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Wood to Solar transition

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Nofossil, Apr 12, 2008.

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  1. Nofossil

    Nofossil Moderator Emeritus

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    Just about the end of the wood season for me - got heat from both wood and solar in the last 24 hours.

    Graph show boiler heating storage tank, then storage tank heating house, then solar panels heating storage tank. One of my glazed panel suffered freeze damage. I was heating with only two until late in the day when I brought the third back online, too late to do much.

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  2. antknee2

    antknee2 New Member

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    It 's my first spring with this solar system taking over the job of DHW and the last of the heating requirement's . Very good feeling to capture some of the sun's awesome power and store it for later use . My personal feeling is every home should have a DHW system to help supplement hot water needs .

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  3. heaterman

    heaterman Minister of Fire

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    What prompted your choice of evac tubes vs regular panels?

    I agree that a well engineered and integrated solar collector should be included in all heating systems.
  4. antknee2

    antknee2 New Member

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    What I like about the tubes is there ability to produce very high temperatures in the dead of the winter all they need is a clear day and some sort of storage system that exchanges with main heat loads .
    The other reason I like the EV tubes is I tend to work by my self and all the parts are light weight and easy to assemble especially on a flat roof only 13' off the ground . There are allot of parts. Anthony
  5. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Aside from the efficiency, this is a big plus for do-it-yourselfers and contractors, alike.

    I don't want to think about the liability involved in installing a multi-hundred-pound traditional panel on a roof using only ladders, or the equipment rental costs to get power scaffolding involved. Evacuated panels go up in little, lightweight pieces. The heaviest component is the manifold, and I don't think that weighs more than 50 pounds...

    We put up a 30-tube Thermomax panel in the dead of winter on a standing-seam metal roof, a few months ago. Got the system up and running with no trouble at all.

    By the way, to anyone looking to do solar, check out Caleffi's SolFlex piping system. Two flexible stainless steel pipes and a wire for the collector sensor, insulated and wrapped with armor. It's like working with PEX, and greatly simplifies things compared to rigid pipe. We were able to come out the end wall and wrap up over the edge of that metal roof, rather than having to penetrate the roof and risk a leak. I can't say enough good about this stuff. Saved a lot of man-hours and a lot of liability, even on a small, single-collector job like that. Other than a big commercial installation, I can't imagine that I will ever pipe solar with rigid pipe again.

    Joe
  6. wdc1160

    wdc1160 New Member

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    Anthony D, I really think that your approach of year round mitigation of energy requirement is the model I would like to emulate. One thing that would be awesome would be if you could estimate output. You know the real world performance.
  7. SteveJ

    SteveJ Member

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    Anthony,

    Thanks for the pictures...

    Questions (as usual :) ):

    1. Is the chimney in the first picture for the Seton? If so, what type of cap are you using?

    2. When did you get the solar tubes installed?

    3. Did you do any estimate of a payback period on the solar?

    4. Did you get the Federal Tax Credit?

    Thanks as always and nice job!!
    Steve
  8. SteveJ

    SteveJ Member

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    nofossil,

    In your graph, is the first dip in the "Solar In" due to reverse thermosiphoning?

    Do you run the solar panels all winter or drain the system?

    Thanks,
    Steve
  9. antknee2

    antknee2 New Member

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    I agree with you 100% , A new differential controller that has energy calculation capabilities is on my wish list , would be even better if the data could be downloaded to a computer . Any suggestions or recommendations would be very much appreciated .The Goldline GL 30 is a great controller , which is in service on this system , only problem no data .

    Any thoughts on this controller
    http://www.thermomax.com/BTU_Meter.htm
    Thanks Anthony
  10. antknee2

    antknee2 New Member

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    Hi Stevej good to hear from you .
    The camo green chimney is for the Seton .
    The solar system went on line the first or second week of 01/2008.
    Pay back for me is had to calculate because we have always use free wood to heat this house and work shop . We will save about 600 gallons of fuel oil for DHW and keeping my home brew endless pool at 83 degrees F all year.
    We did not take a tax credit ,my accountant acted weird when we talked about the subject .
  11. Nofossil

    Nofossil Moderator Emeritus

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    No - it's the not-quite-famous 'cold lock' phenomenon. When the panels start to heat up first thing in the morning, there's a slug of cold water in the lines between the panels and the storage. This cold slug has to be pushed through the system before hot water can flow. I provide a bypass for it, but it has to happen nonetheless. The sensor is right at the storage inlet, so it sees the cold slug passing by.

    I drain them. If it's cold enough for the panels to freeze, then I'm burning wood and I don't need the panels. During the winter, the best I could hope for from the panels if I optimized everything would be only enough to offset half an hour of wood burning on a good day - hardly worth the aggravation.

