1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

Got Solar Quotes and Have a Couple of Generic Questions...

Post in 'The Green Room' started by velvetfoot, Jun 21, 2012.

  1. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,536
    Loc:
    Sand Lake, NY
    I got 2 quotes yesterday; one for 6kW PV and the other for a Velux domestic hot water system - not sure of the quality of the quotes since they did it over the phone with Google maps, but whatever-it's a start.

    I know there was a thread lately about solar thermal being dead, but that kind of assumed a heat pump water heater, which I don't think will work out for me. Would using solar for hot water still be practical in the northeast for a southeast facing roof?

    The numbers I'm sure are flakey, but they claim $2,500 after incentives and tax breaks for the hot water, and $7,200 for the PV. If the numbers are not that crazy off, is this tipping in the direction of PV?

    For PV, I'd probably have to put in a electric water heater, since I don't use that much electricity (I'd prefer to cover the roof just for looks), and I'm trying to displace oil The Velux system comes with a tank that has an electric element.

    It's seems crazy not to take advantage of the incentives, especially since I'm paying for them for everybody else through my electric bills and taxes, and who knows how long they'll be around.

    Maybe thermal now and pv later

    Wadya think?

    Helpful Sponsor Ads!





  2. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    47,003
    Loc:
    South Puget Sound, WA
    $1.20/watt installed for the PV? That sounds too good. Something seems to be missing.
  3. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,536
    Loc:
    Sand Lake, NY
    $4.20 per watt installed = 25,700
    -ny state rebate -9,180
    -fed tax credit -4,957
    -state tax credit -4,131
    final cost after incent. 7, 435
  4. woodgeek

    woodgeek Minister of Fire

    Joined:
    Jan 27, 2008
    Messages:
    2,608
    Loc:
    SE PA
    Gotta crunch the numbers....how are you getting your DHW now? If its oil-tankless coil, and you can shut down the unit in the summer (many can't be) if you have another source, then an electric tank will be cheaper to run. oil vs electric BTUs are pretty comparable (1 gallon of oil at 80% delivers the same BTUs as 32 kWh at 100%), but with a tankless coil you can burn three BTU for every one you deliver to a tap in DHW, which pretty much makes it a no-brainer. If you have an indirect tank with a condensing boiler, then you can compare 1 gallon oil vs 32 kWh, for price per DHW BTU.

    So, that's option 1: straight elec tank, like a Marathon.

    Option 2 is solar DHW: I looked into this and rejected it: the main reason, low 'solar fraction'. In the NE, we get a bundle of sun each year, but only a tiny fraction of it in the winter. So, any solar DHW will fall short in the winter, and might make too much in the summer (which needs to be dumped). On an annual basis, it can be hard to get more than 60% of your DHW BTUs from the sun, the rest you are buying from the elec co, see above. The 60% figure can be improved by oversizing, but that will affect payback. The worry is that some studies have shown many residential installs delivering <20% solar fraction due to bad design or improper controller settings!! That's like buying a Prius with the MPG of a hummer. Again, it comes to lack of owner awareness....if the solar harvest and water usage are not being tracked by most customers, then there is no check in the system. Bottom line: don't figure a 'zero operating cost' for solar, figure it being 50% of the operating cost of option #1, to be conservative.

    Another concern with solar is a site survey....many incentives require a >80% resource (i.e. <20% shading).

    Option #3 is HPWH: IMO a lot of misinformation and skepticism out there on this technology (which I opted for in the end). Folks in the north are worried about heat stealing, but not doing the calculation correctly. If the unit is delivering X BTUs at COP=2, is not sucking X BTUs from the living space...it is sucking X/2, with the rest coming from the electrical work done by the compressor. Installed in a semi-conditioned space, it will be even less than that. If your space heating BTUs are cheaper than resistance heat BTUs (wood) no worries, you are still saving money net over conventional elec DHW. If your space heat BTUs are comparable (oil) then you are still breaking even in the winter, but you are saving in the summer and shoulders. IF you don't have a utility/semi-conditioned space, then of course, this option is off the table. Bottom line: figure an operating cost which is 45% of elec if your space heating is from wood, or 60% of conventional elec otherwise.
  5. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,536
    Loc:
    Sand Lake, NY
    You touch on why PV could be attractive because of the way the net metering works here. Far as I know, they reconcile it at the end of the year. So, when you generate more kwhs in the summer and, of course, day, vs. night, it all gets squared away at the end. Then, you'd be heating the water with PV, with the utility acting as storage.

