I need an always-on solar system

System
System Posts: 2,511 admin
PIease, I need someone to give me detailed specification of d components dat wil be required to meet my need as stated below. My need is as follows:
I need a solar system dat will power up a 100 watt device for a MINIMUM of 15 hours in a day (9 hous in d day & 6 hours in d night). D system shall be completly independent of utility supply (GRID), i.e. d 100 watt device shall TOTALLY depend on solar energy . The solar system must be able to power up d 100 watt device during d day (sunlight) while at d same time, simultaneously charging d backup deep cycle battery for use in d night, when there wil be no sunlight.
So, please, i need someone to help me do d maths of d solar panel, charge controller , deep cycle battery, inverter & any other component u think I will need to be able to meet this ALWAYS- ON, GRID-INDEPENDENT, 100 - WATT DEVICE.

Am not living in d US, bt d country I live is on 7 degrees north of d equator. Being close 2 d equator means we have very good sunlight both in winter & in summer.

Thanking u in advance.

Comments

  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    Re: I need an always-on solar system

    Expect to get about 1000 W of solar panels for this project. What is the device you are powering? What country are you in? Can you provide coordinates of your location?
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: I need an always-on solar system

    What happens on 1 cloudy day. 3 cloudy days?

    100W x 15 hours = 1,500watts or 1.5 KW consumed

    You don't say what the device voltage is. 12Vdc 240VAC 120VAC 50hz 60hz
    Just tell us what the device is, we've heard of most things by now.

    Will someone be around to add water to the battery every month?

    I guess you want the device to work for at least 15 hr, and let the low battery, shut it off ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2
    System2 Posts: 6,290 admin
    Re: I need an always-on solar system

    D device is a 65 watt dell laptop. D 35 watt I added on it is just 2 allow for future expansion.

    Am in Lagos, Nigeria, West Africa.
    We use 240V AC 60Hz electricity.

    If u can help me do the maths, I should be able to cut up or down, depending on the size of my pocket.

    Thanks.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I need an always-on solar system

    Yes it would help to know the end use. 12 VDC or 24 VDC or 120 VAC or 240 VAC ... Makes a difference.

    But, a simple calculation:

    550 Watts of panels @ 75% efficiency (might be worse in the heat) = 412 Watts usable over 4 hours good sun (probably more near the equator) = 1648 Watt hours. Estimated usage; 1500 Watt hours. 400 of which will be supplied directly during charging? So you only need to store 1100 Watt hours - call it 1200. On a 12V system that's approximately 100 Amp/hrs. A couple of T105's could handle that @ 50% DOD, and could be easily recharged by the 550 Watts of panels (412 W / 14.2 V charging = 29 Amps current). 30 - 45 Amp charge controller would do.

    But that's very generalized. To be more specific we'd need more specifics about your site & use.
  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    Re: I need an always-on solar system

    Where did you get 65W number from? From the power supply? If yes, then that is not continuous load that laptop uses. It should be more around 25 - 40 Watts. What is the model of your dell laptop? Can you afford AGM battery? Fullriver batteries from China are cheap and good.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I need an always-on solar system
    ayanex10 wrote: »
    D device is a 65 watt dell laptop. D 35 watt I added on it is just 2 allow for future expansion.

    Am in Lagos, Nigeria, West Africa.
    We use 240V AC 60Hz electricity.

    If u can help me do the maths, I should be able to cut up or down, depending on the size of my pocket.

    Thanks.

    This hadn't shown up yet when I posted. :D

    Getting 240 VAC is a bit more problematic. Any chance you can get a US power supply for your laptop and run it off 120 VAC? Otherwise you're going to need either a 120 to 240 transformer or a 240 inverter. Both of those options will add expense and complexity.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: I need an always-on solar system

    Cariboocoot WHY is the 240v ac a problem?? just buy a 240v 50 or 60 hz inverter . It most likely he is using a powersupply made for grid connection to power the laptop.? most switchmode power supplies work no problems anyway on either 50/60 hz input.
    In Philippines its 230v 60hz and here in Aus its 240v 50hz and have never had a problem using power supplies from the opposite.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: I need an always-on solar system

    I think he needs about 500w solar panels ,Where he lives would have above 5 solar hrs a day. One 12v 300w inverter 240v 50 or 60 hz . a 60a charge controller. 3 batteries the size you use in say 3.ton truck 12v and wired in parallel...
    Before you all jump on me and say he needs deep cycle batteries not truck type ones. THINK FIRST he doesnt live in USA or some place with ready access to such things he lives in a part of Africa where there most unlikely to be available.And you cant go posting or FEDex deewp cycle batteries around the world.. far far too expensive. and would also be involved with high import duty.
    Sure if he can get deep cycle batteries where he is he needs abouy 2x 100ah 12v or one 225 ah 12v.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I need an always-on solar system
    john p wrote: »
    Cariboocoot WHY is the 240v ac a problem?? just buy a 240v 50 or 60 hz inverter . It most likely he is using a powersupply made for grid connection to power the laptop.? most switchmode power supplies work no problems anyway on either 50/60 hz input.
    In Philippines its 230v 60hz and here in Aus its 240v 50hz and have never had a problem using power supplies from the opposite.

