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View Diary: Solar Power: Making the right choice, the easy choice ... (260 comments)

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  •  The weather reports show clouds and precip (5+ / 0-)

    there now, solar output is way down under clouds.Add in the fairly low efficiency of photovoltaics, and it become clear that if heat is what you are after, direct use of sunlight as a heat source is much more effective and cheaper. Even on overcast days solar space heating can give a 10 degrees C rise with simple systems that cost far less than PV panels. Solar generated electricity is a pretty poor way to heat a home, solar thermal is much more effective.

    •  Sorry, I wasn't clear (8+ / 0-)

      in my house solar space heating isn't an option.  I'm in the lower unit of a 2 family with close neighbors on all sides.  I don't get much direct sun in my unit.

      But if I could generate just enough electricity to spark my natural gas furnace on I could be toasty and keep pipes from freezing.  And on most days it would be possible to at least do that.

      Darwinic pilgrims claim the image fills them with an overwhelming feeling of logic. --The Onion

      by mem from somerville on Sun Dec 14, 2008 at 07:00:43 AM PST

      [ Parent ]

      •  Ah, OK, just run the controller and blower (6+ / 0-)

        I suspect that a simple off-the-shelf UPS would be as effective amd much cheaper.   The batteries will run down at some point, but they could be sized for X days of running.  You'll need batteries anyway, several days worth to handle cases where the power goes out early in several days of storm.  I suspect an extra week worth of batteries is no more expensive than the PV panel would be.

        •  I don't even have a blower (6+ / 0-)

          I have a boiler and hot water.  All I need is the spark for the initial flame.

          However, the way the current wiring is I don't see an easy way to add a UPS.  So I figured as part of the larger panel project it would be time to re-configure that.

          Darwinic pilgrims claim the image fills them with an overwhelming feeling of logic. --The Onion

          by mem from somerville on Sun Dec 14, 2008 at 07:26:09 AM PST

          [ Parent ]

          •  "Wondering if" is right... batteries needed. (7+ / 0-)

            You would need either an 'off grid' system with a batteries, or a hybrid, 'grid-tied' system with a
            battery backup.

            To run pumps and fans, which use a lot of electricity,
            you would need a fairly substantial battery bank =
            lots of dollars.

            The cheaper 'grid-tied only' systems will not run without grid power. Part of this is a safety mechanism  to prevent backfeeding power into the utility's wires while the linemen are working on them.

            Your boiler hot water circulator pumps probably pull 80 watts each+-, which adds up pretty quick over a 24hr. period. To get 3-4 days of backup power 'could' require a good sized battery bank.

            •  I can't find the specs for my furnace (4+ / 0-)

              it came with the house.  But even 80 watts doesn't sound like that much to me.  It isn't like that runs continuously.  

              It wouldn't have to run much to keep my house above freezing.  And over several days there would be several more opportunities to re-charge.  

              Darwinic pilgrims claim the image fills them with an overwhelming feeling of logic. --The Onion

              by mem from somerville on Sun Dec 14, 2008 at 08:33:45 AM PST

              [ Parent ]

              •  Boiler specs... (6+ / 0-)

                Here's what you can do... take a look at the boiler.

                If it is forced hot water (not a steam boiler), there will be anywhere from one to four or five circulator pumps to push the hot water through each 'zone...' usually 2 or 3.

                Sometimes one circulator runs domestic hot water from the boiler too, but just count your circulators. You can look up the brand and model to get an idea of how many watts they use.

                One typical circulator is a "TACO 007." This uses about 80watts per hour of running time. Even though the boiler only fires periodically, the circulators could be running a lot of hours each day.

                If you've got 3 circulators at 80watts running 10 hours a day in 10deg. to 20deg. weather, you're using 800watts each per day, or 2.4kwh of juice.

                You would be making new power to recharge the batteries, but you'd probably want to size the battery bank for at least 3 to 4 days of autonomy in case you got 3 cloudy days in a row. You want to keep battery discharge to a minimum to maximize the life span. You can spend anywhere from $500 to $1,000 each to get good ones.

                BTW, what type of solar hot water collector do you have? We have an evacuated tube collector. It works great. We make about 75% of our hot water up here in NH.  

                •  It is steam (4+ / 0-)

                  And no separate zones.

                  I have a Sol 25.

                  I can't tell how much of my hot water I'm getting because the backup hot water tank is also natural gas.  I can't separate out the heat/cooking/hot water pieces individually.  But my last gas bill was down 25% over last year's.  And that was already down 15-18% over the prior year due to the insulation.

