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Our new off-grid home
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The Chinese copies are about half price than the Navitron ones-I have a rack of 50 Chinese tubes as a swimming pool heater-I busted a few installing them(they interface in a st/steel manifold with silicone rubber mounts) and got some local Navitron ones as replacements.
The Chinese tubes are based round a copper based anti reflection coating,whereas the Navitron still look dark blue but are semi translucent-but deffo not copper.As an expt I stood one of each side by side strapped to a ladder in the garden,in full sun,and filled with water-they hold around 2 lts each,and both boiled the water in just over two hours-the performance difference seems negligible,and they are on there 3rd or 4 th season now with no sign of degradation.
Location: UK | Registered: October 14, 2008Reply With QuoteReport This Post
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Originally posted by taralec:
Any thoughts on evacuated tubes for solar water heating-though once you have expanded the solar pv,might not be much south facing roof left

We haven't decided on the solar hot water system yet, but I'll check out evacuated tubes. Thanks.


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Location: Maui, Hawaii | Registered: June 09, 2003Reply With QuoteReport This Post
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I have a really good idea for solar water heating. I want to combine a solar collector with tankless water heating. This is a company that makes a wide range of tankless. And they work as boost heaters.

Basically my idea is to mount a standard tank waterheat outside and remove the two electric elements and in there place install the solar collector. Have a circulator pump mounted to the tank, powered by a solar panel. On the output of the tank that goes into the house hot water supply line mount a tankless "boost" heater. If the water is hot the heater never turns on. If it needs heating it works. The smallest tankless is less than $250 retail new. If you are good you can make your own collector out of framing insulation glass and copper pipe. Or you can buy a 4 X 8 collector for about $800. The dc pump is $$275 and the dc solar panel about $75. That is about $1500 with a little give. Ideally you could find a good tank used without heating elements for free. If you have to buy a new one that is about $300.

Tell me what you think.

In Fort Lauderdale running a 2006 Jeep Liberty CRD 2 veg tanks HOH 2 upgraded greasecar vavles 3/8 fuel line 5/8 heater line HOH Hose wrapped filter. Injector Line heater on the Common Rail. 2nd car 2005 Mercedes CDI, Raw Power fuel pump, 36 gallon veg tank in trunk coolant heated HOH, rubber hose wrapped fuel filter, FPHE, 3 greasecar valves, Common rail line heater.
Location: Ft Lauderdale, FL | Registered: June 01, 2002Reply With QuoteReport This Post
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Yup, it works extremely well. I made one years ago for an off-grid home. Used a propane fueled tankless heater for back-up. A tank of propane 'lasts forever'. The more sun the more speed on the pump, it's almost self regulating. Simple, easy, cost effective.

Location: coldest N.America | Registered: May 03, 2005Reply With QuoteReport This Post
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If you assemble a heat exchanger in the supply tank and mount the tank higher than the hot water solar collector you can use a thermosyphon approach to circulate the solar heat to the tank and eliminate the added complexity and expense of the electric circulation pump and electric solar panel. Even better if you also paint the tank black and put in a glass topped insulated box directly exposed to the sun.
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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