Hybrid Car ā€“ More Fun with Less Gas

How many panels ? ( to run 230 volt sprinkler pump 30 minutes a day?) - Page 6

register ::  Login Password  :: Lost Password?
Posted by bealiba on July 10, 2008, 3:53 am
 

As I have already pointed out it is a recommendation for minimum
battery capacity and not a recommendation for a particular battery.

But as you asked, the total removed from the battery would be 122.5Ah
from 180Ah storage in half an hour. Which is as close as you can get
with only the recommendation for minimum battery capacity.

On the other hand "YOU" have recommended a very definite 28 Amps of 12
Volt panels to run a 230 Volt, 2500 Watt pump and specified no
batteries and no spreadsheet. As you do not want the batteries or the
spreadsheet why do you keep harping back to them?

This is your second post in a day where you have failed to answer the
question of how 10 panels at 28 Amps total will run 2500 Watts of pump
without batteries.

Why is no one surprised?


Posted by Ron Rosenfeld on July 11, 2008, 10:47 pm
 
On Wed, 9 Jul 2008 20:53:42 -0700 (PDT), bealiba@gmail.com wrote:


*I* never claimed that it would.  Your "straw-man" technique of debating is
pretty transparent, George.

You, on the other hand, have posed at least three systems which you claim
would work -- but none of them will work reliably 24/7.
--ron

Posted by Ron Rosenfeld on July 11, 2008, 11:17 pm
 On Wed, 9 Jul 2008 20:53:42 -0700 (PDT), bealiba@gmail.com wrote:


Yes, but you have failed to recommend a battery that meets the
specifications that you put into your useless spreadsheet.

In your useless spreadsheet, you specified a minimum battery capacity of
180Ah at the 100 hr rate.  Now you are writing that this battery will also
have a capacity of 180Ah at the 30 minute rate.

But you remain unwilling to specify a real world battery that would have
those characteristics, along with the 90% efficiency and 30% maximum DOD
that you also specified in your useless spreadsheet.

Did you just make up some imaginary battery specifications, George, or do
you really know of a battery that has the same capacity at its 100hr rate
as it does at its 30 minute rate, along with a 90% efficiency and a 30%
maximum DOD?

For those who might be following along but not cognizant of battery
characteristics, the problem here is that the usual lead-acid battery may
have a capacity, at its 30 minute rate, of maybe 20% of the capacity at the
100 hr rate.  Since George is specifying a battery in his spreadsheet that
has a capacity of 180Ah at the 100 hr rate, its capacity at the rate that
must be used in this system is only going to be maybe 35Ah.  

*Unless* there is something special about the battery which George is
unwilling to disclose.  

Clearly, George, your knowledge of battery current vs capacity curves is
fairly limited.  But you could probably research Peukert for some
information about this factor.

Here's what you entered into your useless spreadsheet, with regard to the
battery you are recommending for this system:

B1     Number of days of autonomy = 1
B2     Maximum allowable depth of discharge = 70%

B6     Adjusted battery capacity (B3 / B5) = 180.5

B7     Selected Battery
B8     Selected battery discharge rate 100
B9     A-hr capacity of selected battery = 180Ah
B10     Number of batteries in parallel (B6 / B9, rounded off) = 1
B11     Number of batteries in series (A7 / battery voltage) =1
B12     Check Capacity of selected battery at l00 Hr rate = 180
B13     Capacity of battery bank at 100 hr rate (B12 x B10) = 180
B14     Daily depth of discharge (100 x A8 / B13) = 68%

C4     Battery efficiency = 90%

So far, you've made a number of errors in trying to design for the OP's
system, even with your last attempt.

1.  You specified your battery incorrectly, specifying a 100 hr rate to
determine the capacity instead of the 30 minute rate which you should have
been using.  

Although your message above seems to indicate that you finally understand
that, you show no evidence of understanding that a battery with a 180Ah
capacity at the 30 minute rate might have as much as a 1200 Ah
capacity at the 100 hr rate you entered into your useless spreadsheet.  

And you have been unable to specify a real battery that does have the
characteristics of the one you entered.

2.   You have assumed that 1 day of autonomy will be sufficient at the OP's
location.

3.   You have assumed that the OP requires battery storage.

4.   You have accused me of oversizing the array, when, even your last
attempt, is for a system that includes 11 panels vs the 10 panels I
recommended.

5.   You have attempted to shoehorn my recommnedation for array sizing into
your useless spreadsheet in an attempt to convince yourself that my panel
array size recommendation somehow means an inappropriate battery size.  And
even there, you still used the same, incorrect, 100 hr capacity figure.

6.    You have used an inappropriate daily temperature figure for the
OP's location.


7.   You seem to have specified the OP's panel incorrectly

OP: Assume for instance the panels are 50 watt, 17 vdc, 2.94 amp

So GG enters into his spreadsheet:
C8     Selected module I at 14 volts at NOCT 2.94A

which equates to about a 41 watt panel.  You then apply various corrections
to this number, to further reduce its output.

You've been at this game long enough that you should have learned how not
to make these simple errors, or to correct them promptly if you do.

It is sad, but clearly you have not advanced since 1999 when Nick Pine
wrote about you: "Who would hire this PV nitwit?"
--ron
--ron

Posted by bealiba on July 12, 2008, 12:33 am
 
No, not failed. 180Ah is the correct minimum required. The actual
battery to be chosen. You clearly stated that you didn't want a
battery included so why are you crying now?

