Simple Solar Water Heater panel

[CmeBREW]

Hello RE-Friends, (Hope you are all enjoying spring and solar panels power!)

Here is my basic attempt at a solar water heater panel. Please keep in mind I am NOT a plummer but am trying different things with this unusual set-up until I can at least make it a Semi-automatic system with a thermostat (shown below) And without burning out my little 12v 65 Watt pump.

For the last two summers I have been using a 100 ft. black rubber garden hose in two separate (side by side) CLEAR plastic bags sitting out in the yard and pumped it into my hot Water Heater with this same 12v (boat) pump every 30 minutes for a one minute duration, all day long. It worked pretty good actually.

But now, here is the new and improved version. (Don't laugh too hard-- 'cause it WORKS !)

 






Before you say it... YES, it is SUPPOSE to be either an old extra steel water heater, or COPPER piping.  I am aware of this thanks.  But as of yet, I can not afford the hundreds of bucks for new copper 1" piping and am still looking for a decent price for copper piping at local metal scrape yards. (the few who even still allow someone to buy scrap that is, despite Insurance and law suits!)

For now, I HAVE to use just an old 75'ft. black rubber hose AND a 25' ft. hose from the thermostat. (total of 100' ft of hose. Normal 5/8" inside diam. equals about 2 gallons of water in the hose)

My medium size 28 gallon Electic hot water heater is just on the other side of the wall where the hoses go in, in a closet with the electrical breaker box.

Yes, It is simply Treated wood decking boards for sides and the same size 1/8" single pane tempered glass as I used for my Solar AIR Heater here:

http://www.fieldlines.com/story/2009/3/14/03312/6467

Same dimensions of about 6.5' ft. long by almost 3' ft. wide.

In fact, I made it the SAME way for the most part except I left out the insulation board in the back (for now) since I was afraid it would melt the rubber garden hose by getting too hot in the panel.  The metal roofing is held in place by wood cleats all the way around.  One other change with this water heater is I put two cross support boards across the bottom.

It is still a work in progress though. I have yet to paint the metal roofing inside a flat black and the outsides of the wood sides. I may put some extra vinyl siding over the sides for better looks.  When it is finished, I will then put clear silicone caulk around the glass edges to keep rain out.

And now to the nightmare PLUMBING! (Must be a thousand different ways to do it!)

This is NOT as easy as I had thought it would be.  Even though it looks all nice and stuff, I realize now I am going to have to change some things to make it more reliable with the automatic thermostat control due to bizzare and unpredictable 'back pressures' that can bear down on the 12v pump every 'once in a while' if I'm not there to manually stop it and release this mystery back pressure.

(I may need to put in some one-way check valves--not sure)

Notice I also wrapped an extra 1" of carpet padding around the tank to try to improve thermal insulation to hold in the 105-115F degree hot water until I actually shower about 15 hours later the next morning.  

I think it helps some.  Depending on the previous day of sunshine or semi-sunshine, the actual temp I shower in 15 hours later is from 100-110F degrees which is really good to me for just one person.  Anything over your body temp is pleasantly warm.

I like 105F degree the best.  I take a 7-8 minute shower with ALL water coming ONLY straight out of the hot water tank. The shower head is not one of those fine stream 'efficiency' heads either, like in RV's. It has a fair amount of water falling.

I could use some help and possible suggestions from the group as to how to stop this occasional bizzare 'back pressures' from EVER occuring in the lines and at my 12v pump , so I can make this a mostly fully automatic system using the thermostat out at the solar heater----so that It won't bear down and  burn out my pump when the water can not flow in the loop and I am not present.

So the following is what I have been doing in order to sequence the hot water (per 2 gallons of water in the 100' hose)  in a 'loop' thru the 28 gallon hot water heater tank:

When I know it is time to sequence the hot (around 120-140f) water from the solar heater into my hot water tank, I first must turn of the main water valve and then relieve the water pressure from both the cold and the hot lines.

I do not have an upstairs, so it only takes several seconds to do this from a sink a few feet from the hot water tank.

Then I turn on the 12v (boat type pump from Harbor Freight $35) pump to sequence the hot water in the loop for ONE minute exactly is all it takes. I use a stop watch.

Then I repeat this procedure every 20-30 minutes when the sun is out.

