Solar Guppy - All Things Solar Forum

It is currently Tue Nov 24, 2020 9:44 pm GMT EthGMT

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 46 posts ]  Go to page Previous  1, 2, 3, 4  Next
Author Message
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Thu Mar 27, 2003 1:24 am GMT EthGMT 
<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Originally posted by Ron Schroeder:


1. the ability to select logging once every 1, 2, 3, 4, 5, or 6 seconds and possably also once per minute instead of just every second to allow for smaller files/ day. (Excel limits files to 32,000 records for graphing which is less than 12 hrs at once per second.)
<HR></BLOCKQUOTE>

One workaround I have done is to do a quick filter for power < X Then I delete those rows. This usually results in less then 32K rows left.

Also, there is a program here http://www.timnolan.com/hparticle/hparticle.htm called decimate.exe which will extract every x number of rows. For example, every fifth row.


Top
  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Thu Apr 03, 2003 3:47 pm GMT ErdGMT 
Hi Henry et al,

On Monday, my system (48 SP75s and a ST2500 XR/GP set at 22 degrees, pointing due south in San Diego County) produced a System Best 19.82 kWh! My best result with the old ST2500 was 18.8 kWh in late April 2002.

However, I'm starting to think that my SP75 are underperforming. As I see it, DC current from the array is almost entirely proportional to insolation. I have observed, during times when the inverter is NOT power limiting and insolation is over 1000 watt per meter squared (clear day insolation chart and actual insolation measurements) that my DC current is 48 amperes (as measureed by fishbowl) when, the name plate current ratings should produce 53 amps at Max. Power Point* with 1000 watts per meter squared insolation. Important Point: This is not an issue of DC power, that falls as PV temperatures climb due to reduced voltage -- simply current that isn't strongly related to temp.

The ST2500XR/GP is working so well that the real characteristics of PV array are showing through quite clearly.

Gordon

* The MPPT as shone on fishbowl matched up very well with MPP from IR Measurements and calcuation of MPP.


Top
  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Thu Apr 03, 2003 5:48 pm GMT ErdGMT 
Offline
Red Cobra Delta Guppy
Red Cobra Delta Guppy
User avatar

Joined: Sun Jun 02, 2002 1:01 am GMT EndGMT
Posts: 1158
Location: Lakeland Florida
Hi Gordon,

Isn't it fun , now instead of spending your time with the inverter , you now get to focus at other parts of the system [img]images/smiles/icon_biggrin.gif[/img] [img]images/smiles/icon_biggrin.gif[/img]

Your panels angle will match the sun angle about the 3rd week of april , since your fixed mounted , this will be the only time you will get STC current.

Also , get up on the roof and wash the panels once a month and spray down once a week.

If you do the wash next week , you will get a good idea of the panels ability for maximum output.

Having said all that , I'm not sure how you can make this measurement on your system (peak current) since if they really are putting out the maximum STC power , your inverter would be needing to make 2700-2800 watts , which it can't do.

For the current measurement , I would pull a string to get the STC watts below the limit of the inverter. Also , you not taking into account wire losses , the FishBowl DC amps will be net , not gross

Henry [img]images/smiles/icon_razz.gif[/img] [img]images/smiles/icon_razz.gif[/img]


Top
 Profile  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Thu Apr 03, 2003 8:01 pm GMT ErdGMT 
Henry,

Wire losses don't produce a loss of current, only voltage -- current proportionality to insolation is where my concern is.

Since DC power is voltage x current, when the cells are hot, the loss in performance is due to the loss of voltage -- that is a lower MPP, not current falling off.
I figure it like this:
Each cell's voltage falls by 2.3 mV per degree C above their nameplate MPP rating at a cell temp. of 25 degrees C. So, if the cells are at 55 degrees C (as per my IR thermometer measurement) this is 30 degrees above the rating temperature.
So I calculate as follows:
Voltage Fall = 0.0023 x 144 x 40 = 9.9 volts.
The 144 is the number of cells in each circuit. The voltage fall of 9.9 volts puts MPP at about 58 volts -- which matches the operating MPPT on the XR/GP at the time. This calculation yields an almost 15% power fall below nameplate rating.

Current, however, has only a slight change (actually upwards) with temp. So, current ratings should be observed. That said, it would be best, for array testing, to measure its short circuit current (58 amperes for my system) rather than MPP current (53 amperes).

As for sun angle, I was measuring at the plane of the array.

One of the great things about your work on the inverter is that I can now turn my attention to physics/performance of the PVs. This is great.

Gordon


Top
  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Thu Apr 03, 2003 10:56 pm GMT ErdGMT 
Offline
Red Cobra Delta Guppy
Red Cobra Delta Guppy
User avatar

Joined: Sun Jun 02, 2002 1:01 am GMT EndGMT
Posts: 1158
Location: Lakeland Florida
Me Bad , your right only the voltage is effected on IR loss. Heat actually increase current in SI panels, by about 1/10th the effect of the voltage drop

Unless your getting edge of cloud effect I doubt your getting 1kWmsq, in clear conditions , you will not usally see 1kWmsq , typical clear conditions here in Florida would be in the 930-950 range.

