First RE System is Planned

20 Posts
Jul 7, 2008 03:15 pm
First RE System is Planned

Well, I'm ready to begin working toward my first system.  My plan calls for a 900W windturbine(already available to me, so that's a small savings) and about 1kw of PV. I want to make this joined together into a hybrid system that will be used off-grid.

First, the wind turbine will be located 375 feet from the battery room.  I anticipate using 48 volt to keep the buried wiring size reasonable from the turbine back to the battery room.

Second, the PV will be located above the battery room on a roof area that is approximately 20 x 20 feet.

Batterys will be 6volt 200ah.  Bank will be 8 in series set up in two parallel banks.

I'm seeking advice about components I will be needing. And, how to set all this up to run power to a distribution panel that will be in my basement about 30 feet horizontally and 8 feet vertically from the inverters.

That's about as far as the plan goes at this point.

I look forward to helpful comments from the forum.   Thanks for putting up with a new member.

Eric

Jul 8, 2008 08:39 pm
Re: First RE System is Planned

Wow! 375 foot, thats a long ways even for 48 volts nominal at only 900 watts. the Alt-E Stores wire sizing calculations would call for nothing less than 3/0 (pronounced three aught) at 3%. 750 foot of 3/0 even at \$3.78 per foot would come to \$1,475.50 good thing that wind genny is free!
http://wesbellwireandcable.com/THHN/THHN3_0.html
http://howto.altenergystore.com/How-to-Size-Wiring-and-Cabling-for-Your-System/a62/
Check my math though.
900 watts at 48 volts is 18.75 amps
18.75 x 375 = 7031.25
3 x 48 = 144
7031.25 / 144 =  a VDI of 49

Somebody please prove me wrong. Thats just too much!

20 Posts
Jul 9, 2008 10:02 am
Re: First RE System is Planned

I have no problem with your math.  However, I'm planning on using #2 AWG wiring for the long run.  I am calculating using about 5% to 10% voltage drop, which isn't uncommon for wind turbines.  Yes, the wiring is expensive.  But to get to the clean air this is where the turbine must go.

If I build my power base (battery room, inverters, etc.) at the tower base, I still need #4AWG to run the 115/120v to the house.  And, I then have to go 125 yards just to check and maintain the equipment.  I am planning on an annex to my garage which will be firewalled and vented.  It will use passive solar and a heat sink to keep the room above 10F here in northern Wisconsin winters.

I am actually more curious to hear what others are using for a charge controller to handle a hybrid system.  And I am still stumped on what PV panels I should be looking at.  I have many other questions that I'm sure will arise as I get further along.

Has anyone had any problems with zoning ordinances in their locale?  How have your worked through those concerns?

I appreciate comments, they really help me think through all this.

Jul 13, 2008 12:03 pm
Re: First RE System is Planned

Sorry Eric if that came across as being facetious. I wanting to have a wind genny but my site is just not suitable enough to make it cost effective.  Among other things, a free standing tower over 100' would have to be constructed. I guess cynicism, prompted by jealousy, came through in my writting.
As for ordinances, the best place to find that out would be your local planning and zoning office. Those type of things can be way different from; state to state, county to county, city to city, town to town, well you get the idea.

If your in a rural agricultural area, you might see silo's. This could give you idea of how high a structure is allowed to be in your vicinity. Geology plays a role. It might be that the ground where you want to plant a tower cannot support or may require additional concrete to support it.
Heights, ground stability, proximity's, restrictions, petitions, permits, etc., etc., these are all the things that your local planning and zoning office will want to address and chances are they may have allready.
Here is an example of something that has been done by the Massachusetts Division of Energy Resources.
http://www.mass.gov/Eoca/docs/doer/renew/model-allow-wind-small.pdf
I can't help but feel that I am telling you a lot of stuff you may already know or have searched and found on the internet... But here it goes anyway. Just in case.
http://www.newfarm.org/features/0604/wind3/index.shtml
http://www.greengold.org/wind/documents/84.htm
http://www.wind-watch.org/news/category/locations/americas/us/wisconsin/

While searching I found several other sites from different states and read through them. My overall impression, for Wisconsin, is that the power companies what to desperately hang on to their monopoly of energy. If this is true, I wouldn't be at all surprised if they (the power companies the want to build megawatt wind farms) are influencing decisions made by law makers concerning small scale privately owned wind genny's in the residential arenas.

