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  • #16
    Originally posted by estes53 View Post
    Surely someone out there has done something similar and tell me what size tank I need to find, because that is all I am asking. Probably not - the tank size you are thinking of is far too small (1000 gallons). How much water do you have to recirculate through the system?

    This old man is having a hard time understanding what this site is supposed to be for. For people to come along and ask off the wall questions?

    If I had read some book, why would I need to come here and ask questions? If you had read the book you would understand the futility of what you are in to.

    Some of you young people have never had to "get by with what you had", so have this idea that knowledge is the answer to everything and are soon in for a very rude awakening. This young one is 69 - the old guy card doesn't work here.

    If you don't like me asking my questions, then don't read them. Get the chip off and get a thick skin

    I'm looking for practical experience, from someone who has a similar situation and I'm not sure that living in San Diego and having a lot of book knowledge qualifies anyway. Alan - I tell people this all the time - quit whining.

    Alan
    Comments in bold in the text.

    You can try www.builditsolar.com some good stuff there and a lot of flaky stuff as well.
    [SIGPIC][/SIGPIC]

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    • #17
      Originally posted by estes53 View Post
      1 BTU required to heat 1 # of water 1 degree F - 8.3 # per gallon.

      I think this is exactly what I have been looking for, but do not understand what the # symbols represent.

      Alan
      The # symbol represents the word "pound". So 1 BTU is needed to heat 1 "pound" of water 1 degree F. With a gallon of water weighing 8.3 pounds it will take 8.3 BTUs to heat a gallon of water 1 degree F.

      You can calculate the number of BTU's needed to heat 1000 gallons of water to 60 degree F but then you have to determine how to keep that heat in the tank and how much you are losing when you circulate that hot water to heat the house or room.

      I am sure someone with a Thermodynamics background can wip up an answer for you but my background is electrical so I too would have to go to a book to get my information.

      Comment


      • #18
        Originally posted by estes53 View Post
        I have a 12 x 15 x 9 cellar, with poured concrete walls, that I would like to use for a solar utility room.

        The ceiling and floor are concrete and the back and side walls have earth behind them.

        It has a standard door so my tank would have to be constructed in it.

        Any advantage or disadvantage to selecting a corner, then adding 2 more (partial) concrete block walls for a tank?

        I need something sufficient to store enough, and be hot enough, to heat a 20,000 cubic foot house (50 x 50 x 8), with wood stove backup.

        The BTU output from my, planned, trough collector array should be 105k on a sunny day.

        I posted earlier about using this system to generate enough steam for a generator but have decided against that.

        Thanx for input, Alan
        My wood stove alone is able to put out 110,000 BTU an hour. I am afraid that your 105K a day will not be enough.

        Comment


        • #19
          Here in NY the rule of thumb for a heat loss calculation is 35 btu per square ft per hr. that is for an outdoor ambient of 5 degrees F. This would be newer 1990's construction.
          2000 sq. Ft x 35 btu= 70, 000 btu per hr required to keep the house at 68 degrees at 5 degrees outdoor temperature.
          As the outdoor temp rises you would need less btu's.

          Do a search for an online heatloss calculator and perform the calculation for your house in the state that you live in.

          A 1000 gallons of water would be heated 12.6 degrees with your collectors per sunny day.

          Are you planning on using radiant heat at 110 degrees? If so plan on using no more than a 150 gallon tank probably less.

          Your other option is to imbed the radiant tubing in your concrete slab and use the concrete as your storage instead of a water. This way you would be able to use 90 degree water, easier to attain than 110-130 f.

          Comment


          • #20
            Ok, I have come to the conclusion that that nothing I read here, or anywhere else on the internet can be believed.

            Everything I have been told since I started this has been contradicted by someone else.

            I'm getting tired of people implying that I am some sort of moron.

            Adios, mi amigos.

            Comment


            • #21
              A.M.F. (Adios, my friend)

              Comment


              • #22
                Originally posted by LucMan View Post
                Here in NY the rule of thumb for a heat loss calculation is 35 btu per square ft per hr. that is for an outdoor ambient of 5 degrees F. This would be newer 1990's construction.
                2000 sq. Ft x 35 btu= 70, 000 btu per hr required to keep the house at 68 degrees at 5 degrees outdoor temperature.
                As the outdoor temp rises you would need less btu's.

                Do a search for an online heatloss calculator and perform the calculation for your house in the state that you live in.

                A 1000 gallons of water would be heated 12.6 degrees with your collectors per sunny day.

                Are you planning on using radiant heat at 110 degrees? If so plan on using no more than a 150 gallon tank probably less.

