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Wind, solar, storage and back-up system designer - Page 6

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Posted by ads on July 8, 2019, 3:25 pm
 
On Mon, 8 Jul 2019 10:02:33 -0400, "Jim Wilkins"


That may depend on the controllers being compared.  I have a generic
20 amp PWM controller that idles around 9ma.  The 20 amp Tracer
LS2024B PWM controller idles at 14ma but it has RS485 data collection
capability, as does the 30 amp MPPT controller (Tracer 3210A) which
idles at 17ma with the Load turned Off and 33ma with the Load turned
On.

The generic PWM unit has a small LCD.  The LS2024B has a pair of LEDs
for status, plus the RS485 for the MT50 meter or a link to a PC
running their free monitor software (Win 7 and up).  The 3210A has an
LCD and the RS485 connection.  The RS485 connections support their
wifi and bluetooth inteface modules for talking to a PC, tablet or
phone and a solid state logger that reads data every 11 minutes and
can save about 4 or 5 months of data.  The LS2024B and the 3210A (and
its larger and smaller brothers) can be configured for battery type,
battery bank size, all the various battery parameters (boost volts,
float volts, equalize volts, over voltage, low voltage disconnect,
etc, etc), from the MT50 or the PC/phone interface.

Posted by Scottish Scientist on July 8, 2019, 3:27 pm
 
On Monday, 8 July 2019 04:21:21 UTC+1, ads  wrote:

) LOL.  

Thank you for your on-topic questions Ads.  



There's the off-grid table for 4KWh maximum daily usage and 8% solar capaci
ty factor.  
http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calc  
ulator.htm?usage=4&units=kw&spc0&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 generat
or 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 tech
nology, 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% di
scharge if you started with a fully charged battery and used up 4.48 KWh th
at the designer specifies.

If for technology reasons, you want a lower discharge percentage then add b
atteries to suit your supplier recommendations for maximum discharge.


The designer depends on the average daily energy value (that's the column h
eaded "Wind + Solar *Wh per day", in the Off-grid daily usage) being about  
right for that time of year.

So in the case of 100% solar or mainly solar powered systems in parts of th
e world that have significant seasonal solar power variation, I would recom
mend to to use a seasonal or monthly solar capacity factor or even a monthl
y solar capacity factor. If designing a system for all-year round then pick
 a winter solar factor.

Beware that if you are designing using a yearly solar capacity factor then  
the system may be underpowered in winter.

In the example, I quoted to Jim, I made explicit that I was designing for s
ummer and used an assumed solar capacity factor.


"Let's just assume that a New Hampshire residential utility customer's maxi
mum daily usage was worked out to be 40 KiloWatt-Hours and for that max usa
ge the customer wanted to construct a solar power system to supply that pow
er in the summer.  

So for that customer requirement, the Wind, solar, storage and back-up syst
em designer, "Off-grid daily usage Focus Table" can be seen at this link.
  

http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calc  
ulator.htm?usage@&units=kw&spc0&scf#off  

As you can see, I have assumed a solar capacity factor for the New Hampshir
e summer of 16% - but that's just my guess. You would need to research your
 own solar capacity factor for yourself. "

If you need a system that performs well in both winter and solar then you n
eed to mix up your generation sources in winter, wind, biofuels, hydroelect
ric hydrogen from power to gas etc.  

I appreciate that for home owners they don't have the wide choice of genera
tors that states do so home powered systems may not have good renewable ene
rgy winter generating options.

Wind is probably the best bet for reliable winter power, if you can get per
mission to put up a wind turbine or two near by.

In all cases the designer page is going to give the best results if you kno
w what your local solar and wind capacity factors are.

Posted by Jim Wilkins on July 8, 2019, 8:20 pm
 
In the example, I quoted to Jim, I made explicit that I was designing  
for summer and used an assumed solar capacity factor.

I've noticed that my Grape Solar panels can output 100% of their power  
rating into a rheostat load as early as mid February, apparently  
because they are cold and the winter air is cleaner.



Posted by Jim Wilkins on July 8, 2019, 10:27 pm
 On Monday, 8 July 2019 04:21:21 UTC+1, ads  wrote:

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.



Posted by Scottish Scientist on July 9, 2019, 12:14 am
 On Monday, 8 July 2019 23:26:51 UTC+1, Jim Wilkins  wrote:


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 a
ny wind turbine, though none are specified in the configuration quoted) gen
erate 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 wh
at they normally generate of a winter's day - only 2.5KWh, that's a bit ove
r 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 sy
stem is generating 200 Watts+ - on a bad day.

So depending on the starting conditions and the demand profile, the system  
could supply the maximum usage of 4 KWh and add 0.9 KWh of energy to the ba
ttery.

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 to  
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 h
ours, 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 me
et the specified demand.  

That's why you have an emergency stand-by legal generator burning fossil-fu
els, for those worst-case scenarios.

But in most expected generating and starting conditions and demand profiles
 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 b
ack-up power - in just 9 hours.

If a faster battery charge from back-up power is your thing and you don't m
ind the back-up power providing a majority of the energy consumed by the sy
stem and providing more of a "base-load" than a "back-up" then you might wa
nt 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


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