Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Solar Panel Capacity Planning  (Read 1274 times)
K6BRN
Member

Posts: 489




Ignore
« on: November 22, 2017, 10:51:39 PM »

I'm currently putting together a transportable solar power system built around a surplus 100 amp-hour SLD (sealed lead acid) emergency lighting battery (Universal Battery UB121000) from which I expect to source about 40-50 amp hours (about 500 watt-hours) when fully charged.  It will be discharged by connected comms gear/computers at a C/10 rate (10 amps) to give about 4 or 5 hours of operation by itself ( I hope).

My current plan is to supplement this with a portable solar panel array that is rated at 180 watts peak (18 volts @ 10 amps, or 54 volts at 3.33 amps).  I have access to both PWM and MPPT charge controllers (30 AMP) and I live in Southern California in Los Angeles county, USA.  My question to experienced solar power users is:  What net/usable power rate (watts not watt-hours) should I expect to actually get from the panels in this solar/battery arrangement.

I've been told to count on 50-60% of the rated solar panel peak output (on a sunny day) after Ohmic losses due to wiring, charge controller inefficiency, panel pointing angle errors and atmospheric haze. 

If the panel can provide at least 90 watts to the connected system (7.5 amps) for 4-5 hours, then I might expect (on most sunny days) to run for an additional 3-4 hours, for a total of about 8 hours of operation before the SLD battery is depleted but not damaged (50% charge), which is a goal.

Thanks for your input!

Brian - K6BRN
Logged
K5LXP
Member

Posts: 5330


WWW

Ignore
« Reply #1 on: November 23, 2017, 09:21:27 AM »

Being portable you won't always have the optimum installation but it would probably pay to know up front what the system is capable of rather than find out after you deploy.

On a raw output level, use the insolation tables online:

http://solarinsolation.org/

With these numbers you can apply your specific panel efficiency and get the actual peak number.  From there you can get a Wh estimate for a typical day.  Manually tracking the panels gives a nice boost but requires frequent adjustment so factor that, or just pointed for peak.  50% is pretty conservative, I've seen closer to 70% here.  But your plan should also include 10% for cloudy days unless you live in a place like sunny New Mexico.  The backup plan could be more battery, or a long cord to reach the car.

You don't have to guess at interconnect losses, either calculate it or hook the stuff up on the bench and measure it.

For a portable system, I think charge controllers and PPT's are superfluous.  It would be a rare occasion you would have more "source" than "sink", and in the event you do, just unplug the panel or shade it.  By not having these things you reduce cost, complexity and potential RFI.

I wouldn't be concerned about the 50% DOD point on the battery.  You will never cycle that battery often enough to impact service life.  80% DOD is "safe" enough.  You bought the capacity, and are lugging it around.  Use it up.

Know the input ranges of your loads.  I find most "digital" loads have a broad input range but things like HF rigs can get fussy below 11.5V.  So factor that into run time, or come up with a booster supply.

Timing is a factor.  Your first day you may have more charge than you can use because you're starting with full batteries.  So it wouldn't be until the next day after you've depleted the charge overnight that you have some room in the battery for your charge capacity.

Mark K5LXP
Albuquerque, NM



Logged
K6BRN
Member

Posts: 489




Ignore
« Reply #2 on: November 23, 2017, 12:23:40 PM »

Hi Mark:

Thanks for the detailed reply!

I've connected the (Bioenno BSP-180) solar array this morning and have been checking/playing with it while the Thanksgiving feast cooks.  Its a very sunny, hot day here in SoCal (85 degrees at the beach)

At near noon, through a PWM controller, they are supplying 88-95 watts (8 Amps at 11.8 battery volts) to the battery, when I put the battery under a 30A load.  The MPPT controller appears to be yielding about the same result - but I'm missing the status monitor for this device and had to use a DC clamp-meter to measure current (may have significant error).  The panel is rated at 10 amps @ 18 volts at the max power point.  Leads from the panels to the controller are 25 feet of 10 Ga. wire and with the connectors are yielding Ohmic losses of about 1 volt/11% power.  I'm going to guess that the controllers may cost another 5-10% and pointing errors perhaps another 10%.  That adds up to 25-30%.  Not sure where the missing 15-20% of loss is coming from.  Leads from the charge controller to battery are relatively short (2 feet/12 Ga).

