OFF Grid Newbie Looking for advice with first system

oliverbutthead
oliverbutthead Registered Users Posts: 4
in Off Grid Solar & Battery Systems #1
I am buying the equipment a piece at a time to go off grid. I currently have 10 210 watt Sunpower Panels with a 48v VOC. I am currently looking for a good inverter to go with these in my next step. I would like the option to be able to add a wind generator or more panels if need be. I shouldn't need to add too many more as my current usage is below 300 kw/month.

Looking for suggestions for a good long lasting inverter.

Thanks
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: OFF Grid Newbie Looking for advice with first system

    No offense but you're really going about it the wrong way.

    You need to know how much power will be required before you can pick anything. This includes the inverter, as you don't need an 8Kw inverter to run loads that never exceed 1kW and you can't run loads that are more than any inverter's power rating. The amount of power you need to store up will influence what system Voltage is used, and thus what inverter you pick. So does the question fo whether or not you need 240 VAC or only 120. Without a complete plan you're going to have headache and heartache trying to get mismatched equipment to meet your needs. I know because I spend a lot of time fixing systems that were built with just such an absence of plan.

    300 kW hours per month is roughly 10 per day, which is substantial for off-grid. So the first tactic is conservation; reduce power consumption as much as possible, or pay a lot more for the system.

    What you've got so far is enough panel to construct a 2100 Watt array. Given the size and Voc spec of 48 (Vmp & Imp are the most important numbers for planning, btw) you are definitely in need of an MPPT type charge controller.

    With that much array you probably won't be running a 12 Volt system, as it would require two charge controllers and a lot of extra wiring. So let's skip that choice (I rarely recommend 12 Volt unless there is a specific need for it).

    On 24 Volts the array would be the right size for 670 +/- Amp hours. This would require an Outback FM80 or MidNite Classic controller to handle the maximum current. It would provide a maximum of around 7kW hours AC. Fairly good size for off-grid.

    On 48 Volts the array would be the right size for 335 +/- Amp hours. You could use any 60 Amp MPPT controller or even Morningstar's 45 Amp unit (but that would not allow for much expansion). Same amount of kW hours, a bit more expensive accommodating 48 Volt circuit protection and disconnects but somewhat cheaper in wiring (smaller wire due to less current demands).

    Another thing to look at is the expected "harvest". You can utilize PVWatts to get an idea of what it may be for your area. But in essence you're looking at 2100 Watts * 4 hours equivalent good sun * 0.52 over-all efficiency = 4.3 kW hours per day AC which is no place near your present consumption figures.

    The reason why you are going off grid has to be asked. If grid is available it usually makes little economic sense to choose to pay more per kW hour which will be the case in almost every install.

    Just some things to think about.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #3
    Re: OFF Grid Newbie Looking for advice with first system

    I moved off-grid in steps. First, I bought generator, and I could use it. Then I bought inverter and batteries, so my power supply became uninterrupted. Then I installed solar panels. The reason for such gradual move was that I could use things that I had already installed.

    Solar panels, inverter, charge controller cannot be used without batteries, so it doesn't make sense to buy them in advance (unless you get a good deal of course). If you buy an inverter now, you won't be able to used it before you buy your batteries. And then you'll need a charge controller to connect solar. It is therefore, very beneficial to design the whole sytem, then buy things.

    As to inverter recommendation, I have Xantrex XW and it works well for me. I would recommend it.
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  • oliverbutthead
    oliverbutthead Registered Users Posts: 4
    #4
    Re: OFF Grid Newbie Looking for advice with first system

    Thanks for the information. I really need to get a book or read up for many many hours and try to understand everything a lot better. I have a gentleman I know in the area that does solar well installations that I might be able to pay to help me plan out a suitable system for my needs. Thus, I will have a list to go by and be able to buy the equipment in pieces.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: OFF Grid Newbie Looking for advice with first system

    i'm sure the guy you know would be glad to help you, but he can't educate you in limited time or second guess all of your wants, needs, and likes. it would be good if you did some reading on the forum so you can give your buddy some better input to solicit a better opinion from him.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #6
    Re: OFF Grid Newbie Looking for advice with first system
    oliverbutthead wrote: »
    ... I really need to get a book or read up for many many hours and try to understand everything a lot better.....

    We have a lot of people who read the forum and learn from the responses. Describing solar panels by their VOC and then asking for inverter recommendations doesn't show much clear thinking, yet, you'll get there.

    FWIW- I plan on about 400-450Kwh usage per month during the summer and have a 4000 watt array, and 800Ah 24 volt battery, and hope to add to the array to make things easier... For 300Kwh usage per month in the winter, I would need a substantially larger array/battery/system and/or a generator.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #7
    Re: OFF Grid Newbie Looking for advice with first system

    Like the others said 300kWh/month and 2.1kWp dont match. Somethings gota give there. If the 2kWp wins then you might find something helpful in our system documentation, see sig. If the 300kWh wins then you are in the big league, see the recent series of postings here "Gulf Island". $50K territory.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #8
    Re: OFF Grid Newbie Looking for advice with first system
    zoneblue wrote: »
    Like the others said 300kWh/month and 2.1kWp dont match. Somethings gota give there. If the 2kWp wins then you might find something helpful in our system documentation, see sig. If the 300kWh wins then you are in the big league, see the recent series of postings here "Gulf Island". $50K territory.

    Not necessarily. I am in $25K territory with my 6kW array.
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