As for the PV, take your pick. Apples are Apples. Its of little matter wether its a Delicious Red or a Granny Smith, they are all good to eat. Personally, I perfer the Poly crystalline type. Hot climates may necessitate a higher voltage PV module. The trend would seem to be high voltage and high wattage PV modules and MPPT charge controllers. There seems to be very little information about singular charge controllers that can handle both wind and PV simultaneously unless it comes with a particular wind genny.

1 Posts
Jul 14, 2008 10:36 am
Re: First RE System is Planned

Hi Eric,
In checking the NEC 2008 book, Table 8 Conductor Properties. Your suggested #2 wire in copper is .201 ohms/kFT and in Aluminum is .313 ohms/kFT.
The issue here is what is my wattage loss through this long cable run and what is the final voltage drop at the end of the cable run?  Ohms law and basic power formulas will give you these answers.

I squared * R = Power loss
and
E = I * R ,  for the voltage drop

Given: max amperage (I = 18.75 A)
Max voltage (E = 48 vDC)
Cable Ohms  #2 Copper@ .201 ohms per 1000 feet * 375 FT
#2 Alu@ .313 ohms per 1000 FT * 375 FT
Note: This being a closed loop DC circuit I must consider the cable run in both directions thus doubling my ohms total for the cable.
#2 copper ohms  (R = .15075 ohms total)
#2 aluminum ohms (R = .23475 ohms total)

Power Loss
I sq * R = 18.75sq * .15075 = 53 watts on copper
I sq * R = 18.75sq * .23475 = 82 watts on aluminum

Voltage Drop
E = I * R = 18.75 amps * .15075 ohms = 2.8 volts on Copper
E = I * R = 18.75 amps * .23475 ohms = 4.4 volts on Alu

Are these numbers tollerable??? Maybe!
Will your cable run be melting the snow between your wind tower and the garage with 53 watts? NO.
Will your wind mill be usually be outputting its maximum 900 watts and therefore 18.75 amps? No, so these numbers are based on a theoretical maximum which may not be achieved.
Will your batteries fail to fully charge? Yes, Your batteries really want 2.1v per cell ( 12.6 volts for a 6 cell battery). So hopefully the wind mill outputs just over 48 volts and the ocassions when your voltage drop over the wire is above 1 volt it will have little overall effect on your final delivered wattage to the garage.

Now increasing your cable size to 3/0 will give you a maximum voltage drop of 1.12 volts and only 21 watts of power loss.  Better? YES, but at what cost??? Price of #2 copper vs 3/0 copper.
MikeH.

« Last Edit: Jul 14, 2008 01:14 pm by Mike Harrison »

20 Posts
Jul 15, 2008 03:59 pm
Re: First RE System is Planned

Hi Eric,
In checking the NEC 2008 book, Table 8 Conductor Properties. Your suggested #2 wire in copper is .201 ohms/kFT and in Aluminum is .313 ohms/kFT.
The issue here is what is my wattage loss through this long cable run and what is the final voltage drop at the end of the cable run?  Ohms law and basic power formulas will give you these answers.

I squared * R = Power loss
and
E = I * R ,  for the voltage drop

Given: max amperage (I = 18.75 A)
Max voltage (E = 48 vDC)
Cable Ohms  #2 Copper@ .201 ohms per 1000 feet * 375 FT
#2 Alu@ .313 ohms per 1000 FT * 375 FT
Note: This being a closed loop DC circuit I must consider the cable run in both directions thus doubling my ohms total for the cable.
#2 copper ohms  (R = .15075 ohms total)
#2 aluminum ohms (R = .23475 ohms total)

Power Loss
I sq * R = 18.75sq * .15075 = 53 watts on copper
I sq * R = 18.75sq * .23475 = 82 watts on aluminum

Voltage Drop
E = I * R = 18.75 amps * .15075 ohms = 2.8 volts on Copper
E = I * R = 18.75 amps * .23475 ohms = 4.4 volts on Alu

Are these numbers tollerable??? Maybe!
Will your cable run be melting the snow between your wind tower and the garage with 53 watts? NO.
Will your wind mill be usually be outputting its maximum 900 watts and therefore 18.75 amps? No, so these numbers are based on a theoretical maximum which may not be achieved.
Will your batteries fail to fully charge? Yes, Your batteries really want 2.1v per cell ( 12.6 volts for a 6 cell battery). So hopefully the wind mill outputs just over 48 volts and the ocassions when your voltage drop over the wire is above 1 volt it will have little overall effect on your final delivered wattage to the garage.

