Posted by Scottish Scientist on July 9, 2019, 12:26 am
On Tuesday, 9 July 2019 01:14:46 UTC+1, Scottish Scientist wrote:
> On Monday, 8 July 2019 23:26:51 UTC+1, Jim Wilkins wrote:
>
> > On Monday, 8 July 2019 04:21:21 UTC+1, ads wrote:
> > > On Sun, 7 Jul 2019 16:34:14 -0700 (PDT), Scottish Scientist
> > >
> >
> > Here's the text configuration page for row D.
> >
> > Wind, solar, storage and back-up system designer
> > - hide quoted text -
> > Configuration text page.
> >
> > Daily Usage of Energy: 4 KWh
> > Solar Power Capacity: 2.64 KW
> > Solar Capacity Factor: 8%
> > Solar energy per day (average): 5.07 KWh
> > Storage Energy Capacity: 4.48 KWh
> > Back-up power: 0.093 KW
> >
> > So 3KW of solar panels, 4 of your 12V105Ah batteries and a 100 Watt
> > generator if you can find one that small, would do that, if that's all
> > you need to get you through your power outages?
> >
> > -----------------------------------------------------------------------
-
> >
> > I don't understand that. If the batteries are fully discharged in
> > calm, overcast winter weather a 100W charge would take 50 hours at
> > 100% efficiency. 4 KWH per day is 167W continuously.
> >
> > I sized my home made fast charger for my APC1400 sine inverter's two
> > series 12V 105Ah batteries for 25A at 28V. A full recharge would take
> > at least four hours if the batteries could be permitted to rise above
> > float voltage and generate hydrogen. As-is the current at constant
> > float voltage starts to drop when they reach 70-80% charge. I'm hoping
> > a week at no more than 80% SOC followed by equalization outdoors won't
> > hurt them too much.
>
> Let's assume for the sake of argument that the system specified is design
ed for winter and on an average winter day, the solar panels (together with
any wind turbine, though none are specified in the configuration quoted) g
enerate 5KWh.
>
> 5KWh on average but supposing however that it is a particularly bad day f
or generating - very overcast - and the solar panels only generate half of
what they normally generate of a winter's day - only 2.5KWh, that's a bit o
ver 100 Watts on average.
>
> The back-up power of 100W is on full blast so that day it generates 100W
x 24h = 2.4KWh
>
> So the total generated that day is 2.5 KWh + 2.4 KWh = 4.9 KWh and the
system is generating 200 Watts+ - on a bad day.
>
> So depending on the starting conditions and the demand profile, the syste
m could supply the maximum usage of 4 KWh and add 0.9 KWh of energy to the
battery.
>
> Sure if you want to impose unusual circumstances, like you start at night
, only solar power but at night there is none, there's no wind generators t
o take advantage of any wind, and the batteries start at flat and you want
to run a 1 KWh heater for 4 hours at night and use no power for the next 20
hours, so still technically you are only wanting to use a maximum of 4KWh
a day, then under those very unusual circumstances the system will fail to
meet the specified demand.
>
> That's why you have an emergency stand-by legal generator burning fossil-
fuels, for those worst-case scenarios.
>
> But in most expected generating and starting conditions and demand profil
es the system can supply the maximum daily usage specified, no problem.
>
> The configuration quoted above was a row D configuration.
>
> The row H configuration allows for much faster energy store charging from
back-up power - in just 9 hours.
>
> If a faster battery charge from back-up power is your thing and you don't
mind the back-up power providing a majority of the energy consumed by the
system and providing more of a "base-load" than a "back-up" then you might
want to look at a Row H configuration.
>
> Wind, solar, storage and back-up system designer
> Configuration text page.
>
> Daily Usage of Energy: 4 KWh
> Solar Power Capacity: 0.8 KW
> Solar Capacity Factor: 8%
> Solar energy per day (average): 1.54 KWh
> Storage Energy Capacity: 1.34 KWh
> Back-up power: 0.149 KW
It is past my bed-time and my typos are coming thick and fast.
Corrections.
"a 1 KW heater for 4 hours at night"
"an emergency stand-by legacy generator burning fossil-fuels"
Right I am off to bed!
Posted by Jim Wilkins on July 9, 2019, 1:38 am
On Monday, 8 July 2019 23:26:51 UTC+1, Jim Wilkins wrote:
> On Monday, 8 July 2019 04:21:21 UTC+1, ads wrote:
> > On Sun, 7 Jul 2019 16:34:14 -0700 (PDT), Scottish Scientist
> >
>
> Here's the text configuration page for row D.
