Looking for feedback

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System
System Posts: 2,511 admin
in Solar Beginners Corner #1
I just wanted to get feedback on my proposed installation. I have a remote property in Southeast, Alaska where I am going to put up a cabin. I am also putting up an electric fence to protect the kids and livestock from the many wolves and bears. I am planning on going with a single Kyocera KD135GX PV with a Sunsaver MPPT 15L charge controller and a sealed battery or two (not sure yet)>170Ah (hopefully greater than). I also want to add an inverter for charging my laptops.
We get lots of full sun in the summer and not much in the winter (I think we’re rated for 1.25 avg. low peak sun hrs), but the fence energizer doesn’t use much (650mAh on full power) and the laptop can charge awhile or we can fire up the generator. Other than that we have a 12Watt panel for the phone and battery charger and a 5000W gas generator. Eventually we want to add wind power as we’re on a bit of a low pass between two hilltops and get good winter winds (we lived out there last year from Apr-Oct).
I think it is overkill for the summer and we’ll likely have to come up with a parasitic load to divert to once in a while (water heating element maybe). Of course during long rainy spells and short winter daylight hours I think it should keep us going without having to have a huge expensive battery bank, any flaws in my thinking, advice direction?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Looking for feedback

    Okay before you go diving off the deep end of your bank account ... :p

    You really should get some idea of your loads in terms of maximum Watts and total Watt hours per day; that is the best way to design any off-grid system.

    Some things wrong with your selections so far:
    135 Watt panel. This will actually function around 108 Watts on average. It might supply slightly more than 400 Watt hours of power per day (I can't run PV Watts on my Linux netbook, but it can give you a more accurate picture). It could probably handle recharging one 150 Amp hour battery, but with zero to spare for running things. This is the Number One mistake people make with solar: over-estimating panel production and/or under-estimating load requirements.

    Your charge controller could handle two of those Kyoceras.

    Before you spend any money on Wind turbines, be sure you get some accurate real-world data on how fast and sustain the wind is in your area. The Number One mistake people make with wind is over-estimating how much actual wind they get. The Number Two mistake is believing the sales hype about "produces in 4 mph winds" and "output up to 9000 Watts" (or whatever). Take all such claims with a bag of salt.
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  • System2
    System2 Posts: 6,290 admin
    #3
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    Re: Looking for feedback
    It could probably handle recharging one 150 Amp hour battery, but with zero to spare for running things.
    Are you saying that it would take all the PV's output to maintain the charge on the battery without any load?

    All this talk about Solar efficiencies and cost effectiveness are starting to look like rubbish if you're saying that it takes an $800 system to float charge a battery without any load.:confused:
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  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    #4
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    Re: Looking for feedback
    Pitchfire wrote: »
    Are you saying that it would take all the PV's output to maintain the charge on the battery without any load?

    This could be true in winter. Battery is cold and you aren't getting enough sun brightness to generate enough power to reach absorption charge mode.
    Pitchfire wrote: »
    All this talk about Solar efficiencies and cost effectiveness are starting to look like rubbish if you're saying that it takes an $800 system to float charge a battery without any load.:confused:

    Don't choose flooded lead-acid battery, but go with sealed AGM lead-acid instead. They are more expensive, but don't need as much current to reach full charge. You are also choosing an expensive solar panel. Look for Evergreen blemished panels or even re-brands that can be had for $1.80 per Watt. When choosing solar panel, always do the math to figure out price per Watt of capacity. Divide total price including shipping by rated power output ($price + $shipping) / Watts. There seems to be lots of people trying to make a living by overpricing solar equipment.

    Edit: Research good small wind turbines. Look for honest wind speed to power output charts. For your location solar power may not be the solution, especially in winter when you should be getting decent wind and practically zero solar.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Looking for feedback
    Pitchfire wrote: »
    Are you saying that it would take all the PV's output to maintain the charge on the battery without any load?

    All this talk about Solar efficiencies and cost effectiveness are starting to look like rubbish if you're saying that it takes an $800 system to float charge a battery without any load.:confused:

    :confused: Where did you get the idea that solar is either cost effective or efficient?
    In general, grid-tie solar power comes at a cost of $0.50 per kW hour over the life of the equipment. Off-grid is at least twice that cost. It does not stack up to utility power unless they're buying it back from you at a premium and/or you get some decent rebate/subsidy to off-set the capital cost.

    Efficient? Panels are about 18% efficient at best. Charge controllers and inverters run in the 90% range. Batteries suck up 20-25% more power to recharge than they are able to give back.

    Where solar shines (sorry; couldn't resist) is where there's no grid power available or it is unreliable or you need 'silent' back-up power. For occasional back-up, a good generator is usually a better use of $.

    As for charging ... there is a big difference between "Float" charging and recharging. To keep a battery up against self-discharge or mild draw is fairly easy. To make full use of the battery's deep discharge cycling ability and recharge it after using 25-50% of its capacity is another issue, especially if you want to keep the battery going for a long time (which is good economic sense). Remember that solar panels do not put out full power 24 hours a day. Most of the day, in fact, they put out nothing. So the battery is there to provide the power and the panel(s) are there to recharge it in the brief window of opportunity - usually about 4 hours of "equivalent full sun".

    We all know there's a lot of hype about solar out there. It isn't tolerated on this forum. Even though our host NAWS sells solar equipment, they prefer everyone knows the truth about what they're getting in to.
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