I am still somewhat afraid that if I failed to sequence the hot water for a few hours, there is a chance it could melt the rubber hose in the collector or possibly melt the rubber 'O ring' in the 12v water pump since it was not made for very hot water.  

This brings me to my second problem, which is the thermostat control. It is a simple attic fan thermostat that I soldered a piece of copper pipe into which transmits the heat from inside the collector into the thermostat box (shown in picture below).

Then the thermostat is connected to the cool return line/hose.

The idea is that when the water inside the hose in the solar collector gets hot enough, it transmits the heat thru the piece of copper pipe, then into the (air type) thermostat box which turns on the pump to circulate the hot water, and at the same time the cool water immediately comes into the thermostat box and SUPPOSE to begin cooling it back down and the shut the pump back off.

So far the first part of this works fine.  The thermostat DOES turn on at the right time when the water gets hot --- But, it does not turn back off again in only one minute of running the pump.  This is the problem.  Because I cannot allow the 65 watt pump to keep running since it is WAY to much power for my small 12v batt system.  It needs to run about ONE minute every half an hour. (Or about 12 cycles thru the day)

Here is my simple idea for theromstat control:

I spray painted alittle flat black paint on the box to help it heat up a little faster.  When the pump does turn on at the right time, the cool water line immediately runs thru the piece of copper and DOES cool down the metal box quickly, but the actual thermostat metal/contacts take too long to seperate back and open the contacts and stop the pump from running in only one minute.  It usually takes a few minutes for the contacts to open and this is unexceptable for what I am trying to accomplish.  If cool water 'layers' inbetween the hot layer in the tank, then at some point the thermostat will NEVER (or rarely) be able to stop!

Wow, this is difficult to explain!  I will just leave it at this.

Is there a better type thermostat I can use here that will be QUICKER to respond to the temp changes in the thermostat box??  And the other problem was how do I eliminate any  bizzare back pressures from locking up my pump and burning it out?

I am thinking about two more shut off valves for both the cold and hot lines right before they proceed into the house lines??

I really do enjoy doing this though, and being able to take SOLAR showers almost every day with NO grid power!!

-I'm sorry for not being able to explain better, but this plumbing junk is a real pain and quite the puzzlement.  

-Any comments, help, or questions welcome!!

[Norm]

Hmmm.....looks like you've been busy!

I very very seriously doubt that you

could ever melt the rubber hose as long

as there is water inside ?....Now if you

had a fresnel lens on a very concentrated

focus.

   (by a strange coincidence I ran across

one of my 8 x 10 lens.... focused a dime

size spot on the picnic table...instant smoke )

   I'm thinking of heating water by running

water over the south roof of my shed into a

plastic barrel....that dark green roof gets

pretty hot.

[Madscientist267]

What about rather than controlling the pump purely by hysteresis from only a thermostat, use a timer for the pump that is triggered thermostatically? A few bucks and a little soldering could conceivably solve this issue.

Since you know the pump only needs to run for 1 minute, you could set up the timer for 1 min on, 30 min off, and have it enabled by a thermistor only when the temp inside the collector is above a certain threshold.

To solve the pressure issue, see about drawing up a schematic of the plumbing for us. A few different ideas come to mind, but the complete 'picture' isn't exactly clear just from the pics.

As for heat melting the rubber, this is highly unlikely. Rubber can withstand some serious temps before it starts breaking down; I doubt very seriously that 1:1 collection can hit those temps (ie no lenses, mirrors, etc).

The only two real 'problems' with heat buildup I potentially see are

1. - You won't be efficiently collecting that energy, since you're not pulling it away from the collector.
   
2. - Worse case, although far fetched, it is remotely feasible that you could possibly generate steam, which of course could be a problem due to pressure.  
   
   

Other than that, I gotta say nice project - it definitely has the backyard DIY feel to it!

Steve

[kenputer]

If you are using a pump to move the water then that is giving you the pressure problem,you need a circulating style pump.

Ken

[luv2weld]

Shouldn't you feed the hot from the collector into the cold

input of the tank???

As you have it hooked up now, you are back feeding the hot water tank.

Reference your first picture, you are fighting the pressure

build up of the heater.

Just my 2 cents.

Remember advice is worth what you pay for it.

