Rechecking current state of art...

Gooserider
Gooserider Solar Expert Posts: 48 ✭
in General Solar Power Topics #1
We live in New England, just north of Boston. Our contemporary style house has a 12/12 pitch roof, which faces south, or close to it. (see photos)

Last time I checked, about a year ago, typical installed solar prices (after gov't rebates) were on the order of $3-4 / watt for grid tied, which translated to about a 10-12 year payback... Up front cost was quite high as well.

OTOH, one could do glazed solar hot water, and use it for heating the house in the winter (partly) DHW, and use the excess production in the summer time for heating our 16Kgal in ground swimming pool (currently not heated at all, so ANY heat input to it would help)

Upfront cost was considerably lower (about half), and payback looked to be in the 3-5 year range.

Another possible advantage to doing hot water, is that I've noticed a fair amount of intermittent shading - that chimney casts a shadow over much of the roof in the afternoon, and there are also some tall trees that get into the act. While I agree that no shading is good, my understanding is that solar water doesn't get as much of a hit from partial shade as solar electric does.

Have prices changed very much over the past year or so, or are my numbers still reasonably accurate?

In addition, If I wanted to get really greedy :roll: and maximize my solar collection area, how feasible is it to extend panels up past the peak of the roof?

Thanks,

Gooserider
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Rechecking current state of art...

    as to the solar hot water, you are right that it's not as prone to as much degradation as pvs are and you can get to use the sun more efficiently using the heat as compared to generating electricity over the same area. i can't say for sure what prices will be after rebates as rebates do vary from one place to the next and not everybody can get a rebate.
    as to your roof, that you had better ask a professional roofer or some other construction expert for pvs not only add weight, but also a wind load. to extend the roof is a possibility if engineered by a professional and inspected. even if you live where there's no inspectors, find somebody to inspect the work done and make the final payment contingient on it passing inspection. get a warranty for the roof work from somebody that has been in business for awhile and you can see them staying in business as many do foldup voiding a warranty.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
    Re: Rechecking current state of art...

    The first thing I would consider is look to add roof insulation. From the looks of your pictures it would seem that your snow is melting considerably faster over the heated space. It looks like you may have a vaulted ceiling which would make adding insulation difficult,, but you could add rigid foam on top of the existing roof, and cover it with standing seam steel roof,,, a good base for solar,, both PV and DHW/Space heat.

    As we say all too often,, every dollar spent on conservation will pay back with a ten fold reduction of solar cost.

    Tony
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  • Gooserider
    Gooserider Solar Expert Posts: 48 ✭
    #4
    Rechecking current state of art...
    icarus wrote: »
    The first thing I would consider is look to add roof insulation. From the looks of your pictures it would seem that your snow is melting considerably faster over the heated space. It looks like you may have a vaulted ceiling which would make adding insulation difficult,, but you could add rigid foam on top of the existing roof, and cover it with standing seam steel roof,,, a good base for solar,, both PV and DHW/Space heat.

    As we say all too often,, every dollar spent on conservation will pay back with a ten fold reduction of solar cost.

    Tony

    The house is divided into roughly thirds... The part closest to the chimney is a cathedral ceiling (24' high! :cry:) running over roughly to where that vent stack sticks up. The rest is attic space w/ cellulose in the floor, but nothing under the rafters. We are considering putting in more insulation (we have an extensive list of things we want to fix, now that the mortgage goes away in a couple months 8) ) Most of the snow melt (other than around the chimney, which has a wood stove running 24/7) seems to be along the rafters for whatever that's worth...

    I know metal roofs are nice, OTOH, the idea of a 12/12 pitch metal roof is scary, as we've had avalanche problems even with the current shingles, not to mention the challenge of getting around on something that steep and slick...


    niel wrote: »
    as to the solar hot water, you are right that it's not as prone to as much degradation as pvs are and you can get to use the sun more efficiently using the heat as compared to generating electricity over the same area. i can't say for sure what prices will be after rebates as rebates do vary from one place to the next and not everybody can get a rebate.
    as to your roof, that you had better ask a professional roofer or some other construction expert for pvs not only add weight, but also a wind load. to extend the roof is a possibility if engineered by a professional and inspected. even if you live where there's no inspectors, find somebody to inspect the work done and make the final payment contingient on it passing inspection. get a warranty for the roof work from somebody that has been in business for awhile and you can see them staying in business as many do foldup voiding a warranty.