Now increasing your cable size to 3/0 will give you a maximum voltage drop of 1.12 volts and only 21 watts of power loss.  Better? YES, but at what cost??? Price of #2 copper vs 3/0 copper.
MikeH.

Mike,

I have only one quibble with your numbers.�  My chart for #2AWG says the max ohms are .159 and the weight per 1000 feet is 201#.�  Did you jump columns?

In any case the voltage drop using #2 is still 2.23V.

Here's the really funny thing.�  If you download the Southwest Windpower Manual for the Whisper 100 you find they say you can go many more feet with only # 6 or even #8 wire.

http://store.altenergystore.com/mmsolar/others/REVC-3-CMLT-1033-01-Whisper_100_Owner%27sManual.pdf

See Page 9 of 42.

I do not understand.�  Can anyone explain this (what appears to be a) discrepancy?

Eric F.

163 Posts
Jul 15, 2008 05:39 pm
Re: First RE System is Planned

Here's the really funny thing.�  If you download the Southwest Windpower Manual for the Whisper 100 you find they say you can go many more feet with only # 6 or even #8 wire.

http://store.altenergystore.com/mmsolar/others/REVC-3-CMLT-1033-01-Whisper_100_Owner%27sManual.pdf

See Page 9 of 42.

I do not understand.�  Can anyone explain this (what appears to be a) discrepancy?

Eric F.

Voltage drop calculations are really only applicable in situations where you have fixed voltage, such as 120V in a panel box or the output from your charge controller.

Lets say for example that the output from your turbine is 50V. Any loss at all from that, or even 50V itself, would not be able to charge a 48V system.

Now lets say that you can crank up the output voltage of the turbine up to 80V. Here you have a situation where even a 10% drop in voltage is not going to prevent the turbine from charging the batteries. What you will have is power losses in the wire because of the resistance of the wire. The less ohms per foot, and hence the larger AWG number and more expensive the wire, the less losses you will incur.

In pv systems, the voltage drop has much greater relevance for the distance between the charge controller and the battery, and is not that important between the source and the charge controller. Remember in PV systems mppt charge controllers actually vary the incoming voltage along the I/V curve to maximise the power gain.

I would imagine that the Whisper Controller acts in a similar manner to a MPPT charge controller for the wind turbine to give you a bit more flexibility in keeping the costs down.

220 Posts
Jul 16, 2008 12:17 am
Re: First RE System is Planned

hi eric f.

it's great to see that you are trying to nail down these details before just diving in with your wallet. you are sure to find something you missed along the way. but that is the fun of the learning.

i see the wire run problem as a mixed bowl of fruit. we are attempting to use our dc wire tables for the turbine run. this turbine feed comes all the way to your power room with "three phase wild ac current" and then is sent through a bridge rectifier and changed to ripple dc and then right to the battery bank. we may well see 150vac @ 150hz comming from the turbine...a word of caution here about trying to measure it with a regular multimeter. don't. it took me three meters to learn that one. also you will find that your batteries love that dc ripple charge current until they get to the very top of their charge, then you have to start dumping. the c40 should work out nice for that. and the suggested wire gauge per manual is the way to go.

for some great wind advice check out paul gipe and the guru of wind hugh piggot.

all the best, dave

also sometimes it's easier to beg for forgivness than to jump through all those permiting hoops. my local inspector was by on another matter and happened to notice my set up. and all he said is that looks nice. your ahj may not feel the same. in any case be sure to follow at least the fall rule. that if it comes down it lands on your property. build strong!
« Last Edit: Jul 16, 2008 12:36 am by david ames »

20 Posts
Jul 16, 2008 10:36 am
Re: First RE System is Planned

My thanks to David and John for their explanations.