Ralph

[Airstream]

Home made collectors are very cool thing, but worse case scenario is when you have stagnation, flow stops and the risk of system over pressure happening when plain water - mixes achieve hot spots flash that into steam.

Thermosiphon systems can get stagnation easily from air bubbles in the lines/corners reducing flow. Providing for an over-pressure event is a sober idea, having a blow-out stack with either a water column 'cap' alone or a pressure sensing vent.

Atmospheric pressure and altitude act on boiling point (the suns 'clear sky' brightness increases 7% per 1000m/3250' elevation) so at 9000 foot elevation the boiling point lowers to make steam at 193° to 196° THEN add in the solar boost it's too darn easy even with a nearly uninsulated collector...

Some closed-loop systems have a temperature valve that opens an extra loop in the shade of the collector to passively radiate heat away from a coolant-boil possibility that self-closes when the temperature drops.

Whatever - just have some provision for a perfect clear day with no wind that tests your system!!

[ghurd]

I must be missing something.

Is the black garden hose pressurized 24/7?

Are you Sure there is back pressure, or could it be an air bubble in the pump? Might be able to solve it by mounting the pump a bit different.

G-

[CmeBREW]

Thanks guys for all the suggestions.

I will try to answer everyone with questions separately as soon as I can.  

I will try to clarify a little more.  It is difficult to explain almost without a 60min Video!!

This basic system is NOT pressurized 24/7.  It is NOT being used as a simple PRE-Heater system.  Rather, as the way it is right now, when I want to sequence the 2 gallons of HOT water from the Solar water heater (every 20-30min) into my Hot water tank VIA the 12v water pump, I MUST turn OFF the MAIN Water Valve and then release the 'normal' 50 lb pressure from all lines in order for the pump to operate without burning up.  It cannot operate under this high pressure. (I have tried it)

I try to just leave the incoming MAIN VALVE off as much as possible during the day so it is less likely to let air in the line(S) and possibly cause occasional 'back pressures' to build up in unknown places and lock up the water flow and the pump.

This is one of the things I am going to change, because when I have to flush the toilet in the middle of the day numerous times, I am tired of messing with turning on and off the MAIN VALVE each time and re-draining the pressure out of the lines.

Therefore, As soon as I can, I am going to re-plum it so that at least the MAIN and the COLD line that goes into my house will always be ON and never have to be off or the pressure drained everytime 'I' have to be drained.  Instead, I will just isolate the HOT side with the Hot water tank and only have that line turned off with the pressure removed so I can sequence the Solar water heater automatically during the day.  

And then anytime after 6pm (SunDown/ No more Solar heating) I can turn on the HOT lines and the hot water tank with the normal 50lb of pressure from the MAIN.  And then repeat the whole thing the next morning after I shower.

The pump I have been using for the last two summers and now is here:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=9576

It has worked fine and goes thru the one minute pumping/running sequences without even getting warm. (unless it boggs down from mysterous back air pressures in the lines)   I wanted a simple 12v pump that takes little power to be run off my small 12v RE-system, and this one does the trick as long as all/most pressure is released from the lines that flow the water in a 'Loop' thru the Hot Water tank and out thru the Solar heater and back again.

In fact, on occasion, I can even use this 12v pump to take a hot shower if the Grid power goes down. (but I rarely do it. And I have to reverse the In/out lines on the pump which is easy.  But the water pressure is a little lower than the normal 50psi, but it is actually quite decent pressure out of the shower head)

 I am also going to add a 10amp fuse in-line with the pump and see if it will blow the fuse when it boggs down with a bog down back pressuer situation.  I recall the ammeter was about 10amps when it bogged down. Normal running amps is about 6 amps. (70watts)  I hope this would at least save the pump from burning out just in case.  

I now highly believe I can solve the 'back pressures' myself when I replum it soon and add a few things.

There is a chance the unwanted back pressures are coming from the MAIN VALVE. (Ball type shown in photo)  It might be leaking in some of the 50lb of pressure a little bit since there is no rubber seal in it, rather some kind of soft plactic seals.  If there is a tiny leak in the Main Valve, it could slowly build up pressure in the lines and bogg down the pump.

So I will go buy a normal rubber o'ring type Valve and replace it just to make sure of that.

So I can fix that problem soon and will show it here when done.