>
> Wind, solar, storage and back-up system designer
> - hide quoted text -
> Configuration text page.
>
> Daily Usage of Energy: 4 KWh
> Solar Power Capacity: 2.64 KW
> Solar Capacity Factor: 8%
> Solar energy per day (average): 5.07 KWh
> Storage Energy Capacity: 4.48 KWh
> Back-up power: 0.093 KW
>
> So 3KW of solar panels, 4 of your 12V105Ah batteries and a 100 Watt
> generator if you can find one that small, would do that, if that's
> all
> you need to get you through your power outages?
>
> ------------------------------------------------------------------------
>
> I don't understand that. If the batteries are fully discharged in
> calm, overcast winter weather a 100W charge would take 50 hours at
> 100% efficiency. 4 KWH per day is 167W continuously.
>
> I sized my home made fast charger for my APC1400 sine inverter's two
> series 12V 105Ah batteries for 25A at 28V. A full recharge would
> take
> at least four hours if the batteries could be permitted to rise
> above
> float voltage and generate hydrogen. As-is the current at constant
> float voltage starts to drop when they reach 70-80% charge. I'm
> hoping
> a week at no more than 80% SOC followed by equalization outdoors
> won't
> hurt them too much.
Let's assume for the sake of argument that the system specified is
designed for winter and on an average winter day, the solar panels
(together with any wind turbine, though none are specified in the
configuration quoted) generate 5KWh.
5KWh on average but supposing however that it is a particularly bad
day for generating - very overcast - and the solar panels only
generate half of what they normally generate of a winter's day - only
2.5KWh, that's a bit over 100 Watts on average.
The back-up power of 100W is on full blast so that day it generates
100W x 24h = 2.4KWh
So the total generated that day is 2.5 KWh + 2.4 KWh = 4.9 KWh and the
system is generating 200 Watts+ - on a bad day.
----------------------------------------
I monitor the raw solar panel voltage, current and wattage going into
the controller as well as the net delivered to the battery or drawn by
the inverter.
https://www.amazon.com/bayite-6-5-100V-Voltmeter-Multimeter-Amperage/dp/B013PKYAV6
On an overcast day the panel output wattage may be only 10% of its
rating, or less. Thin haze can cut it in half. They are
polycrystalline Grape Solar panels, but I also have some amorphous
ones on an older,smaller system that do no better.
One reason for watching the controller input is to detect battery
voltage leaking back out at night, if a component shorts. That's
already happened to me though it caused no problems.
Posted by ads on July 9, 2019, 1:46 am
On Mon, 8 Jul 2019 08:27:32 -0700 (PDT), Scottish Scientist
>On Monday, 8 July 2019 04:21:21 UTC+1, ads wrote:
>> On Sun, 7 Jul 2019 16:34:14 -0700 (PDT), Scottish Scientist
>>
>> >On Sunday, 7 July 2019 22:50:11 UTC+1, ads wrote:
>> >
>>
>> >Breaks my heart to design you a system that generates so little power. ;) LOL.
>>
>> Some questions for you:
>>
>> How far do you plan on discharging those batteries?
>>
>> How many days of little or no sun do your calculations include?
>>
>> I know that we can easily have a week or more of cloudy, rainy days in
>> winter and my best solar panel only produces about 5% of its rated
>> output on a rainy day.
>>
>> The past two weeks, we've had summer thunderstorms almost daily, with
>> there being less than 50% of "normal" sun most of those days.
>
>Thank you for your on-topic questions Ads.
>
>
>> How far do you plan on discharging those batteries?
>
>There's the off-grid table for 4KWh maximum daily usage and 8% solar capacity factor.
>http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calculator.htm?usage=4&units=kw&spc 0&scf=8#off
>
>Here's the text configuration page for row D.
>
>Wind, solar, storage and back-up system designer
>- hide quoted text -
>Configuration text page.
>
>Daily Usage of Energy: 4 KWh
>Solar Power Capacity: 2.64 KW
>Solar Capacity Factor: 8%
>Solar energy per day (average): 5.07 KWh
>Storage Energy Capacity: 4.48 KWh
>Back-up power: 0.093 KW
>
>So 3KW of solar panels, 4 of your 12V105Ah batteries and a 100 Watt generator if you can find one that small, would do that, if that's all you need to get you through your power outages?
>
>The configuration species "Storage Energy Capacity: 4.48 KWh" but it doesn't specify "batteries" or "pumped storage" or "power to gas".
>
>The numbers in the designer are technology neutral.
>The numbers don't take account of any safety margin for the particular technology, so you have to add that yourself.