    Maybe it wouldn't be a problem. I don't know. But here in Canada you'd be hard-pressed to find a low Wattage 240 VAC inverter, which means you'd have to buy a 'big' one and that means more $ and more power used just to run the inverter. So the logical choice might be to go with a 300 Watt Morningstar and a transformer that can step up to 240 Volts, but there again you have the potential availability issue. I thought perhaps a "US" power supply for the laptop might be the cheapest/easiest work-around. Maybe not.

    Frankly, I have no idea what you can/can't get in Nigeria. And for that very reason I agree with you about the truck batteries; maybe they'll wear out faster than deep cycles, but they could also be far more cost effective for being cheaper and more readily available.

    I actually put the panel Watts up a bit because I figured the heat there might have an even greater adverse effect than in most places. Notice how close we are on that? :D
  • System2
    System2 Posts: 6,290 admin
    Re: I need an always-on solar system

    Thanks 2 all dat showed concern 2 my needs. Am indeed grateful beyond words.

    Let me clarify some issues.

    I have every solar system component within my reach here in nigeria - deep cycle batery, charge controler, inverter etc. Infact, i have seen Xantrex, MorninStar products in stores that I've bin to. D only thing dat is imposible 2 get here is an inverter rated at 120Vac, dis is becos d standard grid voltage here in nigeria is 240Vac, so u wuldn't expect an importer 2 import any 120Vac device into d country. He'll definitely nt find a market 4 it.

    Concerning d power rating of my laptop, let me state it as written exactly on my laptop =>
    wide range input at 100 - 240Vac (1.7A) 50 - 60Hz
    output at 18.5Vdc (3.5A) 65W

    From d above laptop rating, its obvious my laptop can work on both 120Vac & 240Vac, but d chalenge is dat its virtualy imposible 2 get a 120Vac inverter in my country.
    But according 2 my engineering knowledge, I THINK d voltage level at which d inverter supplies does not matter. Wat matters is d power 2 be consumed by d device connected. For example, a 240watt device wil take only 1A from a 240V source bt wil draw 2A from a 120V source (ignoring electrical losses).
    Well, pardon my 'claiming to know'. If am wrong, pls correct me, & I wil consider d cost of importing a 120Vac inverter & d cost of total watt hour consumption of a 240Vac, den pik which is more cost efective.

    Concerning d thought dat d laptop wuldn't consume up 2 d rated wattage.
    U av 2 understand dat d power consumption of a laptop depends on wat aplication u are running. If u turn ON wireless & simultaneously watchin video, while a file search is being conducted in d background, den u should b expecting d laptop 2 consume up 2 d wattage rated on its power adaptor.
    So, 2 play safe & allow 4 d extremes, calculation shld b made based on d 65watt.

    Am using a Dell Inspiron Dual Core, 15" wide screen, wireless, bluetooth, web cam laptop.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: I need an always-on solar system

    ayanex10,

    You are correct in all of your assumptions... An 240 VAC vs 120 VAC inverter powering a 65 watt "universal power supply" of a laptop computer will be pretty much no difference.

    In general, solar power is expensive (as you well know) and you don't want to over estimate your loads. If you can get a Kill-a-Watt meter (230 VAC rated kill-a-watt) or equivalent meter to measure your actual Watt*Hour usage per day will help you better design your system.

    You are also correct to take your estimated usage and multiply by 2x -- your loads will increase, and there is always bad weather (no sun) to contend with.

    Another issue is the AC inverter itself... Finding one that is efficient at your power requirements (say a 300 watt inverter vs a 1,200 watt)... It is not unusual for an inverter to be 85% efficient + use 6 watts even with no load... So, your actual power needs could look like:
    • (65 watts + 6 watts) / 0.85 invtr eff = 85 watt DC (battery) Load
    • 85 watts * 15 hours per day = 1,275 Watt*Hours per day
    Sizing of the battery... Deep cycle batteries should not be cycled more than 50% for long life. You can plan on 1 day of "no sun" support, 3 days or more... We usually use 3 days of "no sun" as a reasonable sized battery bank:
    • 1,275 Watt*Hours * 3 days * 1/0.50 max discharge = 7,650 WH battery bank
    Assuming you use a 12 volt battery bank:
    • 7,650 WH / 12 volts = 638 AH (for 3 days of "no sun").
    Lagos is located right on the coast -- So, you may have a lot of coastal clouds (marine layer) vs if you where more inland...

