine every day. At least you should have above average hours of sun when it does shine!

    Beyond that it's hard to be more specific without more specifics. ;)
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  • System2
    System2 Posts: 6,290 admin
    #3
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    Re: Off Grid Beach Lot System

    Thanks Cariboocoot,

    I have never even heard of Xantrex until now!

    I cannot see a time when I would have all of the stuff running at once, I am thinking it might get to 5kW-5.5kW/hr , but I would just have to manage the usage.

    The desalinator Plant would only be used to make potable water and that can be switched on and off manually, as can the pump for dispersing the treated wastewater effluent.

    Looking at the Xantrex Data, it can handle 12,000W surge for 10 seconds is such a surge possible bearing in mind the above?

    The Split A/C will be around 1.4kW - 1.6kW depending on the manufacturer and the rest is just down to lights, TV, Fridge and Laptop etc so no real sweat there,.

    One very basic rookie question, when you have your electrical appliances drawing electric on a normal day , does the electric produced by the PV Bank power those appliances directly or is power always drawn from the battery bank and replenished by the PV Bank???

    See , I told you that I knew nothing!!

    Also I see u recommended Trojan Batteries what is your view of Sun Xtender AGM batteries as an option??

    Thanks

    David
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: Off Grid Beach Lot System

    I recommend Trojans as a kind of default, not because they're the best choice for every application. Almost a kind of industry standard. :D There's nothing wrong with SunExtenders, except that being AGM's they cost more per Amp hour than a FLA battery like the Trojan. Usually he flooded battery is better to start with because they are more forgiving of mistakes. Over charge an AGM and it's done. One battery I do not recommend is Surrette; they used to be top-of-the-line but lately there have been many problems with them shipping dead/defective batteries. So far they've been good about replacing, but who wants the problem in the first place? For a premium priced battery their quality is slipping.

    Rule #1 of off-grid power is reduce the loads as much as possible. Electric appliances? If that includes anything that heats look for an alternative. Heating is murder on electric. Burn dried coconut husks if you have to. :p

    The way the system works over-all is that the power is supplied by the batteries which are recharged by the solar panels. There comes a time during the recharge cycle when the batteries will be in "Float" stage, at which point they are fully recharged and you're not making use of the panels' full output capacity. This is the time to switch on those heavy loads, as the panels will supply much or all of the power needed to run them without draining the batteries. Saving battery capacity for when the sun doesn't shine. This is called "load shifting" and can add significantly to your system's over-all power.

    Is it possible you'd hit the Xantrex's 12kW surge? I don't know. There are too many possibilities of what you'd plug in and turn on all at once. I run the whole off-grid set-up with 3.6 kW inverter and it never comes close to capacity. It runs an electric 'frige, computer/satellite modem/phone/office equipment, lights, water & septic pump, and even microwave. But what devices you run and for how long and when makes a difference. I use about 2.4 kW hours per day, and the peak load is managed to be under 2 kW (don't confuse Watts with Watt hours) by switching the water pump and septic pump on a controlled basis. The water pump draw 850 Watts running, with a start-up surge well over that but only runs for 6 minutes a day. Run at full sun, it uses nothing much from the batteries and the water is stored in a large pressure tank for use as needed. The septic pump is 1 HP and draws a staggering 1.2 kW - but runs less than 1 minute per day. Again; on during "float" and the batteries stay happy.

    Since batteries are the heart of an off-grid system I suggest you read through the battery FAQ's to start getting familiar with them: http://www.windsun.com/Batteries/Battery_FAQ.htm

    And for terminology the Glossary: http://forum.solar-electric.com/showthread.php?t=6136

    There's tons of info in the forum FAQ too, for independent reading and consultation: http://forum.solar-electric.com/forumdisplay.php?f=14
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,748 ✭✭✭✭✭✭
    #5
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    Re: Off Grid Beach Lot System

    Tony,

    Any hard data on the Surrette failures? I would appreciate your insight! --Dave

    As for David here,

    The Marine environment has plenty of challenges also to keep in mind. An island offgrid is also a fun project. What is your timeframe?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • System2
    System2 Posts: 6,290 admin
    #6
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    Re: Off Grid Beach Lot System
    Dave Sparks wrote: »
    Tony,

    The Marine environment has plenty of challenges also to keep in mind. An island offgrid is also a fun project. What is your timeframe?