                Your other option is to imbed the radiant tubing in your concrete slab and use the concrete as your storage instead of a water. This way you would be able to use 90 degree water, easier to attain than 110-130 f.
                So what you are saying is that this person would need to generate 1,680,000 btu per day if 70,000 btu's are required per hour for an 2000sqft house.
                Also you have to be able to store that much energy in water or concrete and how much mass would that take?
                If my calculation is correct it would take a little more than a 2000 gallon tank that would have an temperature rise of 100 degrees and it would be a system/panels that is 16 times bigger than the poster was planning to use. If the temperature rise is lower, than the mass or gallons has to increase to keep the same amount of energy stored.

                Comment


                • #23
                  Another way to look at a building heat load might be using something like the Degree Day method.

                  First, each building component (walls, ceiling (roof), windows, foundation, etc. has an estimated heat loss (gain) calc'd using known, or estimated and probably different "R" values for each component.

                  Then, air infiltration is (probably) estimated in terms of ft^3/hr. and multiplied by the sp. heat of air ( ~ .24 BTU/lbm) X .0762 lbm/ft^3 = ~ .0183BTU/ft^3 at sea level. All of those individual components losses(gains for air conditioning) are summed. The result is a rough estimate of the building heat loss (gain) for 1 degree of temp. diff., inside to outside for 1 hour. Multiply by 24 hrs. for an estimate for 1 Degree Day (DD) heat loss.

                  Next, get the annual heating(or cooling) DD's from a weather almanac or call the local weather bureau, or other source.

                  Next, multiply the est.DD heat loss by the # of DD's/year. Voila: estimated annual building heating or cooling load. There is also something called the "latent" A/C load dealing with moisture content of warm air, but I'm leaving that out just now.

                  Other things can modify that load, such as internal generation by cooking, bodies, washing, etc. and may be accounted for or ignored as desired or deemed appropriate.

                  Another way to get an empirical heat loss that is hopefully close to the calc'd method is to actually measure how much heat goes into a dwelling by using a stopwatch and a known BTU heating device firing rate and an estimated combustion efficiency. Sounds weird, and maybe it is, but I did it that way on my first house in Buffalo in the winter and got results that agreed quite closely with temps. in/out that I recorded and CH4 use that I recorded 1X /day.

                  FWIW; I got the net heat loss in the house down to about 6,200 - 6,500 BTU/DD as a quasi steady state heat loss. The house was about 1250 ft^2, 1 1/2 story. The effective thermal mass was about 3,800 - 4,000 BTU/deg. F. for an effective thermal time constant of about (3,900)/(6350/24)) ~=14.7 hrs. That was after the house was insulated, etc. The house was built in 1928 and was pretty solid. I learned a lot taking it apart and putting it back together with a few mods along the way.

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                  • #24
                    Originally posted by Johann View Post
                    So what you are saying is that this person would need to generate 1,680,000 btu per day if 70,000 btu's are required per hour for an 2000sqft house.
                    Also you have to be able to store that much energy in water or concrete and how much mass would that take?
                    If my calculation is correct it would take a little more than a 2000 gallon tank that would have an temperature rise of 100 degrees and it would be a system/panels that is 16 times bigger than the poster was planning to use. If the temperature rise is lower, than the mass or gallons has to increase to keep the same amount of energy stored.
                    Exactly! Solar space heating in cold climates makes no sense.
                    It can work for the shoulder seasons when sunlight is abundant and temperatures are mild (50-60F), or in the sun belt where the sun shines and there is no cloud cover. The system also has to be a low temp radiant system preferably 110 F or less, so that a temperature rise of 30 degrees can be maintained. I have come to the conclusion that a combination of mass & a smaller amount of water storage is the best solution. It's fairly easy to maintain a well insulated slab at 80F
                    The system can't be designed for the coldest day like a conventional heating system, the cost would be astronomical.

                    Here is a simulation for a Solar thermal space heating job in NY for an approximately 2000 sq ft area with a proposed 256 sq ft of Buderus Hybrid panels and a 200 gallon storage tank. The first floor is a 6" insulated concrete slab and the second floor has low temp radiators sized for a max of 130F.
                    This job never happened because the cost was close to 100K for the solar portion.
                    Attached Files

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                    • #25
                      Originally posted by LucMan View Post
                      Exactly! Solar space heating in cold climates makes no sense.
                      It can work for the shoulder seasons when sunlight is abundant and temperatures are mild (50-60F), or in the sun belt where the sun shines and there is no cloud cover. The system also has to be a low temp radiant system preferably 110 F or less, so that a temperature rise of 30 degrees can be maintained. I have come to the conclusion that a combination of mass & a smaller amount of water storage is the best solution. It's fairly easy to maintain a well insulated slab at 80F
                      The system can't be designed for the coldest day like a conventional heating system, the cost would be astronomical.

