Schottky Diodes

[tecnodave]

dgd

The whole system is way too complicated but I started on a shoestring as my local utility is very unreliable in the winter, I live way out of town and need small power for a medical device.

Most of the system was scrounged from recycle, the CdTe panels were from a forklift dropped pallet of new ones, most did not survive. They were free. The Siemens were bought at scrap price and do seem to work ok. For $30.00 each I have got my use out of them. The Suntech were the best deal at $60.00 each for a brand new 280 watt panel, left over from a 25 house construction project, so I have built my system from junk and leftovers. I paid full price for my Tracer controllers which is the worst investment but they have paid off as well.   I am in the situation where the building inspectors will not let me do anything without a $70,000 permit, so the whole solar setup in on an old worn out motorhome which my house plugs into, seems that they can not do anything about that, not that they didn't try. The whole thing plugs in with an OSHA compliant tempower cord. NEC only covers up to the cord and plug. I am building the system here in California to take to Alaska with me in a few years. There are many things that I would like to do better but I am regulated out of California.

I no longer have to switch panels as the Classic easily handles the power of all the banks. I have been doing electricity since 1965 including communications and computers so I will do things way different than the norm but everything is safe and meets the national safety code.

The CdTe panels will be the first to go but they work very well in low light and fog, on that I have locally dense fog April through July so I need every watt I can get. The Seimens will probably go to Alaska with me.  I am constantly tinkering the system as I am still new to solar but not to electricity. I have done DC to microwave professionally. I am a commercial electrician but I do not do solar at all commercially.

Have you ever heard of panels that will not be warrantable if left at v.o.c.?  I'm stumped at that but First Solar actually has a part of their warranty that states that you must notify them if you let the panels go to v.o.c.!   These are not meant for small scale use, they were developed for Multi gigawatt power plants in the desert. For free I will use what I get my hands on, I have a pile of dead panels that I picked up on speculation.

I just got a power out service call so I need to go as a storm is moving in off the pacific.

tecno

[tecnodave]

dgd

Reread your comments again, I see that you had never heard of that unloaded issue, stumps me not one other article or manufacturer has never said anything like that.

The CdTe panels are way different , they are 2 2 foot by 4 foot sheets of 3.2 mm glass vapor deposited with Cds/CdTe then bonded together, no frame, just the sheets of glass. Junction box bonded onto glass with epoxy with two 5 mm pigtails with MC-3 connectors.

I find them very useful besides working in fog very well , I burn sulfate on off battery cells with them directly connected to two stainless steel probes that I insert through the vent caps to the individual cell plates. They are very high v.o.c. and have high internal resistance so that they work as regulated current supplies,  still experimenting with this and it will be the subject of another thread as I have done apprenticeships at Alaska Husky Battery Co. In Fairbanks, Alaska ( they make batteries that will start your car at 70 below!) and at Trojan Battery back when they were a local outfit out of San Francisco. I will cover Tungar Bulb chargers as well as other hidden secrets in the battery industry, but that deserves a thread of its own.


I am having junction box issues that you describe in your post and have seen evidence of water seepage at the junction boxes.    I just checked the panel shunts this morning and found two dead strings, no time to check it today as I have a laundromat to finish and the storm is moving in. More time on the Onan, not the cheapest on fuel but they always run! First crank every time!

tecno

[boB]

Strings:

4 ea. Siemens M55  36 cell mono in series       X5       v.m.p.  69.6.     V.o.c.     85.6
2 ea. Suntech STP-280/24/Vd. 72 cell poly in series.   V.m.p.   70.4.    V.o.c.     89.6
10 ea First Solar FS-275. 154 cell  CdTe. In parallel.    V.m.p.   69.4.    V.o.c.     92.0

Tecno

I looked up the First Solar FS-275

Data sheet says they don't have any bypass diodes.

Is that common for all CdTe modules ?

boB

[vtmaps]

I burn sulfate on off battery cells with them directly connected to two stainless steel probes that I insert through the vent caps to the individual cell plates.

