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How much energy from solar panels can you really use?
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Pete S
Feb 2, 2012, 1:36:46 PM2/2/12
to
This question is for those who store their solar panel energy in batteries.
"How efficient is a modern battery storage system in storing solar power for
later use?"
I have heard that using batteries for storing electricity is about 25%
efficient.
That is: If you charge your battery bank at the rate of one kilawatt
hour/hr of energy into the battery bank, only about 25% or 250 watt hours,
is actually useable due to heat losses, chemical reactions, or whatever.
Maybe they meant the the whole making/storing process, including losses
from an engine/generation system is what's only 25% efficient? I don't know
for sure and that is why I am asking.
An example of one way to answer would be as follows:
-On a given day , a solar array produces 5KW of electrical energy and it is
all sent to the battery bank, but no power is taken from that battery bank
during the test.
-Once the sun goes down, read the specific gravity of the electrolyte in
the battery bank and then apply a reasonable load to it.
-Continue to take and measure power being extracted from the battery bank
until the specific gravity of the battery bank is back to the same reading
as it was when loading began.
-Read the power consumption meter to obtain the total power that was drained
from the battery bank during the test.
-Divide output power by input power to determine the efficiency of the
storage/power recovery system.
If there's a better way to measure the efficiency, I'm wide open to it.
Pete Stanaitis
---------------
"How efficient is a modern battery storage system in storing solar power for
later use?"
I have heard that using batteries for storing electricity is about 25%
efficient.
That is: If you charge your battery bank at the rate of one kilawatt
hour/hr of energy into the battery bank, only about 25% or 250 watt hours,
is actually useable due to heat losses, chemical reactions, or whatever.
Maybe they meant the the whole making/storing process, including losses
from an engine/generation system is what's only 25% efficient? I don't know
for sure and that is why I am asking.
An example of one way to answer would be as follows:
-On a given day , a solar array produces 5KW of electrical energy and it is
all sent to the battery bank, but no power is taken from that battery bank
during the test.
-Once the sun goes down, read the specific gravity of the electrolyte in
the battery bank and then apply a reasonable load to it.
-Continue to take and measure power being extracted from the battery bank
until the specific gravity of the battery bank is back to the same reading
as it was when loading began.
-Read the power consumption meter to obtain the total power that was drained
from the battery bank during the test.
-Divide output power by input power to determine the efficiency of the
storage/power recovery system.
If there's a better way to measure the efficiency, I'm wide open to it.
Pete Stanaitis
---------------
NotMe
Feb 2, 2012, 7:51:47 PM2/2/12
to
"Pete S" <sp...@baldwin-telecom.net> wrote in message
news:GdSdnRb9-ZNMSrfS...@bright.net...
I expect your assumptions is that lead acid batteries are used.
Further you are not taking into account the charge or discharge rate
(typically measured as C/delta T) The greater the delta T the more
efficient is the process. I might mention that pure DC is less efficient
for charging than a system that allows a partial discharge as a cyclical
function (most are 50 or 60 Hz)
The issue is not how much energy or how efficiently it is stored/use but
that the system provides 'enough'. We had a place in the W NC mountains
that was totally off grid. We had a back up gen set but with the exception
of monthly maintance runs (~2 hours under load) it went unused for the
better part of 15-20 years.
news:GdSdnRb9-ZNMSrfS...@bright.net...
Further you are not taking into account the charge or discharge rate
(typically measured as C/delta T) The greater the delta T the more
efficient is the process. I might mention that pure DC is less efficient
for charging than a system that allows a partial discharge as a cyclical
function (most are 50 or 60 Hz)
The issue is not how much energy or how efficiently it is stored/use but
that the system provides 'enough'. We had a place in the W NC mountains
that was totally off grid. We had a back up gen set but with the exception
of monthly maintance runs (~2 hours under load) it went unused for the
better part of 15-20 years.
Pete S
Feb 2, 2012, 9:09:44 PM2/2/12
to
Thanks for your comments, NotMe.
But no matter what kind of batteries are used, there must be some loss of
power in charging and discharging them, and that is at the heart of my
question.
For those who have to buy PV collectors, I would assume this would be really
important.
You have to buy enough collectors to offset the power lost in the
storage/recovery process, don't you?
So, what IS that loss? And, since you mention lead acid batteries as being
my assumption, how does that loss vary with other types of batteries and
their input/output systems?
Pete Stanaitis
----------------
--------------------------------------------------------
"NotMe" <m...@privacy.net> wrote in message news:jgfb3a$lmv$1...@dont-email.me...
