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Forum Index : Solar : Evacuated Tube to solar PV conversion setup

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rosspeel
Newbie

Joined: 27/03/2020
Location: Australia
Posts: 17

Posted: 05:45am 06 May 2020

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Just a project that i am going to trial over winter here in Australia, I am intending to set up this tube arrangement to act the same as my evacuated tube collector on my roof and hook of the temperature probe on top and circulation pump turn take the hot water away to my storage take heat exchanger, going to trial different configurations of solar elements in the bottom as it will take two screw in types, will lagg it will insulation

Davo99
Guru

Joined: 03/06/2019
Location: Australia
Posts: 1578

Posted: 01:36pm 06 May 2020

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Thats some Bloody Nice Fabrication there! Wish I had the skills and talent to do that.

If this is going to be on the ground and your hot water tank is on the roof, I wonder about the need for a Circ Pump?

I have run old water cooled stationary engines with thermosyphon cooling with a lot less height difference than you have there and it is amazingly effective.

Even just in your heater tank the amount of rise and subsequent Pull is is going to be significant. It's hard to put into perspective how effective and powerful Thermosyphoning can be till you have witnessed it. I never for a second thought it would be anything like I saw.

The difference between the top of my engine and the radiator was probably only 600MM and that thing Circed like a beauty. Was a 6 HP engine so putting out a decent heat and It worked fine with just 3/4 Hose. I had an open header tank on top of the low roof that was "T'ed into the system to provide a no pressure, self bleed system. The heat that went into that heater tank always amazed me. The heat had to deviate across and slightly downwards but it warmed that tank real well.
The biggest problem I had was in fact over cooling. Thermostat in the cooling Circuit fixed that.

I have been thinking of something similar to your design. I want a large Jacketed hollow tube with an inlet and outlet I can put an oil burner under and let that go up the Middle. I'd get a strip of metal and cut fingers in it or twist it to break up the gas flow boundary layer and cause some turbulence for better heat transfer.

If this doesen't provide enough heat, you can always lay that along a fire. :0)

Try the setup without the pump and see how you go. I think you may well find the thermosyphon will eliminate the need for a circ pump. The difference between the inlet and outlet is a big advantage as is the fact you will be sending the heat up high.

Damn nice work there!

rosspeel
Newbie

Joined: 27/03/2020
Location: Australia
Posts: 17

Posted: 02:20pm 06 May 2020

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The Hot water tank is ground based and has a recirc pump on it, I am going to use the controllor that came with the system and temperature probe from the evac tube on this 2 metre cylinder to control the water flow out of the cylinder.

On my calc, my existing evacuated tube is producing equal to about 470 watts per hour, so far in trials on a 80L old hot water service with a 72V element i am producing approx 900 watts with the 2.5kw of panels facing south away from the sun, the PV setup starts heating the water up by 7.30am, and the evac tubes setup starts moving water at about 10.00am

Edited 2020-05-07 00:26 by rosspeel

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