solar questions, plans for expansion

[maple flats]

I put this question out on a solar forum but they must be dead. I checked for answers after a week and the entire forum has no entries except my question and one additional reply to further define the question in the past week. I know the FF is much more active every minute of the day than they are in 7 days. So my question is:
I now have 300 watts solar, pole mounted 250' from the rest of the system. Overhead wires carry 24V to my sugarhouse where it goes thru a PWM charge controller, to a 4 battery bank of Trojan T 125's wired in series for a 24V bank. Power then goes to a modified sine wave inverter producing 240V power for use. It turned out the inverter had no neutral and was only for 240V appliances such as a 240V motor. I had to get a transformer to have 120 power.
I now want to expand and design my system with proper planning rather than knee jerk planning. I will be building a home on site that will be about 140' from the array but for now everything will be in the sugarhouse and distributed from there.
I plan to add 600 watts more of the same panel I have, 4 more batteries (the old ones have only been used 6 months) for a 8 battery 48V bank. The panels will be wired in 48V strings for better power transfer over the 250'. (my wire between is 2Ga aluminum triplex like what would be used to bring utility power into a home) I want to get a MPPT charge controller such as a Outback Flexmax 80. I also want to get a pure sine wave inverter of at least 4000 watts, preferably 4500 watts that is 48VDC to 120 VAC that would eventually be stacked for 240VAC at some point in the future. I have 2 generators that are 5500 and 6000 watt, a gas and a diesel that make 240 if needed. I plan to make a gasifier to fuel the gas one from my mill slabs (chipped) for charging as needed when the sun won't do it. Eventually I will have about 3000 watts solar and when the house is built I will get a new battery bank of the proper size that the equipment I get now will be used together. For now I am just adding as I can afford and I think I will never be grid connected so I get no incentives and I need to replace batteries as needed. On the batteries I am looking at info on a nickel Iron battery invented by Thomas Edison that has a 50yr plus life with no damage from deep or even complete discharge and only needs a change of electrolyte every 15 yrs or so. In fact some of these batteries are still in use after 100 yrs. For now my power use is mainly a 5th wheel camper on site for seasonal use except I use every bit of power I can during my 4-6 week maple season until the batteries need to be recharged at which time I start the generator and use that. The few hours of silent power is golden while I can use it.
Can anyone make any system suggestions., FDH maybe, you were in the business at one time? Thanks for any design help

[WH_Conley]

Member ThomasinKentucky has built quite a solar system, Knowing Thomas personally, it is very well researched. I don't think he mind a posting to his blog.

http://massiehouse.blogspot.com/2009/10/finally-up-to-75-kw-of-solar.html

There are several posting about his solar experience, you will just have read through.

[Gary_C]

Wow! Perhaps the reason for no responses is you seem to have a better grasp of this stuff than anyone else. 

I have a limited knowledge of a similar type of solar system in a fifth wheel camper that I just bought last year. It has solar panels on the roof with a solar controller that charges four 6V batteries feeding the 12V system in the camper and also feeding a large inverter for 120 V. I don't remember the sizes of the equipment and the camper is sitting at a job site away from here.

I've not really used the solar system yet as I have had power available where I am located. But I've had trouble with the system. The dealer I bought it from had to replace the dead inverter at a cost to him of $2400. And then when I started using the camper last winter the batteries were all froze up and dead. Turns out two of the connector cables between batteries were corroded and open and thus the batteries were not being maintained and were junk. And as you probably know they are about $125 each.

The only thing I could tell you is that distance is your enemy for those low voltage solar systems. So you should consider either having the solar panels on the home or at least have the batteries next to the solar panels. You cannot stand losses even in large cables.

The other thing is to consider using the highest efficiency lighting available which may be LED. Not sure about price right now as it may still be very expensive but there are some good lighting available in low voltage RV lighting.

I do know there are some complete packages available from Cummins/Onan with generator-batteries-inverter that run automatically. Not sure if they have provisions for solar systems for charging. It seems like the most difficult thing will be to get all systems working together with out conflicts that blow up any one component. 

[maple flats]

Solar panels on the roof will not be an option because the home will be in the woods and I WILL NOT remove those shade trees. Voltage drop is why I am going to 48VDC. Right now I lose about 3-4% of my energy in the cable according to my readings and a good meter. Going to 48V I should be able to get that down to 2% or less, I am currently at 24VDC. When I build the house the shorter distance will help reduce loss too. My current layout was installed with consultation from a solar engineer, but he only helped make what I had work. He never suggested getting the inefficient equipment I have. That engineer is on a solar forum but I am getting no activity there. The whole Off the grid section of the forum has no entries except mine for a week. I am ready to buy what I need now, I just need some help knowing which specific equipment is best for my needs and plans.

[WH_Conley]

Could put a solar "farm" out away from the house with the inverter and cable the high voltage to the house? Disclaimer, I am just guessing, I know nothing about this stuff.