Onward to my next area of questions:

Do I need separate charge controllers for the PV and the wind turbine?  Do they both connect to the battery bank in the same way?  Must there be separate battery banks?

Thanks for any help, again.
Eric

163 Posts
Jul 16, 2008 09:40 pm
Re: First RE System is Planned

Eric,

I believe that the "Whisper Controller" is a charge controller of sorts. The Whisper Controller and the pv charge controller should be able to connect to the same battery bank if they are the same voltage. Charge controllers for wind turbines usually have a "diversion load" to dump any excess current once the batteries are fully charged since spinning blades in high winds do not turn "off" as easily as pv panels. Heating elements in water heaters make good diversion loads.

18 Posts
Jul 17, 2008 04:00 pm
Re: First RE System is Planned

First about that wire run.  I would look into doing what a power company would do - step up the voltage.  Since it is 3 phase AC you would need 3 transformers (at the base of the pole in a box) to "step up" the voltage to something like 200-300 volts (AC).  Then use 3 more transformers at your power shack to step down the voltage.  You might save a lot of money on copper wire.  There might be a single 3 phase transformer that you could get if you check the web.

Next, the charge controllers. When I got my H40 it came with a control box (to handle 3 phase AC to DC convert) and diversion load.  You may want to order a matching set (power handling) for yours.  I did use a C35 for my panels (even though there were terminals to add solar to the genny box).  I set my wind control box to "divert" power above what the C35 had for shutoff voltage so as not to divert the solar panels before the batteries were actually charged.  The wind controller had a much better voltage selector for diversion then the C35.  The C series of charge controllers are very good charge controllers as they will accept various DC inputs and divert if needed.  You can get panel meters for them which will keep track of amp hours from your array.

The solar panels.  When I built (in design phase) my system I realized that I might have to maintain the system by myself.  So in keeping with the thought of moving panels about - I decided on panels that were not too big (feel bulky to handle) and used 80 watt panels.  At about 2 by 4 foot I could get my hands on both sides and the weight was aournd 17 pounds each.  Also the cost per watt was around 3 (dollars - \$3 per Watt) which is much better then the smaller panels (\$10 per Watt).  The bigger panels are for grid tie applications to reduce the amount of wiring.   The bigger panels do have lower cost per Watt but not by much.  So I would still go with 80 to 120 (123 Watt panel on sale) panels that you can get your hands around.

18 Posts
Jul 17, 2008 04:24 pm
Re: First RE System is Planned

Oh, forgot to add that you may not be able to use the same charge controller for wind and solar.  You will need to fuse (or breaker) them each to the power they can put out.  My H40 required a 100 amp fuse and I had only 30-40 amps from solar panels so the breaker size used is 60 amp.

I did not comment on the rest of my system.  I use a Zantrex breaker box (DC250) for all breakers (try getting 200 amp fuse at night on Sunday), and a Prosine 2 inverter for 15 amp service.  The inverter will accept line power (in your case a genn set) and has built in transfer switch.  Two inverters will stack for 240 AC.  This is my setup, if you find those step transformers you could go for 24 volts but something tells me your gonna use a 48 volt inverter.

220 Posts
Jul 17, 2008 06:07 pm
Re: First RE System is Planned

eric

i was thinking about your system today and i believe i may have muddied the waters with the three phase comment. it should be made clear that a three phase run is in no way immune to ohms law and the closed loop calculations for wire resistance still stands. i have since downloaded the manual and it does indeed say to use an awg#8 wire run for your distance! i think we can all agree that that recommendation is ridiculous. i think they are just covering themselves for safety (amps). i like mikes transformer idea. the new whisper 200hv model is using that method.

if your unit does not have the whisper controller included consider using the c40. you will have to buy/build a bridge rectifier and a resistance dump load of some kind.

for that nice 1kw of solar you have planed i would start looking at the apollo or the outback mppt controllers. both of these are true open format controllers and will handle most any array you decide on going with. and yes everything should be fed into the one battery bank.
sorry for the confusion, all the best, dave

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