    From this link, we get:

    [PDF]Microsoft PowerPoint - Boyo
    File Format: PDF/Adobe Acrobat - View as HTML
    Nigeria. • Also the global solar radiation on horizontal surface is measured at Meteorological Office,. Oshodi, Lagos, Nigeria. ...
    www.wcpsd.org/posters/environment/Boyo_Adenike_2.pdf
    • From the available data, the following general conclusion can be drawn about the nature and availability of solar radiation in Lagos. The annual average of measured daily global irradiation on a horizontal surface in Lagos is 4323WH/M2/Day.
    • The monthly average varies from a maximum of5861WH/M2/Day in February to a minimum of 3231WH/M2/Day in July.
    So, assuming 3.2 hours of sun in July (using 1,000 W/M2 as "full sun"), and 0.77 derating for solar panels + charge controller; and 0.80 for battery efficiency:
    • 1,275 Watt*Hours per day * 1/0.77 * 0/0.80 * 1/3.2 hours of sun per day = 647 watts of solar panel minimum
    Anyway, that is how I would do the calculations... You could easily justify 2x (or 1,300 watts) of solar panels to allow for bad weather and to use more power (a few lights, printer, etc.)...

    Just use the above equations and change them to suite your needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: I need an always-on solar system

    I should add that battery bank size vs Solar Array size should be taken into account too...

    My recommendation for ~650-1,300 watts or so of solar panel is based on the 650AH battery bank--if you choose a bank 1/2 that size, then the solar array should not be much more than 700 watts or so (5%-13% of battery AH rating is typical recommendations for battery charging current).

    Too little current, battery never gets charged. Too much current can be a waste of money (lots of solar panels) and could over heat a battery too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    question

    One more question please:
    where will d inverter draw its DC current from during sunlight, considering d fact dat during sunlight, d battery is going 2 be in charging mode, & d inverter is still expected 2 be powering d laptop during dis sunlight-battery-charging-mode.
    Am asking dis question becos I heard from a friend dat it is not good 2 be charging a battery & simultaneosly discharging d same battery at d same time. Please, correct me if am wrong.
    If d above statement is true, then, dat means I wil only be left wit d option of connecting d inverter 2 d charge controller or directly 2 d solar panel during d sunlight period (not to battery).
    Put into consideration d fact dat d DC current from d solar panel is NOT regulated (depends on amount of sunlight), but though d DC current from d charge controller is regulated, its regulation is a function of d terminal voltage of d battery 2 which it is conected to, and in dis case of connecting an inverter 2 a charge controller during dis sunlight battery charging mode, there wil be no terminal voltage from d inverter 2 bring about current regulation from d charge controller.
    So, how wil d system be configured 2 deliver power during sunlight wen d battery is being charged.
    How????

    Please, correct me at any stage dat am wrong, cos am only talkin from d idea I've acquired so far from dis forum, not from a technical perspective.

    Thanks to all for your contributions.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: question

    We've mentioned a small 120VAC inverter, because there is one model out, Suresine, that is pretty darn efficient, and could support just a few other things.
    I see now, there is a 220V version http://store.solar-electric.com/mosu300wasiw.html available too, which would be perfect for your situation.

    As to charging the battery by solar, and using the computer at the same time, you are only reducing the charge current, you are not "discharging" the battery, And we're taking that loss into account bu increasing the solar array.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • rschoolf
    rschoolf Registered Users Posts: 8
    Re: I need an always-on solar system

    I will chime in here because I am running a home office off-grid, and have pretty much the same needs as you.

    I have a Dell computer, with a docking station, two LCD monitors, an audio system, and LED lighting. My high power draw is 130 W, my low power draw is 55 W, and my average power draw over 15 hours is 78 W.

    I have 350 W of solar panels, 345 Ah (now, added a battery) of 12 v batteries, and I am able to draw down the batteries only 30%, leaving 70% in the bank, daily. I also have a manually adjusted tracker, which gives me a ~35% improvement in solar harvest.

    One idea I have been toying with is buying a 12 v power adapter for the computer. This 12 V power adapter is designed to power the laptop from your car battery, and it does so with a DC to DC converter, which increases the 12 V to about 19 V for use by the computer. The theory here is that since it will be able to operate from the battery without having to go through the losses of the inverter, it may be more efficient in the long run. One also has to consider the losses of the up converting, so it might be a wash.

    But that might be an attractive idea for you, because you may be able to handle your situation without having to purchase an inverter.