1st post & 1st project

kurt
kurt Registered Users Posts: 13
Hello everyone. i'm starting my first project . i'm wanting to start small and looking for guidance . the battery will be a AUTOCRAFT Marine/RV 11o amp hr and the converter will be a 400 watt inverter . i'm undecided on the solar pannel , i'm thinking around a Kyocera KD135GX-LP 135W 12V Solar Panel . i have only about 4 hrs of direct sun light . as for my usage it will vary so it's kinda hard to put that down . but here is a rough idea ,lap top maybe once a week . the rest of items listed will be used more , 13 watt light bulb , small radio , can opener. the main thing i'm after is to get some experience behind me and to buy that first pannel for my home and thought this would be a decent start. thanks for reading my post and thank you for your guidance. kurt

Comments

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: 1st post & 1st project

    Can opener? That has got to be one of the odder things I have heard mentioned as a desired solar powered load.

    Tony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: 1st post & 1st project

    ok lets talk in generalities about your proposed system. the battery you would not want to go below 50% dod so that means up to 55ah is usable from the battery. inverters will deliver the required wattage to your loads, but will need power to run itself too and does vary from inverter to inverter. i'm betting you're going with a cheaper modsine and the efficiency could be anywhere from the 60% range on up to the 90% range with most cheapos around 70% or so. if you were to use the entire 400w to the load this is 400/12=33 and 1/3 amps. add to that the extra from the inverter so 30% of 400=120w extra. 120/12=10 amps. the total is now 43 and 1/3 amps drawn. it will only take about an hour or so to drain that battery down to about 50% dod just so you know.
    now in charging the battery with that pv the charge % is in the good range. 7.63a/100ah=7.63%. you did not state at what time of the year you have this 4 hrs of full sun. is this in the warm months or cold for if that's in your warm months the colder time of year could be a bit of a problem in producing enough power for you. based on the stated 4hrs though this will replenish 30.52ah per day. this is now another limiting factor for you and doesn't account for bad weather days when output will be next to nothing.
    if you know your loads and can track the time of usage well enough it may work for you. you might have need of more pv depending on your usage and amounts of sun you get. you may need to conserve the power at times too so for example skip the can opener for a manual opener if you can.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: 1st post & 1st project

    In addition to what Neil suggests.

    If you are doing this as a learning exercise,, great. There is no substitute for real, hands on experience.

    In my limited experience here is a way to do a rough calculation on the Pv side.

    If you take the rating plate capacity of the Panel, divide that number by 2, multiply THAT number the number of hours of GOOD sun you expect in a day (usually 4-6 in most cases) and that will give you about the max number of watt/hours you can generate in a day. This takes into account Pv panel ef, (80%?) Charge controller ef (~95%?) battery charging ef (~80%) inverter ef (50-98%).

    So in your example, your 135 watt Pv panel, 135X .5 X 4 hours =270 wh day. This would allow you to burn a 15 watt cfl for ~18 hours,, or a 125 watt tv for 2.16 hours, or a 60 watt lap top for ~4.5 hours. In this example, I have built in nothing for reserve for less than perfect days, or occasional over draws etc.

    That 270 wh would translate to ~23amp/hours out of your battery. With your 110 ah battery, that would be ~20% depth of discharge (dod) a nice number, for a daily draw. Some suggest that a 50% dod is permissible but I prefer only 20% for maximum battery longevity.

    It is also suggested that you have enough Pv capacity to provide between 5-13% of battery ah capacity. So in your 110 ah battery you would like a charge rate of 5.5- 14.3 amp. Your panel, in the best solar conditions,, might put out something like 9 amps,, but more likely perhaps 6-7 depending on the controller, panel temps, battery voltage etc. So you would be in the proper range.

    Now what you need to do is do some figuring on your load sides. Use the rating plates of your subject loads,, figure how long they will run per day/week etc, or buy a kill-a-watt and use it to figure them out. Then,,, you can get an idea of how much your described system can power.

