Compound Parabolic Concentrator.

[Azee Mehr]

Hi All,
I want to know if I use an six feet long evacuated tube as an obserber within the Compound Parabolic Concentrator with glass cover on the top, if I will need to vacuum the concentrator to enhance its efficacy. If so, what wil be vacuum pressure enough for the concentrator. I want to keep the water at boiling point within the evacuated tube to get some distilled water for certain use. Awaiting assistance.

[inetdog]

Hi All,
I want to know if I use an six feet long evacuated tube as an obserber within the Compound Parabolic Concentrator with glass cover on the top, if I will need to vacuum the concentrator to enhance its efficacy. If so, what wil be vacuum pressure enough for the concentrator. I want to keep the water at boiling point within the evacuated tube to get some distilled water for certain use. Awaiting assistance.

Hello Azee Mehr and welcome to Solar Panel Talk!

I think you do not fully understand how an evacuated tube (heat pipe) collector works.
The heat absorbed along the full length of the tube vaporizes a working fluid (sometimes water, sometimes acetone, other possibilities) and that vapor condenses at the manifold end of the tube.
When they are working properly no part of the evacuated tube is significantly hotter than the manifold end and the heat transfer is far better then it would be by simple conduction.

If you want to get distilled water, you will have to get it from the manifold. I do not know of any way to withdraw working fluid from an evacuated tube and make up the loss with less pure water without totally messing up the vacuum in the tube and accumulating impurities in the tube from the makeup water.
Each evacuated tube is a closed system.

Now if you can manage to get more than 100C at the manifold, you will have your source of distilled water.

The conduction/convection cooling of the tube inside the parabolic collector will be small, particularly if the tube temperature is kept low, as it would be for a domestic water system. Trying to hold a reduced pressure outside the tube seems like it would be a mechanical nightmare, require active pumping, and for little gain. But I have not actually run the thermal calculations to support that feeling.

[Azee Mehr]

Dear inetdog,
Thanks for your reply.
I will not use heat pipe. I have enough sun light in my area. If I simply place an evacuated tube in sun with water in it, the water gets boil and even that boiled water splits out of the tube.
I'm intending to place whole body of evacuated tube within the compound parabolic concentrator with its opening side (mouth) out of the concentrator. Tube opening side will be connected to the one side of the heater hose and the second end of the heater hose will be connected to a glass chamber in which vapours raised from the hot water will get collected and will get drain outside of the glass chamber as distilled water.
Metal float valve with in the glass chamber will control the hot water level in glass chamber. As the level of horizontally placed evacuated tube connected with glass chamber through heater hose will be lower than glass chamber so it will remain full of water all the time whereas the hottest water will travel upto glass chamber as per thermosyphone theory.
So I want to know if vacuuming of concentrator chamber will spead up the water boiling process as I am using evacuated tube as observer or it will be useless to vacuuming compound parabolic concentrator with glass cover over it.....?
Awaiting comments.

Hello Azee Mehr and welcome to Solar Panel Talk!

I think you do not fully understand how an evacuated tube (heat pipe) collector works.
The heat absorbed along the full length of the tube vaporizes a working fluid (sometimes water, sometimes acetone, other possibilities) and that vapor condenses at the manifold end of the tube.
When they are working properly no part of the evacuated tube is significantly hotter than the manifold end and the heat transfer is far better then it would be by simple conduction.

If you want to get distilled water, you will have to get it from the manifold. I do not know of any way to withdraw working fluid from an evacuated tube and make up the loss with less pure water without totally messing up the vacuum in the tube and accumulating impurities in the tube from the makeup water.
Each evacuated tube is a closed system.

Now if you can manage to get more than 100C at the manifold, you will have your source of distilled water.

The conduction/convection cooling of the tube inside the parabolic collector will be small, particularly if the tube temperature is kept low, as it would be for a domestic water system. Trying to hold a reduced pressure outside the tube seems like it would be a mechanical nightmare, require active pumping, and for little gain. But I have not actually run the thermal calculations to support that feeling.

[J.P.M.]

How much water do you require ? Litres ? Barrels ? truckloads ? And, does the water need to be sanitary or sterile, or just not too dirty ?

[Azee Mehr]

Just want to get pure drinking water for home consumption. Though the requirement is 10 liters a day in winter season in processed. But think it would not be more than 5 liters. I am using Reverse Osmosis filter at home but it stays expensive and requires membrane and other filter replacements very often. Moreover it wastes 2/3 of the water as contaminated water.

How much water do you require ? Litres ? Barrels ? truckloads ? And, does the water need to be sanitary or sterile, or just not too dirty ?

[J.P.M.]

You want a solar fired still.

There are many web sites with many workable schemes and ideas for doing that. A starter: Check out: builditsolar.com. --->>> cooking and drying --->>> solar stills.

A few minutes there will give you more info/ideas than you can get here in an hour.