Tinkering with idea of stand alone solar for remote rf tower

Snowyverdure
Snowyverdure Registered Users Posts: 10 ✭✭
in Off Grid Solar & Battery Systems #1
Just playing with the idea if solar alone could be used for a semi remote internet repeater? Constant draw of ~100 watts max. Estimate ~ 2,500 watts a day. Pvwatts says lowest solar is about .71 in month of dec. with panels angled ~85deg to south. Has unobstructive skies as its on top of a hill. Solar Does look like it will produce some current over ~1/2dozen hrs. Temps avg ~ -20f. Class 1 wind with class 2 on some nearby hills. No really good wind in dec. a remote start gen. Being preheated for 2 hrs when need would work but added cost and trouble.
So figure need a good 4-5 kW of solar panels, combiner box, 2 mppt charge controllers with current limited for max bat charge ~10% of bat capacity. So summer doesn't fry batteries in spring. Flooded 48v bank min 440 amp hrs. probably a good 600 amp hrs needed factoring only about 30-50% capacity in those cold temps. Would use some surplus to heat battery box but not much available. No inverters used unless a router to view system info wanted. At least Weekly snow sweeping icy frosty panels and water batteries ~spring fall mid summer. Change batteries every ~5 yrs
Anyone think this may reliably work on solar alone?
100watts doesn't sound like much but sure adds up in cold low light temps.
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Comments

  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #2
    Hi Snowy..,,

    WOW!!! 100 watts for an Internet Repeater sure seems HUGE!... we "host" an Internet WAP at one of the ridge top locations, here. There are two Ubiquity radios, each probably requires several watts, maximum.

    EDIT: Just looked at the NanoStation M5 Data Sheet, and it needc about 8 watts Max.
    AND, some of the very Long Haul radios in the AIrFiber class seem to be hungry. about 60 W Max ... and POE, at that .... Over one amp on the Ethernet cable, seems like a lotta current. So, depending on what you need to do, guess that 100 W may not be out range ... whatta I know?!!

    Half of the backbone of this system -- over 30 hops, IIRC, is run from solar and GC batteries, all using Ubiquity radios.

    Anything is doable, just a matter of dollars, cents and sense. That sure must be some REPEATER!
    FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • Snowyverdure
    Snowyverdure Registered Users Posts: 10 ✭✭
    #3
    It would probably be 2 ubiquity airfiber 5u. Specs say max draw is 40watts on one. But factor power supply inefficiencies at max figure 50watts. One would be max draw the other maybe not. Thanks.
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  • Snowyverdure
    Snowyverdure Registered Users Posts: 10 ✭✭
    #4
    Actually think just having about 800watts of solar and a auto start gen. And bat. info fed to internet. And a 48v 440 amp hr bank is probably the way to go
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  • Imurphy
    Imurphy Registered Users Posts: 16 ✭✭
    #5
    We use off grid power systems in the telco world all the time. I just got done engineering "prime power" cell sites. Using a 40 ft conex, 6kw generator, 1200AH flooded battery system at 48v 1.5Kw of solar. The Solar was a bit of a stop gap and a fun item on the project. But they originally wanted a prime power site, being a generator running 24/7 365. I was able to pull them from that. To using different batteries, no air conditioners, solar a smaller generator and cycling the battery plant instead of constant float. it increased the start up cost by about 50k per site. But we will be saving almost 30k a year in fuel and maintenance. and instead of replacing the gensets every 3.5 years we are now looking at a 7 yr life span. In the winter the generator will run about 4-6 hrs a day to recharge the batteries. In the summer it should almost never run. I have a microwave repeater site running on 1.2kw of solar and the generator has not ran since March 26th.

    Anything can be done if you are willing to pay for it. Each of these sites are costing us about 145K. And that's just for the building and power system. Telcom gear, property and tower is in addition to that. These sites will be 3 to 7 hours away to respond to issues, so they needed to be fairly autonomous.

    I think I would double your battery bank, between the cold and lack of solar in the winter you will be hitting them fairly hard for a month or two. If you are going up the hill to clear snow, you cant drag a small gen and give them a boost and equalize charge monthly. Or have a few packs you rotate out. You can get a 3k auto choke 2 wire start gas generator fairly cheap these days. I would definitely not count that option out. Coupled with a magnum AGS and charger and you are golden.
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