But no matter what kind of batteries are used, there must be some loss of
power in charging and discharging them, and that is at the heart of my
question.
For those who have to buy PV collectors, I would assume this would be really
important.
You have to buy enough collectors to offset the power lost in the
storage/recovery process, don't you?
So, what IS that loss? And, since you mention lead acid batteries as being
my assumption, how does that loss vary with other types of batteries and
their input/output systems?
Pete Stanaitis
----------------
--------------------------------------------------------
"NotMe" <m...@privacy.net> wrote in message news:jgfb3a$lmv$1...@dont-email.me...
Ron Rosenfeld
Feb 3, 2012, 10:09:41 AM2/3/12
to
On Thu, 2 Feb 2012 20:09:44 -0600, "Pete S" <sp...@baldwin-telecom.net> wrote:
>Thanks for your comments, NotMe.
> But no matter what kind of batteries are used, there must be some loss of
>power in charging and discharging them, and that is at the heart of my
>question.
>For those who have to buy PV collectors, I would assume this would be really
>important.
>You have to buy enough collectors to offset the power lost in the
>storage/recovery process, don't you?
>
>So, what IS that loss? And, since you mention lead acid batteries as being
>my assumption, how does that loss vary with other types of batteries and
>their input/output systems?
>
>Pete Stanaitis
>----------------
The calculations are more complex than just the battery losses, but you are on the right track in assuming you have to adjust for system losses in deciding how much PV panel you require to generate a given amount of usable energy.
>Thanks for your comments, NotMe.
> But no matter what kind of batteries are used, there must be some loss of
>power in charging and discharging them, and that is at the heart of my
>question.
>For those who have to buy PV collectors, I would assume this would be really
>important.
>You have to buy enough collectors to offset the power lost in the
>storage/recovery process, don't you?
>
>So, what IS that loss? And, since you mention lead acid batteries as being
>my assumption, how does that loss vary with other types of batteries and
>their input/output systems?
>
>Pete Stanaitis
>----------------
But for typical lead-acid battery "round-trip" efficiency, you could guesstimate about 80%. The mfg should be able to supply more precise values.
You also need to account for losses in wiring, aging of the panels, real output of the panels if they are not rated under the same conditions they are being used at your site. If you are converting your battery DC to AC so as to use normal household appliances, there will be losses in the inverter also, which will vary with the load on the inverter as well as the type of inverter -- again these are details you can obtain from the mfg.
So, for your original question, using lead-acid batteries (the most common in an off-grid household system), storage efficiency is probably about 80% (1 kWh in --> 0.8 kWh out) but the mfg has more accurate figures.
Mho
Feb 7, 2012, 10:08:18 PM2/7/12
to
You need to get more familiar with energy and power terms. You have mixed
and confused the terms repeatedly to the point of total nonsense.
I can pump 1000 Watts into my batteries to charge them and remove 2,000
Watts anytime and not violate any laws of physics.
--------------
"Pete S" wrote in message
news:GdSdnRb9-ZNMSrfS...@bright.net...
and confused the terms repeatedly to the point of total nonsense.
I can pump 1000 Watts into my batteries to charge them and remove 2,000
Watts anytime and not violate any laws of physics.
--------------
"Pete S" wrote in message
news:GdSdnRb9-ZNMSrfS...@bright.net...
argusy
Feb 6, 2012, 8:46:00 PM2/6/12
to
On 03/02/12 5:06 AM, Pete S wrote:
> This question is for those who store their solar panel energy in batteries.
>
> "How efficient is a modern battery storage system in storing solar power for
> later use?"
>
> I have heard that using batteries for storing electricity is about 25% efficient.
> That is: If you charge your battery bank at the rate of one kilawatt hour/hr of
> energy into the battery bank, only about 25% or 250 watt hours, is actually
> useable due to heat losses, chemical reactions, or whatever.
I can charge a battery bank with only a 10W charger, but it would take some time
> This question is for those who store their solar panel energy in batteries.
>
> "How efficient is a modern battery storage system in storing solar power for
> later use?"
>
> I have heard that using batteries for storing electricity is about 25% efficient.