Without the controller, battery voltage is floating up to 15+ V (no load) which is just a little too high for comfort.

The main rig I will be using with this is a Yaesu FT-991, well proven on many trips, and it drops out at 10.5-11 VDC on TX (depends on mode and output power).  The battery box is also supporting a Samlex PST-300-12 DC-AC true sine wave converter driving some accessories, including a computer, USB chargers and LED light.  Main modes expected for operation are high duty cycle digital, into very non-ideal antennas, hence the overall demand for about 10 amps average current (worst-case).  This is not the most efficient arrangement and the intended modes are power-hungry.  But that's where I am, today.

Thanks again!

Brian - K6BRN

Logged
KD8SKM
Member

Posts: 9




Ignore
« Reply #3 on: November 27, 2017, 11:03:45 AM »

Brian:

with 180 watts STC you should get 81% of that on a sunny summer day or abut 146 watts of usable solar power.  The problems are your chosen charge controller since you are only getting 88-95 watts.

With our Apollo charge controller and a 245 watt STC Canadian solar panel we see about 210 watts comng out of the controller... which is right on the calculated value based on cell temperature of 65 degrees C and full sun.

Your panels with the Apollo will yield the 146 watts under the same conditions.... we use a pair of 100 watt panels at trade shows and the Dayton Hamvention and see about 158-165 watts in full sun out of our Apollo connected with 25 feet of 12 gauge wire between panels and controller.

check out our site: www.diysolarforu.com

Regards,

Rob
KD8SKM
Logged
K6BRN
Member

Posts: 489




Ignore
« Reply #4 on: November 27, 2017, 06:29:14 PM »

Rob (KD8SKM):

Thank you for your reply.

Quote
The problems are your chosen charge controller since you are only getting 88-95 watts.

I've tried one PWM and two different MPPT controllers with similar results.  Why do you believe the problem is in the controller(s)?

Thanks,

Brian - K6BRN
Logged
KD8SKM
Member

Posts: 9




Ignore
« Reply #5 on: November 28, 2017, 05:49:52 AM »

Brian:

There are a *LOT* of substandard Solar Charge Controllers out there - which is why I designed my own 5 years ago...and started DIY Solar for U 3 years ago.  Being an expert in DC-DC conversion and coming from an Automotive Electronics background I knew how to make a 98%+ power converter and keep it RF quiet....I also write code in C++ so coming up with my own MPPT routines was not that difficult.  The result of my hard work is the Apollo and Ra charge controllers and there are more in the works.  A high power buck-boost model is in development and will take a 10 to 50 volt input to charge either 12 or 24 volt batteries with extended MPPT operating range.  This allows any panel to charge either 12 or 24 volt batteries within the power limits of the controller.

Based on your panels STC rating which is a 25C cell temperature (Labratory Condition) and my experience with solar panels in real world applications they produce about 81% of STC conditions in the summer.  Your panels will produce 146 watts or so in full sun based on the 180 watt STC rating.  In winter they will do a bit better as solar panels have a negative power versus temperature of about 0.45% per degree C.  The colder the cells the more power.

 A PWM charge controller does not operate at the maximum power point of the panel ever.... thus it looses a lot of available power and your 88-95 watts confirm that.  There are a lot of "MPPT" ones out there that really are not true MPPT or just lousy at power conversion.

The real trick is getting power out of a partially shaded panel and extracting the most power in cloudy conditions...  the Apollo does exactly that.

So I hope I have answered your question.

Cheers,

Rob
KD8SKM
Logged
K6BRN
Member

Posts: 489




Ignore
« Reply #6 on: November 28, 2017, 07:59:04 PM »

Thanks, Rob.

I looked at your site - very interesting.  Is that really a 25W MPPT controller (Ra)?  If so, it is probably the ONLY MPPT controller I've seen for small power applications.  Very cool!

Regarding my solar panel issues...

