Using solar concentrator to vaporize greywater?

dragonfly Jafe · Post by **dragonfly Jafe** » Thu Sep 20, 2007 6:45 pm

Anyone ever try using a solar concentrator (parabolic mirrors or fresnel lens) to vaporize greywater?

A 31"x41" supposedly puts out 1.4kw at full sun. Over an 8 hour period that should vaporize at least 50 gallons (assuming you use a solar tracker).

31"x41" fresnel lens; http://www.goldmine-elec-products.com/p ... variation=

cheap solar tracker circuit; http://www.redrok.com/electron.htm#led3x

unjonharley · Post by **unjonharley** » Thu Sep 20, 2007 7:00 pm

my head has been playing with the idea.. but i wanted to catch the vapor for reuse.. maybe i should start smaller..

some where in my junk i have the plans for a parabolic lens coffee maker..

see what you did? now i have to dig for it.. hmmm back about 5 years with a solor oven and rocket stove...now where would that be??¿¿

stargeezer · Post by **stargeezer** » Thu Sep 20, 2007 7:34 pm

I designed the solar system that provides my domestic hot water, and a significant portion of the heat for my home. From all of my experience I believe that you are heading in the wrong direction.

I have given several suggestions in other threads on ways to help evaporate greywater. While adding solar heat is an obvious choice, I have refrained from suggesting this step for several safety reasons. My biggest concern here is that the most benefit would be achieved by heating the entire greywater storage and watch the steam rise. This sounds very nice, but you now have enough scalding water to seriously injure campers that are not too sharp.

If you are really interested in solar heat collection, PM me and I would be happy to discuss this with you, but I do not want to discuss this where others may take some ideas and create a dangerous environment. I have just seen too many implementations that could put somebody in the hospital, which is not exactly close to the playa.

EB · Post by EB » Fri Sep 21, 2007 11:11 am

No fair.

If you've discovered a way to turn water into steam you have to share it with everybody.

EB

p.s. Except Iran.

stargeezer · Post by **stargeezer** » Fri Sep 21, 2007 2:10 pm

Using solar to generate steam is not a problem depending on how much you want to generate and how much area you are willing to dedicate to the project. The problems are containing the steam and the building pressure, and dealing with the temperature issue.

Commercial products are available, and home brew is possible, but it can also be very explosive. In my system, I keep the temperature low enough that I do not develop steam and therefore no pressure problem, but 170 F water can still cause serious injury.

CapSmashy · Post by **CapSmashy** » Fri Sep 21, 2007 4:18 pm

A little signage designating the gray water area as HOT and SCALDING DANGER or similar notices, perhaps a small picket fence with some firmly attached greenery for aesthetics and if anyone gets hurt after warning signs and a barrier, its on them. That whole radical self reliance coupled with the warning on the back of the ticket...

And vaporizing grey water via solar power sounds fantabulous. Set up a solar still to catch the steam and reclaim some of the water for later use.

dragonfly Jafe · Post by **dragonfly Jafe** » Fri Sep 21, 2007 4:44 pm

...yes, of course there are a few safety concerns (but this is burningman).

the focus will be at 1000 degrees or more, and dangerous to look at (welding goggles required to avoid retinal damage). Proper shield design could greatly reduce this risk.

If the focus wanders (from the collector going off target, or being knocked over, or whatever) a new target could catch fire. A strong design and perimeter control can minimize this risk.

and of course the water will be at 212 degrees, so people could get burned (if they somehow come in contact with it).

If you try to create pressurized steam (I am not advocating that, yet) there are a whole bunch of additional dangers to consider.

Then there is the stench potential.

At the moment I am considering a well shielded thermal mass that gets water dripped on it by a float valve. 1/10th to 1/5th of a gallon each minute would be required. The storage tank would have a cheese cloth filter and bleach tablets. The whole thing would be guarded by a fence with signs (about the size of a evap pond).

In addition to vaporizing water, by switching out the target other things could be melted, such as aluminum cans (this apparently also stinks). Lastly, it is allegedly possible to conduct the energy down a fiber optic cable, and wood burn (etc) with the other end.