> That is: If you charge your battery bank at the rate of one kilawatt hour/hr of
> energy into the battery bank, only about 25% or 250 watt hours, is actually
> useable due to heat losses, chemical reactions, or whatever.
to be fully charged. Don't confuse the _capacity_ to charge a system with the
_ability_ to charge a system
> Maybe they meant the the whole making/storing process, including losses from an
> engine/generation system is what's only 25% efficient? I don't know for sure and
> that is why I am asking.
actual power that eventually can be used (the solar array). It has nothing to do
with what the output is connected to (the batteries). More below
>
> An example of one way to answer would be as follows:
>
> -On a given day , a solar array produces 5KW of electrical energy and it is all
> sent to the battery bank, but no power is taken from that battery bank during
> the test.
The solar array _PRODUCES_ 5KW, and that has nothing to do with how much energy
> An example of one way to answer would be as follows:
>
> -On a given day , a solar array produces 5KW of electrical energy and it is all
> sent to the battery bank, but no power is taken from that battery bank during
> the test.
is required to charge the batteries. That may only be a few hundred watts or
less, or whatever it takes to fully charge the batteries. Unless you use that
power elsewhere, it is wasted power
In fact, depending on the charge current required, it's more efficient to use a
100 watt generator (providing the voltage is more than the battery voltage, and
current controlled). Using a generator with the capacity to supply 40-50 Amps
(110V, 5 Kilowatts) could damage the batteries, when all the batteries need is a
(controlled) trickle charge of a few amps
> -Once the sun goes down, read the specific gravity of the electrolyte in the
> battery bank and then apply a reasonable load to it.
> -Continue to take and measure power being extracted from the battery bank until
> the specific gravity of the battery bank is back to the same reading as it was
> when loading began.
> -Read the power consumption meter to obtain the total power that was drained
> from the battery bank during the test.
> -Divide output power by input power to determine the efficiency of the
> storage/power recovery system.
in no way reflects the efficiency, as the capacity might not be used to it's
fullest extent to charge the batteries.
What if you've got the array hooked up to your house as well, and while those
batteries are being charged, you've turned on the oven for 15 minutes, had the
TV running, put your laptop charger on, used an electric drill for a few seconds.
the solar array has the _capacity_ to supply all that power, but when it's not
used, it's just not being used!!! It's wasted!!
A good analogy is your water supply. If you want a bath, it takes 3 minutes to
fill to the level you want. Go turn on every other tap in your house. It will
STILL take five minutes to fill the bath to that level. The _capacity_ to supply
the water far exceeds the ability to drain it from one tap or several taps.
>
> If there's a better way to measure the efficiency, I'm wide open to it.
Mho has a good point about supplying 1KW and then using 2KW. Think about it
>
Graham
> Pete Stanaitis
> ---------------
>
>
>
argusy
Feb 8, 2012, 3:27:46 AM2/8/12
to
<snip>
sorry, my date/time was out. (been fixing a program that stuffs up at midnight)
Graham
sorry, my date/time was out. (been fixing a program that stuffs up at midnight)
Graham
Mho
Feb 9, 2012, 1:10:01 PM2/9/12
to
It's just a reminder that we throw terms around carelessly, sometimes, and
sometimes people throw tech terms around and have no idea what they are
talking about.
Funny we never use mph (or kph) for a distance we travel to somebody's house
or miles (or km.) for how fast our car is travelling. This confusion is used
frequently for scammers and techies being careless. We forgive the
latter...LOL
-------
"argusy" wrote in message news:4F308258...@slmember.on.net...
sometimes people throw tech terms around and have no idea what they are
talking about.
Funny we never use mph (or kph) for a distance we travel to somebody's house
or miles (or km.) for how fast our car is travelling. This confusion is used
frequently for scammers and techies being careless. We forgive the
latter...LOL
-------
"argusy" wrote in message news:4F308258...@slmember.on.net...
NotMe
Feb 9, 2012, 2:44:44 PM2/9/12
to
"Mho" <Impe...@UgotOCD.invalid> wrote in message
news:VZTYq.12111$DZ1....@newsfe07.iad...
> It's just a reminder that we throw terms around carelessly, sometimes, and
> sometimes people throw tech terms around and have no idea what they are
> talking about.
>
> Funny we never use mph (or kph) for a distance we travel to somebody's
> house or miles (or km.) for how fast our car is travelling. This confusion
> is used frequently for scammers and techies being careless. We forgive the
> latter...LOL
>
The ones that tickle me are those that think of a batter as a similar device
> sometimes people throw tech terms around and have no idea what they are
> talking about.