    Tony

    I still say,, ditch the can opener!
  • MadJack
    MadJack Solar Expert Posts: 47 ✭✭
    Re: 1st post & 1st project

    Tony, your last post finally allowed a slow enough and well explained example to allow it to sink into my hard (& sometimes slow thinking) head!

    Neabie reality check . . .
    You guys who have been into Renewable Energy for a while can get to using way too many abbreviations and lose some of us with a *wtf?*. I'm slow but I'm learning.

    Could someone please fill me in on what all this means: (?)
    These evergreen modules offer 0% to 5% output. Evergreen is the first manufacturer to offer a positive 5% output.

    This module provides:

    * 195 watts
    * 10.96 Imp
    * 17.8Vp.
    This is off the SUN website...

    5% of what?
    I got the 195 watts.
    What is Imp? Impedance? What does it mean in all this, resistance?
    What is 17.8Vp ? I know V=volts but the little "p"?


    I understand it is annoying to some, repeating things but questions are the only way to learn.

    Thanks

    p.s. electric or rechargeable can openers are awesome for those of us who have arthritis.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: 1st post & 1st project

    The nomenclature does get a bit daunting. As for your question

    Vmp= Voltage at maximum power
    Imp= Max current (amperage)
    Voc=Voltage open circuity (no load on the panel)

    Remember, Solar panels (PV) will put out differing amounts of useable power depending on the voltage. The design voltage must be higher than the battery that one is trying to charge. (~17vdc for a 12v battery for example) Vmp is the point where the panel can put out is' maximum power. (V x A = Watts)
    Lower the voltage, (by connecting to a load for example) and the power goes down.

    (I have to run now,, but I will elaborate later if no one else does T)
    I don't know what the 5% refers to.

    Sorry if I ridiculed the can opener. It just shows how we can jump to conclusions!

    Tony
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 1st post & 1st project

    MadJack,

    I believe the 0-5% is the out of box power rating (first 60 days?) of the panel:

    195 watts -0% +5%

    Most panels will warranty:

    xxx watts +0% -5% or+0% -10% of rated output...

    and over time, -20% over 20-25 year life maximum drop in output.

    For details, you will need to read the Evergreen Warranty (PDF download):
    Limited Warranty: Materials or Workmanship

    Evergreen Solar warrants the modules to be free from defects in materials or workman-ship under normal application, installation, use, and service conditions. The panels must be installed according to the latest Safety, Installation and Operation Manual provided by Evergreen Solar otherwise this warranty will be void. If the product fails to conform to this warranty, then, for a period ending sixty (60) months from date of sale to the original consumer purchaser, Evergreen Solar will, at its option, either repair or replace the product or refund the purchase price. The repair, replacement, or refund remedy shall be the sole and exclusive remedy provided under this warranty.

    Limited Warranty: Power Output

    Evergreen Solar warrants for a period of ten (10) years from the date of sale to the original consumer purchaser that the power rating at Standard Test Conditions will remain at 90% or greater of Evergreen Solar’s Minimum Specified Power Rating. Evergreen Solar further warrants for a period of twenty-fve (25) years from the date of sale to the original consumer purchaser that the power rating at Standard Test Conditions will remain at 80% or greater of Evergreen Solar’s Minimum Specified Power Rating.

    Evergreen Solar will, at its option, repair or replace the product, refund the purchase price, or provide the purchaser with additional modules to make up lost power, provided that such degradation is determined to be due to defects in materials or workmanship under normal installation, application, and use. The panels must be installed according to the latest Safety, Installation and Operation Manual provided by Evergreen Solar otherwise this warranty will be void. The relevant Minimum Specified Power Rating is defined in Evergreen Solar’s product data sheet at the time of shipment. Standard Test Conditions are irradiance of 1000 W/m2, 25° C cell temperature, and AM 1.5 light spectrum.

