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Forum Index : Solar : I’m In Hot Water Now!
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MacGyver Guru  Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Crew As most here already know, I live in my Land Yacht (RV) full time and just recently added a 20-gallon electric water heater. It extends my shower time from 5 minutes to nearly a half hour. A 5-minute shower is great when you're in the Navy, but I'm 62! Anyway, I threw together a small solar water heater today: 
It's approximately 27 inches square. The clear window is Lexan and the frame was formerly a frame to something else (I found the metal at the junk yard heap). I cut the original frame in half, sandwiched the Lexan between the aluminum frame and some wood (so as not to crack the silly stuff!), painted things black and screwed it all together. Here, you can see how stuff was sandwiched together using screws and wood: 
Here's a tight shot of everything cramed together: 
The coil is a nearly-50-foot roll of 1/2" soft copper painted black to absorb the sun's heat. I wound the pipe in what's called a "flemish". It's like a snail's shell, which starts at the center and slowly increases in diameter as loops of pipe are added. The finished product is a "spiral". The water will be pumped through it from one end of the pipe to the other (not sure which way will be in and which will be out -- but that doesn't matter). I'll draw the cooler water off the bottom of my 20-gallon storage tank and return it to the top using "T" fittings on both the cold and hot lines at the side of the heater. All lines exposed to air will be insulated with thermo-cell pipe insulation and painted to resist UV decay. Here's a shot of the finished product perched atop my new 20-gallon electric heater: 
Tomorrow, I'll try to get the pump and pipes fitted and mount the collector on my RV's roof. Maybe I'll have a solar shower tomorrow night, eh? The most peculiar thing about this post is the pictures all look like they were shot on black and white film, but in reality, my camera shoots color. Belay that! Oh, my; I just checked my camera and found that it is in "Black & White" mode. How'd that happen? Go figure! I'll pop back by here after it's a "done deal" and post more (COLOR) pictures, probably tomorrow. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Project Update It took me all day fumbling around to get the rest of the stuff built. I have it mounted on my roof now and piped all the way to the ground, where I have installed a recirculating pump on a timer. I installed a horizontal swing-check (valve) in the pump's output line to prevent the whole setup from reverse thermo-siphoning when it's colder at night and the hot water in the tank (mounted at ground level) is looking for a place to go (heated water rises if left to its own devices). All that's left to do is insulate all the lines, fill it and drain off the air, then it's good to go. It should provide me with years and years of hassle-free FREE solar-heated water. I'll post more pictures tomorrow, after I get everything where it goes. By the way, about the only thing that can go wrong with this kind of thing, excluding pump failure or a pin-hole leak, is freezing weather. All solar applications should include a way to drain the collector in case of freezing weather. An over-night freeze will burst the pipes and then it's all just scrap metal. A way to cheat the system is to have the pump come on intermittently throughout the night to send a shot of hot water through things, but that's chancy. A quick word about construction "costs" here: The R-16 20-gallon electric water heater set me back about $320. The nearly-full roll of 1/2"soft copper I had kicking around, but it would have cost me something like $1.40 per foot wholesale. I had the little pump from a former solar heater and then of course there is extra pipe, fittings, solder, welding gas, pipe insulation and mounting hardware. All in all I think I would have spent in the neighborhood of about $600 and maybe even a bit more, if I'd gotten everything brand new like the heater. The other side of that coin is I get free hot water forever! With the cost of electricity what it is presently, it costs me 3 KwHr per day. What that actually costs depends on what "tier" I fall into, based on the rest of my usage, but suffice to say, it would be at least $1 a day and likely a little more. At a dollar a day, this puppy will be paid for in about 2 years or less based on electricity savings. The project could be done cheaper if a used electric-assist water heater were utilized, but I'm kinda picky, so I bought that new. After it's been operating for a week or so, I'll post output information just in case anyone else wants to build one for themselves. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Mac Looking good mate, it will be still going when the cost is well and truly forgotten, you shouldn't have to worry about it freezing where you are. All the best Bob Foolin Around |
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mac46 Guru Joined: 07/02/2008 Location: United StatesPosts: 412 |
Mac, I have been thinking of doing this also, but thought I might also need a expansion tank. I've never tried this. Looking for a huge sucess on you'r project. Keep us posted. .....Mac46 I'm just a farmer |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Crew It's flying! I tied in the panel, the tank and the little pump today, filled it, purged the air and am now getting solar-heated water rolling in a loop between my storage tank and the little flat-plate panel on my roof. Here's a shot of it mounted on the roof. The in and out pipes are each insulated. If you don't insulate the pipes, which are exposed to the air, it doesn't work very well, if at all; gotta insulate! 
This next shot is from the roof looking down the inlet and oulet pipes. The pipes are anchored to the side of my RV with clamps over the thermo-cell insulation. 
This next shot shows all the plumbing connections, with the little pump in the background. The pump is mounted on a wood base to keep it off the cement. The pigtail (electric cord) plugs into a timer that is mounted in a plug just under the RV's skirt (not showing in this shot). The pump runs from 10 a.m. to 5 p.m. daily in the summer. 
Here's a tight shot of the little swing-check valve I put in the output side of the pumping system. This will prevent back-flowing of water. I also put in what's called a solar loop (see photo above--large half-circle insulated pipe) in the outlet pipe leading to the upper (hot) outlet on the receiver. Heated water doesn't like traveling against gravity (down) and the "loop" facilitates that and keeps the hot water in the tank. Without the loop, if the check valve sticks for some reason in the open position, the fact that the water in the tank is heated will cause it to rise by thermo-siphon all night, since the heated water is below the collector on the roof. If this happens, the collector becomes a "radiator" or heat exchanger and all your precious solar heat radiates to the night sky and in the morning you have a cold shower! 
That's about it. I'll let it perculate for a week or so and get back to everyone as to how much and how hot the water gets courtesy of our nearest star. Edit: Typos . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=Mac46]I have been thinking of doing this also, but thought I might also need a expansion tank. Hi, Mac. If you use water, you don't need an expansion tank. If you use some other working fluid, such as oil (which can get up to around 500*F!) an expansion tank is a must. To facilitate this, all you do is weld a stand-pipe into the end of a cylinder that has rounded ends (like an air tank). The stand pipe or tube is welded at the inlet to the tank and terminates about 5% above the bottom of the inside of the tank. I usually bias-cut the end. When you build it, you fill the tank with oil so the internal level is just above the open end of the pipe inside the tank. When you connect this to your system, as things start to heat up, the oil expands and enters into the tank forcing the trapped air to compress. This gives the hot oil a place to go rather than bursting a seam and either scalding or killing someone nearby. It's an absolute MUST if you're using oil as a working fluid. I have done this in the past and will do it again, but I don't recommend it unless you are really, really careful. I inted to someday post my oil-filled system on the 4m, but I'm going to rebuild it so it's really tiny. In the rebuilt model, the "receiver" atop the one-square-foot collector will hold only about a liter or two. I intend building a loop from the hot receiver into a return line to the panel to facilitate my using that loop as a heating element to heat water, make steam or cook with as well as an active thermo-siphon, so I don't need a pump. The panel will be below the receiver to make that happen. The entire contraption, with the exception of the heating-element loop and the open face of the collector will be insulated with at least 3 inches of beach sand (silica) as it's the best thing to use to keep the outside cool to the touch. I should mention also that I intend using 4 mirrored panels to concentrate sunlight towards the small flat-plate collector panel that will heat the oil. If you decide to build an oil-filled unit, please be careful. Oh, did I mention that you need to be really careful? That's no joke. Mess up with an oil-filled collector and you could die! . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Solar Update One thing I forgot to mention, but which was glaringly obvious to me when I took my first solar shower is this: Whenever you solder copper pipes, the flux imparts a nasty smell to the water for a couple of days. It won't kill you and it doesn't linger when you've dried off, but when you get your first face full it's pretty nasty. It'll go away with useage. 
. . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
A Day Later I've had two days in a row of partial clouds and today was cloudier than yesterday. It occurred to me that I maybe should have made the solar collector a little larger. I think I'll build another one, but this time, along with being two or three times as large, I'm going to weld a somewhat "surpentine" run of 1/2" copper pipe to a slab of 1/8" aluminum plate (I have a special braizing rod that will do this). The plate will be painted black to absorb the sun's heat and the aluminum will transfer that heat to the water-filled tube running along its surface. My thinking is it'll be less resintance to the water flow, so it'll travel over the whole contraption faster and being it is two or three times larger, it'll garner that much more heat. Of course, it means redesigning the frame and purchasing new glass or Lexan for the cover, but what the heck? It's only money! Should work! . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi mack Use a couple of car radiators from the wreckers and a glass sliding door from the house demolitions it will be much cheaper than copper and special brazing rods to stick it together. All the best Bob Foolin Around |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
VK4AYQ Thanks, Bob. That's excellent advise and were it not for the fact that it leaves out the "fun" factor, I'd take it. I know money gets in the way of many of our projects, but to my way of thinking, it's only money. I know it'd be cheaper to do it any of several other ways, but I'm in it for the fun. With all the money I've spent on windmills, steam engines, toy airplanes, sailcars, sailboats, ad infinitum, I could have sailed first-class around the globe several times, but it all comes back to one thing: I enjoy tinkering in my shop more than anything else. Oh, and let's not forget that I'm the KING of doing things the hard way! 
Thanks again. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Update News Flash! This just in: I made it too small. Does that surprise anyone? Kinda thought that might be the case when I built it, but I had to give it a go. Bottom line here is -- I'm building a new version. The new version will be a little bit bigger than twice as large as my first try. Instead of using so much tubing, I'm shifting gears and making the new one with only a forth the amount of pipe. The pipe will be attached to an blackened aluminum heat sink. The idea is to capture a little more than twice the energy and remove it with a little less water flow. That means the output water will be much hotter. Another thing, the first model takes the cold water from the bottom of the receiver (water heater tank) and puts it back warmer at the top. This is the "traditional" method. I'm going to change all that and do it backwards. The reason is, the water from the new system will be several times hotter than the old one and it's my intention to use that hotter water to preheat the greater volume of water housed in the tank (heat rises). It sounds like it'll work (but then so do ALL my little projects until I build them). If it doesn't work, changing the flow direction back to what it is now is a walk in the park; remember -- I'm a plumber. I already scrounged the framework. It's 1 1/2" square welded aluminum tubing. Next, I'll add a back (probably aluminum or plastic). Next comes a layer of foam insulation, then the blackened aluminum heat-sink backing. The copper pipe will be attached to the blackened heat sink. Above that will be a layer of glass. The new model should be twice as large and half as heavy. I haven't yet figured out how I'm going to attach it to my (NEW!) roof; maybe I'll strap it down so the wind doesn't turn it into a kite. I'll update with pictures as it happens. . . . . . Mzc Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| petanque don Senior Member  Joined: 02/08/2006 Location: AustraliaPosts: 212 |
would a reflector like no a solar box oven to direct more sun onto the collector also be another way to increase the amount of energy collected? |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=petanque don]Would a reflector like on a solar box oven, to direct more sun onto the collector, also be another way to increase the amount of energy collected? Yes and no. If I use any reflectors or other "concentrators" I have to worry about tracking. All I'm after here is a "passive" solar application and for that, I'm shooting for a stationary flat-plate collector. I've done this in the past and been successful at it. This first run was merely a "quick-and-dirty" attempt to see how much area I'd need for a 20-gallon receiver. I found out; I need about 2.5 times the area. The rebuild is just days away from replacing the model shown in the pictures above. Thanks for your input. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206 |
Hi Mac Im planing to build a solar collector, but i plan to have a tank mounted above it so for circulation i dont need a pump. I plan to use this tank as a preheater and have it piped inline between my mains water and the inlet into my hot water service. I am not shore how effective this set up would be or if there are problems with it that i have not recognised. If this is workable it will increase the volume of hot water even though the water in the preheater may not be as hot, it should keep the water in the mot water tank hotter for longer. Which should be an advantage on a small hot water service. Im still at planing stage. All the best Dean. |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Air Bender Pre-heating your water is a good idea. Here's the deal with water: It takes 540 kilo-calories to effect a "phase change". That means 540,000 calories are required to change one gram of liquid water into steam. I know we don't want steam here, but the point is, it takes a lot of heat input to get water really hot, so if you pre-heat the water using a solar application, that will do the majority of the "work" necessary and you can then use either an electric or a gas-fired heater to kick it up to whatever temperature you desire, if solar alone is not enough. Using an elevated receiver (tank) with a solar application is a great idea, since the water inside will "thermo-siphon" and like you said, you don't need a pump. I live in a land yacht and the only place I have room for the collector is on my roof, so I'm stuck with using a small circulating pump. My pump has a magnetically-coupled impeller, so it'll never leak, no matter how hot it gets! My receiver is on the ground because I have to maintain a low profile; a tank on the roof would catch too much wind! . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Project Update I was telling someone just last week how I was great at starting new projects, but not so great at finishing old ones. I'm happy to say, I've finished a project: the second-generation solar water heater for my land yacht. This current model is nearly 4 times the surface area of my first one. Although the first one works, it doesn't have the capacity to do what I want it to do, namely heat 20 gallons of water to about 120*F on a daily basis, courtesy of Mr. Sunshine. Here's what I did; 
I started with a 1 1/2" square aluminum tubing frame formerly used as a screen-printing frame. The corners are welded and each run is concave on one side to discourage warping. I laid in two sheets of about 12 gauge aluminum (couldn't scrounge one piece large enough) then drew lines representing the pipe's flow through the unit. 
Next, I purchased a Lexan garden-shed roof panel for around $9 at the Home Depot. This will be used for the unit's window to let in light. 
Here I've laid out the run of copper tubing and "benched" it on top of a few other pieces of pipe to allow me to "wet-wipe" my solder joints. 
This shot shows one of those typical joints. Note how the solder is run all around the fitting. That's important to insure a good seal. 
I placed a spare piece of sheet metal below my solder joints to insure I didn't drip excess solder and flux onto my concrete patio. 
Here's a quick look-see showing how the copper tubing will fit inside the unit sandwiched between the sheet-aluminum heat sink and the clear cover. 
Here's that same shot with the heat sink slipped beneath the run of copper tubing. 
Here it is with a coat of flat-black paint. Anybody see anything wierd about the attachment to the heat sink? I got it backwards and had to take it apart and put it back together on the other side; kinda like building two left wings when you're making a plane from a set of plans! 
This shot shows the 1/2" sheet of builder's foam insulation. The heat sink will sit perched on top of this in hopes it will help concentrate the heat and prevent losses. 
Since this whole contraption will be strapped in place on top of my rubber-roofed land yacht, I didn't want anything to protrude, which might catch and tear the roofing material, so I pop-riveted a sheat of luan to the back side of everything. The luan will be protected from the elements for the most part because it is exposed only at the edges and my roof is crowned, so no water can stay. 
Here's the entire panel with the back cover on, leaning against my fence. 
In order to keep air circulation to a minimum, I filled all the wavy open ends of the Lexan plastic lens using expanding foam. This stuff is tricky at best. My last fill job beats the heck out of my first, but nobody except the birds will be seeing it, so it won't matter much. I'll trim the overages with a cerrated blade after stuff cures over night. 
This shows the foam-filled edges from another angle. 
And here's the done deal. I'll let the foam cure over night, then trim off all the protruding edges. All that's left to do is install it on my land yacht's roof and hook up the plumbing. I'll use it for a week or two and then share some data on how it works. My hope is that with nearly 4 times the surface area of the first attempt, this will make hotter water. I'm also going to change up the direction I pull and push water through the receiver. Now, I pull the cold off the bottom (with a pump) and push the solar-heated water in at the top. If in fact the water from this new panel is very much hotter than the first one, I'm going to reverse the flow direction and put the heated water in at the bottom. This will allow it to "thermo-siphon" or migrate by itself up through the cooler water in the tank and maybe heat things more uniformly; maybe not. I'll let everyone know the results if I do reverse the flow. I'm so glad to have actually "finished" a project. One down and 3 zillion to go! . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi mack looks good and should work well. now you are on a roll and cast off the anchor we might see some more projects finished. I think put the hot water in the top and draw from the bottom cooler water, as this will give the highest temp grading and make the heat collected work for you more efficiently. All the best Bob Foolin Around |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Mac, now that your collector is 4 times as big why not make that 5 times by connecting Mk. I in series? What struck me odd with your Mk. II design is your use of soldered elbow joints. Surely, as a plumber, you would have the equipment to bend the copper pipe into a nice U and do away with all that soldering? Too much time to mess about perhaps? Klaus |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Tink Two excellent ideas. I don't think I have enough room to put both atop the coach. I kinda saw that coming, so I painted the Mk. I with latex paint in case I needed to recycle it. The latex will merely peel off and I can use the 50 feet of soft copper for something else, as I merely had it sitting about any way. As for bending pipe in tight "U" shapes, it is possible, but it's a pain in the drain. What you have to do is fill the pipe with very fine sand, like beach sand. This prevents the pipe from kinking when you crank it about a tight radius. The sand is solid enough to support the inside of the pipe as well as not compress while also allowing movement at the same time. I've never tried it with half inch, but pipe size shouldn't matter. I once made a flash boiler this way using 3/8" soft copper and wound it into 1 1/2" coils, which were nested inside a boiler housing. I stayed up all night watching old movies on the boob tube, so I haven't gotten the Mk. II up on the roof yet. I'll get to it sooner or later. Thanks for the input. Edit It's later in the day and the new larger panel is now mounted on my roof. I bled the trapped air, switched on the pump and now it's just a matter of sunlight exposure. The entire morning was heavily overcast, so I didn't miss much sunshine by getting a late start. The panel's been up about 3 hours now and the water in the loop is 'warm'. I'll log the tempertures for a week of full-day exposures and post the results here. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Mac, now you *really* surprise me, I had no idea the plumbers in good old USA still use stone age pipe bending methods 
Ever heard of a thing called a pipe bender? There are several types, the fancy ones (I have one of them as well) use a half circle die and a matching straight section to wrap the pipe around a fixed diameter radius, around 3". This one does bends up to 180 degrees. Even fancier is the three roller type that can roll bends of many different radius's and even full circles (I have a home made one of these to bend the ss tubes to make the rails etc. for my sailboat). But the simplest for soft copper pipe is just a spring section (comes in a kit for various pipe sizes) that is inserted into the pipe at the right place to prevent the wall collapsing - just like your stone age sand does
The spring is then pulled out and set to bend the next U... Consider yourself dragged into the 21st century now  Klaus |
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