    No, we will almost certainly have to get inspected - this is MA, where they want to charge you for EVERYTHING, and often insist that you pay to have the work done by incompetents with peices of paper, as opposed to doing it right yourself...

    Assuming I didn't try to extend the roof, how likely is it that adding panels would be a problem? IIRC, the rafters are 2x8 on 16" centers, but the roof has two layers of shingles on it (replacing them would hurt, as we did 25 year shingles about 10-12 years ago, so they are still in good shape...)

    Mostly I was wondering if any of the potential price lowering "breakthroughs" we keep hearing about have actually happenned yet, or if prices are about the same as they were a year or two ago.

    Thanks

    Gooserider
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #5
    Re: Rechecking current state of art...

    Look into adding insulation in the attic sections that are accessible. Your dividends are great and the payback is quick.

    Steel roofs can handle snow sliding issues by using snow breaks and good installation techniques. I understand navigating a 12/12 especially with steel,,, but even that can be over come.

    Good luck,

    T
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Rechecking current state of art...

    gooserider,
    do you mean the 'breakthrough' hype like in this thread?

    http://forum.solar-electric.com/showthread.php?t=1915&highlight=nanosolar&page=4
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  • Gooserider
    Gooserider Solar Expert Posts: 48 ✭
    #7
    Re: Rechecking current state of art...
    niel wrote: »
    gooserider,
    do you mean the 'breakthrough' hype like in this thread?

    http://forum.solar-electric.com/showthread.php?t=1915&highlight=nanosolar&page=4

    Them, among others... Or even an improvement in production of current design panels, or what ever else that would lead to a lower dollar cost per installed watt...

    IOW, without worrying all that much about the tech behind it, if I walk into my local / virtual solar store, am I going to see price tags that are higher, lower, or about the same as a year or two ago?

    Gooserider
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #8
    Re: Rechecking current state of art...

    From what I have seen--Solar PV grid tied systems are significantly going down in price at this time... My 3kW rated GT system (3,500 watts of solar panels) was about $28,000 (before rebates) ~4 years ago. Now--I heard a generic quote of ~$20,000.

    The majority of the price reduction, I would guess, is due to solar panels collapsing in price (cheaper production, over supply) and probably installers cutting their "profit" in this slow economy.

    I would guess that those $1.00 per watt systems (thin film panels) may cause you some issues though--from what little I have seen, they are less efficient than mono/poly crystalline panels at collecting power... So your installation will require more space and probably more structure to hold the panels (roughly $1.00 per watt for crystalline panels).

    Lastly--you may wish to re-roof the 15 year old section of your roof where your panels would be mounted. The solar panels should last well over 25 years--I would hate to have to pull the panels just to re-roof... Basically, paying to reinstall your solar system again.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #9
    Re: Rechecking current state of art...
    Gooserider wrote: »
    but the roof has two layers of shingles on it (replacing them would hurt, as we did 25 year shingles about 10-12 years ago, so they are still in good shape...)
    Gooserider

    No matter what you do, this is a problem. With the second layer, you have reduced you roof load limit.
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  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    #10
    Re: Rechecking current state of art...

