Announcement

Collapse
No announcement yet.

Where do I start with Solar heating

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Where do I start with Solar heating

    Currently/original house is a lot home, heated/cooled by a Fujitsu 36K mini-split.
    Basement (900 sq feet) was built with radiant floors in mind (5 pex loops). Basement insulated with Superior Xi walls (estimated to be R9, see link below)
    New addition was built, including basement. Basement floor was also prepared for radiant heating (9 pex loops.. about 800sq feet)
    Not sure why loop count is different, no good answer there.
    New basement outside block is 12", mostly filled with concrete (it holds a heavy garage on top).
    Both floors have some insulation at bottom (estimating 1")
    I have all the totals on how much concrete was used, as I have receipts
    I also have some flat plate solar panels (7 units of 3x5)
    The new space is bare block walls, only painted inside outside for water protection.
    The idea was to take advantage of thermal mass..

    House does have a 10k Solar array facing south. It's working out rather well (only have bills nov-mar, averaging below 150$.. not heating new space yet)
    I am a little efficiency obsessed, but also want to have a system have a reasonable payoff

    Initially I thought of getting a wood boiler.. but it seems very expensive and overkill for my application.
    Now I am leaning towards drainkback solar with Backup (for simplicity, maintainability, and being DIY friendly), with backup being a super efficient (4-5COP) Sanden water heater
    Discounting the fact that this setup may not be 100% supported by the manufacturer.
    What's my path to figure out what I really need?
    E.g. how do I calculate taking advantage of heat mass.. how do I determine what R value I will need to add to all walls.. how do I determine what storage outside of concrete I need (e.g. solar tank), how do I determine that what I am thinking is a good option.

    Thanks,

    R9 reference.
    http://www.greenbuildingadvisor.com/...superior-walls

  • #2
    Originally posted by NetComrade View Post
    Currently/original house is a lot home, heated/cooled by a Fujitsu 36K mini-split.
    Basement (900 sq feet) was built with radiant floors in mind (5 pex loops). Basement insulated with Superior Xi walls (estimated to be R9, see link below)
    New addition was built, including basement. Basement floor was also prepared for radiant heating (9 pex loops.. about 800sq feet)
    Not sure why loop count is different, no good answer there.
    New basement outside block is 12", mostly filled with concrete (it holds a heavy garage on top).
    Both floors have some insulation at bottom (estimating 1")
    I have all the totals on how much concrete was used, as I have receipts
    I also have some flat plate solar panels (7 units of 3x5)
    The new space is bare block walls, only painted inside outside for water protection.
    The idea was to take advantage of thermal mass..

    House does have a 10k Solar array facing south. It's working out rather well (only have bills nov-mar, averaging below 150$.. not heating new space yet)
    I am a little efficiency obsessed, but also want to have a system have a reasonable payoff

    Initially I thought of getting a wood boiler.. but it seems very expensive and overkill for my application.
    Now I am leaning towards drainkback solar with Backup (for simplicity, maintainability, and being DIY friendly), with backup being a super efficient (4-5COP) Sanden water heater
    Discounting the fact that this setup may not be 100% supported by the manufacturer.
    What's my path to figure out what I really need?
    E.g. how do I calculate taking advantage of heat mass.. how do I determine what R value I will need to add to all walls.. how do I determine what storage outside of concrete I need (e.g. solar tank), how do I determine that what I am thinking is a good option.

    Thanks,

    R9 reference.
    http://www.greenbuildingadvisor.com/...superior-walls
    If you are cost and efficiency conscious, know that thermal mass by itself is of little use without insulation. The two are not the same. A well insulated and sealed space with little thermal mass will have HVAC bills that are about the same as an equally well insulated and sealed space with lots and lots of thermal mass. A poorly insulated space with a lot of thermal mass will have bills close to those of a poorly insulated space with lots of thermal mass. The key to low heat loss is insulation, not thermal mass. Buildings with equal HVAC requirements can often get by with smaller equipment capacities if the building has a lot of thermal mass and large mass buildings sometimes seem a bit more comfortable with fewer hot/cold spots.

    Spend your money and effort on insulation and a tight building envelope. A massive concrete wall has a very high heat transfer coefficient compared to that of an insulated frame wall of equal dimension.

    Comment


    • #3
      Thanks for your feedback. Insulation is certainly on my list. How much to insulate is part of the 'cost' equation, as it has diminishing returns.
      The heat mass can be used to store 'free' heat from solar, but I agree i also have to figure out how to not lose that heat to the outside.

      So were do I start in figuring out how much insulation I need and determining a sweet spot with solar system/storage tank?

