solar energy isn't rocket science. know the basics like your load/daily power usage and your good to go.
contrary to general misconceptions, you don't need millions to start enjoying solar:

http://www.bdbatteries.com/panelcalculator.php

@ sathob,
I am referring you back to the very first post you made on this thread: Re; Solar Energy, A Comp. to FTA.
So it means you will need not less than a 84Ah, 12V battery (deep-cycle batteries, not ordinary car batteries) to do the job.

NB. Another way of calculating battery capacity is explained in this example. Should my battery be rated at 84Ah, 12V the watt hour (energy) will be 84Ah x 12 V = 1008Ah

It implies that the battery can supply a 150watt appliance for 1008/70 = 14hours

Pls don’t just play around with batteries they are dangerous.
In the quote from that post, the calculation in red I dont understand, how you come about dividing by 70, while talking of 150W appliance.
I would be glad if you can make this clear.
You know say me i no do maths for school.
Thank you bro.

@spaceman
Thanks, that should be a clear error if the calculation is referring to the time energy is distributed to the load from the battery. The danger with this error is that your battery will discharge quicker than the estimated error time of 14hrs.

Don't play around with batteries they are dangerous - the danger here is particularly about terminal / polarity handling short circuiting or pairing of batteries. there is no guess work here only go by the rules.

sathob,

i think there is a fundamental error in your calculation which does not account for battery depth of discharge and the fact that amp-hours is same as watts (power).

going through the calculation again, a 12v battery of 84ah will supply a total of

1008watts (84x12)

but that is 100% of stored energy and by extracting all 1008w we will be draining the battery completely flat (which is not advisable). so we stick to a battery depth of discharge (d.o.d) of 80% and this translates to

(1008 x 0.8 ) = 806.4w

so, we can only extract a maximum of 806.4w from this battery instead of 1008w.

now, ignoring system losses (wiring, battery internal resistance, inverter efficiency, etc)

150w load will give you a total run time of:

806.4w divided by 150w. this equals 5.376 hours,

which is exactly 5hours, 22mins.

sathob,
you can use this link for an independent confirmation. just input the battery amp hour and system voltage and it will output your expected run time based on the load (watts) you feed in. being an online calculator however it will not take you through all the steps used to achieve the results like i did.


http://www.alternate-energy.net/batteryamphours03.html

@George & Spaceman

Thanks for the attention, a cent more earned.

sathob,
solar energy is a continous learning process. cheers!

all,
testing out my system with my newly acquired tristar meter.
now i know what i'm really getting from the sun!

using a solar charge controller without a meter is like driving a car without a dashboard. you know the car is moving but you don't know the speed neither can you see all other parameters like oil temp, milleage, etc! your driving blindly! 

George_D:

using a solar charge controller without a meter is like driving a car without a dashboard. you know the car is moving but you don't know the speed neither can you see all other parameters like oil temp, milleage, etc! your driving blindly! 

True word my brother.
But this new stuff, na how many million dollars you buy am?

spaceman,
the tristar meter is just an addition to the already installed charge controller and it costs less than 25k. just take my earlier analogy of driving a car without a dashboard: you bought the car alright and you been driving without knowing the speed and milleage but now you decide its time to know what speed your actually driving at any given time so you go to the market and install a dishboard on your car. certainly the dashboard cannot be expected to cost more than the car itself, will it?

all,
i finally hit the 2kw mark on my solar array. no mean feat indeed and i also used the opportunity
to do an overhaul/upgrade on my wiring system (to cope with the additional load).

testing already in progress.

pictures will follow very soon.

George_D:

. . .
. . .testing already in progress. . .

pictures will follow very soon.

Oga George i dey envy you real bad o o o congratulations!!!
One day. . Just One day we will get there

freshp,
yes! one day, just one day, we will all be using power directly from the sun.

a few years back nobody ever thought solar panels would be a commodity to be purchased
commonly in the market due to thier very high price tag. then it was only government institutions
and big companies like telecoms that could afford them.
fastforward to today and even better solar panels are appearing in domestic houses. although
they are not completely as cheap as we would like but the good news is that prices keep falling.
and by projection if they continue falling at this rate, it's only a matter of time before they become
cheap enough to be affordable by all.

all,
i'm hitting 25amps on my solar array-more than nepa light is giving me. looks like the investment is worth it after all. monitoring still in progress!

Gr8 work George!

