Multiple unit setup

System
System Posts: 2,511 admin
in Wind Power Generation #1
This is my first post so excuse my ignorance. I have been reading up on possible ways to use generators with a wind mills for homes. If I were to do this I would most likely go with a 2 unites that were 5-6 ft diameter. Ive found folk's plans on the Net and lots of good starting info but in terms of how to transfer that power to usable electricity there's not much out there. I have seen the harbor freight solar panel kit so I have a basic understanding on the inverter and that process. If I were to have 2 separate units working together how does the wiring schematic look differently than just one, or do most people just get multiple deep cycle batteries to charge that run to the inverter? I am the first to admit I know less than nothing about electric so I need some pointers or possibly a smack in the face. Can anyone better explain the wiring setup?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,623 admin
    #2
    Re: Multiple unit setup

    More or less, you have it correct... For an Off-Grid system, think of the battery as the "heart" of the system...

    You have sources of power (solar, wind, water, generators), and consumers of power (DC loads, inverters, etc.).

    You make a battery bank with bus bar (common connection to all of the batteries, with very low resistance--in the old days, a heavy bar of copper on the positive and negative bus). And everything connects to the bus bar with its own wire and protective fuse/breaker.

    As always, the devil is in the details. Typically, the charging current into the battery should be around 5%-13% min/max for proper charging (some batteries can take more, some can do OK with less).

    And loads, you ideally, your average daily load would be about 1/6 of the battery bank's capacity... 3 days of no power and discharged to a maximum of 50% of capacity (3d*1/50%=6).

    The next level of complexity--some DC to AC inverters can include their own internal battery charger--supplied by either grid power and/or generator power. So, the "load/Charger" is combined in some cases.

    Other issues are that with multiple independent chargers (2 wind, 3 solar solar, and a genset)--you can end up with un-synchronized charging (one is bulk charging, another is trying to equalize, and another is forced into early float)... Not typically a huge problem--but some vendors offer chargers that can synchronize their charging cycles together. Configuring the chargers so that only one does the equalization, and using chargers with Remote Battery Temperature Sensors will help.

    Batteries don't like being over or undercharged, and you want to make sure that you can diagnose your multiple charging system so that you can ensure that all are operating correctly (amp/volt meters, vs a simple green LED, etc.).

    Logging of Watt*Hours / kWatt*Hours / Amp*Hours from each of your charging system can be a help too to ensure everything is working well.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,623 admin
    #3
    Re: Multiple unit setup

    I should also add that some vendors offer example wiring diagrams (like Outback)....

    Before you get to involved with the details (which can be overwhelming when viewed all at once)... You would do much better to first define how much power you need (by day, week, season, etc.). And what sources of power you have available (solar, wind, water, diesel/gas/propane).

    And, remember that off-grid power (US professional installation with new components) and fuel driven genset for backup--can easily run $1.00+ per kWhr (vs the $0.10-$0.20 per kWhr for most utility power).

    So, any power you don't need (through very efficient appliances/designs, conservation by not using, and just making do with low-tech alternatives) will be saving you some very expensive electricity.

    If, you are looking for "green" alternatives--looking at solar hot water (domestic hot water, space heating), building insulation and window replacement, and Grid Tied Solar (utility interactive) Inverters--are going to offer you a better investment (many are eligible for government rebates and credits--may get $0.15 to $0.35 per kWhr costs for Grid Tied Solar) vs off-grid power (many are not eligible for gov R&C's).

    So, look at the above needs analysis first, before getting bogged down in the hardware.

    While you can do much of your own work--grid tied systems typically need permits and licensed electricians following NEC/Building Codes. Not doing this can result in serious failures (fire, death) and other issues.

    And like everything, experience helps... After you have seen/helped install your first system or two--the next ones are much easier (and you see where all of the mistakes were made in the first installation).

    Lastly, even though it makes sense for your first system to be small (so you can make "cheap" mistakes)--it is difficult to design and build "expandable solar systems"... For many reasons, it is usually not cost effective to assume that you will be able to spend a couple of $k every six months to grow out your system.

    At least design/cost out your "final system" to see if you want to save up for that onetime big cost.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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