[maple flats]

There a couple of reasons not to put batteries at the array. Main one is warm batteries do better than cold. A shed would need to be built to house the batteries and equipment. I choose not to have another structure out there. Even a shed would not keep batteries warm so the temp would need to be calculated and extra panels and batteries would be needed to handle the needs. I also want to have it more convenient to monitor the status of everything.

[Fla._Deadheader]

www.fieldlines.com  Solar Board. Several guys in the business. Very helpful.

[Radar67]

If you are looking for kits, backwoodssolar.com is a good company.

[JSNH]

I have added a grid tie solar similar in size to what you want. Look at everthing, Look at the Massie blog. My neighbor has been off grid for years he went from a small 12 volt to a moderate 24 volt to now a good sized 48 volt system. 48 is the right choice. Much less line loss and just works great.

I have 1600 watts of solar going to a MX60 outback charge controller works great. Another 1400 watts on order. I have a single gvfx3648 inverter works like a dream. The Outback is well designed and stackable. A design you can grow into.

My pannels I purchased from Sun Electric
http://sunelec.com/

delivered at under $2 a watt.
 I plan on adding more solar and another inverter. The back up feature for me was a selling point and I like the gridtie option I have with my utility.

JSNH

[Gary_C]

I plan on adding more solar and another inverter. The back up feature for me was a selling point and I like the gridtie option I have with my utility.

JSNH

Can you parallel multiple inverters or will they interfer with each other?

[JSNH]

Yes. The outback off grid can be stacked. You can stack two per leg to up the wattage from 3,600 to 7,200. you can also run the inverters for 220 volts parallel of even do 3 phase with 3 of the inverter and can stack those too. Tom Massie has four inverters and they are set for 220 and stacked for 7,200 watts per leg of 110.

[Gary_C]

Solar panels on the roof will not be an option because the home will be in the woods and I WILL NOT remove those shade trees.

You should talk to your insurance company first. Some insurance policies are now requiring "defendable space" around homes in the woods. It may depend on what part of the country you are located.

[maple flats]

Thanks for the defendable space warning, I'll run it past my agent.
Update on my solar progress. I bought a Flexmax 80 Outback charge controller (far more efficient than my current one and good for up to 4000 watts at 48 V battery bank and 5000 on a 60V bank) and have some small parts coming to complete the installation. I still need to order some more batteries and solar panels AND decide which inverter to get. It will be a pure sine wave inverter but am toying between a Outback VFX 3648 (3600 watt, 48V input/120v out) and a Xantrex XW 6048 (6000 watt, 48V input/120/240 output). Both units are stackable if needed (more units can be added that will syncronize for 240V [from 120] as well as more wattage. I am leaning towards the VFX 3648 but not sure. I have questions out on a solar forum to help decide. I hope to order everything within the next week or 2. After this my next hope is to make a gasifier to power a gas generator using my slabs to help charge the batteries as needed and power heavier loads from time to time..

[Thomas-in-Kentucky]

Good choice on the MPPT.  I have the 60 amp version... the 80 amp version wasn't out when I bought mine.  You can wire your panels for over 100 volts at the array to really cut down on the line loss from your panels to your house.  The MPPT will step it all down to 48 volts for your batteries.

ONE big thing to keep in mind when deciding between the outback and Brand X...  when the genny kicks on, the outback inverters go into battery charger mode (they no longer work as inverters), and shoot the output of your genny straight to your house.   I believe the Xantrex can work as an inverter and a battery charger at the same time and sync up with the genny to "assist" when the loads are too great for the genny alone.  The implications are not at first obvious... but if you have a small genny, and big loads in your house, it would be nice to be able to do what the Xantrex can do.  I own the Outback inverters and I love them, but they lack that feature and I miss it.

One other thing...  you will probably want two outback inverters if your generator is a 240v generator.  Otherwise, you are always trying to charge your batteries with only one leg of the generator.  Not only do you get less out of the genny, but it's bad for the life of the genny.  There is a work-around... a big honkin transformer that will take the two legs of your generator and feed them at 120 volts to your single inverter.  Outback sells the big honkin transformer if you decide to got hat route.

I'd be glad to share my experiences with my own system... or another smaller system that I installed for a guy near here.

where are you in the system build right now?

[maple flats]