    What I'm leary about is putting the panels on my exposed fastener (Fabral) metal roof. I've read that Fabral markets solar panels for that roof system, but don't know if the brackets can be bought separately, or made. I don't want any more penetrations in roof. Just a little nervous about the whole roof situation. It's about 7 years old, in good shape, but we get snow here, etc. Then again, plenty of other people do it.
  6. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    47,003
    Loc:
    South Puget Sound, WA
    Wow, that state rebate is unreal. I'd be on it in a NY minute! ;)
  7. woodgeek

    woodgeek Minister of Fire

    Joined:
    Jan 27, 2008
    Messages:
    2,608
    Loc:
    SE PA
    Exactly, the gist of the 'thermal is dead' is that grid-tie allows you to 'store' your solar harvest on seasonal time scales. In solar thermal, you are dead in the winter, and have to run conventional and that hurts your ROI. You can then pile on by saying the PV is lower maintenance, cleaner install, etc.
  8. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,536
    Loc:
    Sand Lake, NY
    Yep.

    One thing that concerns me is how they would install it on my metal roof.
    It has ridges - Maybe a spacer screwed on to space it above the ridge?
  9. woodgeek

    woodgeek Minister of Fire

    Joined:
    Jan 27, 2008
    Messages:
    2,608
    Loc:
    SE PA
    I'm clueless on this point....but I thought that metal rooves were well suited to solar...clips on the standing seams??
  10. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,536
    Loc:
    Sand Lake, NY
    After doing some reading, it seems that the Fabral system is, I believe, flexible amorphous type, that is glued in the trough of a standing seam room. Alas, with the exposed fastener system (read, cheaper) I have, they do something where they bridge the high points or something like that. Not sold separately.

    I'm not sure my site is good for this stuff-trees and facing southeast.
  11. woodgeek

    woodgeek Minister of Fire

    Joined:
    Jan 27, 2008
    Messages:
    2,608
    Loc:
    SE PA
    The stick on thin film units are made by a co that is currently in bankruptcy....and there have been many warranty claims re loss of performance. Caveat emptor.
  12. peakbagger

    peakbagger Minister of Fire

    Joined:
    Jul 11, 2008
    Messages:
    1,595
    Loc:
    Northern NH
    You may want to check the Arizona Wind and Sun Forum about fasteners. If you have distinct standing seams, there are definitely clip systems that clamp on over the seam. If the profile of the seams is not straight its a lot trickier, the normal method of attachement involves lagging a mount through the roof to a rafter and hoping that the some sort of resilient waterproofing lasts 20 years. This is major issue with solar installs, the majority of solar contractors are on a tight margin and they really arent that skilled or interested in a 20 year roof penetration, all they want to do is get the system installed and paid. You could get a roofer to install the mounting posts but that costs more.

    I am not sure on the NY rules but in NH, there has to be a on site audit of the solar potential prior to the state committing to a rebate. Its a good idea as a solar system with partial shade is not worth much. You will get lots of production in the summer as generally the sun is high enough to clear any trees but you need quite distance between your roof and any trees to the south in the winter. a SE exposure also limtis your production.

    Flat panel SHW is great for a wood burner that has a way of heating water during the winter but the rules of thumb is that the SHW only heats up the water 80 degrees over ambient temps, during the summer at 70 F thats 150 degrees but in the winter at 30 deg F all you get is 100 deg F. THis works great for me in NH as it allows me to turn off the oil boiler from april to october and then swtich over to wood using the SHW as a preheat for my well water. Evac tubes cost a lot more but will give you higher temps in the winter, the rules of thumb is 130 to 160 deg F over ambient. They are a PITA in the summer as you have to dump the heat somehow as if you dont, the glyclol breaks down quickly.

    A good site survey takes about a half hour with someone who knows what they are doing. Bascially they need to get up to roof level and take a digital picture with a specialized piece of equipment. If you have access to a transit you can get a good idea by setting up and taking a sweep from east to west at 10 degree increments and determine the vertical angle of the highest object thats blocking your sun. From there you can go to the US naval observatory website and look up the suns angle for winter and summer for your latitude and longitude. If the suns angle is lower than the angle of obstructions from about 9 to 3 pm at anytime in the summer then you have a big potential for loss of generation and if you have blocking from 10 to 2 in the winter, then you need to get into a lot of detail.

