solar system design

[Sunking]

it's average sunshine availability in a year

You should not use the yearly average on a battery system, otherwise you will likely go dark in the shorter daylight months.

[russ]

What city are you near? I'll look up the insolation on PV Watts

Russ

[vikas maurya]

Two problems here. Unless this is a AGM battery, efficiency is around 80% at best. You say 5.5 hours? Is that average, peak summer, or low winter. In a battery system you have to design for worse case or the shortest Sun Hour day in the year. Very few places receive 5.5 hour in winter or rainy seasons.

it's average sunshine availability in a year

[greenHouse]

ya mike sorry i forget to give time.
I want to design for 5.5 hours.
Total load 450 W*5.5 h = 2475 Wh
so Total energy demand per day is 2475 Wh.
Now pls go ahead

And for battery sizing take DOD 70% and battery efficiency 85%
sunshine availability in India is about 5.5 Hours

Got a few minutes, then coffee and annoy some solar installers.

You need to provide us with more accurate, as well as more realistic, information. Very few places average 5.5 hours per day. You'd have to be in the tropics, which much of India is, but then you have to allow for the rainy season, which much of India has.

Also, there is no such thing as an 85% efficiency, measured in full-cycle watt-hours battery. For a stand-alone system, efficiencies are a lot lower because they have to be designed more robustly. You gain some efficiency when recharging from a discharged state, but we don't even know what that is for your system, because 5.5 hours for winter (Northern India) or rainy season (the rest of India) doesn't happen.

You =can= decide that 70% DoD is your design point, and there are valid reasons to do that, but it's a lousy design point, especially since foul weather tends to last more than one or two days, and that gets back to "rainy season".

Anyway, time for coffee!!!

[greenHouse]

Hush girl, we got to keep the communist confused.

I dunno if he's a commie, but he's keeping himself confused

[Sunking]

SunKing,

You're taking DoD as a per-day figure.

Hush girl, we got to keep the communist confused.

There are technologies that will handle very deep cycles. Many of the larger traction batteries will do 50% DoD on a daily basis and last for years. The HuP Solar-One batteries are rated 2,100 cycles to 80% DoD. 2100 / 365 is several years. It's all about plate chemistry, thickness and the rock well.

I understand that as I have worked with the manufactures for decades. However designing for 50% DOD on a daily basis is a poor idea for RE applications. That same battery discharged to 50% DOD each day lasting 2000 cycles can go 10,000 at 20% DOD. It is all about cost, location, and backup which has to be factored in.

[greenHouse]

SunKing,

You're taking DoD as a per-day figure. It's 70% DoD after 2 days no-sun (see 2 days autonomy up above), or 35% DoD per day. A bit steep, but not total suicide. Not that he's told us minimum insolation either, or that 3 days is enough total storage to stone-cold-dead.

There are technologies that will handle very deep cycles. Many of the larger traction batteries will do 50% DoD on a daily basis and last for years. The HuP Solar-One batteries are rated 2,100 cycles to 80% DoD. 2100 / 365 is several years. It's all about plate chemistry, thickness and the rock well.

[Sunking]

I want to design for 5.5 hours.
Total load 450 W*5.5 h = 2475 Wh
so Total energy demand per day is 2475 Wh.
Now pls go ahead

And for battery sizing take DOD 70% and battery efficiency 85%
sunshine availability in India is about 5.5 Hours

Solar panel Wattage = [2475 x 1.5] / 5.5 hours = 675 watts if using MPPT controller and you actually get 5.5 Sun Hours which I doubt in winter.

No way should even consider taking a battery to 70% DOD, that is suicide, your battery would be worthless in a few short months, and just 1 cloudy day and you go dark. Try 20% DOD or 5 day reserve which is equivalent to 2.5 days real reserve to 50% DOD. You did not say what voltage you wanted the battery, or was it 48 volts?

At 48 volts the battery AH capacity needed is [2475 wh x 5 days] / 48 volts = 257 AH @ 48 volts.

Charge controller size assuming MPPT is Panel wattage / nominal battery voltage = 675 watts / 48 volts = 14 amps minimum.

[Sunking]

And for battery sizing take DOD 70% and battery efficiency 85% sunshine availability in India is about 5.5 Hours

Two problems here. Unless this is a AGM battery, efficiency is around 80% at best. You say 5.5 hours? Is that average, peak summer, or low winter. In a battery system you have to design for worse case or the shortest Sun Hour day in the year. Very few places receive 5.5 hour in winter or rainy seasons.

[greenHouse]

Try this battery, Look up in your broswer:

HUP Solar-One Battery

Find me where it says the full-cycle efficiency, as measured in watt-hours, is 85% or better and I'll be impressed.

Here's the problem -- something called "activation energy". The activation energy is additional energy needed for a reaction to occur at all. You see it when charging a battery as the easy increase in voltage that doesn't result in any charging current.

When you take volts * amps, you get watts. And the "volts in" includes that activation energy, while the "volts out" doesn't. Added to that, the typical amp-hour efficiency is less than 95%, so you are losing both amp-hours and volts on a full-cycle. Finally, a full-cycle charge requires considerable amounts of energy to complete the last 10 to 15 percent of the charge (depending on current at the time the battery reaches the "Absorb" voltage). This charge results in both gassing and heat. All of the heat is waste, as is all of the energy that goes to gassing.

[DeltaFox 25]

Try this battery, Look up in your broswer:

HUP Solar-One Battery

[Mike90250]

ya mike sorry i forget to give time.
I want to design for 5.5 hours.
Total load 450 W*5.5 h = 2475 Wh
so Total energy demand per day is 2475 Wh.
Now pls go ahead

And for battery sizing take DOD 70% and battery efficiency 85%
sunshine availability in India is about 5.5 Hours

In post #3, Julie did all the math for you, you can just insert your new #'s into her calculations, and see what comes out.
or just divide the results by 4.3, and you would be close.

[greenHouse]

ya mike sorry i forget to give time.
I want to design for 5.5 hours.
Total load 450 W*5.5 h = 2475 Wh
so Total energy demand per day is 2475 Wh.
Now pls go ahead

And for battery sizing take DOD 70% and battery efficiency 85%
sunshine availability in India is about 5.5 Hours

Where can I find me an 85% efficient battery?!? I want one!

[vikas maurya]

Watts without time, well, it was guessed at the load being on always. 24 hours a day.

Like the old math problem, if 2 trains are travelling toward each other, one at 12 mph and the other at 38 mph, how far apart are they after 10 minutes ?

we have to guess at the missing part.

ya mike sorry i forget to give time.
I want to design for 5.5 hours.
Total load 450 W*5.5 h = 2475 Wh
so Total energy demand per day is 2475 Wh.
Now pls go ahead

And for battery sizing take DOD 70% and battery efficiency 85%
sunshine availability in India is about 5.5 Hours

[greenHouse]

Watts without time, well, it was guessed at the load being on always. 24 hours a day.

Like the old math problem, if 2 trains are travelling toward each other, one at 12 mph and the other at 38 mph, how far apart are they after 10 minutes ?

we have to guess at the missing part.

8 1/3rd miles less than before, unless they were less than 8 1/3rd miles apart?

Are they on the same track? Are they ghost trains? Do they have to slow down for pedestrians playing on the tracks? And why is one only going 12 mph?