      Comment


      • #4
        There is individual called John Siegenthalet that writes columns for several magazines, he is a heating guru and big advocate of low temperature radiant emitters or radiant panels. I found this free webinar that may be helpful https://www.pmmag.com/events/910-fre...dronic-systems. If you have net metering and no annual reset, the way to go is put in more PV build up a credit and use a minisplit. Flat Plate SHW is not a great idea for heating as you have all sorts of heat in summer when you dont need it and not enough in the winter when you do. At best you get 80 degree rise over the outdoor temp and at 20 degrees that only 100 degrees out at best. Unless you put in lot of radiant panels or a radiant slab the temps just not hihg enough for most heating applications. Far better to spend money on having an energy audit and picking way at high air infiltration points first and then go after typicla poorly insulated spots like box sills in basements and the sill plates.


        Far better to build up credit from net metering and then use the KW with the minisplit.

        Comment


        • #5
          You might want to consider how you want to heat your spaces. Is it important to heat your entire house (ie every sq. ft.) to a comfortable level or do you want to heat the space you are in to a comfortable level?

          The answer to that question will determine how and what your heating strategy will be.

          Comment


          • #6
            First step is always to calculate heat loss for your structure. This will tell you exactly what your BTU requirements will be for heating at any given outdoor temperature.
            Software is available, just enter all the info and the software will spit out the BTU loss' s. You can then play around with changing insulation values to find the sweet spot for your application.
            Your above post indicates that you have excellent understanding of what you want to accomplish.
            Good luck
            ps HVAC CALC works well and it used to be available for purchase for one time use.
            http://www.hvaccomputer.com
            Last edited by LucMan; 03-08-2018, 08:32 AM.

            Comment


            • #7
              The problem with a drain back system in cold cloudy climates, is it works the least well when
              you need it the most. Thermal storage is not going to carry through bad weeks. The big
              advantage to net metering, is being able to use summer energy in the winter. I see the
              ways to do that are the latest high efficiency low temp mini splits combined with great
              insulation. Bruce Roe

              Comment


              • #8
                space differene with outside R btu's to maintain
                old wall 900 80 9 8,000 80F inside 0F outside
                old foor 900 30 15 1,800 80F top of floor, 50F bottom of floor
                new wall 540 80 2 21,600 80F inside 0F outside
                new floor 800 30 15 1,600 80F top of floor, 50F bottom of floor
                windows 2
                room upstairs 320 80 20 1,280
                34,280
                This would be my BTU calculation with current setup (as is).. If I get the walls to R20 or about, my requirement becomes about 10000 BTU (ignoring windows for now).

                This is within range of the Sanden (15000BTU, although officially they claim no more than 8000BTU load to support radiant heating).. Since my current Fujitsu still has 2 ports available and we still want radiant heating, that's what I will need to pursue (Fujitsu mostly for cooling, as it may not keep up with heating.. but technically it has 13000BTU unutilized as well (current two ports are 14K and 9K BTU units)

                Not even sure I need to fiddle with solar at this point although I probably still will.
                Last edited by NetComrade; 03-08-2018, 04:15 PM.

                Comment


                • #9
                  Originally posted by NetComrade View Post
                  space differene with outside R btu's to maintain
                  old wall 900 80 9 8,000 80F inside 0F outside
                  old foor 900 30 15 1,800 80F top of floor, 50F bottom of floor
                  new wall 540 80 2 21,600 80F inside 0F outside
                  new floor 800 30 15 1,600 80F top of floor, 50F bottom of floor
                  windows 2
                  room upstairs 320 80 20 1,280
                  34,280
                  This would be my BTU calculation with current setup (as is).. If I get the walls to R20 or about, my requirement becomes about 10000 BTU (ignoring windows for now).

                  This is within range of the Sanden (15000BTU, although officially they claim no more than 8000BTU load to support radiant heating).. Since my current Fujitsu still has 2 ports available and we still want radiant heating, that's what I will need to pursue (Fujitsu mostly for cooling, as it may not keep up with heating.. but technically it has 13000BTU unutilized as well (current two ports are 14K and 9K BTU units)

                  Not even sure I need to fiddle with solar at this point although I probably still will.
                  Get some information about how to calculate building HVAC loads. You're missing a lot, starting with the idea of design temps. Also, know that infiltration losses/gains can often add ~ 25 - 75 % or more to the simple conduction loss, or that R20 insulation will not give you an R20 wall.

                  Comment


                  • #10
                    Originally posted by NetComrade View Post
                    space differene with outside R btu's to maintain
                    old wall 900 80 9 8,000 80F inside 0F outside
                    old foor 900 30 15 1,800 80F top of floor, 50F bottom of floor
                    new wall 540 80 2 21,600 80F inside 0F outside
                    new floor 800 30 15 1,600 80F top of floor, 50F bottom of floor
                    windows 2
                    room upstairs 320 80 20 1,280
                    34,280
                    This would be my BTU calculation with current setup (as is).. If I get the walls to R20 or about, my requirement becomes about 10000 BTU (ignoring windows for now).