                      Here is a simulation for a Solar thermal space heating job in NY for an approximately 2000 sq ft area with a proposed 256 sq ft of Buderus Hybrid panels and a 200 gallon storage tank. The first floor is a 6" insulated concrete slab and the second floor has low temp radiators sized for a max of 130F.
                      This job never happened because the cost was close to 100K for the solar portion.
                      The way I learned it, most active or passive residential solar heating systems in northern, cold and cloudy climates were never designed to carry an entire design heat load to begin with. In such climates, most active systems were found to be cost INeffective, and most existing dwellings are not usually amenable to passive retrofits from a practical or architectural standpoint.

                      What Lucman seems to be talking about is a design heat load - the worst case situation that most HVAC equipment is likely to ever see and then some for good measure. Not every day is the worst day in a heating season, and for the example given, not every winter day causes a heat loss of 1,680,000 BTU - hopefully, none of them will - if so the equipment is, by most common definition, undersized because it can't handle the worst case load. On the other hand, most every (other)winter day the equipment will be able to handle the heating load because most every day (for the example given) does not have a constant 63 deg. F. temp. diff.

                      Also, cost effective or (probably) not, a well designed solar heating system can make a significant (from the standpoint of being measureable anyway) difference in reducing the amount of energy needed to maintain a dwelling temp. while using less fossil fuel or electrical energy - heat pump or resistance. As Lucman points out, and I agree with him, FWIW, when looked at on a yearly basis, depending on system size and design, residential solar heating systems can contribute a small amount in the dead of winter (for some periods of time approaching zero), and increasing amounts of energy (called the solar fraction) the farther away from the winter solstice as the weather is warmer and more solar friendly. This solar fraction at some point will reach 100% of what is by then a small heat demand in the early fall and late winter/early spring, lowering the conventional fuel demand and shortening the heating season a bit.

                      All of this says nothing about a solar heating system improving (lowering) the cost of the conventional equipment. It will not. That cost is not lowered when adding solar heating capabilities. The fuel cost MAY go down some, but the furnace size and capabilities must remain at least the same, maybe larger, if for example, passive solar fenestration increases the design heat loss or increases heat loss when the sun isn't shining more than it provides heat when the sun is shining.

                      No one in their right mind ever started out with the idea that a residential solar heating system would provide 100% of a Jan. heat load in, say, Buffalo, NY. Trust me on that. Probably many other places as well. Most things are not all or nothing anyway. Probably no way cost effective either.

                      I designed a passive sunspace on the back of my first house in Buffalo. It was no way cost effective, but it did supply about 6 MM BTU of heated air to the dwelling through ductwork that was not supplied by the CH4 fired furnace. That was about 14 -15% of what was a very low annual heat load to begin with. Small but measureable. Besides engineering textbooks and process economics, that's where I first learned conservation is almost always more cost effective than solar. I also grew some tomatoes and green peppers over the winters in defiance of the weather. Paid my money and took my choice. Some of the best veggies I ever grew. By far the most expensive and non cost effective as well.

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                      • #26
                        JPM
                        Buffalo to San Diego, did you get tired of the snow or the cold or both.
                        My daughter arrived in San Diego on Saturday for a clinical rotation at the marine base. She called last night and said is was 70 degrees!!! We were at 17

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                        • #27
                          Originally posted by LucMan View Post
                          JPM
                          Buffalo to San Diego, did you get tired of the snow or the cold or both.
                          My daughter arrived in San Diego on Saturday for a clinical rotation at the marine base. She called last night and said is was 70 degrees!!! We were at 17
                          The short answer is yes. I got tired of the 5 months every year called winter, but better described, IMO, as a running battle. And after one short comment, I'll return to the topic that's the sign over the door - Solar Panel Talk - and get off this self indulgent walk down memory lane.

                          The Buffalo winters are terrible. However, most of the folks who live there are such that their quality and civility makes the winters almost bearable. Almost.

                          I've been in San Diego since '95 and I'm staying with no complaints, but if I could magically swap out a few people in S.D. for a few people in Western NY, this place would be a step or two closer to paradise.

                          Come on out + visit your daughter. Supposed to be 81 F. today and sunny for the next week+. Current temp. @ 0725 P.S.T. at my house, +68 F., cloudless. Current Buffalo temp., +13 F., snowing. Q.E.D.

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