    By the way, dont even consider the stick on panels. They degrade quickly and look like crap eventually.
  13. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    47,003
    Loc:
    South Puget Sound, WA
  14. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,536
    Loc:
    Sand Lake, NY
    Thanks very much for the info guys. My site might not be at all appropriate. I attached a photo - up is north.
    The S5 system needs a seam, but one of the Orion systems might have some potential, but if they have to drill holes to try to find a rafter, that wouldn't be good either. house Capture.JPG
  15. woodgeek

    woodgeek Minister of Fire

    Joined:
    Jan 27, 2008
    Messages:
    2,608
    Loc:
    SE PA
    pole mount in the back yard? With a tracker. Neighbors aren't going to complain!
  16. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,536
    Loc:
    Sand Lake, NY
    Back yard is septic field, but I think the right side is unused spare.
  17. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    47,003
    Loc:
    South Puget Sound, WA
    Can you put it over the septic field?. I visited a local system where they did what they did that.
  18. velvetfoot

    velvetfoot Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    6,536
    Loc:
    Sand Lake, NY
    I don't know. Was that one you saw on a pole or on a frame of some sort?
  19. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    47,003
    Loc:
    South Puget Sound, WA
    The system I saw was 5KW? in two racks, frame mounted on poured concrete piers. Here's a shot of it.

    MackeyGroundMount004.jpg
  20. pdf27

    pdf27 Member

    Joined:
    Feb 14, 2012
    Messages:
    143
    Loc:
    UK
    Just another note on ground mounting - you can get the orientation better (a quick look at PVWATTS for Albany and a few guesses about your roof suggests about 6% more annual generation). There are also small effects from the better cooling of the panels (close to the roof they can get very hot indeed, which reduces efficiency) and from the fact that you can actually clean dust/bird lime/snow off ground mounted panels, unlike on the roof. That might be worth as much as 10% more annual generation, which is enough to pay for a reasonably substantial frame. Looking at it, the frame could probably be made very cheaply - see http://www.builditsolarblog.com/2010/08/nice-simple-pv-panel-ground-mount.html for an example.

    Few other points to consider:
    - Solar PV can cause fairly large voltages to be generated, so you may have extra costs involved in suitable electrical insulation.
    - The panels are more vulnerable to damage from e.g. stones thrown by mowers at ground level.
    - If you're considering selling the house in the forseeable future, the potential buyers may find the roof penetrations for a solar system a turn-off. This is a bit of a theoretical risk, but a ground mounted system avoids this.
    - Watch out for the height of the trees around the septic field - if they shade substantial areas for part or all of the day, this may limit where you can site it. Same applies to the house.
    - There has been a lot of squabbling about fire risks of roof-mounted systems over in the UK (the risk essentially being that if there's a fire during the day, the firemen can't isolate the electricity to the house so easily, particularly if the fire is in the roof and so won't use water). I'm not sure if this has been resolved - or was ever a problem in the US - but that's another thing ground mounts save you the risk of.
  21. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    47,003
    Loc:
    South Puget Sound, WA
    Very good points pdf27. I am considering raising our rack mounted array. Weedeaters can toss small stones at high velocity too. Don't ask how I know.:(
  22. peakbagger

    peakbagger Minister of Fire

    Joined:
    Jul 11, 2008
    Messages:
    1,595
    Loc:
    Northern NH
    During mowing season, the panels will be angled up at 60 degrees from vertical, so they tend to be out of the line of direct fire. In theory a pole mount could be installed in a leach field but I expect a inspector would nto approve it asits out of the ordinary. As long as you miss the laterals all you are going to hit is a layer of hay or geotextile and then washed gravel. It is an issue in wintter and they would be angled down to 30 degrees. Do note that in winter the snow slides down the panels and piles up in front, if you are not carefull the bottom of the panels could get covered and that basically shuts down the array. I run my snowblower in frotn of mine every few storms as it makes it easier to remove snow off the panels if it builds up.

    One note about going tall with a pole mount. Make sure that the concrete base is sized for the higher heigth along with making sure the pole diameter is adequate. The stress on the colum and the base goes way up the taller it is.
  23. Bob Rohr

    Bob Rohr Minister of Fire

    Joined:
    Jan 9, 2008
    Messages:
    744
    Loc:
    SW Missouri
    Solar Checker is a free ap for your phone. Position the phone on the roof or in the yard and get the output, yield and return.

    Also consider ground screws for any yard mounting. This job is in up-state NY.

    Attached Files:

  24. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    47,003
    Loc:
    South Puget Sound, WA
    Neat rig. How well do those ground screw work in rocky soil? We have glacial till here and full of rocks in some places.
  25. Jags

    Jags Moderate Moderator Staff Member

    Joined:
    Aug 2, 2006
    Messages:
    14,893
    Loc:
    Northern IL
    Okay, now I want that giant green screwdriver. Could you elaborate on ground screws??

Share This Page