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  • #16
    Originally posted by PNPmacnab View Post

    Yes, the panels are operated at power point with excess solar and this feeds into standard heater elements. Too bad these systems haven't reached the general public yet. A couple of panels can maintain tank temps from heat loss.

    I bought a NYLE external HPWH. Should the tank go, just buy another tank. The compressor, fan and Gundfoss pump are also easy to replace if into that. They will fail eventually. I got a deal on this one for $385 shipped. Payback on that is a no brainer. Wife likes it dehumidifying the basement.

    Like politics, all solar is local. Heating water is very complex. Exporting power tends to be worthless. might as well put that into heating water with resistance heating. So you want to turn on the water heater those two hours of max sun. They have controllers that do this, but not sure how well they actually work around your life. It can take 70W just to maintain tank temperature. An extra panel probably won't help as you likely have excess now. I heat water solely with PV in the summer without an issue. Come October I don't even have a chance due to almost continual clouds.
    Actually, water heating is quite simple. It's the methods that non technical and non savvy folks get suckered into that makes it overly and unnecessarily complex.

    1.) Reduce the DHW load as much as possible.
    2.) Add thermal energy in the safest way possible using the most cost effective fuel in the least complicated fashion possible.
    3.) insulate all storage devices and distribution lines to the creates cost effectiveness.

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    • #17
      None of that is easy for people. You are putting energy into a tank that may or not be used. Keeping temps as low as possible till the time that cheap energy will be available. Makeup water tanks that extend use time at the expense of more energy lost. It can be horribly complex making it efficient. Good thing solar is free energy.

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      • #18
        Originally posted by PNPmacnab View Post
        None of that is easy for people. You are putting energy into a tank that may or not be used. Keeping temps as low as possible till the time that cheap energy will be available. Makeup water tanks that extend use time at the expense of more energy lost. It can be horribly complex making it efficient. Good thing solar is free energy.
        The thermal energy put into a tank will be either used or dissipated via heat loss. First law of Thermodynamics.
        Keeping temps. as low as possible while maintaining usable temps. is common sense and a goal that's easily met via appropriate tank sizing and thermostats.
        Standby losses are dealt with via appropriate and no brainer insulation.
        All those measures have been and can be dealt with in using well known, highly reliable and long available ways. They are not the least bit complicated as proven by how little folks actually need to even look at their conventional DHW systems.

        The energy from the sun is indeed free. The equipment that allows it to be transformed and put to a useful purpose is not. The trick is to find a renewable source that's available enough to meet the load, and equipment that uses the solar resource in ways that's as safe, reliable and cost effective as what's come to be known as conventional methods.

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        • #19
          I use 2 passive water heating systems, daisy chained. First is a 90 gal storage tank above the masonry heater. It is warmed via thermosiphon to about 90F. It then feeds a 40 gal rooftop solar tank, heated by a glycol loop in a flat plate collector. Wintertime, I'm feeding the tankless heater 90 - 100F water, and the propane only needs to add 15 degrees as I'm using hot water. Summer, the flat plate heats the rooftop tank over 130F and a mixer valve cools the water entering the tankless heater, to about 110F
          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

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          • #20
            It's like the sports channel when they say, We just need to get the ball, run with the ball, and keep the ball to win. That is pretty simple!

            Back to the OP. HPWH or extra panel should have a payoff. He is moving to low use. We don't skimp with water and still our needs are small. For a three month period fall and winter we averaged 47 cents a day with a HPWH. Hard to pay off much with those numbers. That would be double if just resistance heating was used. There is a lot of data from the utility hotshot program on a variety of usage levels. Exporting energy if not almost worthless now will soon be unless panels face West. Using that cheap energy makes an extra panel or HPWH a poor choice. Best payoff would be a smart controller that sends proportional energy to the water heater based on exporting and time. At high production times raise the temp to 150F or above. Even so, from minimal useful temps to 150F that much energy can't be stored. Does one need that much water? Some controllers operate the heater elements independently and use stratification of the tank temps to minimize energy use. Control will be the future as the smart meters will start billing different rates every 15 minutes. My small town has at least two Solar farms. The homeowner producer is a nuisance and future rates will reflect that.

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            • #21
              Originally posted by PNPmacnab View Post
              Exporting energy if not almost worthless now will soon be unless panels face West.
              For many, if not most situations, if grid tied and on a T.O.U. NEM tariff, a 270 deg. azimuth will be less cost effective than a 180 deg. azimuth.

              For just about all SO. CA users for example, the ideal azimuth is ~~ 200 - 225 deg. azimuth if tilt is the common ~ 20 or so deg.