Wow.  I'm very impressed.  You must have nerves of steel.  And no fear!   --vtMaps

[dgd]

tecno,
Good to see you are taking advantage of free and low cost PVs, even better to know that the Classic has no problem dealing with this mixed bag of panel types although you have properly configured them in series to get almost identical voltages.
The eTracers are really popular here is NZ, every little PV dealer and his dog seem to sell tracers to match their PVs. One dealer I know has about 20 or more 10 to 60amp Tracers including the MPPT eTracer 60A models in their junk bin. No tech support at all, replace is only support, after 12 months, your loss.
Those M55s must be at least 17 years old now, I'd think near the end of their useful life.
WIth the real low PV prices now and the Chinese apparently dumping panels at giveaway pricing, its just so easy now and cheap too to put together a several Kw array of identical panels. Even planning arrays too large for the Classic to allow for poor weather days.

Sorry to hear about the planning and building  issues but love your solution to use a motorhome

dgd

[tecnodave]

boB

I think that is true for all of the types like the First Solar.  GE , BP , & Siemens make almost identical panels,they are built with Cds/CdTe vapor deposited on the glass, 154 cells about 2/3" X 2' wide, bonded between two sheets of glass. Very cheap way to make panels, about .40/watt production cost.  No way to put diodes between the glass. They do specify landscape orientation if there are any shading issues. I do measure reverse current through them, so I just turn them off and dummy load them during days of good sun. I had some CIGS panels that were wired the same, no cell bypass diodes and no blocking diodes, hard to do with bonded glass panels. Their voltages were not compatible. Have you ever heard of panels that are not to go to v.o.c.? I never heard of such a thing! Oh well they were free so I will get what use I can out of them.


vtmaps

Quote from: tecnodave on December 06, 2013, 11:56:20 PM
I burn sulfate on off battery cells with them directly connected to two stainless steel probes that I insert through the vent caps to the individual cell plates.

Wow.  I'm very impressed.  You must have nerves of steel.  And no fear!   --vtMaps

Or just plain nuts & no fear.  Or something like that.   I did time in battery building shops, have melted a few things!  I got knocked across the room doing a 12 kW FM broadcast transmitter 5kv DC to the final amp, got great respect for electricity!   Do illegal power upgrades a lot, Deal with live utility wires, 120/240/480 3 phase,  no it's about focus, focus, focus, one big mistake is all it will take. Shorting 240 volt within 50 feet of 25 kva transformer can produce 70,000 amps. Even if you sag the 240 down to 120 that's still 8.4 megawatts for 400 milliseconds until the utility fuses blow.

Read my upcoming post about burning sulfated cells and you will know just about nerves of steel, if you are not comfortable doing it, don't even think about it!

dgd

I too have several dead tracers and many other cheaper Chinese controllers but I got them dead, I opened them to attempt salvage but they are throwaway. No marking on the chips, etc,  well built but very limited. Their universal answer to any technical question is "How many units do you want"  Well at least they are consistent......lol.  I looked at the eTracer 60 amp but here they are $489. USD and The Morningstar TS MPPT 60 is $485. No way I am going to pay more for Chinese than well made American product.  I paid $610 for my Classic 150 from NAWS and it is probably one of the best buys of my system. Well I paid $950 for 4 Interstste L-16's 380 ah so I'll not complain there, and Suntech poly 280 watt for $60 each, I'm laughing!   The Siemens are at end of life, but it have 2 Arco M75's that are even older, burnt bronze, and still produce full power. At least 25 years old, used in the Arizona desert for an earthquake monitoring station.

On the motorhome, well our building department is a work!  Any way I can stick my thumb in their eye. Almost 99% of the construction jobs that I do are done without a permit! they force you to do it.
I still remember the inspector who tried to outlaw my 40' Gillig bus workshop,registered as a motorhome, he could not find any regulation against it. Stormed off my place, furious that he could not do anything.  Wanna be cops!  Oh well!

tecno

[zoneblue]

You do hear hear storys about commando raids on these calfifornia desert backlots. For the horendous crime of having a shipping container or something. Whats the deal, why so twitchy?