So now all I need is a reliable means of control by either thermostat or a timer. I will talk about that above.

-Thanks for help.

[CmeBREW]

Thanks for suggestions Madscientist-

I have been looking for a low-cost 12v TIMER that would meet my criteria for this project and waste less than 2 watts (less than 2W X 10hrs= 20Wh per day), but I cannot seem to find anything.

I looked at Surplus Center, Ebay (the Deer feeder timers do not sequence enough or long time time durations), etc...

I think I can get something working adaquately with this or another (air)thermostat if I keep messing with it.

Or, does anyone here know of a low-cost WATER type thermostat that actually responds to the temp changes in the water line??  I suppose it would be called a Hydro-thermostat?? (that sounds expensive)

Concerning the plumbing and mysterious 'Back pressures'--  I am quite certain I can fix this problem now, I just need a few days.  I can isolate the 'loop' much better than it is, I can see that now.  I will draw this simple plumbing diagram as you suggested, since it would be a lot more understandable.  It might take me a few days or so, since I want to put in 3 more shut-off valves in the lines which is easy.

BTW, there is no way the problem could be Steam-- since it doesn't get near that hot in the solar heater.

Probably max of 150F when I forget to sequence the water in the hose for a whole hour on a hot sunny day. When it is that hot, I can't even keep my hand on that metal pipe on top of the hot water heater (in photo) for a second.  When the incoming solar hot water is about 130F degrees, I can hold my hand on it for about 3 seconds.

-Glad to hear about the Rubber hose not melting. It shows no sign of melting so far.

Thanks again.

[CmeBREW]

Thanks Luv2weld,

Good eye-- Yes, this is in fact what I am doing.  Numerous reasons. This is another hard thing to explain.   I actually tried feeding the incoming solar hot water into the Cold/input side of the tank, but did NOT like it because the Cold/input side goes all the way to the Bottom of the tank and if there is a semi-sun day, or I miss some of the half hour sequencing, then it only fills up the Bottom half of the tank with my Solar Hot water, and the Top half is cold or cool, and this was a pain in the wazoo to sequence around the loop each morning AND it made the hot water cooler doing so.  

So I would rather always be putting in the Solar HOt water at the TOP of the tank DOWNWARD-- so I can use it first and it will blend with the WARM water at the top after I shower in the morning, instead of the 50 degree Cold water at the bottom of the tank.  YOu see, I rarely actually sequence the entire 28 gallon tank per day.

The manual way I have been doing it, I usually sequence 20-24 gallons per day. (10-12 cycles x 2 gallons at a time)

So I need to have the new hot water always at the TOP of the tank ready to be used first, when I reverse the flow out the hot water tank later in the evening and next morning.  Strange thing about this tank is the varriing water temps do not seem to  'blend together' very well at all.  10 hours later, and the cold water is still at the bottom and the hot at the top.  They do not seem to blend together. This also baffles me.

As for unwanted pressures building up in the Tank because of doing this, I do not know for certain if it is or not.  I'm not completely sure how these hot water tanks are made.  Seems I recall they have about an inch of air at the top of the tank for some reason?? Is that right.  So you may be right, me doing this reverse flow thing could be part of the 'back pressure' problem I encounter once in a while.

Remember, I shut off the Main and release most, possible ALL, pressure from the tank.

I'll see soon if this is the problem or not.

-Thanks.

[CmeBREW]

Luv2weld,

I forgot to mention something else about the hot water tank.  You see, I am only ONE person living here, so I only shower about HALF the tank per day. (about 15 gal)

This was the smallest electric tank locally I could find when we built this house a few years ago.

I actually leave the bottom 3500 Watt element DISCONNECTED (off) on purpose since it is a waste in my case.  I only have the TOP 3500 watt element hooked up to grid power when I need it.  If there is a semi-sun day and I know there was not enough Solar hot water pumped into the tank, then I simply turn on the top 3500 Watt heating element for 5 minutes and then back OFF, and it is then adaquate for my needs.  I do not ever just leave the Top element ON, since it would over-work and be a waste of power anyway.  

[jondecker76]

I think you would have better luck using a separate thermal storage tank/heat exchanger setup (Plywood EDPM boxes are cheap to make and reliable). I recently made a 365 gallon Plywood/EDPM tank with a 300' plastic heat exchanger coil in it. Then you can choose to either run the system alone (relying on the heat exchanger coil), or as a preheater for the normal watertank.