Update. I have everything needed to do my solar install as far as equipment and major supplies. I bought 4 Kyocera 185 watt panels (to start) that will be run in series for 96V into the charge controller at 240' away. I bought an Outback FX 80 MPPT charge controller, capable of 5000 watts at the 48v my battery bank will be. This controller is field programmed to charge any voltage from 12-60 in 12v incriments, but whichever voltage you use can only be up to 80 amps max. The input voltage can be anything from 12-150V. For now I will use 96V but may buy 6 panels next year as I expand and go to 120V in, changing my 96 to 120 and wiring the second string to 120 in series. The panels are 185 watts at 24V nominal, but can at times produce 30V (5x30=the 150v max). Then in the sugarhouse after the charge controller, I feed the battery bank, consisting of a string of 8x6v in series. For now I will only have 1 such string. When I start to use more power, I will buy all new batteries in 2v (Rolls Surrette) with 24 in series to be my final size bank. These batteries will feed my inverter, a Xantrex 6048, which can feed up to 6000 watts continuous at 240v at a pure sinewave power curve (grid quality power). I have not decided yet, but for now I will be off grid, at some point in the future I may go grid tied to use the net metering and utilize the tax credits. This inverter can be run as either, and it can even use generator power and still match it to the grid and feed the grid. This would not normally be done because I could not usually run a generator cheaper that the grid power, but I have future plans to build a gasifier to run one of my generators. This would be fired with either wood scrap in nugget form or wood chips thru the gasifier. Just for giggles I could run the gassifier I could to run my meter backwards to make sure I ended at net zero or even get a little check on each anniversary of connecting with net metering. I would not try to get more that a little check because after the net meter zeroes at each anniversary, the utility no longer is required to buy my power at retail, at that point they start paying at their cost, which is very low and would never be worth the time or effort.
The last of my ground mount racking just arrived a few days ago.
This last week I started clearing the array site which had the remains from several trees that were dropped last year. I had a hired man who I discovered had not removed and processed the brush or limb wood. It was all supposed to become sugarhouse wood for my maple syrup operation. The weeds had covered it. Now cleaning up is more time consuming. At this point I have the area about 75% done and another couple of hours will finish it. Then I will dig two rows of 3 holes each for sono tubes to be poured with concrete to mount the racking for my panels. AS I buy more panels each year, I will expand the mount racking and attach the panels. I already bought enough racking for up to 4,625 watts which will be my final size. (5 strings x 5 panels x 185 watts each)
In off grid mode the inverter can recharge the batteries via the generator if needed too.
I will be starting the concrete next weekend.

[maple flats]

After working on many other projects, I now have turned on my solar system. I now run 4 x 185 watts in series, thru 240' of overhead entrance cable (just like most use into the house from the grid) Upon entering the sugarhouse it goes thru a FX80 Outback charge controller to the battery bank. From there to the XW6048 inverter charger and then to my entrance panel. There are fuses/breakers and disconnects as needed. Then the generator cable feed into the inverter too. When the generator is running the wave forem/cycles of the inverter match the generator's, while the generator also charges the batteries. I have lots of room for solar expansion with the equipment I bought and installed. This controller at 48V will run 5000 watts of solar, and the inverter is rated 6000 watts, 240V from the 48V battery bank. Someday I plan to make a wood gassifier to supplement the solar by running a generator. Life is good!!

[maple flats]

Yesterday I discovered something I thought rather interesting. I was at the sugarhouse and I looked at the charge controller. It was charging the batteries. The surprising thing was that there was about an inch of light fluffy snow on the solar panels and while it was daytime, the sun was overcast,barely make out where the sun was. But it was still charging. Had I needed more power I surely would have needed to brush off the panels but none the less, this pleasantly surprised me.

[pineywoods]

Maple flats, there's a sound reason why the solar panels were still charging the batteries. Visible sunlight is not what makes the panels produce electricity. They are sensitive to either infrared or ultra violet radiation, neither of which is visible to the eye. Some of the better panels convert both types, thus are considerably more efficient. I have trouble convincing folks that my solar kiln will heat up nicely on an overcast day..same reason..

[maple flats]

I never thought of that. I do like seeing the charge controller working though. Now I've got to take some time to run the rest of the system. I just can't break free from expanding my maple operation to do it. It will happen sooner or later.

[OlJarhead]

Just did a system late last summer  

615 watts of solar 50 feet from cabin (205 watt panels @18vdc in series to give 54vdc to allow 10awg wire to cabin)
6ea 6v 220 ah batteries (Golf Cart Batteries actually) in series parallel to give 12vdc and 660ah
2500 watt Modified Sine Wave Inverter (5000watt peak)
Zantrex C40 Charge Controller
Iota 750 watt charger (for generator charging)
Midnight solar disco box and Midnight solar Panel Box
Lightning arrestor.

Comments:  Not sure why you are using 48vdc though I know folks are doing that more these days.  Truth is you can get very inexpensive 12vdc inverters (mine was $200) that will provide lots of power.  The 12vdc is fine as long as you don't plan on running it over great distances and the bank voltage is separate from the panel voltage these days -- so panels can be much higher voltages to reduce wire size.  In your case you need some big honking wires to get that power to the batteries!  Like 2-0 or bigger I'm thinking.  Running 10awg past 50 feet requires voltages above 48 -- I think above 60 even.  Heck I'm not sure you could run 150 feet with 120 volts on 10awg wire.

The reason I mention wire size (besides the loss you'd get if you are running something that small) is the cost of running 300 feet of wire (150feet twice) to get the panel voltage back to the charge controller.  Anyway, I'd run all 4 panels (if that is what you're doing) to get around 60+ volts and push that into a Xantrex C40 which you can then use to charge the 12/24/48vdc bank (your choice in that case).

I personally like 12vdc because I'm not running any DC stuff except a small fan in a compost toilet and maybe a car stereo and CB in the future -- makes wiring a sinch