    I'm an inveterate cheapskate. My total solar investment in panels, plumbing, controls, instrumentation, and heat exchangers is about $200. Payback was pretty quick. It provides 100% of my hot water needs June through August, and better than 75% during the shoulder months. Wood provides 100% mid October through mid April.
  12. drizler

    drizler Minister of Fire

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  13. wdc1160

    wdc1160 New Member

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    Anthony. The primary thing this controlller lacks is logging. Take it from a computer scientist, they made logs for a reason. We don't want to hover over our equipment all day long.

    I am so interested in the outcome of this antony I would send you a controller. I just havne't found one that is user friendly. I have been working with a similar controller to Nofossil's. But, for people who don't want to learn the finer points of php and linux, its not likely a good fit. I wanted to contribute to the board by donating a setup script of a controller like nofos. And, I still think I will, but I haven't found the time yet.

    I will have more time to wrestle with an answer to the question after april 15.


    I really have spent most of my controller time on my controller. Maybe someone can find a simplier controller that has logging. PS If you'll notice from nofo's logs we can see most aspects of his energy use. He happens to put his data in graph from which helps analysis, but I think even a txt file would help enormously. We could turn the txt into a graph easily enough. I am getting off topic.

    in summation, the btu meter you show has only a delta t of 50F, which I think is a deal breaker, and no logging. Which means that at best its not a controller, just a bad sensor.

    I will spend a couple hours on Wed or TR looking at the problem.


    Thanks for your pioneering and sharing anthony.
  14. VeggieFarmer

    VeggieFarmer New Member

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    NoFo: I friend of mine says I should plumb the solar coil into the dhw tank, not into the main storage tank, because the main storage tank will never get hot enough from my two panels to make dhw. I recall you writing that the stratification in the main tank is more than adequate, and I notice that the goal of your first mixing valve is to prevent the main tank water from scalding the shower occupants. Did you always have it set up this way, or did you start off running your solar into the dhw tank?

    From another angle, if you're draining the solar in the winter, and not using/needing the big storage tank in the summer, why not just go straight from the solar to the dhw? (Do you think you're getting enough heat off the panels in the shoulder season to make it worth it?) Thanks.
  15. Nofossil

    Nofossil Moderator Emeritus

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    I've always had it set up this way. Part of the issue is that I can thermosiphon from the panels to the big storage tank, but my DHW tank is too low. If I could design my ultimate system, the panels would heat the DHW tank first, then the big storage tank. This would require the DHW tank to be above the storage tank. With three glazed panels and an above-ground pool heater, I got the top of my 880 gallon storage tank above 150 degrees last summer.

    It's the thermosiphon problem mentioned above. I do get quite a bit of usable heat even in the shoulder months. I was getting 150 degree water off the panels yesterday, for instance. Had to drain them today, though. Supposed to be upper 20's tonight, and lower 20's tomorrow night.
  16. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Resol controllers have always worked well for me, and offer data logging (with an external data logger that is attached to the controller).

    They are re-sold by a number of companies. I happen to use Caleffi as a supplier, because I buy most of my other solar piping and controls from them...
    http://www.caleffi.us/en_US/caleffi/Details/News/files/257_Series.pdf

    That file doesn't show the data logger, but if you look for the Resol data logger on the web, I'm sure you can find it...

    Joe
  17. ISeeDeadBTUs

    ISeeDeadBTUs Guest

    Joe. . . . I have 16" seams, what sort of mounting hardware is available? How much wind can it withstand? Does anyone make a mounting system that would reposition the panel as the sun progresses throughout the day?

    Jimbo
  18. Moosestache

    Moosestache New Member

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    I always wondered about the possible payback on a solar system if you are using a wood boiler. Solar vs oil at $3 or more seems like the payback would be quick, solar vs wood seems like the payback would take quite a while. I guess it depends on how much the solar system costs, and how much of your summer hot water costs are, if you decide to stop using your wood boiler. What kinds of costs should one expect to put in a solar system to cover the "shoulder" and summer months, and hopefully do away with oil usage almost completely? Thansk
  19. VeggieFarmer

    VeggieFarmer New Member

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  20. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Depends on your roof pitch. This was a 6/12 pitch. For summer performance, you want the panels to match your latitude. For winter performance, check a solar chart. In this case, we wanted to enhance winter performance, to provide a small amount of backup space heating as well as to avoid overheating the tank in the summer, so we decided on an angle around 60 degrees. To mount the panels, we used a flat roof frame (similar to what's shown in the pictures in this thread) to bring the panels up at a steeper angle than the roof.

    I've never heard of a problem with wind. The evacuated tubes let a lot of the wind flow right through. For actual wind performance numbers, I'd contact the manufacturer.

