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Solar Electric - 6.5 kw system

Post in 'The Green Room' started by jebatty, Oct 24, 2013.

  1. jebatty

    jebatty Minister of Fire

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    Forgot ... no sales tax in MN too. There is a form to fill out when buying things for the solar system that you give to the seller to justify no sales tax. Since 99% of my system was sold to me and installed by the designer and contractor, sales tax was not an issue.

    My wife was gone yesterday visiting grandchildren, just me at home and I was out most of the day as well, so electric usage was down from normal, but never-the-less, sweeeet: production was 23kwh; total usage was 9kwh, of which 5kwh bought from the grid and 4kwh provided by solar; and solar sold back to the grid 19kwh.

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  2. peakbagger

    peakbagger Minister of Fire

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    Some general answers. Many folks get confused between W and Wh. W is the equivalent of mph, you are driving 70 mph, your solar panels are rated at 6600 W when illuminated with a specific light source. If you drive or run the panels for one hour you have gone 70 miles or have generated 6600 W for one hour (thus Wh) if the sun intensity is the same as the standard test condition (it rarely is). If the panels are tilted or the sun is at an angle to the panel you also have to do some trig. When you buy power you are buying kWhrs (Whrs divided by 1000). The daily output of a panel is for 24 hours and panels dont run at night plus the sun is rarely optimal and some days it is cloudy so the daily output varies. Thus a 6600 kW array could end up producing 2800 kWh.

    In order to estimate the average output for a particular place, the government long ago looked at sites all over the US and took long term data on how much sunlight is available on a yearly basis and that data is incorporated in some free sizing programs. The simplest on is PVWATTS. Plug in your location, panel info, angle of tilt and a few other items and it will calculate a yearly and monthly output.

    Cost for roof mounts which is the simplest way to do an install if you have a flat roof is around $3 to $4 a watt installed. Ideally you want the roof angle to be roughly your latitude. If your roof is complicated with lots of dormers and vent pipes or chimneys or at the wrong angle to the sun then you may want a pole mount. It costs more up front. A pole (or ground) mount can be slightly more efficient than a roof mount as it runs cooler and the tilt angle can be adjusted seasonally which increases the average output.

    If you want to be off the grid, the panels are the same but the wiring and equipment used is different. The fed rebate only applies to grid connected units. Some folks install a hybrid grid tied system that has battery backup and get the 30% rebate. Cost wise a rule of thumb is add at least 30% to the system cost for a hydrid system so the out of pocket cost is higher. I am not aware of any leasing companies that will support hybrid systems.

    A truly off grid system is generally 4 to 6 times the cost for grid power kWh. The initial cost is possibly 3 to 4 times more expensive with no rebates. Unfortunately for year round use the solar resource is lowest in winter when most folks want the most power. Usually off grid systems are designed for two to three days with no sun and then its generator time to recharge the batteries.

    Proper deep cycle batteries properly treated may last 10 to 12 years and have to be replaced at a high cost. Poorly specified or treated batteries may be scrap in 3 years. This is applicable to hybrid systems so having a hybrid system for "just in case" events rarely makes sense. There is recently an option by one company to have "emergency power" on a grid tied system that allows limited 120 volt power production when the sun is shining, its a fairly inexpensive option but requires a central inverter based system. Most leasing firms use microinverters as its easier to design and stock the parts in a warehouse. The cost per watt for microinverters is higher but the installation cost is lower.

    The most important thing to realize is that the technology and pricing is changing rapidly and any system installed today will be somewhat obsolete in a year. It still will pump out the power but it may be slightly less efficient or have cost a bit more than the latest and greatest. Its easy to put off the decision to install waiting for the next hyped improvement but they frequently don't pan out. Meanwhile the monthly power bills keep coming. The real driver is cost of money, with real rates on secure investments at 3% and super safe (bank or CDs) rates closer to zero, installing solar generates a long term basically guaranteed return. In new england with high power rates the payback is 5 to 7 years but local and state incentives can shift that significantly. Mass currently appear to be the best state in NE to install.
    Laszlo and Redbarn like this.
  3. jebatty

    jebatty Minister of Fire

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    November clouds can be really dense, along with snow. Total 3 kwh Sat-Sun, but 26 kwh on Friday. It all evens out.
  4. Brick (ware)House

    Brick (ware)House Member

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    Don't forget the tax benefit of the accelerated depreciation. The solar PV equipment is classified as 5 year property. Also, since you completed installation in 2013 you should be eligible for 50% bonus depreciation. Basically you will be able to deduct depreciation expense of 50% of 85% (100% less 1/2 of the 30% Federal Tax Credit) of the cost of the solar property on your 2013 return. You may want to make sure your accountant is familiar with the IRS regs for passive activity loses, proper qualification and documentation for the Investment Tax Credits, and the bonus depreciation rules.
    flyingcow and woodgeek like this.
  5. Brick (ware)House

    Brick (ware)House Member

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    Although the cost of solar PV is below grid parity with incentives in many places, it is still extremely difficult to cost effectively design a system to provide back up power when the grid is down.