As for the drop off , it is the COS off the angle difference

Henry


Top
 Profile  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Fri Apr 04, 2003 3:52 am GMT EthGMT 
<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Originally posted by Gordon:
Hi Henry et al,

On Monday, my system (48 SP75s and a ST2500 XR/GP set at 22 degrees, pointing due south in San Diego County) produced a System Best 19.82 kWh! My best result with the old ST2500 was 18.8 kWh in late April 2002.

<HR></BLOCKQUOTE>

I had 19.67 kWh from 44 BP585s last Friday. It's been partly cloudly recently so I haven't had "perfect" days. I'm about 30 degrees east of south in Silicon Valley.

arnold


Top
  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Fri Apr 04, 2003 10:44 am GMT EthGMT 
Offline
Red Cobra Delta Guppy
Red Cobra Delta Guppy
User avatar

Joined: Sun Jun 02, 2002 1:01 am GMT EndGMT
Posts: 1158
Location: Lakeland Florida
First one to 20 kWr and sends me the FishBowl Log get a gold star!!

Looks like Gordon has some competition !

Henry [img]images/smiles/icon_biggrin.gif[/img] [img]images/smiles/icon_biggrin.gif[/img]


Top
 Profile  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Mon Apr 07, 2003 1:24 pm GMT EthGMT 
Henry et al,

Two Items:
Yesterday my system 9 (a cool day) produced 19.89 kWh -- ever closer!

By my calculations, PV current climbs with temperature at a rate to negates only about 3% of the power loss due to reduced voltage. The power loss due to temperature is large enough that it really should be considered in the mapping of the country for PV generation potential. As an example, a location rated at 6 solar hours (annual average) in a very hot location may not actually be better than my 5.5 solar hour location.

Gordon


Top
  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Mon Apr 07, 2003 10:01 pm GMT EthGMT 
I have one inverter 19.94 kWh for the day. I don't think there is enough daylight left for it to make it to 20.

arnold


Top
  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Tue Apr 08, 2003 2:26 pm GMT EthGMT 
Hotter day, less energy yesterday 19.4 kWh. MPPT ran 2 to 3 volts lower than the day before (April 6) due the higher air temps and less wind. The inverter works so well that the physics of the array is really showing through.

Gordon


Top
  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Tue Apr 08, 2003 11:54 pm GMT EthGMT 
Ditto, only 19.68 kWh today. Hmmm, wonder I can make up the little difference if I clean my array a little bit.

arnold


Top
  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Wed Apr 09, 2003 4:30 pm GMT EthGMT 
Arnold,

If you clean your array, I'm going to have to clean mine! I was down to 19.33 kWh yesterday, the high air temp was 90 degrees F. You've got a little bit larger array and cooler weather, I'm worried.

Gordon


Top
  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Wed Apr 09, 2003 5:17 pm GMT EthGMT 
Offline
Red Cobra Delta Guppy
Red Cobra Delta Guppy
User avatar

Joined: Sun Jun 02, 2002 1:01 am GMT EndGMT
Posts: 1158
Location: Lakeland Florida
You should BOTH clean your arrays , I rinse mine down each morning and wash every other week

Henry [img]images/smiles/icon_biggrin.gif[/img] [img]images/smiles/icon_biggrin.gif[/img]


Top
 Profile  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Thu Apr 10, 2003 7:50 pm GMT EthGMT 
Offline
Catfish
Catfish

Joined: Sun Sep 22, 2002 1:01 am GMT EndGMT
Posts: 42
Location: Sunnyvale, California
I've located several optoisolators that might work with Fishbowl, but it's not clear how to power the isolator. They are available at www.bb-elec.com/protect_system/isolator_chart.asp for $75 or $80, depending on whether the unit is port powered or transformer powered. The port powered unit (9SPOP2) needs a handshake line powered on both sides, but it's not clear that the ST2500 will power its side. Also, it doesn't pass CTS. The transformer powered unit (9POP4) looks like it would work.


Top
 Profile  
 
 Post subject: Nice efficiency, fun with fishbowl
PostPosted: Thu Apr 10, 2003 10:07 pm GMT EthGMT 
Offline
Red Cobra Delta Guppy
Red Cobra Delta Guppy
User avatar

Joined: Sun Jun 02, 2002 1:01 am GMT EndGMT
Posts: 1158
Location: Lakeland Florida
You must use opto's that are externally powered , The Suntie only has data send (#2) and receive (#3)and ground (#5) on the db9 connector.

This is the opto I recommend
recommend opto and since it's USB , it doesnt need a wallwart

The 9POP4 will work , but at 79.95 plus 14.95 for the 12 volt wallwart its just about the same price as the USB one ..

Others have used rs232 to rs232 , but they all need the external supply

Henry [img]images/smiles/icon_razz.gif[/img] [img]images/smiles/icon_razz.gif[/img]

[ April 10, 2003: Message edited by: Solar Guppy ]


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 46 posts ]  Go to page Previous  1, 2, 3, 4  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
cron
Powered by phpBB © 2000 - 2020 phpBB Group

phpBB SEO

© SGT 2002 - 2020 Solar Guppy