    To mount the "feet" of the frame, we used lag bolts into the strapping under the metal roof, which held everything nice and steady, then we drilled through the roof and used stainless bolts with nuts and fender washers inside the attic.

    Theoretically, you could use one of those trackers that they make for PV panels, and use the flexible piping to allow it to move the panel around, but you might fatigue the piping.

    But there really wouldn't be much benefit, with the efficiency of the evacuated tubes. They pull in a lot of solar energy, and you can turn each individual tube during installation so that it points due south, even if the roof isn't exactly dead-on south-facing. I don't think there would be a benefit to tracking. I've seen systems where the roof ridge was north-south, where they put a panel on each roof, and use a controller to just switch panels as the sun moved. If you had a roof facing east, one facing south, and one facing west, I suppose you could cycle through the panels as they heated up, and avoid the maintenance issue of a tracker and flexible piping getting continuously flexed. In the long run, that would probably be cheaper than maintaining a tracker.

    Now, being able to vary the pitch of the panels between summer and winter would be a benefit. I think I'll be doing that when I put mine in either this summer or next. I'll manufacture my own frame with hinges and such to allow for that, and have a few "stops" in the adjustment, so I can move it a few times during the year as the sun's angle changes. During the summer, the panels will be just barely steeper than my 12/12 roof (since the latitude is roughly 43* here), and during the winter they will be able to go all the way up to 70* or so. I'll probably just have it work with a hand-crank, since I can walk out onto the roof from one of my windows. Remove the pins, crank it up or down, and they re-install the pins at the new angle.

    Joe
  21. wdc1160

    wdc1160 New Member

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    anthony,

    The Resol RESOL DL1(logger) that Brownian Heating tech mentions does log and save to PC. However, It won't log anthing except 1 thermostat from what I can tell.

    I am still looking at them.
  22. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Hmm... I'll check with them when I get a chance, since I thought it logged more than that. I've never had reason to use one.

    Of course, the controllers communicate by a RS232 serial signal, IIRC, so it might be possible to just connect directly...

    Joe
  23. Bob Rohr

    Bob Rohr Minister of Fire

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    Crunch the numbers carefully when comparing evac tubes to flat panel collectors. Yes they may be easier to install, and they may provide a bit higher temperatures.

    If you run the calcs over a year with a good program using daily radiation, like Maui Solar, you'll be hard pressed to find a 10% difference in performance. At close to 3 times the cost adding additional flat panels would give you better performance, at a much lower cost.

    What the evac tubes bring to the table is a more efficient insulation, the vacuum between the glass layers. But the bottom line is there just isn't much energy to harvest from a cold winter sky. Go to the NASA website and plug in your location to see the Solar Energy Available Tables to compare December, to July for example. And notice the amount of energy available in December for your area.

    The more efficient insulation offered by the evac tubes over the flat panels can't make up for the lack of energy available, regardless of how they spin the numbers.

    The performance of any collector has the most to do with the conditions that the load presents to them. Mainly the ambient air temperature, and the fluid temperature returning to them. Low temperature radiant emitters are a better match for solar than higher temperature fin tube baseboard, for example.

    As you can see on this graph based on ASHRAE 93-77 data the un-glazed pool collectors will outperform both flat panel and evac tubes at the right conditions.

    By their own admission the evac tube manufacturers projected a 10 year realistic life span. Newer models with better seals are looking for 15 years. Quiz the manufacture about the warranty with any panel or tube.

    I visited with a bunch of solar contractors in Denver this weekend. One told me of a 100 tube array installed 5 years ago that has had 25 tubes failures, lost vacuum. A very un happy customer.

    I have 20 year old flat panels on my home and shop that are collecting as well as they did 20 years ago.

    I believe there is a place for the evac tubes, under the right conditions, just be sure to do the numbers by the data available at the SRCC. To say they are better under all conditions???

    here is a free download that will help with your solar planning and design.

    http://www.caleffi.us/caleffi/en_US...gazine_detail_0000063/type/magazine/index.sdo

    hr

    Attached Files:

  24. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    The temps are the big thing. Capturing energy isn't meaningful, if the absolute temperature is too low to put it to use. Efficiency numbers that don't take that into consideration aren't helpful.

    Which manufacturers say that?

    Thermomax tubes have a 10-year warranty, and are likely to last at least twice that, if not longer.

    Actually, the last shipment I got was dropped and speared with a forklift by the freight company. Of 30 tubes, one was damaged. It had the condenser end sheared right off it. Still had vacuum integrity (and still does, sitting in the corner of my shop, a couple months later).

    I would hope no one would say that...

    Joe
  25. wdc1160

    wdc1160 New Member

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