All in all a promising device.

somekind · Post by **somekind** » Sat Sep 22, 2007 12:13 am

Camp hot tub? What's the address?

stargeezer · Post by **stargeezer** » Sat Sep 22, 2007 9:07 am

A 31"x41" supposedly puts out 1.4kw at full sun. Over an 8 hour period that should vaporize at least 50 gallons (assuming you use a solar tracker).

1/10th to 1/5th of a gallon each minute would be required.

I just wanted to point out that your numbers do not work and here is why:

It takes 1 BTU to heat 1 lb of liquid water 1 deg F. I am not sure the elevation of BRC, but let us make an assumption that you only need to heat the water 100 F (80 to 180?) to get it to boil, that means 100 BTU is required for the temperature change. Now let us look at the phase change, it takes 972 BTU to vaporize that same 1 lb of water. Thus you need a total of 100 + 972 or 1072 BTU to vaporize this 1 lb of water.

Now looking at your lens, assuming your number is correct and you get 1.4 kw, that is equal to 4760 BTU/Hr. Thus you could vaporize 4760/1072 or approx 4.5 lb of water per hour.

Water weighs 8.333 lbs per gallon, so this system could vaporize 4.5/8.333 or .54 gal/hr. Even at your 1/10 gpm you have a flow rate 10 times too high.

Overestimating what can be done with solar is a common mistake. Build a prototye of your system to learn what capabilites are, and then you can enlarge it to meet your needs. There are several little tricks you can do to get small increases in performance, but there is no substitute for collection area and you should start with as large as you can tolerate and it will probably still need to grow. Just for a point of reference, my system has 240 sqr ft of active collection area and at some point I may double that.

unjonharley · Post by **unjonharley** » Sat Sep 22, 2007 9:41 am

dragonfly Jafe wrote:...yes, of course there are a few safety concerns (but this is burningman).

the focus will be at 1000 degrees or more, and dangerous to look at (welding goggles required to avoid retinal damage). Proper shield design could greatly reduce this risk.

If the focus wanders (from the collector going off target, or being knocked over, or whatever) a new target could catch fire. A strong design and perimeter control can minimize this risk.

and of course the water will be at 212 degrees, so people could get burned (if they somehow come in contact with it).

If you try to create pressurized steam (I am not advocating that, yet) there are a whole bunch of additional dangers to consider.

Then there is the stench potential.

At the moment I am considering a well shielded thermal mass that gets water dripped on it by a float valve. 1/10th to 1/5th of a gallon each minute would be required. The storage tank would have a cheese cloth filter and bleach tablets. The whole thing would be guarded by a fence with signs (about the size of a evap pond).

In addition to vaporizing water, by switching out the target other things could be melted, such as aluminum cans (this apparently also stinks). Lastly, it is allegedly possible to conduct the energy down a fiber optic cable, and wood burn (etc) with the other end.

All in all a promising device.

I like your idea here and will be watching as you"grow" it into some workable stage..
my problem so far is what happens to the dryed droduct..

that would plug any small tubing

so far i have found the expensive paper towel in a large screen basket is the best filter for playa dust.. been playing with this while cleaning the camp stuff and van.. the paper can be put into the worm bin..

other than solor evap.. there is a in line RV filler filter.. if I were to get most playa & other out.. then run it through this filter.. a bleach treatment and the water would be good to use.. again

Das Bus · Post by **Das Bus** » Sat Sep 22, 2007 10:24 pm

unjonharley wrote:my head has been playing with the idea.. but i wanted to catch the vapor for reuse.. maybe i should start smaller..

some where in my junk i have the plans for a parabolic lens coffee maker..

see what you did? now i have to dig for it.. hmmm back about 5 years with a solor oven and rocket stove...now where would that be????

If you ever find those plans, my hubby (Gordy) would love a copy! He's talked to many people about using the bottoms from spray paint cans to make solar cigarette lighters, but has yet to find the correct focal point.

He was also talking at the burn to some other campmates about solar evaporation.