[tecnodave]

zoneblue,

Yeah that happens here....locked gate....they can't come through that!
It's all about money, Santa Cruz County has the second largest building department in California, second to only Los Angeles county, our neighbors in Santa Clara county have 5 times our populations, but a building department only half the size. It's $70,000 for permits here before you turn a shovel. Just to change a $19.00 flex connector on your water heater it's $80.00 for the permit and if you do that they will find something else to cite you on. Major cash cow, the building departments here. San Mateo county's new head building inspector went before the county board of supervisors to request red lites and sirens for the inspectors cars. Got laughed out of chambers! I live on a small farm which dates to the 1920's so I am largely exempt but that doesn't mean they won't try. My new workshop is a 8 X 40' shipping container and I pay a permit fee for that.  I have cashed in on it as I have a row of new electrical panels mounted on a fence row pre weathering them so I can do upgrades and not look brand new,  did I do that, I have no recollection of that. Ollie North syndrome!  The permits are more than the parts and labor!  It's funny how when you get older that it is convient to forget things that don't matter. My neighbors can appreciate that as I do live wire upgrades without the government getting in there. Genuine utility crimps and seals and all!   Lol!  Government in California is out of hand. I can actually charge more than the total on a permitted job!  Some folks have waited 10 years and more for their permit process!    Moving to Montana soon, gonna be a dental floss tycoon.....lol

Tecno

[boB]

boB

I think that is true for all of the types like the First Solar.  GE , BP , & Siemens make almost identical panels,they are built with Cds/CdTe vapor deposited on the glass, 154 cells about 2/3" X 2' wide, bonded between two sheets of glass. Very cheap way to make panels, about .40/watt production cost.  No way to put diodes between the glass. They do specify landscape orientation if there are any shading issues. I do measure reverse current through them, so I just turn them off and dummy load them during days of good sun. I had some CIGS panels that were wired the same, no cell bypass diodes and no blocking diodes, hard to do with bonded glass panels. Their voltages were not compatible. Have you ever heard of panels that are not to go to v.o.c.? I never heard of such a thing! Oh well they were free so I will get what use I can out of them.

Nope. Never heard of a PV you can't open circuit.  Also don't know of any babies that were born with clothes on.
I don't believe there is a spec that says you can't open circuit one.  It would sure make it very hard to unbox
one of those, assuming it was short circuited in the box, and then install it.

Also, bypass diodes do not have to be embedded inside the glass.  They put them in the J Box.  At least one diode.

Series blocking diodes should not be necessary for PV arrays using like modules and the same number of modules per string as long as you are using a combiner with the proper series fuse or breaker rating  for strings more than 2 in parallel.

boB

[tecnodave]

boB,

I have  not heard that anywhere else but it in in their installation guide for the FS-2 and FS-3 panels , I will sent it to you for your reading including a pointer as to where it is in their documentation. There is also a white paper somewhere on their website.  The white paper talks about copper substrate migration as a result. It does not say ever, just no extended exposure to full sun during construction for more than 90 days. No operation at v.o.c. And no short circuit operation. The panels need to be covered during the installation process. Also they specify MPPT controllers only.

My foggy season is April thru July, in the past that is the only time I have used them for battery charging. In full sun I do not need the extra power that they provide so I cover them with 1/8 inch plywood or dummy load them.

I could not sent as an attachment here but will email it.

tecno

[dgd]

There is a fair amount of internet info about Cadmium Telluride thin film solar panels. I can't find anything about their application where special care is needed if left OC.

They sure do tick all the right boxes for me..

- Use Cadmium, one of the 10 most toxic materials, (we just need more Cadmium mining  )
- Telluride is rare, China appears to be main source but deep sea mining possible
- First Solar cant get regulatory approval (RoHS compliance) and dont seem to want it as its too difficult to achieve.
- Recycling CdTe PVs looks uneconomic so more toxic landfill?
- Damaged PVs mean immediate health hazard and need specialist HazMat clean up/treatment
- Apparently panels are safe in fire as glass melts/seals in the cadmium 
- Recommended for large PV applications only where they can be managed   

dgd

[dgd]

...  I have done apprenticeships at Alaska Husky Battery Co. In Fairbanks, Alaska ( they make batteries that will start your car at 70 below!) and at Trojan Battery back when they were a local outfit out of San Francisco. I will cover Tungar Bulb chargers as well as other hidden secrets in the battery industry, but that deserves a thread of its own.

Thats a thread I look forward to reading.
For some unknown reasons my Century Yuasa FLA circular plate design 1080Ah 24V bank has just kept going for near 15 years now.
The only SOC monitoring I do is observing the voltage, maintenance is watering and making sure terminals are clean and an occasional wipe down with a damp cloth to get the dust away.
Yet in the 1990s an 880Ah 24v bank of R220s was dead within a year, ok 4 parallel strings of 4 series connected R220s, learnt the hard way about parallel strings 
Again with Australian SunCycle 2V 800Ah cells in one string of 12, this got under 2 years as bad design allowed terminal posts to rise up from top of cell and capacity/voltage sagged.  One cell actually reversed its polarity -incredible!  Of course warranty wqs a laugh, company just was not interested.

