Alternative Power sources - Sizing for 3.5kWh/day

Author

Sizing for 3.5kWh/day

bealiba@gmail.com

2007-09-14, 3:25 am

System voltage 24 Volts
Battery Volts 2V
Daily load 3.5kWh
5 days autonomy
Battery bank capacity 1200Ah
Daily Depth of Discharge 13.5%
Array output required 180Ah/day
PV module output 5A
Garanteed current 4.5A
Number of modules in series 2
Number of parallel strings 9

philkryder

2007-09-14, 3:25 am

On Sep 13, 8:35 pm, beal...@gmail.com wrote:
> System voltage 24 Volts
> Battery Volts 2V
> Daily load 3.5kWh
> 5 days autonomy
> Battery bank capacity 1200Ah
> Daily Depth of Discharge 13.5%
> Array output required 180Ah/day
> PV module output 5A
> Garanteed current 4.5A
> Number of modules in series 2
> Number of parallel strings 9

George -
Can one assume that if we needed 70kwh/day, that we simply multiply
your numbers by 20?

bealiba@gmail.com

2007-09-14, 9:25 am

On Sep 14, 2:58 pm, philkryder <alt.goo...@Kryder.com> wrote:
> On Sep 13, 8:35 pm, beal...@gmail.com wrote:
>
>
> George -
> Can one assume that if we needed 70kwh/day, that we simply multiply
> your numbers by 20?

Well, no. I checked it and it seems to work. But you would be better
served by multiplying by ten and doubling the system voltage to 48
volts.

But you have asked this before. Nothing has changed in the technology
to reduce the cost.

Although, according to the world foremost expert on load reduction,
yes that would be wayne, all you need is to use an electric battery
charger to reduce your load.

Martin Riddle

2007-09-14, 8:25 pm

<bealiba@gmail.com> wrote in message news:1189740911.602402.220940@o80g2000hse.googlegroups.com...
> System voltage 24 Volts
> Battery Volts 2V
> Daily load 3.5kWh
> 5 days autonomy
> Battery bank capacity 1200Ah
> Daily Depth of Discharge 13.5%
> Array output required 180Ah/day
> PV module output 5A
> Garanteed current 4.5A
> Number of modules in series 2
> Number of parallel strings 9
>

Speaking of 24V modules, are any of those convertible to 12V?

Cheers

bealiba@gmail.com

2007-09-14, 8:25 pm

On Sep 15, 9:43 am, "Martin Riddle" <martin_...@verizon.net> wrote:
> <beal...@gmail.com> wrote in messagenews:1189740911.602402.220940@o80g2000hse.googlegroups.com...
>
> Speaking of 24V modules, are any of those convertible to 12V?
>
> Cheers

This sizing was done using 75W 12V panels.

If you mean can your convert 24V panels to 12V some yes some no. It is
usually just a matter of where you connect to inside the Jbox on the
panel.

bealiba@gmail.com

2007-09-21, 8:25 pm

We started with 3.5 kWh/day;

System voltage 24 Volts
Battery Volts 2V
Daily load 3.5kWh
5 days autonomy
Battery bank capacity 1200Ah
Daily Depth of Discharge 13.5%
Array output required 180Ah/day
PV module output 5A
Guaranteed current 4.5A
Number of modules in series 2
Number of parallel strings 9

The next step is 15 kWh/day;

System voltage 24 Volts
Battery Volts 2V
Daily load 15kWh
2 days autonomy
Battery bank capacity 1200Ah
Daily Depth of Discharge 57.87%
Array output required 771.60Ah/day
PV module output 6A
Guaranteed current 5.4A
Number of modules in series 2
Number of parallel strings 31.75

So what do these two systems have in common.

Well, the first is the original system and the second is an attempt to
grow a 15 kWh system from the 3.5 kWh system.

So, lets look at the reality. The original system as built contained
16 - 75 Watt Solarex panels that would produce around 1080 Watts in
real use. The builder would have you believe that they produce 1200
Watts.

You will note that the builder used only 16 panels when the sizing
design called for 18 panels. The loss of the two panels is offset by
the use of trackers for the arrays. The builder also added a 300 Watt
wind generator. This number is also high and would be more like 150
Watts

All in all a nice, well balanced 24 Volt system. It will provide a
3.5 kWh load.

Unfortunately the builder did not design this system. He copied it
after seeing it in a magazine. This would not have mattered if he had
the same requirements as the person who designed it.

As it was, the builder found it fell far short of his energy needs so
he set out to grow the system to meet his needs. The result being the
second example in this demonstration.

What he ended up with is a system that has 16 - 75 W panels and 8 -
100 W panels. The 75 W panels will in reality produce perhaps 1080 W
and the 100 watt panels perhaps another 800 in real use. That is 1880
Watts. He also added a second wind generator with a rating of 1000
Watts. Following his established method of operation he believes that
when the wind generator is turning it is producing 1000 Watts. This is
doubtful. You can see this system at

<http://www.citlink.net/~wmbjk/solar30.htm>

bealiba@gmail.com

2007-09-25, 5:25 pm

The system should look more like this;

System voltage 24 Volts
Battery Volts 2V
Daily load 15kWh
2 days autonomy
Battery bank capacity 2000 Ah
Daily Depth of Discharge 34.72%
Array output required 771.60Ah/day
PV module output 6A
Guaranteed current 5.4A
Number of modules in series 2
Number of parallel strings 31.75

I have made some assumptions.

One is using an average of 6 amps output across the 75 W and 100W
panels and have probably erred on the high side.

The only way this system can get even close to doing what is claimed
by the owner is to run all the loads possible during daylight hours.

Of course if he had started with a proper energy audit and designed to
correct parameters the system would have looked more like this;

System voltage 48 Volts
Battery Volts 2V
Daily load 15kWh
2 days autonomy
Battery bank capacity 1000Ah
Daily Depth of Discharge 34.72%
Array output required 385.8Ah/day
PV module output 6A
Guaranteed current 5.4A
Number of modules in series 4
Number of parallel strings 16

Overall, the claims made by Wayne are, at best, pure fiction.

LinkBot