He's not signed up on the eplaya, but I'm sending him a link to this thread, so you might be hearing from him.

stargeezer · Post by **stargeezer** » Sun Sep 23, 2007 8:08 am

He's talked to many people about using the bottoms from spray paint cans to make solar cigarette lighters, but has yet to find the correct focal point.

A small magnifing mirror works great. While it is more fragile than metal, it can be protected with a small case. If you are not requiring it be a reflective lighter, a plastic 'magnifing glass' would be effective, durable, and cheap.

skibear · Post by **skibear** » Wed Sep 26, 2007 9:50 am

The Steam Bath Project at 8:00 and Arctic was close to my camp.
They had a wood fired boiler and used lots of water to make
steam. It was neat for early AM or PM near sunset or later. Way
to hot for mid day use (though open then!!)

I'd bet they'ed like solar for some of the water heating.

phil · Post by **phil** » Wed Sep 26, 2007 11:08 am

Das Bus wrote: ... using the bottoms from spray paint cans to make solar cigarette lighters, but has yet to find the correct focal point.

My hazy recollection is that parabolic curves have focal points. I believe that the bottoms of pressurized cans are spherical and don't have a focal point.

See http://en.wikipedia.org/wiki/Parabolic_mirror for more information on parabolas and http://en.wikipedia.org/wiki/Spherical_aberration for information on why spherical mirrors don't focus. Your husband might get more and better information from the AEZ people, who had a solar reflector made from mirrors.

http://www.ae-zone.org/

dragonfly Jafe · Post by **dragonfly Jafe** » Wed Sep 26, 2007 4:09 pm

...well I got one of those 30x40 lenses yesterday. Enough with the numbers, time to start vaporizing stuff!

unjonharley · Post by **unjonharley** » Wed Sep 26, 2007 4:45 pm

dragonfly Jafe wrote:...well I got one of those 30x40 lenses yesterday. Enough with the numbers, time to start vaporizing stuff!

\/
that's true burner talk..

where did ya get the lenes??
i want to fry some huge carpenter ants..)

Das Bus · Post by **Das Bus** » Thu Sep 27, 2007 2:18 am

phil wrote:
Das Bus wrote: ... using the bottoms from spray paint cans to make solar cigarette lighters, but has yet to find the correct focal point.
My hazy recollection is that parabolic curves have focal points. I believe that the bottoms of pressurized cans are spherical and don't have a focal point.

See http://en.wikipedia.org/wiki/Parabolic_mirror for more information on parabolas and http://en.wikipedia.org/wiki/Spherical_aberration for information on why spherical mirrors don't focus. Your husband might get more and better information from the AEZ people, who had a solar reflector made from mirrors.

http://www.ae-zone.org/

Thanks Phil! He did try twice going to AEZ, and the one time he did find someone to talk to, they weren't very interested. I think this was later in the week, and it wasn't one of the solar death ray guys.

The reason behind spray paint cans, is basically because he uses alot of the stuff.

I have a solar cigarette lighter I bought off ebay in 2000. It's great to watch people who don't believe it works, and then ta da! Cigarette is lit!

Flammepus · Post by **Flammepus** » Thu Sep 27, 2007 5:57 am

[quote="stargeezer"]I designed the solar system that provides my domestic hot water, and a significant portion of the heat for my home. [/quote]

My god! A whole solar system to heat your home? I've been considering using the power of the sun alone

stargeezer · Post by **stargeezer** » Sat Sep 29, 2007 3:58 pm

Flammepus wrote:
stargeezer wrote:I designed the solar system that provides my domestic hot water, and a significant portion of the heat for my home.
My god! A whole solar system to heat your home? I've been considering using the power of the sun alone

The sun works great during the day, but I wanted to collect a little energy at night!!

stargeezer · Post by **stargeezer** » Sun Oct 07, 2007 8:12 am

dragonfly Jafe wrote:...well I got one of those 30x40 lenses yesterday. Enough with the numbers, time to start vaporizing stuff!

Any results yet? I know it has been overcast much of the time, but there should have been a couple of days good for experiments. I am just curious, having data is much more fun than theory, and if there is disagreement, it is fun to figure out what was overlooked!

Good luck, and please post results.