                  Darwinic pilgrims claim the image fills them with an overwhelming feeling of logic. --The Onion

                  by mem from somerville on Sun Dec 14, 2008 at 09:18:39 AM PST

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                  •  Stiebel Eltron makes really good equipment. (8+ / 0-)

                    Re: the Steam. If you have steam you probably have don't have much of a circulator load, so the battery backup 'might' even work with a USP type system.

                    What about the solar loop pumps? Are they DC pumps with  PV power? Or, would they need battery backup too?

                    As for the Stiebel-Eltron collector... they're a good manufacturer. I have one of their 105gal. solar storage tanks. Two internal heat exchange coils and great insulation. Sounds like you're doing really well on the solar hot water and insulation. 25% on top of 15% to 18% is great.

                    I 'hear ya' on the gas use. We use propane for heat,  (now backup hot water), the range and the clothes dryer, so it's hard to tell where we're saving most.

                    We're down about 40% in gas use over the past 2-3 years with solar hot water, new appliances and insulation.

                    Hot water pipe insulation is "the best" investment you can make. You can cut heat loss by 75% in an unheated basement with just 1/2" thick pipe insulation. That's helped us a lot.

          •  Ah, OK (4+ / 0-)

            I'm used to forced air heat, many of the older hoses having been converted from coal or sawdust burning heating systems many decades ago.  Older apartments often have boiler systems, but those have blowers for the burners, as does my natural gas furnace.

          •  Vacumm Tube collectors (0+ / 0-)

            for Hot water is a possibility, MUCH more efficient than a flat panel collectors during cloudy days and more efficient than PV 80% vs 15-18%

            I just started a company to import these and am going to be installing them on my own home, which is a combination of Nat gas forced air & nat gas water heating(radiant) and hope to get 85% of my natural gas bill eliminated.

            Using the blower on the furnace and installing an in line fan to pull more heated air from the top floor back to the bottom and having a water to air heat exchanger as a heat dump for excess hot water should do the job.

            Diary forthcoming..

            Chicago just got your weather this morning, damn it's cold out there, perfect weather for solar..

            stay warm

            A perfection of means, and confusion of aims, seems to be our main problem.- Albert Einstein

            by bldr on Mon Dec 15, 2008 at 09:37:20 AM PST

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      •  work out a share deal with your upstairs neighbor (4+ / 0-)

        go in with them investing in a system and share the benefit. There's some simple agreements that cover all the basics.

        My previous cohousing condo in Oakland shares the roof with the nonprofit that owns the building shell, and we were able to work out pretty quickly an amendment to our roof maintenance agreement/fund that let us put solar in there.

    •  Interested ... (3+ / 0-)
      Recommended by:
      Ed in Montana, RunawayRose, Turbonerd

      What solar hot air systems have you seen? What do you 'recommend'?  Thoughts?

      •  My solar hot water system... (4+ / 0-)

        ...has a loop to a radiator in  the furnace so the gas isn't used until well into the night only, the fan - somewhat earlier in the dead of winter.
        We have a lot of cold temp. days but we also get a lot of sun so I get plenty of hot water even on very cold - but sunny- days.

        The optimist thinks this is the best of all possible worlds. The pessimist fears it is true. J. Robert Oppenheimer {-8.25 / -5.64}

        by carver on Sun Dec 14, 2008 at 08:12:53 AM PST

        [ Parent ]

    •  Also latitude matters. (1+ / 0-)
      Recommended by:
      Ed in Montana
      Incoming solar power is at a more direct angle closer to the equator.  People in Northern states SHOULD be subsidizing solar power adoption in the Southern states rather than installing their own systems.

      -7.75 -4.67

      "Freedom's just another word for nothing left to lose."

      There are no Christians in foxholes.

      by Odysseus on Sun Dec 14, 2008 at 08:38:56 AM PST

      [ Parent ]

      •  Latitude is not as important as a "solar window." (11+ / 0-)

        We're at about 43deg. North latitude here in NH. We installed a 2kw PV system in the summer of 2007.
        Between the power we make and another $250-$300 investment in compact fluorescents and power strips we've cut our average $92/month electric bill down to about $26/month.

        But...we have a good 'solar window' with unobstructed sun from about 9:30 am (this time of year) to 4:00pm.

        On top of that the photovoltaics are 'much' more efficient in cold weather, so if you have a good solar window, and mount your panels "at latitude" tilt angle,  
        northern states are very suitable to making solar power.

      •  Think global, act local (2+ / 0-)
        Recommended by:
        RunawayRose, A Siegel

        Strive to understand the global issues surrounding energy ... but act to make your local market more sustainable. If I lived in Maine, I wouldn't count on Florida selling my electricity if the shit hits the fan. Heck, the grid probably won't survive long if TSHTF. People could tear it down to sell the metal.

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