Newbie choices

garynappi
garynappi Registered Users Posts: 105 ✭✭
edited June 2017 in Solar Beginners Corner #1
Hey, first post from sunny (most of the time) Florida! I'll apologize in advance for the L-O-N-G post!

Now that I'm retired I have more time to diddle with this. For a long time I've been considering a solar addition to my house external DC power scheme (no plans on ever getting into AC) for things I currently have running AC.  Those are:

A filter pump for a goldfish pond, battery charging for my all electric powered boat, and external perimeter mood lighting like a Malibu LED system, and possibly LED security lighting and later on a backup power for my home alarm system and security system. All of my needs can be covered with a 12 volt system.

I have been in electronics my entire adult life ( worked my way through college designing, building, and repairing power supplies and battery chargers) so solar concepts and general application are not new by any stretch but some nuances specific to solar I can use help on.

I guess the first issue is charge controllers. It seem as if they are relatively inexpensive in the neighborhood of ~$40- $85 for a 20-30 amp model.

The questions I have are about selecting the amperage capability. Is there a downside to selecting a 30 A (I'll likely never need this capacity) versus a 10A or 20A version? Would a lower wattage selection "generally" be more efficient? Are claimed efficiency ratings factual or pie in the sky and hit or miss?

Another issue with charge controllers is battery type support. Only a few I've seen (sorry a major Ebay shopper here) show support for sealed, gel and flooded. The ones I've seen from companies that also make solar cells seem to be the only makers that list support for multiple battery types. At $60 I have a hard time believing these work reliably without frying expensive batteries. Does anyone have some Ebay brand / model suggestions for me?

Oh, what about dual output controllers? Other than battery bank and output system segregation is there any benefit? 

Next up is battery selection.

Locally I can source group U1 12v 35Ah AGM wheel chair type batteries for $50. For the price of a decent single ~95Ah group 27 battery I can have between 4 and 8 batteries with substantially more reserve power. What are the general thoughts on quantity versus size?

My thoughts are that given a bank of four 35Ah (140Ah) cells would discharge to the "ideal" recharge point of ~12.1 volt (50%) the life of multiple cells would be much better than a 95Ah cell drained below 50% in the same application?

Solar panel protection

I want to use the south facing side of my house to mount the one or two 100 w panels to my eaves for an unobstructed day of sun or light. I'd like to protect the surface also. What material is best? polycarbonate (Lexan ) or Acrylic (Lucite) and would solar panels suffer / benefit from UV protection?

Outdoor / Indoor wiring (DC only)

Here's where I REALLY am in uncharted waters. I know Malibu low voltage lighting system wires are just minimally covered by dirt. What's the deal on running wire around a yard? Is there a particular type of wire I'd need to  look for? Use conduit? UW rated cable? Cable gauges (nothing over 2 amps) What about bringing DC inside to a security system and or surveillance system for backup power? I have a code book for my county and have not found any details on low voltage systems.

Outdoor power switching.

Ultimately I'll probably design a power steering system that will keep power on my fish pond 24-7 but shut off power for the malibu type lights and security lighting. Rather than run a RTC I'll just use a small solar cell to detect light (or absence of it) to turn on things that are affected by night/day cycles. That will mean at least two separate outputs to run. If anyone has done this, are there any pitfalls you know if?

Again, sorry for the long post, but based on what I've read here this is the place to ask.

Regards,

    Gary

Comments

  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Welcome Gary,  the best systems are based on a good listing of the loads to be powered and the time of day power is needed.  Your experience with line loss will have told you the bigger the better!   the Host has a good library to refer to for all things solar, see the header on this page.....  My experience with constantly adding to a 'simple system' is plan out as much as you can, you have a good start so far..... and if you are going to go for ''off-application'' batteries I feel you would be best with a CC like a MidNite Solar  KID 30 A MPPT http://www.midnitesolar.com/  , there are others you can find such as Morning star.... but you need flexibility and that means more $$

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • garynappi
    garynappi Registered Users Posts: 105 ✭✭
    Jeez, you already saved me the hassle of designing a light timer system. What do you mean by off application batteries? The 35Ah cells I am looking at are solar cells but are also used for "universal applications" like wheelchairs, inverters for power tools.

