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looking for some direction on solar collectors for dhw

Post in 'The Green Room' started by 2.beans, Oct 6, 2008.

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  1. steam man

    steam man Minister of Fire

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    Sorry about the delay. I haven't been home in about 5 weeks to really keep track of my system. I have to depend on my wife to give me the numbers when I call. I will have a web based data logger set up next month to get accurate numbers. November was a crappy month for sun where I live though the tubes almost always make some heat. The tubes seem to be more dependent on having some solar radiation rather than what the outside temperature is. Hopefully I will get some numbers to post eventually. I did just receive an oil fill up today (the last about the time I started the system) and the drop in oil useage seemed significant. Though I don't expect much heat gain this time of year I think with solar you have to think over a longer time frame. My yearly savings is what I am thinking about. I did see my tubes making heat covered in some frost. That was weird.

    Mike

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  2. Techstuf

    Techstuf New Member

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    By jove....I think I've got it! A scaled down, pedal powered version of this:


    http://www.youtube.com/watch?v=yh_-DUKQ4Uw

    http://www.youtube.com/watch?v=V0M2GnQluJk

    You want to wash some dishes? 5 minutes on the stationary bike!

    A bath? 10 minutes!

    Etc....etc.... You get in shape and have nearly on demand hot water no matter the weather.

    Call it the "Cavitation Station".

    Or, if you're really lazy, let the wind make your hot water.


    TS
  3. Rickard

    Rickard New Member

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    Hi Steam man

    I am very interested in your setup. I am looking to put in a Sunmax system this spring. I am thinking of going with a 125 tube system for heat and hot water with a wood boiler for back-up. I am hoping to get temperatures at least to 140F from the tubes. I have two 500 gallon propane tanks for storage where one can be valved off if necessary. It is exciting to hear that you are getting temperatures above that range at this time of year. I am looking to do a drainback system instead of a glycol system. Since it is designed around the wood boiler I would be happy to see the storage aproaching 200F if that were possible.

    What do you think of Sunmaxx? What made you decide on that company?

    thanks

    Dean
  4. steam man

    steam man Minister of Fire

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    Just got home yesterday from being gone a few months. So far since October, my system (with 105 tubes installed out of 120-hoping to get to 180) has averaged 11,650 btus/hr when running. That's the kicker-November was without sun. However, yesterday when temps were in the teens the tubes were cranking out heat because there was clear sun. Its run about 230 hours total. I am checking out a data logger system to be installed shortly. Certainly in NJ you should get more heat than northern ME. I am on my way to getting storage and the radiant tubes going. Seems like still a lot of work. You'll have a lot of variables to consider when installing with a wood boiler. I sent you a PM with my ph#. Give me call anytime-I am a slow typist.

    Mike
  5. velvetfoot

    velvetfoot Minister of Fire

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    Are the tube collectors less sensitive to a southerly orientation?
    I'd like to dabble with solar, but the house roof is facing 45* to the east of south (southeast, I guess.)
    Thanks.
  6. steam man

    steam man Minister of Fire

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    Collectors should face true with a + or - margin of 10 degrees without a penalty. Use a compass to find magnetic south and then correct for magnetic declination (or variation). Go to http://www.ngdc.noaa.gov/geomagmodels/struts/calcDeclination. That would be true south. If you don't get within 10 degrees you would have to add more collector area to make up the difference. Tubes can receive radiation at wider angles than flat plate collectors depending on the manufacturer.

    Mike
  7. velvetfoot

    velvetfoot Minister of Fire

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    Thanks for the link. I'm not so sure solar is in the cards for me.
  8. karl

    karl Minister of Fire

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    How many BTUs an hour do those tubes produce for a given delta?
  9. steam man

    steam man Minister of Fire

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    I am not really sure. I seem to get a pretty consistent 10-12 deg rise right now across 1 collector or 30 tubes at a flow rate of 1.6 gpm. I split my system to make a "reverse-return flow" to balance the flow with a parallel-series scheme. The actual flow rate is twice that or 3.2 gpm. I am waiting for some info on a data collection system before I install it so I don't have detailed data. I have 105 tubes installed (15 more to go) heating a 120 gal tank. I seem to get about 11,600 btu/hour average. I have had no problem heating it over 150 deg (if not using much hot water) with single digit temps outside as long as the sun shines. I am kind of pressed to get a heat dump zone ready, probably the tubes in my basement floor at first. I have some other variables to consider. I'll know more as time goes on.

    Mike
  10. karl

    karl Minister of Fire

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    11,600 btus/hr? Are you sure that's correct?