    In addition, payback calculations need to take into consideration the practical implications of each utility's net metering rules. Be sure to review not only the letter of the law in your specific jurisdiction, but the net metering billing policy of your utility. Example: Missouri law specifies that any overproduction (kWh) in a billing cycle be rolled forward throughout a 12 month period. From a practical perspective, the utility companies have lobbied the public utility commission to allow for monthly settlement of overproduction at a predetermined avoided cost factor. Thus, for overproduction in any month I receive a $.02 per kWh credit to my monthly bill instead of being able to offset kWhs in the next month at a retail rate of $.10. This little surprise pushed my payback out a few years and there is nothing I can do about it.
  6. jebatty

    jebatty Minister of Fire

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    Other than the 30% tax credit, depreciation and the other tax benefits you mention apply only to business property, as best as I know. Thanks for the additional info.

    In MN I get a monthly retail rate credit, and I think annually a check if I actually over-produce for the year.
  7. jebatty

    jebatty Minister of Fire

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    November was cloudier than normal. PVWatts predicted my system would produce 489 kwh during a "normal" November, and actual production was 356 kwh. And December so far has barely seen the sun. The October launch of the solar system has been less than spectacular, but Mission Control predicts solar stellar success.

    I saw an interesting article predicting that by 2030, solar electric will be so pervasive that it will change the world with a new inexpensive energy revolution, just as cheap oil brought on the energy revolution from which we still benefit, albeit at ever increasing environmental and social costs. The quicker fossil fuels will remain fossil, the better.
    flyingcow likes this.
  8. woodgeek

    woodgeek Minister of Fire

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    link?
  9. jebatty

    jebatty Minister of Fire

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    I can't find it now, tried various searches when it wasn't where I thought. I'll continue trying. The article also dealt with vertical agriculture. Sorry.
  10. jebatty

    jebatty Minister of Fire

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  11. jebatty

    jebatty Minister of Fire

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    First issue appeared 3 days ago and was solved yesterday. The monitoring panel (CDD) which provides real-time status and output of each of the 26 panels reported a phantom panel, a 27th non-existent panel which it could not identify, along with an error code. The CDD has a local IP address and outputs via about 280' of buried ethernet to my computer. The 26 real panels were showing output, but one panel showed poor communication with the CDD. The solution was a reset of the CDD's acquisition of the panels and then reconfiguation, all of which is fairly straight forward but it took me awhile to discover the solution.

    I'm not overly surprised by the occurrence of the issue. 280' of Cat5e ethernet is close to the distance limit, plus it has been freaking cold. The CDD is installed in an exterior electrical box at the array, and it is fully subject to our typical temperature extremes, which were as low as -29F in the past week. I don't really know if it will make any difference, but I put a night light in the electrical box to add a little bit of heat.
  12. jebatty

    jebatty Minister of Fire

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    Yesterday was the first all day extremely clear, and cold, day so far in December. Temp never cleared 0F. Production was 20.2 kwh. Sun at noon is only 20* above the horizon right now, but soon will be climbing. Sunrise is about 7:55 am, and I get some morning shading from a stand of aspen trees. The sun first shines through the trees at about 8:30 am and the sun fully clears the trees at about 11:00 am. From that time to within 25 minutes of sunset the panels have no shading.
  13. peakbagger

    peakbagger Minister of Fire

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    Clear cold weather is a good time to check out design compromises on systems. Many designers put panels that are over the output rating of some microinverters (I.E a 250 watt input microinverter with a 200 watt AC output. Its fine during most of the year but when its clear and cold the microinverter clips the output as the panels are putting out more power than the rating. One of my central inverters has the same issue, there are 2150 watts nameplate input on 2KW inverter. Normally not an issue but when its clear and cold, its obviously clipping the output, while one of my other arrays with more headroom on the inverter is putting out well over the panel string rating. I have also seen on central inverters where the designer blew the low temp calculation and the inverter goes over voltage in the early AM when the sun first hits the panels on real cold day. Still nice to see the boost from the snow on the ground.
  14. flyingcow

    flyingcow Minister of Fire

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    Good thread guys. Just starting to look and get pricing for solar now. I've got a clear southern view. Thinking about building a big overhang type of rack for installation. Right over where we park the car next to the garage.(most of the time the garage is full of stuff to actually put the van in there). Basically a type of car port with photovoltaic's on the roof.
  15. flyingcow

    flyingcow Minister of Fire

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    How many sq/ft of panels for a 6.5 to 6.6kwh system?
  16. peakbagger

    peakbagger Minister of Fire

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    If you are in Northern Maine, its important to have the panels capable of changing angles as the winter sun angles are radically different. Your winter angle is ideally roughly 30 degrees off vertical and even then, snow will build up. If you cant make them movable then tilt that at your latitude, 47 degrees off vertical and plan to rake them off.