              For my location (92026) and as an example only, using PVWatts :

              180 deg. az. offsets ~ $448/yr. in electric bill and generates ~ 1,720 kWh/yr per installed STC kW.

              225 deg. az. offsets ~ $453/yr. and generates ~ 1,680 kWh/yr. per STC kW.

              270 deg. az. offsets ~ $414/yr. and generates ~ 1,530 kWh/yr. per STC kW.

              Thinking a 270 deg. azimuth system will be produce better output, and more importantly for most users, better cost effectiveness than a 180 deg. azimuth with a T.O.U. billing tariff is a mistake, at least in CA. and probably many other areas with similar billing times and schedules.

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              • #22
                Originally posted by J.P.M. View Post
                .......
                Thinking a 270 deg. azimuth system will be produce better output, and more importantly for most users, better cost effectiveness than a 180 deg. azimuth with a T.O.U. billing tariff is a mistake, at least in CA. and probably many other areas with similar billing times and schedules.
                The OP is in Tampa. He may be on a TOU rate or not. In California the peak TOU rates seem to be shifting to later in the day. If his situation ai similar then orienting more toward the west may be a calculated gamble that could possibly optimize his financial return. He would have to run the numbers specific to his location and rate schedule. Your mileage may vary.
                Last edited by Ampster; 12-10-2018, 05:33 PM.
                9 kW solar, 42kWh LFP storage. EV owner since 2012

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                • #23
                  Originally posted by Ampster View Post

                  The OP is in Tampa. He may be on a TOU rate or not. In California the peak TOU rates seem to be shifting to later in the day. If his situation ai similar then orienting more toward the west may be a calculated gamble that could possibly optimize his financial return. He would have to run the numbers specific to his location and rate schedule. Your mileage may vary.
                  If the OP is not on T.O.U. then there will be no pricing or generation advantage to a westward alignment and no other advantage besides those of weather patterns of low(er) morning irradiance making part of your above statement moot.

                  CA T.O.U. times are currently stable and have not changed since the AB 327 mandated effects took hold.

                  Once upon a time, maybe 5 or so years ago, T.O.U. pricing for residential customers was almost an afterthought by the CA POCOs, as reflected by the number that about 85 % of CA residential users are still on tiered rates of one sort or another with no T.O.U.

                  After the T.O.U. tariff time realignments were done and took effect to reflect the reality of times of power use in 2017, T.O.U. times of peak pricing, which previously had tended to accidently and/or coincidentally mostly followed the GHI levels have not changed much. And since then, residential T.O.U. rates have bounced around some and actually go down once in a while (see SDG & E peak rate for sch. DR-SES (T.O.U. residential pricing for homes w/PV) pricing: 12/1/17, $0.54257/kWh, 09/07/18, 0.44566/kWh, 11/01/20180.52899/kWh as an example only).

                  Some day, we may and probably will all be on T.O.U. - as the POCOs might want us to think is already a fiat accompli. But that day is not yet upon us. Also, at least for CA POCOs, many existing and planned T.O.U.s are actually a blend of T.O.U. and tiered rates as POCOs try to garner the best of both worlds with a tiered set of levels overlaid on a T.O.U. level.

                  It is always a good thing when folks have and use good information with which to make decisions. Unfortunately, at this time they don't have good info they can understand and wouldn't use it if they did.

                  Also, it may be wise to consider that rates and times change to reflect usage patterns, and there is nothing sacred or locked in stone now or in the future about how POCOs charge for power or even how long NEM will be available or in what form.

                  Or, perhaps more importantly for this discussion, when those times and rates will change. As an example only of how POCO pricing policy might affect system cost effectiveness (and perhaps in a highly improbable but not impossible way), suppose oil becomes unavailable for some reason and EV's REALLY take off, and most folks charge their vehicles at night. That might create a situation where the nite time demand on the POCOs is so high that the time from, say, 2300 hrs. to 0600 hrs. becomes super peak to discourage taxing the system (the logic given by the POCOs now for the latest time shift) with perhaps some realignment of generation buy rates by the POCO from customers with PV that might be above sell rates charged by the POCO. I kind of doubt that or anything like that happening, but the point is setting array alignment to maximize cost effectiveness to current POCO prices and times must be recognized as an imperfect process given the variability of those POCO rate policies.
                  Last edited by J.P.M.; 12-10-2018, 08:45 PM.