I briefly saw a post, was it from you?, about root cause analysis? Did you get to the root of the stiction on the st225? 

dgd

[tecnodave]

dgd

First Solar used to sell to resellers for the public market, they are unavailable now. They focus on Gigawatt power plants, they have just signed a deal with Japan to install PV plants equal in size to two of the nuclear plants which melted at Fukushima. There is a environmental certification document from French government certifying their environmental suitability,   They have a recycle program that takes back damaged panels from users without question. Somewhere in their white papers is where they get their cadmium as a byproduct from some other mining operation.

That said I would not buy these new due to the toxic nature of cadmium , I scrounged mine from a forklift dropped pallet ,only 10 of 60 survived, I did not know the nature of the panels at that time, only that they were free solar panels and my first large set.

I had been using the Arco and Siemens panels for years at communication sites that I had maintained for General Electric, Motorola , and others and am much more familiar with Monocrystalline technology having worked in crystal growing in the semiconductor industry as well.

My system is totally mixed bag with few products purchased as new as this is part of a learning process for me besides not wanting to support nuclear , coal, oil etc. I do have utility power but just don't use it unless absolutely necessary.

My largest mistake was buying more than one tracer, I should have just leaped to better technology but medical issues take priority so I limp along with a cobbled up system. My next purchase will be 12 matching 250 watt panels.   Looking for Suntech Wuxi poly 72 cell panels. 

Looks to me that Warren Buffet is looking to buy big in solar to do a deal with Japan.....Suntech Wuxi will be coming out of bankruptcy court any day now....warren Buffet buying?....waiting to see.

[tecnodave]

dgd

I did indeed work at Slavegate in pre-production prototype root cause failure analysis, but  the ST-225 predates me, The ST-225 family of drives was already out of production by the time I got there.
My charge was the read/write channel of the 9XXA and 3XXA lines of notebook and 3 1/2 inch drives.
As I remember I was on the team that grew the 9150A 150 mb drive to about 4 gb and the 3XXA drives from about 400 mb to 8 gb. before i left there. Lots of learning there but I am a sun worshipper, I hate being locked in a cage with no sun, could not wait to get back in the field. Had to sign non-disclosures and never talk about my work as the disk drive industry is very competitive.

I will be sharing my battery experience but I am somewhat reluctant so as to not endanger people.
Many dangers there......hydrogen gas burns at 5600 feet per second....remember Three Mile Island Nuclear power plant meltdown.   Quote. " We had a rapid Hydrogen Burn".     Rapid hydrogen burn , my butt, damn thing exploded, jellied the entire containment dome....but we can't talk about that can we?  Fukushima power plants exploded when the zirconium cladding of the fuel rods flashed into hydrogen gas at 550 degrees Fahrenheit ..same exact thing that happened at Three Mile Island, loose cooling water, temperature rises, gets to 550 degrees oops......bang......total meltdown follows.....Russians 1.....USA 1........Japan.......3 maybe 4........but nuclear power is safe....yeah right.

On batteries,
Parallel strings never work out....just can't divide the current correctly as the cells age......I have seen cells reverse polarity...rare....but it does happen! There are a lot of battery companies who will sell you product, not that many that will back them up.

Gotta go, some field service work to do

td

[boB]

Well, sure enough, just like tecnoDave says, here is the part in their manual about not exposing them to
Voc for too long....

"Open circuit exposure may accelerate module efficiency loss and should therefore be minimized. First Solar requires that
modules not be operated in open circuit conditions for more than ninety (90) cumulative days to avoid a potential reduction
in energy output over the life of the modules.
Modules must not be operated under short circuit conditions for extended durations. Short circuit operation is not an
approved mitigation technique for open circuit exposure.
"

My question is, how close to Voc do you not have to be in order for the efficiency not to be reduced ?

If operating just near to Voc is not good for them, then this means that you should NOT get your
batteries full because the controller will run them near Voc when batteries are full if you have enough
power from these PVs.

boB