    I think American Solartechnics has panels for sale, they are 245 watt and 39" by 68" so you can do the math. Do note that you will have to do some string calculations and use a combiner box or multiple inverters for such a large system. They are good but not the best efficiency panels but unless you are limited on roof area most folks shop for $per kw.

    Before you do anything check with your utility and see if they offer net metering, You will overproduce in the summer and underproduce in the winter so unless they offer net metering it will have a long payback unless you have unusual summer loads
  17. flyingcow

    flyingcow Minister of Fire

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    I've already been talking with American Solartechnics, just a quick conversation with Tom at this point. He's been in the solar business before it was cool. I've got one of his storage tanks and his customer service has been very good. Easy to talk to. Plus I have a local electrician who has done a ton of solar and large windmills for yrs.

    I appreciate the info on tilt. Out daylight in the summer is long, but we pay for it in the winter. As time goes on we'll see how my design/plan works.

    I have a small windmill now and the power company allows net metering but only for 12 months. The windmill isn't that big so we've never produced more than we used. But i want to check with them on incentives/rebates/etc anyways.

    As i use and really like my Heat Pump, electric solar is something i wouldn't mind looking at for an investment.
  18. Vic99

    Vic99 Minister of Fire

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    I have 25 panels at 255 W each. Gets me 6.35 kW. Each panel weighs 40 lbs, for 1,000 lbs on the roof, plus a small amount more for racking.
  19. jebatty

    jebatty Minister of Fire

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    I have 26 Suniva 265 watt panels, each 65" x 39", arranged in two rows of 13 panels each. Determining the tilt angle is not necessarily one approach is best for all. My panels are tilted at at about 34* from horizontal to maximize summer production. Latitude where I live is nearly 47*N. Yes, I lose on winter production but Nov, Dec and sometimes into early Jan are very cloudy, so tilt to improve winter production is mostly a wasted effort, at least for half the winter.

    Plus, a tilt to improve winter production brings shading from distant trees and buildings into play. Noon sun here is 20* above the horizon. I get some morning shading to about 11:00 am but I have virtually no afternoon shading. And at 20* sun at noon, about 4 hours of pretty usable production, not too much to be gained.

    Best world would be a double axis tracker, but here again ice, snow and bitter cold take their toll on mechanical systems. A large array also is not easy to manually adjust for tilt, etc. Everything may be a compromise.
  20. peakbagger

    peakbagger Minister of Fire

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    Well if someone wants a tracker designed for cold and nasty weather this company makes one designed for VT http://www.allearthrenewables.com/products/solar/ they only sell through dealers. They appear to be very robust but pricey. They were designed to line up with VT feed in tariffs where the goal is to maximize production albeit at a higher initial cost.

    I wouldn't hesitate to install one if I wanted to maximize production year round like an off gridder but with net metering the object is to go the least up front cost and leverage the installation rebates.
  21. Vic99

    Vic99 Minister of Fire

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    "Determining the tilt angle is not necessarily one approach is best for all. My panels are tilted at at about 34* from horizontal to maximize summer production. Latitude where I live is nearly 47*N. Yes, I lose on winter production but Nov, Dec and sometimes into early Jan are very cloudy, so tilt to improve winter production is mostly a wasted effort, at least for half the winter."

    I agree, fortifying your worst months production does not make sense. Best to maximize when sun is more intense and out for longer. Small winter gain wont be noticeable.

    I, too, have Suniva panels.
  22. peakbagger

    peakbagger Minister of Fire

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    I personally do both, two arrays are manually tilted, it takes me the total of about 15 minutes start to finish to change the angle of both of them. One is pole mount and the other is hung off the front of the house and neither would take the snow load at the summer tilt angle. The new array is on a 3.5/12 pitch roof for maximum summer production. A lot of folks at southern latitudes forget that up north the summer sun rises north of east and sets near the north of west so having shallow angles extends the number of hours of daylight in the summer.

    The array hung off the house also works as a overhang to keep summer sun from heating up a room. Its shaded all day in the summer but at winter angle it lets the sun in. I didnt really plan on that advantage but it was a happy coincidence.
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  23. flyingcow

    flyingcow Minister of Fire

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    Good info. Thanks. Just figured my lat is 45.8. Like I stated before, if I do this the location is 100% unobstructed.
  24. flyingcow

    flyingcow Minister of Fire

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    Note to self.....it's 615am and still pitch dark out. No light on the eastern horizon.
  25. jebatty

    jebatty Minister of Fire

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    You're fortunate to have 100% unobstructed. Hopefully you also get some reflection off the snow on the ground. My location is as good as I could get. I will be noting the date when shading disappears. Within a few days morning sun will be earlier and shading will begin to diminish.

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