No. 180AH is the correct minimum required. This minimum must be met or
exceeded by the actual battery chosen with the chosen batteries
parameters entered.


Lying about the numbers is the hallmark of a shyster. The Maximum DOD
is clearly stated as 70%. This leaves 30% remaining in the battery.

Lying about the numbers is the hallmark of a shyster. The Maximum DOD
is clearly stated as 70%. This leaves 30% remaining in the battery.

George did not at any point recommend a battery. In fact Tweedledee is
the only one to recommend a battery, T105 Trojan.

It will be noted that B7 is blank. This is because I have not
recommended a battery.


B8 requires information from user about chosen battery


B8 requires information from user about chosen battery

This is the correct formula for the sizing of standalone PV systems.
It requires user input.


User input required.


180 Ah is the minimum required.

I have not specified a battery.

Oh dear. you need to learn that when you are up to your ass in shit
and sinking fast you should not put your foot in your mouth.

I in fact am on record as saying:

Of course there is still the problem of designing for an autonomy of
only one day. It is more common to design for several days autonomy.

So let's up the ante and change the system for 5 days autonomy. We
will keep the Trojans so we can clearly see the change;

A2      Daily load = 1250Wh
A4      Inverter Efficiency = 85%
A5      Account for inverter inefficiency - Load (A2/A4) = 1470.5
A7      System Voltage = 12
A8      Total A-hr demand per day (A5 / A7) = 122.55

B1      Number of days of autonomy = 5
B2      Maximum allowable depth of discharge = 70%
B3      Battery capacity (A8 x B1 / B2) = 875.35Ah
B4      Lowest 24 hour average temperature c
B5      Temperature correction factor =.97
B6      Adjusted battery capacity (B3 / B5) = 902.42
B7      Selected Battery
B8      Selected battery discharge rate 100
B9      A-hr capacity of selected battery = 225Ah
B10     Number of batteries in parallel (B6 / B9, rounded off) = 4
B11     Number of batteries in series (A7 / battery voltage) =1
B12     Check Capacity of selected battery at l00 Hr rate = 225
B13     Capacity of battery bank at 100 hr rate (B12 x B10) = 900
B14     Daily depth of discharge (100 x A8 / B13) = 13.62%

C1      Design tilt
C2      Design month
C3      Total energy demand per day (A8) 2.55Ah
C4      Battery efficiency = 90%
C5      Array output required per day (C3 / C4) = 136.2
C6      Peak sun hours at design tilt for design month = 5
C7      Selected module
C8      Selected module I at 14 volts at NOCT 2.94A
C9      Selected module nominal operating voltage. = 12V
C10     Guaranteed current (C8 x 0.9) = 2.65A
C11     Number of modules in series (A7 / C9) = 1
C12     Output per module (C10 x C6) = 13.2Ah
C13     Number of parallel strings of modules (C5 / C12) = 10.3


Ah yes. 28 Amps of panels at 12 volts to run a 2500 Watt pump at
230Volts without batteries. Why don't you explain how this works.

Which is the correct information.

Ah yes, good old nick. The man who can barly get his porch light to
work on solar, the inventor of the solar garage. How many of those do
you think he has sold?

Tweedledee said:


-----------------------------------

And he is very adamant about;


So no batteries, no spreadsheet. And 28 Amps of panels at 12 Volts
will not run a 2500 Watt - 230 Volt pump.

All of a sudden Tweedledee wants to talk about Batteries and
Spreadsheets, funny that.

Posted by Ron Rosenfeld on July 12, 2008, 3:35 am
 On Fri, 11 Jul 2008 17:33:53 -0700 (PDT), bealiba@gmail.com wrote:


You're correct George.  I made a typo in quoting your data.  I wrote 30%
maximum DOD when I should have written 30% SOC or 70% DOD.

But you still can't specify a battery that meets *your* specifications of

180Ah at 100 hr rate
90% efficiency
70% maximum DOD
and will also have a capacity of 180Ah at its 30 minute rate.

You can make up imaginary specifications all you want, but if you can't
produce a battery that meets them, or even comes close, your specifications
are useless.

You probably don't realize that a battery with a 180Ah capacity at its 100
hr rate, as you specify in your useless spreadsheet, will have a *much*
lower capacity at its 30 minute rate.

And you can't even read, comprehend, or debate intelligently.  Your tactic
of taking phrases out of context, deliberately misunderstanding what was
written, name-calling, false attributions, and the like, of which you are
guilty, are the true signs of a shyster:  "A person who gets along by
petty, sharp practices".

Thanks for the entertainment, George.  But I'm tired of dealing with your
name-calling and childish techniques.

By the way, I think your final attempt of 11 panels and 8 T105 batteries
should work at the OP's location.  (The T105 is a 6V battery, so I adjusted
your calculation accordingly).

Of course, a system of 10 panels and 4 T105's would also work, with a
minimum SOC of 40% during the winter months, and no less than 50% the rest
of the year.  So your system would have 10% more panels and twice as many
batteries as is necessary to run this system using battery storage with a
goal of no energy shortfall.

One could use more expensive batteries to reduce the number of strings from
your 4 or my 2 to just one, but you'd have to look closely at the
trade-offs, both economic and in maintenance.
--ron

This Thread
Bookmark this thread:
 
 
 
 
 
 
  •  
  • Subject
  • Author
  • Date
please rate this thread