    I use one as a backup in my electric powered boat.



      
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    You need to understand your energy needs... Using "made up numbers": Say you have a 1 amp load @ 12 volts * 24 hours per day (fish). And want 10 hours per night * 2 amps of outdoor lighting. You want 2 days of storage and 50% maximum discharge:
    • 1 amps * 24 hours = 24 AH per day (fish)
    • 2 amps * 10 hours = 20 AH per day lighting
    • =>44 AH per day
    • 44 AH per day * 2 days storage * 1/0.50 maximum discharge = 176 AH @ 12 volt battery bank.
    Battery Bank wise, 6 volt @ ~200 AH "golf cart" batteries are pretty rugged and cheap. Use a pair in series for a 12 volt @ 200 AH battery bank (as an example).

    Next you need to size the solar array for two different issues. One is the minimum current needed to properly recharge the battery bank. For flooded cell batteries, 5% to 13% rate of charge is typical. 5% works well for a weekend/seasonal system. 10%+ rate of charge is highly suggested for a full time off grid system:
    • 200 AH * 17.5 volt solar panel * 0.05 rate of charge = 175 Watt array minimum
    • 200 AH * 17.5 volt solar panel * 0.10 rate of charge = 350 Watt array nominal
    • 200 AH * 17.5 volt solar panel * 0.13 rate of charge = 455 Watt array "cost effective" Maximum
    Then there is sizing the system based on the hours of sun per day... Say fixed array near Miami Beach FL set for winter production (security lighting):
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Miami Beach
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 49° angle from vertical:
    (Optimal winter settings)
    Jan Feb Mar Apr May Jun
    4.90
     
    5.40
     
    5.42
     
    5.47
     
    4.96
     
    4.32
     
    Jul Aug Sep Oct Nov Dec
    4.39
     
    4.45
     
    4.50
     
    5.01
     
    4.79
     
    4.76
     
    44 AH per day * 1/0.95 controller eff * 1/0.80 batter eff * 17.5 volts Vmp array * 1/4.32 hours of sun (June) = 235 Watt array minimum

    So--As you can see, even a small load running 10-24 hours per day adds up very quickly. And summer thunderstorms/marine layer can hurt.

    Personally, I do not like always on security lightning (I think it just makes it easier for people to see what they want to steal, highlight it from a distance--I prefer motion detector triggered lighting (bright lights suddenly turning on, thieves start getting nervous). Also with motion detector lights, you save a lot of energy (smaller batteries, smaller array, etc.).

    Anyway--Just some basics to get you started.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    On charge controllers - there are two basic types; pwm and mppt. Each has a place based on application. As a rule, there is no downside to getting a higher amp rating, but some higher rated ones may have features you don't need and may consume more power in support of those features. Efficiency is a bit of a squishy term. As a rule, they're likely pretty close. That said, if you try to run a 12v pwm controller off a 35vmp panel, you may be disappointed. One thing I would look for in a controller is a remote temperature sensor. Ideally you want the ability to set charging voltages specific to your particular battery, but the standard profile settings tend to be pretty close. Dual output doesn't strike me as particularly useful unless you're charging a house and starting bank on a boat.

    Generally, solar panels are just fine living in the elements. Adding lexan or whatever isn't going to help much. In Florida, your main concern would be making sure they won-t get ripped off in a storm.

    Battery type and size is driven by load needs, and solar panel needs are driven by battery needs, which Bill has given a start on. On quantity vs size, you generally want to use a minimum of 2v cells, so (eg. 2x6v@220ah batteries, 6 cells, would be better than 2x12v@110ah, 12 cells).

    For switching lights, etc., you might wat to consider a charge contoller with load control.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    Too bad it's not that easy to make a professional thief nervous. :) I wish turning on a light with a motion detector made them just walk away.
  • garynappi
    garynappi Registered Users Posts: 105 ✭✭
    edited June 2017 #7
    Looking at your signature files I see that you folks have systems Waayy beyond where I'm planning on going.

    My application as I said is DC only, I never plan on using it for AC, for short term emergency use I have a decent genset.

    The more I read on CC's the less "enlightened" I am. Only a few have lighting management, some support two batteries, others USB, it would be cool to have all three.