    Hi David,

    Island Offgrid may be fun for you, but its a nightmare for me ;)

    The timeframe is around 12 - 24 months, I am still researching everything ( Sewage Treatment, Desalination, Solar, Wind, Foundations, Roofing etc etc at the moment and trying to narrow stuff down.

    However, the more I research, the less I narrow it down as it throws more options up!!

    I am getting there slowly and learning a lot, but at some time I have to make a decision as to what the specification will be.

    :cool:
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Off Grid Beach Lot System

    Dave;

    I know we Canadians all look alike bundled up in our parkas and toques ... :p

    I've got no actual stats, but some of the threads regarding brand new Surrette that seem to be showing up 100% dead:

    http://forum.solar-electric.com/showthread.php?t=11516&highlight=Surrette
    http://forum.solar-electric.com/showthread.php?t=11235&highlight=Surrette
    http://forum.solar-electric.com/showthread.php?t=11262&highlight=Surrette
    http://forum.solar-electric.com/showthread.php?t=10486&highlight=Surrette

    The similarity of the problems plus other posts regarding maintaining SG in Surrettes makes me wonder. I don't see any posts for any other brand of battery suffering the same troubles. Is this a statistical oddity? Perhaps.

    Marc
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,748 ✭✭✭✭✭✭
    #8
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    Re: Off Grid Beach Lot System
    crendonman wrote: »
    Hi David,

    Island Offgrid may be fun for you, but its a nightmare for me ;)

    The timeframe is around 12 - 24 months, I am still researching everything ( Sewage Treatment, Desalination, Solar, Wind, Foundations, Roofing etc etc at the moment and trying to narrow stuff down.

    However, the more I research, the less I narrow it down as it throws more options up!!

    I am getting there slowly and learning a lot, but at some time I have to make a decision as to what the specification will be.

    :cool:

    Whatever you do on the island there may be some comfort in knowing that it will be easier than doing it on a sailboat. I specialized for 10 years in those kinds of nightmares. I still,occaisionally eleven years later, wake up wondering where in the world I left the boat and where am I now?

    At least you have time and you do not have to desal as you can collect rainwater, certainly as a back-up. Speaking of back-ups you may want to think of this project as a boat and design back-ups in. You either have to be able to fabricate a spare, have the spare, or have the airplane ticket. That is the cruising boater mentality.
    I pm'd you! Good Luck!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,748 ✭✭✭✭✭✭
    #9
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    Re: Off Grid Beach Lot System

    Thanks Marc,

    I was involved with a recent failure also but my other 45 have been fine. Surrette has been excellent with replacement to far away places BTW. I saw the links you provided Thx!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #10
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    Re: Off Grid Beach Lot System
    Cariboocoot wrote: »
    As far as I know, SMA doesn't make battery-based inverters. Therefor the only way to use them is with the SunnyIsland option. Nice, but an expensive way to go for off grid only power.

    The SMA Sunny Island is a normal battery based inverter. It just has the added ability to be used with grid tied sunnyboys, but that's not required- just an option.
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  • System2
    System2 Posts: 6,290 admin
    #11
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    Re: Off Grid Beach Lot System
    Dave Sparks wrote: »
    Whatever you do on the island there may be some comfort in knowing that it will be easier than doing it on a sailboat. I specialized for 10 years in those kinds of nightmares. I still,occaisionally eleven years later, wake up wondering where in the world I left the boat and where am I now?

    At least you have time and you do not have to desal as you can collect rainwater, certainly as a back-up. Speaking of back-ups you may want to think of this project as a boat and design back-ups in. You either have to be able to fabricate a spare, have the spare, or have the airplane ticket. That is the cruising boater mentality.
    I pm'd you! Good Luck!

    Dave,

    You have mail!!

    Rgds
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