>
> Funny we never use mph (or kph) for a distance we travel to somebody's
> house or miles (or km.) for how fast our car is travelling. This confusion
> is used frequently for scammers and techies being careless. We forgive the
> latter...LOL
>
as a bank account. No clue how you can put 1KW in and take 2KW out.
argusy
Feb 10, 2012, 3:42:51 AM2/10/12
to
On 10/02/12 6:14 AM, NotMe wrote:
> "Mho"<Impe...@UgotOCD.invalid> wrote in message
> news:VZTYq.12111$DZ1....@newsfe07.iad...
>> It's just a reminder that we throw terms around carelessly, sometimes, and
>> sometimes people throw tech terms around and have no idea what they are
>> talking about.
Electronics techs (like me) have an annoying habit of shortening power usage
> "Mho"<Impe...@UgotOCD.invalid> wrote in message
> news:VZTYq.12111$DZ1....@newsfe07.iad...
>> It's just a reminder that we throw terms around carelessly, sometimes, and
>> sometimes people throw tech terms around and have no idea what they are
>> talking about.
(per time) to just power. We know what we mean, even when we're discussing both
terms, and understand the difference when we use the same terms to mean two
different concepts. I had a devil of a time convincing a secretary how a 1.5 Kw
rated solar array can supply 9Kw during a day of decent sunshine. Yep. She's blonde!
>>
>> Funny we never use mph (or kph) for a distance we travel to somebody's
>> house or miles (or km.) for how fast our car is travelling. This confusion
>> is used frequently for scammers and techies being careless. We forgive the
>> latter...LOL
>>
>
> The ones that tickle me are those that think of a batter as a similar device
> as a bank account. No clue how you can put 1KW in and take 2KW out.
>
That had me going for a second or two - "batter"
>> Funny we never use mph (or kph) for a distance we travel to somebody's
>> house or miles (or km.) for how fast our car is travelling. This confusion
>> is used frequently for scammers and techies being careless. We forgive the
>> latter...LOL
>>
>
> The ones that tickle me are those that think of a batter as a similar device
> as a bank account. No clue how you can put 1KW in and take 2KW out.
>
oh.... missing a "y", then it made sense.
Yeah - and everybody has a credit account. Not many say they have a debit
account, or realise what the difference is.
Bob F
Feb 10, 2012, 11:41:57 AM2/10/12
to
Mho
Feb 10, 2012, 2:30:26 PM2/10/12
to
Mostly off-topic here but....
My favourite is the "A pessimist states, 'The cup is half full', while an
optimist states, 'The cup is half empty'".
Most people jump to contradict to which the response would be "I was trying
to empty the cup"
Another one I like is "clockwise" which depends on your point of view. A
shaft from the other end is turning counter-clockwise...or for the other
half of the world anti-clockwise. I am always quick to add "looking from the
top to clockwise instructions at the table". Most don't get it. LOL
So many things are relative...right cous.?
--------
"argusy" wrote in message news:4F34D88B...@slmember.on.net...
My favourite is the "A pessimist states, 'The cup is half full', while an
optimist states, 'The cup is half empty'".
Most people jump to contradict to which the response would be "I was trying
to empty the cup"
Another one I like is "clockwise" which depends on your point of view. A
shaft from the other end is turning counter-clockwise...or for the other
half of the world anti-clockwise. I am always quick to add "looking from the
top to clockwise instructions at the table". Most don't get it. LOL
So many things are relative...right cous.?
--------
"argusy" wrote in message news:4F34D88B...@slmember.on.net...
Mho
Feb 10, 2012, 2:32:03 PM2/10/12
to
Have we wandering into deep frying now?
LOL
-------------
"NotMe" wrote in message news:jh17qt$6k7$1...@dont-email.me...
LOL
-------------
"NotMe" wrote in message news:jh17qt$6k7$1...@dont-email.me...
NotMe
Feb 12, 2012, 4:25:01 PM2/12/12
to
"Mho" <Impe...@UgotOCD.invalid> wrote in message
Not complaining as the alternative is much less pleasant.
Mho
Feb 13, 2012, 12:32:13 AM2/13/12
to
LOL. I did enjoy the typo though.
Please do not be offended. Most of us do it.
-----------
"NotMe" wrote in message news:jh9anb$gvt$1...@dont-email.me...
Please do not be offended. Most of us do it.
-----------
"NotMe" wrote in message news:jh9anb$gvt$1...@dont-email.me...
NotMe
Feb 13, 2012, 6:19:26 PM2/13/12
to
"Mho" <Impe...@UgotOCD.invalid> wrote in message
I'm always good for a giggle and a grin. And I've long ago reached the age
where I don't mind if the joke is on me or at my expense.
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