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Author Topic: Passive Solar  (Read 453 times)

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Re: Passive Solar
« on: August 24, 2017, 02:10:06 pm »
The most efficient way to heat water is with a vacuum tube

Agelbert NOTE: The most thermodynamically efficient way to heat water is with a vacuum tube. WHY? Because a vacuum has no thermal conductivity. You trap the heat and that heat tranfers to the matter inside it as long as the sun is out. The tube cracking hazard with these tubes is demonstrated in this video and the surprising (i.e. using SAND!  :o   ) solution  is explained. 

By the way, vacuum tube solar water heating for homes is routine in China where they use solar panel  harvested electricity more for other energy needs. Solar panel electricity is obviously better used for other household electrical demands.

If we did not use electricty to heat our water in the USA, an estimeted 30% LESS energy would be required on the grid! That is a gob smacking amount of energy we unnecessarily waste each year!

Much of China is as far north as Canada, so please do not bring up the "cold climate" excuse for not using this method. No matter how cold it is outside, that cold cannot get to the solar heated part of the vacuum tube because there is ZERO thermal conductivity.

While it is true that air has low thermal conductivity, in northern climates the air in the air tube type is being cooled constantly, which counteracts the solar heat and causes excessive cooling of the water at night. Consequently, air tubes for heating water (note: they do work okay for heating house air) are a bad idea for anything but tropical climates.

Metals are excellent thermal conductors, but they have the electrolysis problem of corroding when dissimilar metals are in contact, so a non-metal type material inside the vacuum tube is preferable to a metal that contacts the copper water pipe within.

Thermal Conductivity Chart

The sand used in the video is VERY fine grained. The finer the grain, the more heat you will be able to capture in it. Coarse grained sand is useless.

Beyond aesthetic considerations, there is no valid reason whatsoever for us to use electricity to heat our water in the USA. Lazy human love of convenience and fossil fuel piggery are selfish, but not scientifically valid, reasons. Have a nice day.   

Evacuated Solar Tube Implosion Solar Water Heater Thermal Storage 

Published on Jun 5, 2016

Solar evacuated tubes are extremely efficient at transferring sunlight to heat. This heat is then transferred to the material inside. This video is for lower quality water heaters that may experience rain water infiltration from poor designs. This is also an efficient method for enhancing good designs enabling solar thermal storage. If you use heated water in the morning from a system like this, the standard fins may be a better option. The thermal storage does last several hours.
Rob not the poor, because he is poor: neither oppress the afflicted in the gate:
For the Lord will plead their cause, and spoil the soul of those that spoiled them. Pr. 22:22-23


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