                    This is within range of the Sanden (15000BTU, although officially they claim no more than 8000BTU load to support radiant heating).. Since my current Fujitsu still has 2 ports available and we still want radiant heating, that's what I will need to pursue (Fujitsu mostly for cooling, as it may not keep up with heating.. but technically it has 13000BTU unutilized as well (current two ports are 14K and 9K BTU units)

                    Not even sure I need to fiddle with solar at this point although I probably still will.
                    You can still run a loop directly off the drainback tank to your slab no storage tank required or recommended. The slab will be your storage if you can pump enough BTU'S into it during sunny days.
                    Daikin used to sell the Altherma air to water heat pump here in the US but it was not a good seller so they removed it from the US market. Maybe you can pick one up in Canada or one of the other major brands (Panasonic, Mitsubishi, etc). They are good sellers in Europe but gas and oil are way to cheap in the US for these units to be popular.
                    The Sanden units are a little small unless you can twin them. Have you contacted Sanden about a twinning kit?

                    Comment


                    • #11
                      You can connect as many Sanden units as you want.. They support it for apartment production. Although they prefer you do it for hot water production, not radiant heating.
                      Using it for heating primarily would definitely be a hack from their perspective. But when I spoke to someone on the phone they didn't seem to frown upon it as much as their documentation would imply (would still probably be out of warranty)

                      While gas is cheap, i don't have any as this is a rural location, and propane is a hassle (nor cheap). Each unit is 2200USD.
                      Very efficient unit.

                      Comment


                      • #12
                        had struggle pasting this info out of documentation:
                        Applications Combination Heating and DHW
                        It is permitted to use the SANCO2 system to provide some limited capacity
                        heating (radiant, fan coil, etc.) in certain areas of North America, when combined
                        with a minimum of 25 gallons per day usage of DHW.
                        It is NOT permitted to use the SANCO2 system to provide heating as its only
                        function.
                        Sizing
                        Maximum heating capacity must be less than 8,000 BTU/h.
                        Minimum design ambient temperature must be above 27

                        Comment


                        • #13
                          Re: comment about solar not providing enough during the winter.
                          I think my overall feeling, I need something additional as current system isn't keeping up.
                          Solar is 'free' and I already have the panels (well, plumbing and support for them won't be free). I don't think solar would be able to provide more than 25% of the load in the winter and maybe 40-50 in fall/spring warmer months... that's where the backup comes in. So backup needs to be able to handle 100% of the load on cold and/or cloudy days.

                          Re: comment about Slab being a good BTU storage.. I agree, and yet to calculate it's capacity, however, it can only give off so many BTUs while room temp is dropping, and it's not going to 'run out' relatively quickly, so it will help moderate usage of 'backup', but backup is still needed. In addition, I think external storage at higher temperature may still be beneficial, but the cost-benefit analysis may show it's not worth it.

                          Comment


                          • #14
                            Here is a simulation for a solar heating job I proposed several years ago, the cost was way over the customers budget so it was never installed as proposed. We installed the radiant floor, and used steel radiators for the second floor sized for 130 degrees at 4 degrees outdoor temp.
                            The last page with the graph tells the whole story. Your geographic location may be different but the out come will be the same. Equine_Barn_8SKS4_PL750.pdf
                            The panels proposed were a hybrid panel somewhere between flat plate and evacuated tube, the achievable discharge temps in winter are substantially higher than flate plates as you can see from the graph. The flat plates on my home can only get up to about 90 degrees F in January, not much that can be done in less than 4 hours of sun on a good day.
                            Attached Files
                            Last edited by LucMan; 03-09-2018, 07:46 PM.

                            Comment


                            • #15
                              20180315_124903_smaller.jpg



                              So here's something I came up with
                              Disconnect existing tank (T1) from hot water and make it part of my radiant system (looks to be mostly useless though, although its heating elements are capable of producing 15K BTU)
                              Replace T1 with B1 (Ecosmart Eco11 Instant heater) for hot water.
                              Setup Sanden as primary heating system for Radiant and Hot Water (prewarm well water via heat exchanger H1)
                              Use Eco11 as backup for Radiant, as it can generate up to 35K BTU (11kW).
                              Use Taco RMB Radiant Mixing Block (H2) as radiant circulator, but it will also turn on Eco11 (B1) in case SanDen is not keeping up (e.g. 85F) and add as heat exchanger.
                              Optionally/later add S1 and S2 heat exchangers to prewarm well water or radiant water by Solar

                              I know I am missing check valves, expansion tank in this picture, and something that will maintain pressure, water filtering facility (don't plan on using glycol) and probably other details but what are your thoughts?

                              I am not ignoring heat load calculations, but based on my analysis this will be more than sufficient (and with backup).

                              I am guessing Sanden would cover 70-90% of heat and DHW use, with a portion of that covered with Solar at some point, and Eco11 picking up some load when it's really cold.
                              Last edited by NetComrade; 03-15-2018, 02:25 PM.

                              Comment

                              Working...
                              X