>
>"4 of your 12V105Ah batteries", taking the name-plate at face value, would offer 4 x 12V x 105A h = 5.04 KWh of energy storage.
>
>So I suppose, since you are asking, that would amount to 4.48/5.04 - 89% discharge if you started with a fully charged battery and used up 4.48 KWh that the designer specifies.
That answer just destroyed any credibility you may have had because it
points to your ignorance of battery chemistry and safe operating
parameters.
Not even lithium cells are discharged that low - except by radio
control vehicle fans who have lots of money to spend on replacement
batteries.
Reasonable discharge for AGM batteries (trade-off between useful
capacity and number of charge/discharge cycles is 50%. Maximkum
discharge is 80%. People do discharge them 100% - but very few times.
Lithium cells have the best life when not discharged more than 80% and
most electric/hybrid vehicles also use that value.
Flooded lead acid cells are more limited unless designed for deep
cycle use (fork lift, solar).
I'm tempted to say you're holding a newly minted degree and not much
real world experience.
I won't be watching for an answer.
Posted by Jim Wilkins on July 9, 2019, 3:12 am
<ads> wrote in message
> On Mon, 8 Jul 2019 08:27:32 -0700 (PDT), Scottish Scientist
>
>>On Monday, 8 July 2019 04:21:21 UTC+1, ads wrote:
>>> On Sun, 7 Jul 2019 16:34:14 -0700 (PDT), Scottish Scientist
>>>
>>> >On Sunday, 7 July 2019 22:50:11 UTC+1, ads wrote:
>>> >
>>>
>>> >Breaks my heart to design you a system that generates so little
>>> >power. ;) LOL.
>>>
>>> Some questions for you:
>>>
>>> How far do you plan on discharging those batteries?
>>>
>>> How many days of little or no sun do your calculations include?
>>>
>>> I know that we can easily have a week or more of cloudy, rainy
>>> days in
>>> winter and my best solar panel only produces about 5% of its rated
>>> output on a rainy day.
>>>
>>> The past two weeks, we've had summer thunderstorms almost daily,
>>> with
>>> there being less than 50% of "normal" sun most of those days.
>>
>>Thank you for your on-topic questions Ads.
>>
>>
>>> How far do you plan on discharging those batteries?
>>
>>There's the off-grid table for 4KWh maximum daily usage and 8% solar
>>capacity factor.
>>http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calculator.htm?usage=4&units=kw&spc 0&scf=8#off
>>
>>Here's the text configuration page for row D.
>>
>>Wind, solar, storage and back-up system designer
>>- hide quoted text -
>>Configuration text page.
>>
>>Daily Usage of Energy: 4 KWh
>>Solar Power Capacity: 2.64 KW
>>Solar Capacity Factor: 8%
>>Solar energy per day (average): 5.07 KWh
>>Storage Energy Capacity: 4.48 KWh
>>Back-up power: 0.093 KW
>>
>>So 3KW of solar panels, 4 of your 12V105Ah batteries and a 100 Watt
>>generator if you can find one that small, would do that, if that's
>>all you need to get you through your power outages?
>>
>>The configuration species "Storage Energy Capacity: 4.48 KWh" but it
>>doesn't specify "batteries" or "pumped storage" or "power to gas".
>>
>>The numbers in the designer are technology neutral.
>>The numbers don't take account of any safety margin for the
>>particular technology, so you have to add that yourself.
>>
>>"4 of your 12V105Ah batteries", taking the name-plate at face value,
>>would offer 4 x 12V x 105A h = 5.04 KWh of energy storage.
>>
>>So I suppose, since you are asking, that would amount to 4.48/5.04 -
>>89% discharge if you started with a fully charged battery and used
>>up 4.48 KWh that the designer specifies.
>
> That answer just destroyed any credibility you may have had because
> it
> points to your ignorance of battery chemistry and safe operating
> parameters.
>
> Not even lithium cells are discharged that low - except by radio
> control vehicle fans who have lots of money to spend on replacement
> batteries.
>
> Reasonable discharge for AGM batteries (trade-off between useful
> capacity and number of charge/discharge cycles is 50%. Maximkum
> discharge is 80%. People do discharge them 100% - but very few
> times.
>
> Lithium cells have the best life when not discharged more than 80%
> and
> most electric/hybrid vehicles also use that value.
>
> Flooded lead acid cells are more limited unless designed for deep
> cycle use (fork lift, solar).
>
> I'm tempted to say you're holding a newly minted degree and not much
> real world experience.
>
> I won't be watching for an answer.