My system is not yet finished though, as I am working on my solar collector at the moment, but the DIY tank is very impressive! I built mine from plans on builditsolar.com: (my 365 gallon fully insulated tank with epdm, insulation, lumber and heat exchanger coil costs included came out to under $300. You should be able to get by on around 100 gallons which would last you through a few cloudy days as well)

http://www.builditsolar.com/Experimental/PEXColDHW/TankConstruction.htm

http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Tank/Tank.htm

[ghurd]

"is a chance the unwanted back pressures are coming from the MAIN VALVE"

I don't think so, even if it leaks some.

The solar part is a closed loop, and pressure on both sides of a closed loop is (almost) the same.

"Back Pressure" is confusing.

Both sides of the pump are connected directly to the tank.

And the tank can not have 2 pressures in it.

Could be the order of the valves, and one was not set right.

That's all I can figure.

G-

[CmeBREW]

Thanks JonDecker,

Yes, that fully automatic system design of Builditsolar is awesome for a serious family Re-house.  If I had a family and the funds, that would be the system for me to.  

But I just don't have the funds or the room to make that nice of a system right now.

In fact, I would also have to change things, like build a super insulated box outside on the outside wall of my house for that big of a tank, which presents other concerns and problems I'm sure.

Later on down the road, I may build a smaller version of that.

But this rigged up semi-automatic unorthodox semi-hassle system I am using now only cost me about $130 bucks since I already had many of the parts. (Free hoses, $5 glass, piece of metal roofing, etc. / I got the pump on sale for 30 bucks)

The hastle is minimal, and it works really good (I believe) for a single guy about 7 months out of the year here in Ohio,, and then I just drain the collector outside for the winter.  It is good enough for now, and it will look a lot better in a few days finished and  mounted on the two 4x4 posts (3'high) and with the vinyl siding on the sides, and the two running hoses buried underground.

It already has saved me a LOT of coal burning Kilowatts.      -Hope it lasts.

  Thanks again.  

[CmeBREW]

Hey Ghurd,

I strongly believe I have the unwanted pressure problem solved now.  After work I got the plumbing parts and started re-doing some things much better.

I found out that the MAIN (incoming) VALVE was in fact slowly leaking (one drip per second) and this was over a period of time (hours) slowly pressurizing some of the lines and most likely the Tank too and then causing the pump to be unable to flow (pump;circulate)  the water in the loop at random times.

Also the two lines that went into the house were draining about a pint of water out of the lines each time I drained the pressure out of the lines, which also meant allowing a lot of air in the lines to compress in bizzare and unpredictable ways.

Therefore, I put in two more shut-off valves and replumed it so the MAIN valve and the COLD side are ALWAYS on so I can flush the toilet anytime and wash my hands, cook, and drink water.  I simply isolated the HOT side to be shut-off during the day to be automatically cycled by the Solar heater. In the evening I turn the HOT 'line' back on until after the shower the next morning.  I will make a diagram of the new plumbing and the purpose of each shut-off. (I think there are 5 or 6 now)

BTW, good news, the thermostat set-up actually started to work! But it was a cloudy day with the sun going up and down all day.  It would go off 40-60 seconds after it came on. Good enough for me!!  Hope it works when the sun is out all the time.

I finally realized the incoming black rubber hose was getting about 90-100F degrees which is why it wasnt cooling down the thermostat quick enough.  Now I know what I need to do (bury the hoses)-- and I really believe it will work.

Day after tomorrow is when it will be tested and adjusted good in consistent sunshine.  I will give results here.  

-Thanks for help.

[Bruce S]

CmeBrew;

 Another fine example of taking "stuff" and making something usefull out of it!!

Keep it up!!!

I like the idea of using old garden hoses, why throw them away when they can be used to heat or pre-heat incoming water.

I can't say how many times the water coming out of the garden hose was hot enough to make coffee with!! or a nice warm shower after a walk down to play in the cold creek.

Best of Luck!!

Bruce S

[CmeBREW]

UPDATE:

Ok, here are the new plumbing changes.  Once again, keep in mind I am NOT a real plummer-- but just doing what I think should work (fairly well) in my own unusual situation.

First is the New Plumbing diagram, so hopefully everyone can understand what I am doing. It seems to be working good now. No unwanted 'back pressures'. And the COLD line side (And MAIN valve #1) is ON all the time now since I isolated the HOT line side (AND the HW Tank) for the solar heater cycling during the day.  The Main change is Shut Off Valve (sov) # 2 that made this possible.

Please ignore SOV#6  -- That is an Open-ended (goes nowhere) Shut-off-Valve that I simply use to add a teaspoon of Bleach to take away a horrible disgusting Sulfur smell!! (Smells like GodZilla's Fart after eating a rotten Chicken farm)

It makes it easy to add the teaspoon of Bleach and all the smell goes away. There are Sulfur pockets in our water table.

Sov #3 AND #4 are valves I use to shut-off after each Solar heating day is complete, to prevent an accidental serious leak during the nighttime if a hose were to split or break and wasting an enormous amount of water.  I open them back each morning.

I take my shower in the morning from the previous day of Solar hot water collecting.

Then after the shower, I shut off SOV #2 in order to isolate the HOT side and the Tank as you can see in the diagram. Then I release the 40-50lb (normal) pressure in the HOT line in a few seconds. (a little bit of water comes out)

 Then I close SOV # 5 to isolate that line.  And of course, SOV #3 and #4 have to be open so the water can flow around the whole 'loop'. The line in the diagram that is both colors (black and blue) simply means that cold and warm water can flow thru it.

(confused yet!!)

Here is a slightly different angle photo. Ignore the duct tape. It simply holds down the plumbing pipes a bit due to the Flexible hose pushing the plumbing upward.

The MAIN valve did have a slow leak in it which (I believe) was causing the build up of pressure problems.  But now it don't matter since it and the COLD line are ON all the time so I can flush the toilet and such at any time.

Today, I cemented the poles in the ground, so tomorrow I can mount the whole Solar collector heater on it to make it look better.

Today, while working I did get some time (on and off) to try and tweak the thermostat control.  Today, was partly cloudy (on and off) and their was some wind that was goofing up the thermostat I think.  I need a little more time to perfect (good enough) the  'thermostat control system' (TCS).  Hopefully tomorrow I can.  I had to manually turn on/off the pump a few times though.

But I still got enough hot water for the day though for a fairly hot shower tomorrow morning.

I will keep you informed on my progression and the photo of it finished.

-Thanks

[CmeBREW]

PHOTO and PROGRESS UPDATE:

I couldn't just leave those ugly unfinished looking pictures at the top.

I have it mounted on the two treated 4x4 posts and the hoses are buried a foot under ground so I can mow grass around it easy. The posts are cemented into the ground.

It purposely leans toward the South a bit so I can get some early year sun here in Ohio.  

Here I am still putting the Vinyl siding (extra I had) on the sides and around the posts.  I will replace this photo with the finished one real soon. Once this is done and the grass grows back in, I think it will look pretty good.

I am Still taking 100F (38C) to 105F (41C) showers every day. (Depends on sun/clouds)

Even though I haven't had much time to work on it, I am still having problems with the attic thermostat, and have to often manually sequence the pump by turning on a switch for a minute.  Sometimes the thermostat works, sometimes it don't.  

I will try to find a quicker response thermostat or look for a dependable low power TIMER.

But as I suspected, the unwanted back pressure problem is solved for good.

-Any suggestions always welcome.  -Thanks.

[CmeBREW]

LATE UPDATE:

Well I failed to control the pump with the thermostat consistently and reliably. It acted like it might work, but then it would not shut-off correctly. I even soldered in a 2 foot piece of copper plumbing pipe inside the collector in hopes of raising the 'control temperature' in the thermostat box-- but it failed to shut off in less that a minute many times.

So I have abandoned this attic thermostat control attempt.  I still have been manually turning on the pump to circulate the hot water every half-hour to an hour-- and taking hot showers each day.

But after making the FULLY automatic Solar hot water system for my parents house, I am sold on that!  I am going to change my system to more like my parents system here:

http://www.fieldlines.com/story/2009/7/8/3257/35059

It is a lot more reliable and automatic controlled.

I am happy with that improved version.

-Thanks.