@George you mean 2KVA and not 25 amps?

loluskysat,
no sir! you heard me right. it is 25 amps and i get that from a 2000 watts solar array when the sun is at full blast midday.

my newly installed meter tells me exactly what amps i'm getting from the sun real time and also the accumulated amp-hours produced. it also gives the daily kilowatt-hours to enable comparison with what your getting from public power.

@ George,
That means you are getting 600Watts, i.e 0.6KW. Is that right?

loluskysat,
no sir! the derived power from a solar array obviously depends on daily solar irradiation which in turn is greatly affected by weather, i.e cloud/shading, wind, etc.

however my calculations so far i'm geting up to 1300w from my array on a good day (in bright sunlight). while i'd have loved to get a full 2kw my money's worth, i'm limited by my charge controller's inability to max out what my array is capable of producing.

to overcome this, i'll need an mppt charge controller which will allow me squeeze out as much juice as my array can give me. i'm already making out plans for this.

an mppt solar charge controller is much like a normal charge controller.
only the internal configuration is different.

all,
here's a quick link to help you in building up your battery bank.

http://www.freesunpower.com/battery_designer.php

all,
still carrying out tests on my solar installation. so far so good.

pictures coming - as promised.

something to wet your solar appetite!

@George_D: Solar Oga! I hail o! Since this is my first post on our forum this year I wish everybody here happy new year o! May FTA continue to be enjoyable to us! Please i need a tip or two regarding my office's intended inverter setup. We currently have our server room running IT equipment and 2 APC UPS's to provide backup power supply. Now due to we needing to run all the equipment continuously (i.e. inverter(s) should kick in after office hours, typically from 7pm - 7am ), we plan to purchase an inverter / inverters.
Been the new network admin, I've made an inventory of the equipment running there and i have the total estimated power consumption below.

TOTAL IT EQUIPMENT POWER CONSUMPTION: 2000w approx.
APC Back-ups 1: 2200W
APC Back-ups 2: 3000W

Needed Runtime: 14HRs (adding some tolerance)



What we actually need is an inverter setup to power the IT equipment, but should we then leave out the initial APC ups's we've been using? Or should we also make allocation for those? Also can you recommend the inverter power rating (s), Battery requirements, voltages, maybe an inverter brand with FAST SWITCHING like a typical ups because of the servers & APs that need a TOTALLY UNINTERRUPTED POWER SUPPLY.
Can you please help out the the calculations?
Thanks,
Litaninja

litaninja,
sorry for replying so late. your problem is a simple one.

since you already carried out an inventory of your estimated power consumption, your already on the right track to solving things.

now here we go:

1) total (it equipment) power consumption = 2000w

2) total expected run time/day = 14hrs

3) watt/hours per day  (2000*14) = 28,000watthours

4) assuming your using a 48v battery bank system voltage,

you will need a 28,000/48 = 584ah battery bank

if your using a 200ah battery, you need 4 batteries in series and
at least 3 battery banks wired in parallel, i.e 12pcs 200ah batteries
for your equipment to run without interuption.

5) you will need a minmum 3.5kv inverter to carry your load.

for recommendations, make sure you buy original zenith 200ah batteries.
personally that's what i use and i been using them close to 4yrs now without
fail. also, buy either nexus, sukam or cyberpower 3.5kva inverter for reliability.

also, you will no longer need those apc backup ups anymore. your inverter system
acts as a better and more robust ups system with longer storage.

hope this helps?

litaninja,
please note that the above calculations were done neglecting system loses and factors such as inverter and battery efficiency, depth of discharge (d.o.d) of battery, etc

when you account for all these you may come out with a much bigger battery bank than that.

George_D:

loluskysat,
no sir! the derived power from a solar array obviously depends on daily solar irradiation which in turn is greatly affected by weather, i.e cloud/shading, wind, etc.

however my calculations so far i'm geting up to 1300w from my array on a good day (in bright sunlight). while i'd have loved to get a full 2kw my money's worth, i'm limited by my charge controller's inability to max out what my array is capable of producing.

to overcome this, i'll need an mppt charge controller which will allow me squeeze out as much juice as my array can give me. i'm already making out plans for this.

