James Cormican's posts

I did not check for voltage drop or for current, but 6 in series may be too much voltage depending on your climate.  i would think that 2 strings of 3 in series would be the best bet.  double check on current calculations and voltage drop of safety and performance respectively.

cheers,

james
altE staff

nec 690.71 does not allow for battery banks above 48v nominal in dwellings.  furthermore many charge controllers can't accept pv input voltages at 72v nominal because of the effect of cold temps on pv voc.  you may be in the realm of something custom as off the top of my head, i dont know of any products that qualify.

cheers,

james
altE staff

regarding your pv source and output circuits, nec 690.45 will send you to nec 250.122, which by my calcs will say that for a system of your size that 12awg would be the minimum.  6awg is often used in pv in the pv source circuit for its physical robustness and protection from physical damage as well as fitting many components manufactured for pv equipment grounding.

always select listed grounding methods and products.  follow all local codes and rules set forth by your jurisdiction regarding electrical work and qualified service personnel.

cheers,

james
altE staff

or you can have your solar/electrical pro install a dumb old analog meter between the output of the inverters and the point of interconnection.  i kid about this, but I employ this method with a string inverter and prefer it to having to pay a subscription.

low tech, granted, but should be able to track production old school style.  if you want daily numbers, go outside every day after sunset and write it down.  fire up a spreadsheet and go town. I settle for monthly data. 

http://www.altestore.com/store/Meters-Communications-Site-Analysis/Meters-Battery-Monitors/Power-Meters/GE-Solar-KWHR-Meter-240V-100A-EZ-Read-Meter/p3918/

http://www.altestore.com/store/Meters-Communications-Site-Analysis/Meters-Battery-Monitors/Power-Meters/Kilowatt-Hour-Meter-Base-NEMA-3R/p4227/

james
altE staff

kyocera 40w and 135w modules are the same nominal voltage (12).  they can be wired in parallel if the charge controller can handle the ampacity, and the balance of system equipment (combiner, controller, pv disconnect, pv output circuit wiring) can handle the addition.

this article may help regarding the confusion of voltage terminology as it relates to voc and nominal voltage.

http://www.altestore.com/howto/Solar-Power-Residential-Mobile-PV/Solar-Components/Solar-Panels-PV/Solar-Panels-PV-and-Voltages/a98/

cheers,

james
altE staff

which do you mean, different voc or different nominal voltages?  what equipment do you have and what are you trying to do?

in battery based systems, modules may be put in parallel where each string is protected by a series overcurrent device.  the do not have to be the same exact module, but they should be the same nominal voltage, and the charge controller and all other aspects of the system design must be able to handle the additional current added to it.

james
altE staff

hi jerry,

the siren song of the kaneka thin film pricing is irresistible to some, but for many smaller systems they dont make the most sense.

you said you were looking for around 120 W @STC. here are some rough numbers to break it down.  this is just basic stuff, and much of the necessary balance of system equipment required for a code compliant installation is not included for sake of simplicity and brevity.

2 kanekas - $270
combiner box - $100
shipping by truck - 150
mppt controller (tristar 45) -$445

total - 965

or as eric said, you can go with 12v gear and get more power for less dough.

1 kyo 135 - $390
combiner box - $100
shipping by ground service $ 75
pwm controller (xantrex c35) $105

total 670 and bonus 15W at STC

of course the possibilities are endless, but if cost is an important variable in your system design, the modules are not the only piece to that puzzle to be considered.

cheers,

james
altE staff

you rang?

if the system is for fun occasional use and portable as opposed to permanently installed and subject to electric codes(s), then there are many choices.  for beginners, I often suggest something with a display that can let them know basic numbers relating to what is going on with their system.

something like this

http://www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/PWM-Type-Solar-Charge-Controllers/Morningstar-Charge-Controllers-PWM/Morningstar-Prostar-Ps-15M-15A-1224V-Charge-Cntrlr/p788/


if something like that is too expensive, then I would at least suggest something that has a low voltage disconnect (lvd) so that the load will not destroy the battery (at least not right away)

--

if this is to be permanently installed, then I would suggest listed components, and all the appropriate enclosures and conduits to keep children and their friends (or turtles for that matter) safe. 

