Welcome to the Solar Collector
Brainstorming and Development Page!


 

Home

Hot Air Collector

Hot Water Project 1

Hot Water & Space Heating

Solar Electric

Solar Construction 101

FAQs

Best Collectors

Simply Solar
Sign up Calendar Latest Topics
 
 
 


Reply
  Author   Comment  
sundug

Avatar / Picture

Registered:
Posts: 118
Reply with quote  #1 
Passive solar vapor generation represents a promising and environmentally benign method of water purification/desalination. However, conventional solar steam generation techniques usually rely on costly and cumbersome optical concentration systems and have relatively low efficiency due to bulk heating of the entire liquid volume. Here, an efficient strategy using extremely low-cost materials, i.e., carbon black (powder), hydrophilic porous paper, and expanded polystyrene foam is reported. Due to the excellent thermal insulation between the surface liquid and the bulk volume of the water and the suppressed radiative and convective losses from the absorber surface to the adjacent heated vapor, a record thermal efficiency of ≈88% is obtained under 1 sun without concentration, corresponding to the evaporation rate of 1.28 kg (m2 h)−1. When scaled up to a 100 cm2 array in a portable solar water still system and placed in an outdoor environment, the freshwater generation rate is 2.4 times of that of a leading commercial product.
http://onlinelibrary.wiley.com/doi/10.1002/gch2.201600003/full

__________________
Go Solar!

stmbtwle

Avatar / Picture

Registered:
Posts: 2,837
Reply with quote  #2 
Very interesting, and I can see how it might be more cost-effective. But I don't see how the water vapor is condensed and the purified water collected. This is half the challenge.

What about the impurities that are left behind in the paper? Is the paper simply discarded and replaced?

__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Gordy

Registered:
Posts: 137
Reply with quote  #3 
stmbtwie, These type of solar stills use the glazing as the condenser, placed at an angle the clean water runs down to a trough that drains to an outside container. You can see examples of this on photo # 6 at the link sundug provided.

I wonder if black felt or fleece might work instead of that special paper?

Now i'm wondering (for someone who needed more clean water) about modifying the MTD (Modified Trickle Down) collector. Get rid of the plastic between the felt and glazeing. Add a small sump at the bottom, with a float valve too an outside water source. And a PV panel and a small fountain pump, to pump the dirty water back to the top. Just what I needed another project to add to the list ;-)

__________________
Gordy,
Minnesota
stmbtwle

Avatar / Picture

Registered:
Posts: 2,837
Reply with quote  #4 
I've seen that type of still before, the water still tends to fog up the glass and reflect the sun, just like your cars's windshield in cold weather. Maybe there's some sort of non-toxic coating on the new ones? You can see the fogging in the picture of the floating survival still.

I've wondered if the glass facing the sun were doubled (twinwall?) if it would fog less, and the back away from the sun were aluminum, so the water would condense there instead of on the glazing.

And there's still the problem of salt build up on your evaporating surface, whatever it is. Perhaps you could flush it at night.

__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Gordy

Registered:
Posts: 137
Reply with quote  #5 
Not sure I'd worry about the fogging issue as they still work. It may reflect some light but I have seen commercial solar hot water panels with glazing that looked fogged by design. The sales man said it was to defuse the the light to avoid hot and cold spots both early and late in the day.

The back wall condenser should work if you put something to keep the sun off it. Leave a space at the top and bottom of the partition, to get the moisture laden air to thermal siphon. But how far do we want to take it? We could put fins on the aluminum to make it a heat sink,  add a fan on the outside to help it cool faster, Add inside to increase air flow?

Any design is going to need periodic cleaning. Even the simple design in the photo's at the link were painted black on the inside, with a door on the back wall so you could slide in Pyrex casserole pan's of dirty water. Eventually the Pyrex will need to be cleaned of the build up as it blocks the sun from getting to the black surface under the pan.

__________________
Gordy,
Minnesota
stmbtwle

Avatar / Picture

Registered:
Posts: 2,837
Reply with quote  #6 
Yes some light does get through the fogging but a lot IS reflected, has to degrade performance but hard to determine how much. I had one of those inflatable survival stills nearly 40 years ago, as big as it was it only produced a pint or so a day. I wasn't impressed.

I think if someone could figure out a way to separate the condenser from the glazing I think the whole thing would work better.

__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics