building a parabolic solar hot water heater

7/28/2019 Building a Parabolic Solar Hot Water Heater

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http://www.instructables.com/id/Building-a-Parabolic-Solar-Hot-Water-Heater-using-/

Food Living Outside Play Technology Workshop

Building a Parabolic Solar Hot-Water Heater using 123Dby ben.chapman on June 27, 2012

Table of Contents

Building a Parabolic Solar Hot-Water Heater using 123D ................................................................................

Intro: Building a Parabolic Solar Hot-Water Heater using 123D .........................................................................

Step 1: Is it Possible? .......................................................................................................

Step 2: Designing the Shape ..................................................................................................

Step 3: Creating the Shape in 123D .............................................................................................

File Downloads ...........................................................................................................

Step 4: Slicing the shape in 123D-Make ..........................................................................................

File Downloads ...........................................................................................................

Step 5: Laser-Cut and Assemble ...............................................................................................

Step 6: Create the Surface ...................................................................................................

Step 7: Make it Shiny! ....................................................................................................... 1

Step 8: Test 1: Light things on fire! .............................................................................................. 1

Step 9: Add the Boiler ....................................................................................................... 1

Step 10: Make some Tea! .................................................................................................... 1

Related Instructables ........................................................................................................ 1

Advertisements ............................................................................................................... 1

Comments ................................................................................................................ 1
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Image Notes1. It works! Tap water comes in one tube and boiling water comes out the other(fairly slowly).

Image Notes1. This is what I wanted it to perform like. Just point it at the sun, open up thevalve and fill up your mug for tea!

Step 1:Is it Possible?My first step was to do a calculation to figure out if my idea was crazy. I started with my goal: Make the solar equivalent of the hot-water tap on a coffee machine.How much power do I need?Lets say I want to fill up my mug with hot water in about 15 seconds. That means I'll need to do about 1 liter per minute starting at room temperature (~20C) and endiat tea temperature (~80C). That's a 60C temperature change, and water has a heat capacity of 4.18 kilojoules per kilogram C. So, for 1 liter (one kg.) we need 250.kilojoules. To do that in 60 seconds, we need about 4.2 kilowatts of power. That's a lot!

How big of a mirror is that?In most places, on a clear sunny day, there's about .8 kilowatts of sunlight per square meter. That means that we would need 5.25 square-meters of mirror, which woube a dish 2.6 meters (8.5 feet) across!

That was a lot bigger than I could make, but it gave me an idea of scale. For example, if I could wait 1 minute instead of 15 seconds for my cup of water, I only needed4-foot dish. In the end, I decided to make a 36" dish because that was the biggest I could make on my laser cutter without slicing up my support rings into smaller piec(which is certainly an option.)


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Image Notes

1. A graphing calculator is one way to visualise your curve. (Use "Zoom" "Square" to graph it undistorded)

Step 2:Designing the ShapeMy second step was to define the shape of my dish. The general shape is called a parabola (or technically a parabaloid because it is a 3D surface created by rotating parabola about its axis of symmetry). Parabolas are shaped such that they reflect rays (in our case, sunlight) to a central focal point. They can be described (andgraphed) using a mathematical equation:

y = x2/(4f) Where f is the height of the focal point. For example, I could make a parabola with a radius of 2 feet and a focal point height of 1 foot by using the equation

x2/4 and calculating from x=-2 to 2.

Another way of thinking about your parabola is to use the equation FD = R2/4 where D is the depth of the dish from the center to the rim and R is the radius of the rim.

Using my equation (I used y= x2/4 and calculating from x=-2 to 2), I calculated about 20 (x,y) points between 0 and 2. (I didn't worry about units, because I was plannion changing the scale later.)


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Image Notes1. When aimed correctly, parabolas reflect incoming rays to one focal point.

Step 3:Creating the Shape in 123DOnce I had the set of points, I used 123D to make the 3 dimensional shape. 123D is a free, easy to learn CAD software available from Autodesk.http://www.123dapp.com/123d

In 123D, I created a sketch and entered the coordinates of my points one at a time. Then I connected them with a spline. This is the curve that defines the inner surfacof the dish. I added some more lines to complete the cross-section of the dish, then revolved it 360 degrees about the center line.

Image Notes1. My line of points.

Image Notes1. Making a spline and Offsetting.
http://www.123dapp.com/123d


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Image Notes1. Completing the profile to revolve.

File Downloads

Parabola5S.stl (6 MB)[NOTE: When saving, if you see .tmp as the file ext, rename it to 'Parabola5S.stl']

Step 4:Slicing the shape in 123D-MakeFrom 123D, I exported my dish as an STL file and imported that into 123D Make. This is another free software from Autodesk that you can download athttp://www.123dapp.com/make or the Apple Mac-App-Store.

123D Make lets you turn your 3d shape into a lattice of 2d profiles that you can cut out and fit together. After importing my shape, scaled it to the biggest size I couldmake on my laser cutter and I chose a radial slicing pattern. I chose the slice direction from the dish's center outwards (like spokes) and upwards like rings. 123D Makautomatically calculates the profiles I needed for the lattice and adds slots so that every piece slides into the correct place.

I started by making an 11-inch diameter dish out of cardboard as a prototype, then did a 36" diameter dish out of .25" plywood. 123D Make's nesting algorithm wastesmaterial by putting too few segments on a given sheet. I wanted to lay out the pattern to use the most of my material, so after generating the laser sheets, I consolidatthem in CorelDraw. For the 36" dish, I had to cut the biggest rings in separate pieces, so I split them in CorelDraw before cutting. (Looking back, I would have made thpieces of the ring interlock like a puzzle, adding more rigidity.)

File Downloads

Parabola5-0.eps (710 KB)[NOTE: When saving, if you see .tmp as the file ext, rename it to 'Parabola5-0.eps']


http://www.instructables.com/files/orig/F9U/WD7E/H4AFRZE7/F9UWD7EH4AFRZE7.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/F0V/395Z/H4AGHRM3/F0V395ZH4AGHRM3.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/F0V/395Z/H4AGHRM3/F0V395ZH4AGHRM3.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/F0V/395Z/H4AGHRM3/F0V395ZH4AGHRM3.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/F0V/395Z/H4AGHRM3/F0V395ZH4AGHRM3.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FEN/I1OL/H4AGIIDY/FENI1OLH4AGIIDY.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FEN/I1OL/H4AGIIDY/FENI1OLH4AGIIDY.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FEN/I1OL/H4AGIIDY/FENI1OLH4AGIIDY.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FEN/I1OL/H4AGIIDY/FENI1OLH4AGIIDY.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FLR/NN2U/H4AFVGPK/FLRNN2UH4AFVGPK.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FLR/NN2U/H4AFVGPK/FLRNN2UH4AFVGPK.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FLR/NN2U/H4AFVGPK/FLRNN2UH4AFVGPK.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FLR/NN2U/H4AFVGPK/FLRNN2UH4AFVGPK.eps?utm_source=pdf&utm_campaign=fileshttp://www.123dapp.com/makehttp://www.instructables.com/files/orig/FP2/AECS/H4AFVGOU/FP2AECSH4AFVGOU.stl?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FP2/AECS/H4AFVGOU/FP2AECSH4AFVGOU.stl?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FP2/AECS/H4AFVGOU/FP2AECSH4AFVGOU.stl?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FP2/AECS/H4AFVGOU/FP2AECSH4AFVGOU.stl?utm_source=pdf&utm_campaign=files


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Step 5:Laser-Cut and AssembleI cut the parts on a 120W 24x36 Epilog laser. For the 36" dish parts, it took about 3 hours to get everything cut out of .25" plywood. It's very important that your wood iperfectly flat on the cutting bed, otherwise the laser won't be focused correctly and won't cut well. I used tape to help hold mine flat, but keep flatness in mind whenbuying your material.

Once everything was cut, it was time for assembly. 123D-Make does a neat animation of how your dish can be assembled. For this job, I used a bit of hot glue to holdfirst three supports in place, but after that, no glue was needed. There was enough friction that the dish held itself together perfectly.

Image Notes1. Here are the parts, ready to assemble. I cut a few extra radial supports, whichcame in handy.
http://www.instructables.com/files/orig/FEY/7I23/H4AGHRMC/FEY7I23H4AGHRMC.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FEY/7I23/H4AGHRMC/FEY7I23H4AGHRMC.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FEY/7I23/H4AGHRMC/FEY7I23H4AGHRMC.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FEY/7I23/H4AGHRMC/FEY7I23H4AGHRMC.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FAV/MYGH/H4AGD5XX/FAVMYGHH4AGD5XX.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FAV/MYGH/H4AGD5XX/FAVMYGHH4AGD5XX.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FAV/MYGH/H4AGD5XX/FAVMYGHH4AGD5XX.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FAV/MYGH/H4AGD5XX/FAVMYGHH4AGD5XX.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FTR/WD3S/H4AFRZE8/FTRWD3SH4AFRZE8.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FTR/WD3S/H4AFRZE8/FTRWD3SH4AFRZE8.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FTR/WD3S/H4AFRZE8/FTRWD3SH4AFRZE8.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FTR/WD3S/H4AFRZE8/FTRWD3SH4AFRZE8.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FK1/X40G/H4AFVGPP/FK1X40GH4AFVGPP.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FK1/X40G/H4AFVGPP/FK1X40GH4AFVGPP.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FK1/X40G/H4AFVGPP/FK1X40GH4AFVGPP.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FK1/X40G/H4AFVGPP/FK1X40GH4AFVGPP.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FR7/NYCC/H4AGHRM5/FR7NYCCH4AGHRM5.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FR7/NYCC/H4AGHRM5/FR7NYCCH4AGHRM5.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FR7/NYCC/H4AGHRM5/FR7NYCCH4AGHRM5.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FR7/NYCC/H4AGHRM5/FR7NYCCH4AGHRM5.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FKW/ZAIA/H4AGHRM4/FKWZAIAH4AGHRM4.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FKW/ZAIA/H4AGHRM4/FKWZAIAH4AGHRM4.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FKW/ZAIA/H4AGHRM4/FKWZAIAH4AGHRM4.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/FKW/ZAIA/H4AGHRM4/FKWZAIAH4AGHRM4.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/F9U/WD7E/H4AFRZE7/F9UWD7EH4AFRZE7.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/F9U/WD7E/H4AFRZE7/F9UWD7EH4AFRZE7.eps?utm_source=pdf&utm_campaign=fileshttp://www.instructables.com/files/orig/F9U/WD7E/H4AFRZE7/F9UWD7EH4AFRZE7.eps?utm_source=pdf&utm_campaign=files


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Image Notes1. Start by lining up all of the circles using one radial support. You can usesome hot-glue to hold them in place.

Image Notes1. Continue adding radial supports, making sure the slots are all the way in. Myslots were tight enough that I didn't need to use any glue, the structure holdsitself together!


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Step 6:Create the SurfaceNow that I had the wooden lattice, I needed a smooth, continuous surface to serve as the inside of the dish. I did this using a layer of masking tape, then several layer

spackle. The first layer of spackle filled in the depressions in the tape. The later layers I used a pre-cut wooden form, rotating it around to spread the spackle evenly tocorrect curvature. I used a laser-cut piece of wood glued to a piece of sand paper to sand the surface to the correct curvature.

Once the spackle had the smooth, curved surface that I was looking for, I sealed the surface with three coats of clear acrylic paint. I considered epoxy and polyurethanbut decided on acrylic since i t was the least toxic and had the lowest environmental impact.

Image Notes1. Covering the lattice with masking tape. I painted a small amount of wood glueonto the surface of the lattice to help the tape stick. For this parabola I used 4"wide masking tape, about two or three layers thick.

Image Notes1. Adding the first layer of spackle. Just enough to fill in the depressions. Thereare probably other filler-materials that don't have as high a risk of cracking, butspackle is pretty easy and safe to work with.


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Image Notes1. Using the laser-cut profile to spread the 3rd layer of spackle. I put down a lotof spackle and revolved the wooden form around, scraping off the extra.

Image Notes1. After it hardened, I drew lines on the surface using pencil. These help youidentify the high-spots and low spots when you are sanding.

Image Notes1. Sanding to the correct curvature using sandpaper glued to a wooden cut-out.

Image Notes1. Finished surface ready for a coat of clear paint to seal it and make it even

smoother.

Step 7:Make it Shiny!My next step was to add an adhesive-backed mylar film to the surface of the dish. I got mine online from Green Power Science (who also have some great youtubevideos about making solar parabolas). You can probably get the same stuff elsewhere for less money, but I knew that this stuff would work. I was able to do my large dwith strips cut from one 24"x36" roll.

I used a knife and a straight edge to cut strips about 1" wide. Then laid them down, starting with a strip across the center and working up to the left and the right. At theend, I trimmed off the extra around the rim and it was ready for the first test.

Image Notes1. I started at the center, trying to set the strips down without much overlap,
http://www.youtube.com/user/GREENPOWERSCIENCE/featuredhttp://www.youtube.com/user/GREENPOWERSCIENCE/featuredhttp://greenpowerscience.com/SHOPREFLECTIVEBUY.html


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but without any gaps.

Image Notes1. It gets trickier at the edges, but it's fine to use smaller pieces and overlap thema bit to match the curve.

Image Notes1. Here's the final mirror, trimmed around the perimeter.


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Image Notes1. This is my reflection. It's certainly not optically perfect, but it's quite reflective. Ithere are bubbles or folds in the mylar, take a knife and make a small cut, thenrub it down flat.

Step 8:Test 1: Light things on fire!To test the parabola's performance, I brought it outside, pointed it at the sun, and lit things on fire. I wanted to figure out how small of an area the dish was able to focuthe light. Wearing dark welding goggles, I held a piece of wood at the focal point (about 10 inches above the center) and could get the light to concentrate on a circleabout 2 inches in diameter! That means I'm getting over 250 times the power of the ambient sunlight!

Next, we tried roasting marshmallows. Unfortunately, they hardly cooked at all. They were so white that they reflected all the light that hit them. When we rubbed someblack charcoal on one and it started charring instantly when we put it in the beam.

On a Safety note, always store your mirror covered or out of the sun so it will not burn your house down. Try not to leave your mirror unattended in a sunny spot.


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Image Notes

1. We successfully lit pieces of newspaper on fire and blackened pieces of wood.It was fairly windy, so a calm day might be better.

Image Notes1. Marshmallows were too white to cook.

Step 9:Add the BoilerThe next step is to add the boiler. I decided to use a coil of copper pipe for my boiler, so i t would function like an on-demand hot-water tap. I used 5 feet of 1/4 inch tubI coiled it myself without any proper pipe-bending tools. I used salt to fill the tube so it wouldn't crush and I coiled it around a series of smaller and smaller cylindricalobjects until I got to the diameter I wanted. Check out my instructable on bending copper tubing.

After completing the coil, I mounted it to a piece of scrap pipe going through the center. The diameter pipe is about 1/2 an inch smaller than the inner diameter of the cI filled the empty space with spackle, which will function as insulation for the inside of the coil. Finally, I painted the coil with a coating of black stove-paint. It's paint thadesigned to handle high temperatures and it's very important. Without it, the coil would just reflect most of the energy we are beaming at it.

I drilled a whole through the center of the parabola and mounted a piece of pipe that will hold the boiler using some laser-cut disks of wood. Two plastic hoses come uthrough the center to run water to and from the boiler. There's a needle valve to regulate the water flow.

Image Notes
http://www.instructables.com/id/How-to-Bend-Copper-Pipe-and-Tubing-without-Crushin/


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Image Notes1. The tubing coil turned out beautifully once I learned I needed to fill the tubewith salt to prevent crushing.

1. It's stuck on a pipe using spackle, which helps insulate, and painted with blachigh-temp paint.


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Image Notes1. I drilled a hole through the center of the mirror and mounted the central pipeusing a wood disc.2. The boiler assembly is held in place using a set-screw so the height andorientation are adjustable.

Image Notes1. Hook up a pipe to the tap or to a gravity-feed system and control the flow withthe valve. I used my camelback reservoir.

Step 10:Make some Tea!I brought it outside and pointed it at the sun, using the shadow of the boiler as an aiming device. It gets really hot. A black piece of metal gets up to 600 degrees F(however a white marshmallow barely gets warm). It is able to make steam, and very slowly produce a stream of boiling water. It's about a drop every second. It can acook Bacon!


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Comments

50 comments Add Comment view all 74 commen

nsundqvist says: Mar 24, 2013. 2:00 PM REPNice work!!! Whot do you think about my heater?

http://www.youtube.com/watch?v=a2b7c9WnRhA

nzqwack says: Jan 5, 2013. 10:51 PM REPUsing Copper pipe polish it then Just heat it up with a gas flame and surface will oxidise to copper oxide on air contact in seconds which is black saves

having to paint!

M2Field says: Aug 5, 2012. 6:57 PM REPHow come you did not simply use a discarded satellite antenna for this project? Would have saved a ton of time and calculations. The receivers are alreadmounted at the focus point and the bracket is already made to the correct length.

roccopeterbilt says: Nov 12, 2012. 6:28 AM REPThis was going to be my question. Be really cool to get one of the big old ones that had a diameter closer to what your data showed you needed, thenswap out the copper coil for a magnifying glass and make a death ray!

straight says: Oct 12, 2012. 7:14 PM REPI had an experience like you bt the biggest problem was the sun movement as you know after minuts you have to change the dish location .do you have ansolution for this problem? Id like to know your idea .thanks

person% says: Aug 17, 2012. 4:54 PM REPawesome! i want to try that!

grt57 says: Aug 12, 2012. 7:55 AM REPBacon is good!

rkrayer says: Aug 5, 2012. 11:03 AM REPGreat instructable. Would love to see ideas for heating or supplementing a conventional tank-style water heater.

Buckshott00 says: Aug 9, 2012. 6:41 AM REPThe best way to do this would be to setup a thermal battery and recirculate a thermal fluid between a storage tank and the heating coils of your water

tank. If you're on a budget try it with peanut oil. It has a decent heat transfer coefficient and can go to around 475F before it starts to degrade, plus it isway cheaper than a lot of other materials. You have to really insulate your tanks and lines. Again for the budget minded I would suggest Superwool andDap or Great Stuff. There is better choices but those are pretty good and won't break the bank. The only trick is sizing your thermal battery to be largeenough to meet your hot water demands given losses to inefficiency in the pumps, lines, and transfer. Although if you lived in the southwest US youcould meet the US average quite easily.

icej75 says: Aug 7, 2012. 5:39 PM REPben for some ideas here is a professional solar cooker we make where I work. this is a write up on a customer's opinion on it.http://www.solarcooker-at-cantinawest.com/andersen-solar-cooker-parabolic-with-optional-rotisserie-motor.html

Kold says: Aug 2, 2012. 9:47 PM REPhey, your video is private! i really wanted to see this thing work =D

Linksep says: Aug 7, 2012. 1:12 PM REPWahoo! Video fixed (I like my bacon a little crispier than that though).

ben.chapman says: Aug 7, 2012. 5:38 PM REPThe dark part of the bacon cooks well. The white fatty part is harder to get cooked since it reflects more of the light beaming at it.

alcurb says: Aug 6, 2012. 8:39 AM REPYou need to be in his inner circle :-)
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windshadow says: Aug 5, 2012. 10:52 PM REPYeah dude what is up with the video ?

mikeputnam says: Aug 5, 2012. 8:52 AM REPBump! Cannot view the video.

Linksep says: Aug 6, 2012. 6:19 PM REPBump +1

mbainrot says: Aug 7, 2012. 12:38 AM REPBump +2 :)

ben.chapman says: Aug 7, 2012. 10:33 AM REPHi All, The video should now be public. I forgot to hit save the last time I tried to make it public (and I've been backpacking for the last 4 days). Thanks for athe great comments!

rhino says: Aug 5, 2012. 5:54 PM REPVery worthwhile project. Can I accomplish the heater by gluing mirror tiles to a satellite dish?

ben.chapman says: Aug 7, 2012. 10:30 AM REPYes. I've seen a bunch of successful projects that do that. You can probably find the mirrors that they use for Disco Balls quite cheaply.

RAYLOGAN5 says: Aug 6, 2012. 1:44 PM REPI have gone thru all of the steps and now I am stuck. How about showing where the motor and tracking PHOTO LED'S STRUCTURE is made and where iis placed in order to make it work?

Regards,

Ray E. Walters

maewert says: Aug 6, 2012. 2:32 PM REPThe author didn't show where to place the motor because his instructible didn't include a tracking motor. As is you have to manually point it. Shouldn't b

too hard to add one though.

Wazzupdoc says: Aug 6, 2012. 2:26 PM REPSweet!. If you reversed the "mold" shape, you could do a gelcoat male mold and pop out fiberglass parabolas by the blimp-load!

godbacon says: Aug 6, 2012. 9:12 AM REPcovering the coil with glass would help it retain heat,block wind.Adding some thermal mass around the coil would allow it to store a bit of heat, for passing clouds and the like. If you were to put the coil into a block ofconcrete say inside a mason jar,using a black pigment to color the concrete I think you would get a more even heating of your water. Good luck with theapplication,it was a nice instructable.

devonfletch says: Aug 6, 2012. 6:35 AM REPYou can make a very simple parabolic reflector by taking a flat sheet of Stainless Steel, and bend it in one plane, to conform with a couple of ply (or other)parabolic frames.

Then, a straight piece of pipe across the focus, will harvest the heat and Bob's-your-uncle.This configuration also has the advantage that it does not need a tracking system, just maybe a weekly adjustment up or down, to follow the sun as it'travels' around the ecliptic.Good shiny SS can be found in old clothes-dryer drums (the outer surface, the inner being shot-peened by the metal zippers and buttons), and SSappliances (the inner surface, the outer normally being brushed).This system will not deliver boiling water, unless you live in Mexico, but it's a very good heater for general hot water applications.

tabi says: Aug 6, 2012. 8:48 AM REPCould you post some pics? this sounds great (and I do live en Mexico hehehe)
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maewert says: Aug 6, 2012. 5:30 AM REPI meant a 3" concave mirror shiny side to the coils :-)

maewert says: Aug 6, 2012. 5:28 AM REPNice instructable.

Maybe you'll want to add a convex mirror on the end of the boiler tube to focus any stray light back onto the boiler coils as it appears some light is missingthe coils.See the image for a really bad attempt to show you where to add the convex mirror.

Maybe you will want to add a solar array to generate electricity to run a small pump that would pump water from an insulated tank into the coils and backagain. That way you'll be able to quickly fill your tea cup a few times a day so long as you let the system recharge (and you'll still have a cup of hot waterafter the sun goes down).

Adding a tracking system should not be too difficult. You'll want even more solar PV cells to drive the electronics :-)

guruji1 says: Aug 6, 2012. 4:24 AM REPGreat work my friend although if you had a satellite dish you would have half the job ready. Anyway thanks for sharing this.Regards

AllenInks says: Aug 5, 2012. 9:20 PM REPre tracking: I remember an article fom Mother Earth News from back in the 70's tsome one had a dish he wanted to track the sun.. they had two ramactuators, plumbed to two flat black reservoirs. the reservoirs were mounted to rotate with the dish. the one on right had baffle shading it from sun rays froleft, but could be warmerd by sun rays from right. similarly, the one on left was baffled to be shaded from right and warmed by sun rays from left. thereservoir on right was plumbed to actautor that extended to turn dish and reservoirs to right, and reservoir on left plumbed to actuator to extend to turn dishto left. thus when sun is to tp right of dish, iit warms reservoir on right and not the left, causing dish to rotate toward sun .dish stops when both reservoirs awarmed equally, and dish is pointing at sun. as sun moves, heating is unbalanced again, anf reultant difference in reservoir temps changes volume of fluid

in each system, to cause actuators to work to rotate dish back into alifhnment with sun.... no electricity required.

Bill WW says: Aug 5, 2012. 2:48 PM REPGreat, Ben; I will be back to study in detail!

Re: good comment from Rimar on Juy 2, he recommends 1 m^2 minimum area.

Incoming solar energy is max 1000 W at surface of Earth. So we have about 1 kW to work with, our challenge is to convert as much of this resource as possible to useable heat and electrical or mechanical energy.

Bill WW says: Aug 5, 2012. 9:10 PM REPOops! Sorry Ben, should have read your Step 1 more carefully.You said : "In most places, on a clear sunny day, there's about .8 kilowatts of sunlight per square meter. " That is more realistic than my 1 kW per squameter.

profpat says: Aug 5, 2012. 9:00 PM REPnice one, very nice for the environment!

now if could just recycle those old satellite disk in the dumpster!

breeeez says: Aug 3, 2012. 6:25 AM REPWhy would you heat hot water?

spencer2710 says: Aug 5, 2012. 7:54 PM REPto make it hotter! duh...

JAMEJO says: Aug 5, 2012. 11:19 AM REPExactly right !!!! People always tell me they want a new hot water heater, and I make the same comment: It's "water heater". It could be called a hotwater tank, but it's definitely NOT a "hot water heater". Pet peeve.

AllenInks says: Aug 5, 2012. 8:58 PM REPactually, most water heaters ( tank water heaters) here in US are hot water heaters. even at rhe moment that heaters turn on, the water is hot,heaters just turn on to make it hotter. otherwise, if the water were cold before thermostat would turne on heters, then sometimes when you open howater faucet, you'd get cold water, and sometimes you'd get hot water. Of course, a tankless water heater is another matter...

sorry to rain on your pet peeve....
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rdavis184 says: Aug 5, 2012. 7:35 AM REPGood job.BTW, it's a water heater, not a hot water heater. Hot water doesn't need to be heated ;-)

spencer2710 says: Aug 5, 2012. 7:53 PM REPIt does if you want it hotter!

kev1n1956 says: Aug 5, 2012. 6:27 PM REPShoulda said up front it would cook bacon..........Mmmmmmm bacon...

newbeatle says: Aug 5, 2012. 2:23 PM REPso interesting your work , i have a parabola from a operating room that i have buy once some years ago then i have the mayor part of the work made it. iallways have tinked about how to build the heater, you gave me a great idea. btw i like to know hoy to see the video you attached beacause only says thatprivate...... so ?thankis in advance you can contact me at [email protected]

best regards

Alex, from mexico

Grimshack says: Aug 3, 2012. 8:32 AM REPcould you do this with a tv dish?

Gilo says: Aug 5, 2012. 1:58 PM REPI did. I used a discarded sat dish. Took out the receiver pod and replaced it w a soda can to heat water. I can start a charcoal briquette w it in less thanminutes.

When I was a kid, i stole my Grandma's washing machine lid (circa 1963) and used it as a solar heater using aluminum foil as the reflective material.

I used a mlar sheet for the sat dish version.

Nice work there Ben.

BTW, you can cut out a parabola outline on a plywood piece. Use it to shape a sand or dirt right on the ground by rotating it on center on the sand/dirtpile.

Pour concrete to make the template (negative). or just mold the dish right out of it.

ArrowRoSA says: Aug 5, 2012. 12:09 PM REP

Some idea recomendation for dish solar tracking system.Video is here http://www.youtube.com/watch?v=tekVzmQx6qoelectronics here: http://s017.radikal.ru/i420/1203/e0/4fe708ce3ab2.jpgcomponents are here:* U1/U2 - LM339* Q1 - TIP42C* Q2 - TIP41C* Q3 - 2N3906* Q4 - 2N3904* R1 - 1meg* R2 - 1k* R3 - 10k* R4 - 10k* R5 - 10k* R6 - 4.7k* R7 - 2.7k* C1 - 10n ceramic

* M - DC motor up to the 1* photo LEDs - 5mm 563nmboard of components are here:http://s019.radikal.ru/i639/1203/f4/25cd527e2a44.jpgstructure of sensor is http://radikal.ru/F/s019.radikal.ru/i627/1203/f9/017b5b71d341.gif

totszwai says: Aug 5, 2012. 11:57 AM REPYour video is private...
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batmat says: Aug 5, 2012. 7:45 AM REPVery good. I have a satellite dish plate, old and unused.Can I use this your idea?I would like to see the video that you made, this time as this video is private. You can show me working?I could use the mirror in place of foil, what do you think of the idea?

swilchek3 says: Aug 5, 2012. 11:13 AM REPIndeed you could! Using satellite dishes as a parabolic reflector is common practice in creating high powered home built lights! The benefit is you havethe backing of a million dollar fabrication method to ensure a more perfect surface - with his masking tape technique the efficiency of his design isunfortunately a lot less than the conceptual model on his computer.

frollard says: Aug 2, 2012. 2:58 PM REPAwesome ible - your embedded video is tagged as private however :(

ben.chapman says: Aug 2, 2012. 3:44 PM REPThanks! All fixed!

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