    In the end, Evergreen warranty is better than average for new, and (seems to be) average over 10-25 year warrantied life of panel.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: 1st post & 1st project

    more simply put it is the tolerance of a panel's output as a new panel may actually be higher or lower than the wattage title given it and that tolerance is the range that is acceptable by the company for a given wattage title. for the evergreen example that means it will be no less than the wattage title and up to 5% more than the wattage title when you buy it.
    yes, we use abbreviations sometimes and there's no harm in asking us, but even i know the meaning of the abbreviation you listed starting with a w and i'll ask you to refrain and not use such abbreviations here.
  • MadJack
    MadJack Solar Expert Posts: 47 ✭✭
    Re: 1st post & 1st project

    Thanks guys, and my apologies Niel.....
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: 1st post & 1st project

    you're welcome and no problem, carry on.
  • kurt
    kurt Registered Users Posts: 13
    Re: 1st post & 1st project

    Thought I would allow some time before i posted again, NEIL and EVERYONE thank you putting up with my generalities . I will learn those abbreviations & calculations . the inverter is a cheapo from an auto store . the 4 hr sun light is in the winter & 6 hr sunlight in summer. another question i have is what does '' DOD '' mean ? and my last question for the moment ,is there a way to figure out how long it would take to recharge my battery ? just curious about that one
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 1st post & 1st project

    DOD=Depth of Discharge=0% is fully charged; 100% is completely dead

    SOC=State of Charge=100% is fully charge; 0% is completely dead

    How long to charge a battery... Example:

    100 AH rated battery, charge at 10% rate (C/10)

    C/10=100 AH/10=10 amp charging current

    or 10 hours to charge from SOC 0% to 100%:

    100 AH/10 amps = 10 hours to charge

    Now--in reality, you can charge a battery at maximum current (i.e., constant current charging) from State of Charge of ~0% to 80 or 90%... The last 10-20% is usually a constant voltage charging and the current tapers down--so it will take a few hours to finish the last part of the charging cycle.

    And, of course, you should not discharge a battery below ~50% state of charge to ensure a long life.

    You can read through a couple battery FAQ's (like this one) to get a better idea of how to best manage your battery system.

    There are differing types of batteries, and various physical limits that you need to respect so that your battery bank will be properly charged and last a long time for you.

    Undercharging, or deficit charging (simply too much load vs available charging current from your solar panels), plus lack of clean distilled water (keeping cells properly filled) will kill any battery bank in a matter of months (and we have all killed our first battery banks through improper charging / watering).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kurt
    kurt Registered Users Posts: 13
    Re: 1st post & 1st project

    ok got to checking into what i would like to power up and noticed i'll have to make some changes . but this is what i have in mind a tv, and vcr/dvd combo and a comcast box. the tv i have right now is 113 watts the vcr/dvd combo is 16 watts and comcast box is 35 watts. i'll be looking for a much smaller tv. i'm thinking about going on up to 4 golf cart batteries from sam's . And maybe later adding a nother panel
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 1st post & 1st project

    One issue to watch with digital boxes and recorders is their "standby" power losses... Some of the boxes take almost as much power when they are off as when they are on. And when you take a small load and multiply it by 24x7--the total usage can be amazing.

    If you can turn them off at power strip and easily power them backup when you need them (no need to reprogram settings for channels, preferences, etc.) would make things easier too (I have this issue with an old stereo--takes 20-40 watts when off, and when power strip is off--looses its station settings).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: 1st post & 1st project

    here's a way to look at it. the battery is 110ah and of that 50% is usable so it's 55ah. to convert this to watthours or wh you multiply by 12v and your battery is able to deliver 660wh. your loads add up to 164wh. dividing 660 by 164 is the number of hours your battery will function without a charge to it or 4hrs. know that the battery has lost 55ah during that time and it must be replenished by the pv system to bring it back to full. if it does not you are running a deficeit charge and don't have as much ah to work with. if you get for example 7.5a from your pv for 5 hours that would represent 37.5ah for the day giving a shortage or deficeit of 17.5ah.
    bill addressed the standby loads of these items already so you know you can't leave them on and inverters also draw power in addition to your loads so my guess is you may not be able to use it for more than about 3hrs and more than likely less than that based on what you can replace in power.
  • kurt
    kurt Registered Users Posts: 13
    Re: 1st post & 1st project

    guess i should have mentioned that in my last post , but yeah i use a power strip even plugged into the wall , so i can cut the power off at the power strip button.