After doing some more testing of the individual 60W panels and substituting known good panels in their place, it seems two of the three panels have problems.  With the known good panels in place, power output was between 82% and 95% of rated, at a panel temperature of 57C, near noon with a slight high altitude haze, here in sunny SoCal, using the same three controllers (one PWM and two MPPT).

Bioenno stepped in instantly when they were made aware of the problem.  I have to say they their responsiveness and efforts to make things right is outstanding.

Best Regards,

Brian - K6BRN

Logged
KD8SKM
Member

Posts: 9




Ignore
« Reply #7 on: November 29, 2017, 05:14:26 AM »

Brian:

Yes the Ra is 25 watt MPPT (Actually about 28 watts real output).  It is also buck boost so 10 volts in can still reach 14.4 output.

It would appear you are in one of those areas of the world where full sun is more than 1000 watts  / square meter ... some are as high as 1200 in the tropics.  Here in Michigan I think we are right about 1000 watts per square meter because the math works out exactly.

Running the panels in parallel may not show a huge difference between controllers as your MPPT point is close to the battery voltage... and the MPPT controllers are probably loosing more power than they should.  If they get hot while operating that is a good clue... Heat = Power lost.

Glad to see you got it working - enjoy the sun.... we don't get a lot this time of year here.

73
Rob
KD8SKM
Logged
K6BRN
Member

Posts: 489




Ignore
« Reply #8 on: November 29, 2017, 10:09:39 AM »

Rob:

Hmmm. The Ra is "Buck-Boost"?  Even more unusual.  Most smaller MPPTs I've seen are "buck" (voltage reduction) only.  Another unique feature.  I also noticed the magnetics on the Ra board are very compact.

BTW... Bioenno will not have a similar 3 panel 180 watt portable solar array in stock until later next month, so I took a refund.  Now looking at some Grade A 100W mono panels I may order to roll my own portable array.  But I'll test each panel individually, first.  This is a learning experience.  And I'm learning.   Smiley

73,

Brian - K6BRN
Logged
KD8SKM
Member

Posts: 9




Ignore
« Reply #9 on: November 29, 2017, 10:54:42 AM »

Brian:

I use a pair of 100 watt panels on the Apollo for trade shows including the Hamvention in Dayton - they are about 21 pounds each so not too bad for portable use.  you could possibly hinge two of them to fold up.

As for the buck boost - we have a high power one in development that fits into the same Case as the Apollo.... its in code debugging now and I hope to have it ready for 2018.  The intent is also 16 amps in or out and a 10 to 50 volt input range for either 12 or 24 volt batteries.  So up to about 500 watts at 24 volts... final specs are TBD but that is the target.

The RA is strictly for low power applications - we only offer the board because putting it on a box would double the cost.  The inductors are also too tall to fit the gap.

Happy searching for your panels.... lots of decent options out there.  The 100 watt ones I have seen for 100 with free shipping.

Cheers

Rob
KD8SKM
Logged
K6BRN
Member

Posts: 489




Ignore
« Reply #10 on: December 05, 2017, 02:52:14 PM »

OK - three brand-new 100W LightCatcher  LCS-100M monocrystalline panels have been received and tested with a Tracer 30A, negative ground MPPT controller, just as in my original post.  CONDITIONS:

Bright sunlight in SoCal at noon, very slight haze in air, 120F panel temp.  Load on battery of about 300-350 watts/25-30A.  Charge controller seems to consume ~2W.  Leads are 25 feet of 10Ga wire.

Panel 1:  Produces 89 watts net, 12.2V @ 7.3A into the battery after charge controller
Panel 2:  Produces 98 watts net, 12.1V @ 8.1A into the battery after charge controller
Panel 3:  Produces 92 watts net, 14.4V @ 6.4A into the battery after charge controller

All 3 in series:  265 watts net, 12.6V @ 21A into the battery after charge controller
(panel voltage under load is 54V)

All 3 in parallel:  230 watts net, 12.4V @ 18.5A into the battery after charge controller
(panel voltage under load is 13.5V)

While each panel has some unique characteristics, they are all performing at or better than nominal at 120F (~90 watts), even AFTER lead/connector ohmic losses and charge controller losses.  And this is a pretty imperfect test.

MUCH better than previous 60W panel results!

Brian - K6BRN
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!