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                  • #24
                    Originally posted by J.P.M. View Post
                    .......................................
                    Some day, we may and probably will all be on T.O.U. ..................................................
                    Someday?
                    I thought the California Energy Commission mandated TOU rates beginning in 2019. Maybe this is worthy of a separate thread, since it will not affect the OP. I think it is an interesting topic, at least for us in California on NEM.
                    Last edited by Ampster; 12-10-2018, 09:32 PM.
                    9 kW solar, 42kWh LFP storage. EV owner since 2012

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                    • #25
                      So I am in Tampa and duke energy has net metering. My question originates based on would it make more sense to get another panel to increase overall output or get a hpwh to reduce usage to net me to zero. Obviously getting a hpwh makes immediate sense if there was no solar in the picture. Ultimately I have to see how much my over under is historically as my net metering is reset end of this month. I happen to have one of those hot shot units I bought off eBay for 350 bucks I did mention I f with things continuously, but it ran and died, I got my money back hence my willingness to buy another panel or spend a bit more on an AO Smith hpwh...

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                      • #26
                        The payback on a HPWH will depend on your rate, and the current capacity of your system versus your usage. Perhaps you mentioned that earlier but I am on my phone and traveling. I will reread your posts later.
                        9 kW solar, 42kWh LFP storage. EV owner since 2012

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                        • #27
                          Originally posted by Ampster View Post
                          Someday?
                          I thought the California Energy Commission mandated TOU rates beginning in 2019. Maybe this is worthy of a separate thread, since it will not affect the OP. I think it is an interesting topic, at least for us in California on NEM.
                          Well, that's what you may think and have been led to believe. That is a general direction, policy and strong intent at this point, and as I wrote, may well come to pass. Perhaps in 2019. At this point it's a policy, but not a mandate, at least not at this time. That time may be in 2019. However, at this time it's SDG & E and I believe other IOU statement that customers on tiered rates can stay on tiered rates with a positive election (notification) to the POCO of their desire to stay on tiered rates.

                          I agree that this is worth a separate thread. So much so that it's been discussed several times over the last few years with me as an active participant. I've no intention of rehashing what's already been beaten to death.

                          For this thread, I was responding to PNPmacnab's statement with respect to the (implied) higher value of energy produced by west facing arrays which is generally (at least in most of CA and probably elsewhere) not the case. In that regard, I agree with you that it's necessary to run the numbers. I've done that and for CA at least, a 270 deg. array azimuth at any reasonable, common or optimum tilt, west facing arrays will be less cost effective than south facing arrays under current CA T.O.U. tariffs and most situations.

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                          • #28
                            Originally posted by Ampster View Post
                            The payback on a HPWH will depend on...
                            I questioned a good friend here in the biz about HPWHs and he said in the hot climate of AZ he didn't really recommend them for families with low demand. He said the payback is just too long. Due to the low split between the incoming water temps and the target tank temps, the unit would not be running that often. In my case, nearly six months out of the year, our city water is almost 90 degrees right out of the tap. It takes very little energy to boost it the rest of the way. I don't like the complications of a heat pump either. If I had a growing family of 6 kids it might be another matter of course.

                            To the OP, if it were me, I would add the other panel and not make a water heater decision until it actually fails. Although your current water heater will not be as efficient as a new HPWH, a standard water heater that is already paid for, installed and working is far cheaper than a new one that needs purchased and installed. Don't try to save a few bucks a month by spending a thousand now on a new one if your's is still working.

                            But that's just me. I also drive old cars until they really can't be fixed. That is far better on the environment and my wallet than throwing away a good working car and building/paying for a new one.
                            Dave W. Gilbert AZ
                            6.63kW grid-tie owner

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                            • #29
                              Originally posted by Ampster View Post
                              The payback on a HPWH will depend on your rate, and the current capacity of your system versus your usage.
                              Just like every other energy use related decision. Nothing new there.

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                              • #30
                                Originally posted by azdave View Post

                                I questioned a good friend here in the biz about HPWHs and he said in the hot climate of AZ he didn't really recommend them for families with low demand. He said the payback is just too long. Due to the low split between the incoming water temps and the target tank temps, the unit would not be running that often. In my case, nearly six months out of the year, our city water is almost 90 degrees right out of the tap. It takes very little energy to boost it the rest of the way. I don't like the complications of a heat pump either. If I had a growing family of 6 kids it might be another matter of course.

                                To the OP, if it were me, I would add the other panel and not make a water heater decision until it actually fails. Although your current water heater will not be as efficient as a new HPWH, a standard water heater that is already paid for, installed and working is far cheaper than a new one that needs purchased and installed. Don't try to save a few bucks a month by spending a thousand now on a new one if your's is still working.

                                But that's just me. I also drive old cars until they really can't be fixed. That is far better on the environment and my wallet than throwing away a good working car and building/paying for a new one.
                                Not so common common sense there.

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