hope that helps

james
altE staff

irradiance is measured with a tool called a pyranometer.  essentially irradiance is the rate of sunlight power hitting a given spot at any instant in time.

here is a link to one. 

http://www.altestore.com/store/Meters-Communications-Site-Analysis/Solar-Site-Analysis-Tools/Daystar-Inc-DS-05A-Digital-Solar-Meter-Pyranometer/p7949/

the 85 watts number is measured at what is called STC.  without going too far, standard test conditions (STC) is done assuming 1000w/m^2, 1.5 air mass, and 25 C cell temp. 

irradiance is directly related to current output, so the numbers you measured, even if only characterized by "sunny" conditions, would suggest your module is fine being that you were at 87% (4.35/5) of its current rating without any further technical data at hand.

the voc number was slightly low, but could be easily explained if the module was warm.

for more info regarding pv technology

this is a good book,

  http://www.altestore.com/store/Books-Classes-Educational-Videos/Solar-Electric-PV/American-Technical-Publishers-Photovoltaic-Systems/p5836/

and you could also take classes if you think you could stand 16-40 hours of me in person

http://www.altestore.com/classes/

hope that helps

james
altE staff

for your own knowledge, sure, you could see what the modules are doing.  to get useful information, you will also need to know the irradiance, as well as temperature in degrees celcius. 

i would bet there is nothing wrong, but send more data on exactly how you tested.

james
altE staff

if I had a thousand dollars . . .

I would spend it on efficiency.  either go bananas and switch as many lights to l.e.d. as possible, or find my oldest appliance and have at that.

if all my appliances were efficient, and all my lighting was as efficient as possible,

i would consider insulation and new windows

if that was done,

I would consider a home energy audit, and or a solar site assessment by the respective qualified personnel.

then . . .

I would consider solar thermal, or perhaps a small grid tied pv system that could grow over time.

james
altE staff

for our forum friend thomas,
thanks for your continued support of the forum, as more and more places can sell gear, the number of folks that can miss the devil in the details grows.

for the "package" that you listed, it is noteworthy to me that 8a fuses are supplied, being that kaneka modules have a 7a max series fuse size.

i am no stranger to the occasional mistake myself, but these are the errors that raise an eyebrow. I would suggest that any electrical work that is often described in the forum, be undertaken with due care and planning from the paper stage to the integration stage.  much like the sandwich you described so well in the earlier post, what you see may not be what you get, let alone what you need, regardless of the place one acquires it.

anyway, the burger post made me laugh, thanks for the continued support of the forum.

cheers,

james
altE staff

to tracy,

as far as all the calcs i ran, it should work, it just wont work as well.  it is on the low side of the voltage window in the summer time, but still in the window.  the winter time should not be an issue, as you wont be getting near the high end for the solectria.
  to answer directly, you will get some power output, but that low, you will not get the same efficiency from a more typical array.  as you add strings, your efficiency (and power output) will improve.  work with your solar pro / electrical pro to make sure that the pv output circuit, overcurrent protection, and disconnects are sized appropriately for the full system goal size.

james
altE staff

no problem, sell away, I  was just pitching in for the the FYI factor, for you and our friends on the forum.

james
AltE staff

hello,

as long as you have the space in your flexware 500 dc (or ps2 dc) enclosure, there is no harm in using the dual array GFP device if you only have one array.  sure, the single unit will cost less, and take up one less space, but if you already have it, you can use it.

james
altE staff

I agree with dave.

the problem you have is both units and not accounting for system inefficiencies.  your initial calculations likely doomed the project from the beginning.  your daily loads in watt-hours are more than the array is likely to harvest.

for practical design help, I would recommend this book

http://www.altestore.com/store/Books-Classes-Educational-Videos/Solar-Electric-PV/Photovoltaics-Design-Install-Manual/p481/

you can also use the calculators on the website, or consider taking classes in person if you intend to do more solar work.

http://www.altestore.com/howto/Calculators/c5/

http://www.altestore.com/classes/

james
altE staff

in the winter, with modules flat, that is not abnormal.  anything from 60 to 90v on the input would be pretty normal. 