@GeorgeD
How will the mppt charge controller up the output of your array? Because my experience without a charge controller shows that you lost batteries to overcharging since there is no BOOST and FLOAT charging periods.

ugeh,
never make the mistake of charging your battery bank directly from your solar panels. as you have already experienced, you risk losing your batteries to overcharging and overheating. besides it's very dangerous!
always connect your solar array to your battery bank through a charge controller.

now to your question: how will an mppt charge controller increase the output of your array?

to answer this question, you need to know how a solar charge controller works.

a normal charge controller charges your battery bank at battery voltage irrespective of its rated output. for example, a 200w panel rated at 32v, 6.25a charging a 24v battery bank, you will get

24v*6.25a = 150watts. but your panel is supposed to be 200w, so (200w-150w) you lose 50w on any given day no matter how bright the sun is in the sky. it even gets worse if your battery voltage is low.

lets say you used your inverter heavily overnight and your battery bank voltage dropped to 18v. in the morning your panels will only be outputting:

18v*6.25a = 112.5watts. you lose about 87.5watts! suddenly your 200w panel is only as good as a 100w panel, half what you paid for!

now, with an mppt solar charge controller, the charge controller looks at the output of the panels, and compares it to the battery voltage. it then figures out what is the best power that the panel can put out to charge the battery. it takes this and converts it to best voltage to get the maximum current into the battery. most modern mppt's are around 93-97% efficient in the conversion. you typically get a 20 to 45% power gain in cloudy weather and 10-15% in bright sunlight.


first of all, what is an mppt controller?


an mppt, or maximum power point tracker is an electronic dc to dc converter that optimizes the match between the solar array (pv panels), and the battery bank. to put it simply, it converts a higher voltage dc output from your solar panels down to the lower voltage needed to charge your batteries.

for example using the same 200w solar panel above,

assuming your battery is low, at 24 volts. an mppt controller takes that 32volts at 6.25amps and converts it down, so that what the battery gets is now 8.33 amps at 24 volts. Now you still have almost 200 watts, your money's worth.

24v*8.33 = 199.92 approx 200w.

assume your battery bank voltage is low, it even gets better:

18v*11.1 = 199.8 approx 200w

where with a normal charge controller you lose power the lower you batter voltage,
with an mppt charge controller, you get more current and your panel's rated power
when you need it most.

ugeh,
never make the mistake of charging your battery bank directly from your solar panels. as you have already experienced, you risk losing your batteries to overcharging and overheating. besides it's very dangerous!
always connect your solar array to your battery bank through a charge controller.

now to your question: how will an mppt charge controller increase the output of your array?

to answer this question, you need to know how a solar charge controller works.

a normal charge controller charges your battery bank at battery voltage irrespective of its rated output. for example, a 200w panel rated at 32v, 6.25a charging a 24v battery bank, you will get

24v x 6.25a = 150watts. but your panel is supposed to be 200w, so (200w-150w) you lose 50w on any given day no matter how bright the sun is in the sky. it even gets worse if your battery voltage is low.

lets say you used your inverter heavily overnight and your battery bank voltage dropped to 18v. in the morning your panels will only be outputting:

18v x 6.25a = 112.5watts. you lose about 87.5watts! suddenly your 200w panel is only as good as a 100w panel, half what you paid for!
now, with an mppt solar charge controller, the charge controller looks at the output of the panels, and compares it to the battery voltage. it then figures out what is the best power that the panel can put out to charge the battery. it takes this and converts it to best voltage to get the maximum current into the battery. most modern mppt's are around 93-97% efficient in the conversion. you typically get a 20 to 45% power gain in cloudy weather and 10-15% in bright sunlight.


first of all, what is an mppt charge controller?


an mppt, or maximum power point tracker is an electronic dc to dc converter that optimizes the match between the solar array (pv panels), and the battery bank. to put it simply, it converts a higher voltage dc output from your solar panels down to the lower voltage needed to charge your batteries.

for example using the same 200w solar panel above,

assuming your battery is low, at 24 volts. an mppt controller takes that 32volts at 6.25amps and converts it down, so that what the battery gets is now 8.33 amps at 24 volts. Now you still have almost 200 watts, your money's worth.

24v x 8.33 amps = 199.92 approx 200w.

assume your battery bank voltage is low, it even gets better:

18v x 11.1amps = 199.8 approx 200w

where with a normal charge controller you lose power the lower your battery voltage,
with an mppt charge controller, you get more current and your panel's rated power
when you need it most.

ugeh,
never make the mistake of charging your battery bank directly from your solar panels. as you have already experienced, you risk losing your batteries to overcharging and overheating. besides it's very dangerous!
always connect your solar array to your battery bank through a charge controller.

ugeh,
i'm trying to reply your post but the spambot keeps deleting my reply. i don't know what's going on.
will try again and see what gives.