    That's pretty low isn't it? Sunmaxx 20 tube system is rated at 4684btu/hr. You have 5 times as many tubes. That would be 23,420 btu/hr/ I realize thats under ideal conditions but I would think you would do bettter than half that much.
  11. steam man

    steam man Minister of Fire

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    The 11,600 btu/hr seems pretty consistent based on what my flowmeter registers and what the energy meter calculates. Assuming my flowmeter is right, I think I am slightly under half output from what the tubes are rated for. But keep in mind we are just off the lowest insolation level of the year. I think they are probably about where they should be on the seasonal curve. You piqued my curiousity and I will double check to be sure sure. I do know that at before daylight the collector sensor reads -12 deg F. By 9:30 its over a 100 easily and cranking heat. I have up to 160 gallons to heat and typically by 1:30PM I usually have to use some hot water since the tank could be 160 deg. That is probably not heating from 55 deg as the water may still be warm from the night before. Keep in mind I am in northern Maine with low but clear sun. Its only going to increase from here. I have to get that heat dump zone going pretty soon. I will have a data logger soon enough and will be able to post some graphs.

    Mike
  12. karl

    karl Minister of Fire

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    I got to thinking about my last post and I hope I didn't offend you. If I did, I'm sorry.

    I am curious about a solar hot water system for my house. I'm a guy and I live alone, so DMH isn't a big deal to me.

    I'm interested in using solar to heat my house. I live in West Virginia. Day time highs during the winter are usually in the low 40s. I'm trying to decide if evacuated tubes or flat panels would be better for me. I can fabricate flat panels to save money. I'm guessing I would need 90-100 degree water for a radiant system.
  13. steam man

    steam man Minister of Fire

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    I don't know why you think your post was anyway offensive. No problem. -It got me thinking. I am still collecting performance data. I will probably be expanding to 180 tubes at some point but I have to get the heating part going and I have a pool to heat for the summer. The collector performance in WV would probably be a fair amount higher than northern Maine. Day time highs here may hit low teens. I like good solid numbers to work from. The 11,600 btu/hr is an average since the middle of October. November/first half of December was a real sunless time around here so I think that put the average down. I don't have a peak heat production on a per/hr or per/day but I will be looking at that. If your living alone your hot water demand would be pretty low. I went with evacuated tubes since I plan on using under floor radiant at some point. That generally needs 140 deg water or so. At lower collection temps flat plates may work just fine or even better. A btu is a btu at 90 or 140 deg. BTW-my dad's family was all from WV.

    Mike
  14. Blevesque

    Blevesque Member

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    Just wanted to pop my head in here and tell you my story. In november I installed a 30 tube collector for my uncle in the sugerloaf area of maine. The collector is made by EOS which is a maine based company. We did his a little differant the the normal, he has a Tarm Solo 40 with a 1000 gal. pressurized storage tank with a DHW coil built into it. He wanted me to tie the solar into his existing 1000 storage tank, I was reluctant at first but figured what the heck we can try it and if it doesn't work we already have the 60 gal. superstor that I pipe in. He have been getting very good temperatures from the collectors, but it's been tough to really know what it can do. The reason I say that is because he always builds a fire when the tank gets down to 150-160 he starts a fire usally in the mornings. So by the time the sun comes out his tank is up to 180-190. We have the it set up so the water has to be 185 in order to turn the pump on. Well yesterday he decided not to build a fire in the morning an see what it does. He called me last night and said I'm not going to believe this. 7:00am the tank was at 151 @ 4:00 the tank was @ 162 he gained 11 degrees in the tank yesterday and the high temp at the collector was 232 deg. So these things do work. Brian
  15. 2.beans

    2.beans Minister of Fire

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    any way we could get some pictures? i have a similar setup without solar yet.
  16. Blevesque

    Blevesque Member

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    Hi 2.beans, I just wanted to correct something from my original post. The 232 degrees was because the glycol slushed up and was not pumping well, it was -44 that morning he says the operating temps are usually 175-185 from the collector. His setup is pretty neat because he can rotate the collector to get the most heat from them between the seasons. Brian

    [​IMG]

    [​IMG]
  17. 2.beans

    2.beans Minister of Fire

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    i like it, did you build the whole thing?
  18. Blevesque

    Blevesque Member

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    He designed and built the whole thing by himself and had a buddy of his set it with his cherry picker. You really have to see this thing in person to really appreciate it. All I did was pipe it up and install the controls. I forgot my camera today, I'll try to remember tomorrow.
  19. 2.beans

    2.beans Minister of Fire

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    could you take some pics on how the heat exchanger is built? i want to start gathering parts to build in the spring.
  20. Blevesque

    Blevesque Member

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    Sorry it took so long 2.Beans, here are the inside pics showing the flat plate heat exchanger. Let me know you have any questions.

    [​IMG]

    [​IMG]

    [​IMG]
  21. 2.beans

    2.beans Minister of Fire

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    nice work. whats the black box? a was also interested in the build of the solar collector. did he use copper pipe or plastic?
  22. Blevesque

    Blevesque Member

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    Hi 2.Beans, the black box is the pump station and the controller goes mount in the front. Sorry to confuse you, he didn't build the collector, he just built the rotating stand that it is mounted to. The collector is made by EOS and is vacuum tube. Brian
  23. WoodMann

    WoodMann Minister of Fire

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    HEy Mike- looking at your solar installation, looks good. Is that an open or closed system? And did you make your own heat exchanger if it's a closed system...........
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