also, depending on the battery bank state of charge, and the irradiance, 1.5a of current from that array is not outlandish in winter.

remember, current is direction proportional to irradiance, so without a tool like this

http://www.altestore.com/store/Meters-Communications-Site-Analysis/Solar-Site-Analysis-Tools/Daystar-Inc-DS-05A-Digital-Solar-Meter-Pyranometer/p7949/

it is hard to know at any given moment what the potential for current is. 

even in good conditions in the summer, it is not unusual to see 70-80% of nameplate ratings at any given moment.

james
altE staff

it depends on the variables for the site.

in theory, monocrystalline would be slightly more efficient than polycrystalline.  for the same wattage, the mono module should be smaller. 

this is not always the case in practice.

very few people any more insist on one or the other. 

there are pv technologies with stark differences.  the differences in performance and cost in the consumer market are minimal between mono and poly crystalline in my opionion

james
altE staff

perhaps, but every time a new module comes out, or a new production facility, there is often a surge in B modules as a "work out the kinks" process seems to take place.  by no means is this official, it is just what i have noticed over the years.

james
altE staff

a grid tie inverter will not function unless it is connected to the grid.  so if you are merely checking with the unit outside but not connected properly, it should not function, nor show any voltage.

to actually check if it were working, it would have to be properly installed, and then a clamp on ammeter would have to be applied to the black wire, either inside or outside, as long as the circuit is closed.  with a 120w module, you may see anything at 1a or below for ampacity, but any current at 120vac would indicate that it was functioning.

if you were not going to install it by the way, those units still fetch a few people looking to pay top dollar for them.

james
altE staff

sorry, i misread and thought you wrote tri-star

what specifically is your question regarding the tri-metric?

james
altE staff

here are the setpoints from trojan

http://www.trojanbattery.com/Tech-Support/tips.aspx

http://www.altestore.com/mmsolar/others/TriStar_Manual.pdf

see sections 4.2 and 9.3 in the manual

james
altE staff

do not put anything on the surface of the modules.

if you cant leave them alone, or you need the electricity they provide that badly, you can disconnect the system, use a non conductive broom or something to that effect.

be careful


james
altE staff

based on your responses, it is not easy to put together a system.

since you said you wanted a grid tie system, that could grow over time, and possibly have battery backup at a later date, the possibilities are very few.

with only 400w the likelihood of turning on a grid tie inverter is relatively low barring thin film modules.

so after some thought, i figured it would be better to show the result of the answers to the questions.

here is a system that could work. you are almost forced to start with 1kw to get the voltage high enough to turn the inverter on.

http://www.altestore.com/store/Kits-and-Package-Deals/Grid-Tied-Systems/Alt-E-Designed-Grid-Tie-Packages/AltE-Grid-Tied-Package-System-A-1kw/p6629/

in order to have the possibility of future battery backup, the solectria inverter would likely be swapped out for an sma model like this one.  the sma needs 200v to turn on, that is why the 5 modules would be needed.

 http://www.altestore.com/store/Inverters/Grid-Tie-Inverters-On-Grid/2001W-to-4000W/SMA-Sunny-Boy-3000-US-with-DC-Disconnect/p5666/

this would allow for the future addition of the battery backup portion

http://www.altestore.com/store/Inverters/Grid-Tie-Off-Grid-Capable-Inverters/SMA-Sunny-Island-5048U-OnOff-Grid-Inverter/p6071/

based on your answers, there is a peek at what a system that met your requests would look like.

cheers,

james
altE staff

why 400w?  what are you trying to do?  do you have intentions to expand?  is this a battery based system?  do you intend to sell to the grid?  will this be permanently installed on/in a building?  how many watt-hours per day are the loads that are to be run?

answer as many as you feel comfortable, and we can go down the path.  there is not usually a "best" but rather a response to the variables of the project.

james
altE staff

because at least 80% of the market is grid tied, where they dont care what your batteries like.  so if you make modules, which market segment would you serve? 

there are still 12v and 24v nominal modules around for battery based systems, but they are often smaller in size and higher in cost per watt.

now that there are controllers that can deal with other voltages, in does not matter as long as there is a solid system designer.  what is often the case is that the cheaper larger modules require mppt controllers for battery use, and often require truck shipping, all but eliminating the savings $/watt savings that attracted the new folks with smaller system goals to begin with.

james
altE staff

well, not quite.

you need to know these two variables first

1. what is my array nominal voltage?