This neatly summarizes the battery issues we've brought up.
https://www.powertechsystems.eu/home/tech-corner/lead-acid-battery-downsides/
Posted by Scottish Scientist on July 9, 2019, 7:43 am
On Tuesday, 9 July 2019 02:46:49 UTC+1, ads wrote:
> On Mon, 8 Jul 2019 08:27:32 -0700 (PDT), Scottish Scientist
>
> >On Monday, 8 July 2019 04:21:21 UTC+1, ads wrote:
> >> On Sun, 7 Jul 2019 16:34:14 -0700 (PDT), Scottish Scientist
> >Thank you for your on-topic questions Ads.
> >
> >
> >> How far do you plan on discharging those batteries?
> >
> >There's the off-grid table for 4KWh maximum daily usage and 8% solar capacity factor.
> >http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calculator.htm?usage=4&units=kw&spc 0&scf=8#off
> >
> >Here's the text configuration page for row D.
> >
> >Wind, solar, storage and back-up system designer
> >- hide quoted text -
> >Configuration text page.
> >
> >Daily Usage of Energy: 4 KWh
> >Solar Power Capacity: 2.64 KW
> >Solar Capacity Factor: 8%
> >Solar energy per day (average): 5.07 KWh
> >Storage Energy Capacity: 4.48 KWh
> >Back-up power: 0.093 KW
> >
> >So 3KW of solar panels, 4 of your 12V105Ah batteries and a 100 Watt generator if you can find one that small, would do that, if that's all you need to get you through your power outages?
> >
> >The configuration species "Storage Energy Capacity: 4.48 KWh" but it doesn't specify "batteries" or "pumped storage" or "power to gas".
> >
> >The numbers in the designer are technology neutral.
> >The numbers don't take account of any safety margin for the particular technology, so you have to add that yourself.
> >
> >"4 of your 12V105Ah batteries", taking the name-plate at face value, would offer 4 x 12V x 105A h = 5.04 KWh of energy storage.
> >
> >So I suppose, since you are asking, that would amount to 4.48/5.04 - 89% discharge if you started with a fully charged battery and used up 4.48 KWh that the designer specifies.
>
> That answer just destroyed any credibility you may have had because it
> points to your ignorance of battery chemistry and safe operating
> parameters.
>
> Not even lithium cells are discharged that low - except by radio
> control vehicle fans who have lots of money to spend on replacement
> batteries.
>
> Reasonable discharge for AGM batteries (trade-off between useful
> capacity and number of charge/discharge cycles is 50%. Maximkum
> discharge is 80%. People do discharge them 100% - but very few times.
>
> Lithium cells have the best life when not discharged more than 80% and
> most electric/hybrid vehicles also use that value.
>
> Flooded lead acid cells are more limited unless designed for deep
> cycle use (fork lift, solar).
>
Ads,
If for technology reasons, you want a lower discharge percentage then add batteries to suit your supplier recommendations for maximum discharge.
The configuration species "Storage Energy Capacity: 4.48 KWh" but it doesn't specify "batteries" or "pumped storage" or "power to gas".
The numbers in the designer are technology neutral.
The numbers don't take account of any safety margin for the particular technology, so you have to add that yourself.
So if you wanted a 50% discharge maximum for your battery technology then you would select a battery capacity that would factor the configuration's "Storage Energy Capacity" as follows
Storage Energy Capacity / 50%, or
Storage Energy Capacity / 0.5 or
Storage Energy Capacity x 2
So for the example quoted
Storage Energy Capacity: 4.48 KWh
your 50% maximum discharge gives you 4.48 KWh x 2 = 8.98 KWh.
A minimum of 8.98 KWh in terms of 12V105Ah (1.26 KWh nominal) batteries would be 8 batteries.
8 x 12V x 105A x h = 10 KWh
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>
> > On Monday, 8 July 2019 04:21:21 UTC+1, ads wrote:
> > > On Sun, 7 Jul 2019 16:34:14 -0700 (PDT), Scottish Scientist
> > >
> >
> > Here's the text configuration page for row D.
> >
> > Wind, solar, storage and back-up system designer
> > - hide quoted text -
> > Configuration text page.
> >
> > Daily Usage of Energy: 4 KWh
> > Solar Power Capacity: 2.64 KW
> > Solar Capacity Factor: 8%
> > Solar energy per day (average): 5.07 KWh
> > Storage Energy Capacity: 4.48 KWh
> > Back-up power: 0.093 KW
> >
> > So 3KW of solar panels, 4 of your 12V105Ah batteries and a 100 Watt
> > generator if you can find one that small, would do that, if that's all