    Having a pool helps with your solar HW option, it gives you a place to dump all the excess heat that is produced during warm weather when the heating system is not required. It sure is a waste to have to pay for electric with dump zones in warm weather to keep the solar HW system from overheating.
    What type of heating system do you have now?
    Do you have radiant floor heating in the house? If so then you can easily tie into the HW system for space heating. If not then it will be more complicated to use the lower temperature solar HW to heat the house but it can be done.
    As was stated in some of the other posts having 2 layers of shingles adds a lot of weight to the roof, and solar HW panels are heavy, a 4'x8" panel is about 100#.
    The good thing is that mounted at a 45 degree angle the snow slides off the panels easily.
    They don't have to be mounted on the roof and they don't have to be south, they work pretty well SE or SW or even E, & W, or any combination of the above. You may be able to find another area of your yard to ground mount the panels.
    Solar HW prices haven't really changed in the last few years, there are some cheaper Chinese evacuated tube systems available but they are not SRCC rated so they are ineligible for the 30% federal tax credit.
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  • Gooserider
    Gooserider Solar Expert Posts: 48 ✭
    #11
    Re: Rechecking current state of art...
    LucMan wrote: »
    Having a pool helps with your solar HW option, it gives you a place to dump all the excess heat that is produced during warm weather when the heating system is not required. It sure is a waste to have to pay for electric with dump zones in warm weather to keep the solar HW system from overheating.
    I agree - the pool is probably the big item that tilts the balance towards a large solar water system for me. I could see doing DHW regardless, but the idea of having an array that is enough to both make the winter heating bill mostly go away AND warm up the pool is really appealing.
    What type of heating system do you have now?
    Right now we have a natural gas HVAC system, with a high efficiency side vent burner, which I try to keep off as much as possible by running a Vermont Castings Encore Catalytic wood stove. (We also have a central air unit) This takes 4-6 FULL cords of wood / year, and the house stays about 65*F, which is tolerable, but not comfortable on the main floor, and the finished basement stays uncomfortably / unusably cold.
    Do you have radiant floor heating in the house? If so then you can easily tie into the HW system for space heating. If not then it will be more complicated to use the lower temperature solar HW to heat the house but it can be done.
    We don't currently have in-floor radiant. It would be possible to simply add a water/air heat exchanger to the existing HVAC stack, but I'd rather add the PEX infloor if I do anything. The basement floor needs better insulation, so that is pretty straightforward, and it wouldn't be hard to do staple up under the first floor. The only two real challenges would be whether or not I could put enough BTU's into the floor of the living room to heat it (thanks to the 24' cathedral ceiling and some really BIG windows) and doing the tubing for the 2nd floor master BR suite - if needed...
    As was stated in some of the other posts having 2 layers of shingles adds a lot of weight to the roof, and solar HW panels are heavy, a 4'x8" panel is about 100#.
    The good thing is that mounted at a 45 degree angle the snow slides off the panels easily.
    They don't have to be mounted on the roof and they don't have to be south, they work pretty well SE or SW or even E, & W, or any combination of the above. You may be able to find another area of your yard to ground mount the panels.
    We have some pretty heavy woods (Town owned conservation land) accross the road to the south of us, between that and the other trees on the property, I don't see many places I can put any kind of solar other than on the roof - that 15' plus boost really makes a big difference towards getting all day sun. OTOH, according to the stuff I've read, the optimal year-round mounting angle for solar is about equal to the latitude, we are at 43 and change North, and the roof faces south, so it doesn't get much better if I can do a flat mount on the roof.
    Solar HW prices haven't really changed in the last few years, there are some cheaper Chinese evacuated tube systems available but they are not SRCC rated so they are ineligible for the 30% federal tax credit.
    I have looked at the tube setups and not liked what I've seen, seems to me like glazed panels are the best overall approach for solar water... Tubes may be capable of making higher temperatures, but they seem to not do as well at making total output, and while their makers talk about higher collection per sq. foot of surface, they don't mention that a tube array has far less working surface than the same sized glazed panel... I've also seen a German report that seems to show that tubes don't work nearly as well as panels in places where they get a lot of snow and ice or frost, because they are so efficient that they never clear themselves, while a panel will leak enough heat to rapidly melt off any cover.

    Gooserider
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  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    #12
    Re: Rechecking current state of art...

    You may be able to get 50% of your heating from solar hot water, it's tough to get 100% because of the costs involved, space for collectors, and availability of sun when you need it most in Dec. Jan. Feb., to many cloudy, snowy days and the days are short. The other cold months are easy.

    The radiant in the living room if short on capacity can be supplemented with baseboard or radiators. They would have to be sized for the low water temperature.
    A hw coil on your existing furnace is another option as you stated, coil sizing and air flow would be critical because of the low water temps involved.
    Radiators for the second floor would work, if you can find some old cast iron sections to recycle, or there are steel available.
    Good luck
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