2. what is my battery bank (aka system) voltage?

with those two questions answered, you could move on.  if the answer to Q1 and Q2 are not the same, then you are forced into an mppt controller.  if they are the same than a pwm controller is an option.

given that your answers force you to have an mppt controller you would then ask yourself these questions.

A. is there a controller that can down convert for the parameters i set out in Q1 and Q2?

B. if there is a controller that meets question A, does that controller meet my requirements for ampacity (current) as well?

- so this is a simplification, but this is where some of the mppt string sizing tools, or a solar professional would step in and make sure everything is correct.

regarding the most recent post,   if the answers to question 1 and question 2 were the same, AND you selected a pwm controller with field selectable voltage settings, then YES, you would select the appropriate voltage (same as you answered in Q1 and Q2) on the controller, usually with a jumper of some type.

if however you selected an mppt controller, there is generally no selecting done at all.  all the math is done beforehand, and the controller can auto-detect the battery bank voltage without human intervention in the case of most mppt controllers.

for most new folks, the question of "what am I trying to do?" is the most essential, yet most overlooked.  with this as a guide, a solid solar pro can help somebody along to a functioning system to reach an end goal.  all too often I get calls and emails after somebody has a hodge podge of stuff bought on sale that does not work together.  i would encourage any new folks to get a system goal and a system design on paper before selecting any individual components.

all that being said, this forum is for education and sharing, so if you have specific questions on components, feel free to fire away, usually the community is eager to help.

james
altE staff

no, I believe that you and mr. abel are confusing a couple of things. 

for mr. abel, you are confusing nominal voltage with voltage at max power.  it is true that 12v (nominal) charge controllers will handle 18v (vmp - voltage at max power) inputs.  however, mr. rzeszotko was referring to an 18v nominal module with vmp at 29v, which is not capable of being handled by a 12v nominal pwm or shunt controller.

for mr. rzeszotko, switchable does not mean voltage converting.  while for example, a xantrex c40 or morningstar tristar is "switchable" to the choice of 12/24/48 volt NOMINAL systems, the controller is NOT capable of down converting an array voltage of a higher nominal voltage down to a battery bank of a different nominal voltage.  if using a pwm or shunt controller, the nominal voltage of the array should match the nominal voltage of the battery bank.  the switching only allows for the controller to be adjusted for 12v, 24v, or 48v nominal operation under the assumption that the array nominal voltage matches the battery nominal voltage.

here is an article that may clear some things up.

http://www.altestore.com/howto/Solar-Power-Residential-Mobile-PV/Solar-Components/Solar-Panels-PV/Solar-Panels-PV-and-Voltages/a98/

hope that helps, thanks for contributing to the thread.

james
altE staff

if you intend to use an array in which the nominal voltage of the array does not match the nominal voltage of the battery bank, but instead is higher, the controller will have to be an mppt controller that is capable of down converting voltages and handling the ampacity of the array.

here is an article that may help you.

http://www.altestore.com/howto/Solar-Power-Residential-Mobile-PV/Solar-Components/Solar-Panel-Charge-Controllers/Sizing-MPPT-Charge-Controllers/a61/

james
altE staff

welcome to the forum.  before you buy anything, i would recommend some more reading and education.

here are some links that may help you

http://www.altestore.com/store/Books-Classes-Educational-Videos/Educational-Videos/Educational-Video-Solar-Electricity-Basics/p6053/

some of the info is a little dated, but it is still good for starters.

http://www.altestore.com/howto/Solar-Power-Residential-Mobile-PV/Off-Grid-Solar-Systems/c33/

http://www.altestore.com/howto/Calculators/c5/

lastly, i would suggest giving some insight to your project.  the classic "what are you trying to do?"  will help others help you with system design and component selection.

good luck.

james
altE staff