top of page

Hot Water Solar Panel

This passive hot water heater was made in the eighties and from what I can tell there were two major manufactures, one making the container, and the other supplying the prism glass, which is the primary item used to complete the process. The third aspect of the panel is the design of the element its self, and even though anything of size can be made, There is a fall off efficiency factor involved with passive anything.

One design being a pump design, as seen here.

and the other design being the upward flow of heat with water as it medium of exchange,

The pump design simply pumps water through the panel and as the medium is passed through the panel, it is heated by convection and brought to its desired location, either a domestic hot water tank, or to say a baseboard radiator where it gives off its heat and is returned to be reheated, antifreeze needs to be added to prevent the cold from damaging the pipe in the panel or the panel drained during short cold spells in southern locations.

The panel I have is not best used as a pump through panel design, (although I am going to test it too check the performance), it instead uses the principle of heat rising and then transfers the rising heat to a container above which stores the heated medium, and from there it can be used in a number of applications by pumping to the desired location.

So that is the one I'm going to begin with.

The trick to creating the heated environment is within the prism glass, which allows light and the heat that goes with it into the panel but does not allow the light to escape, but in turn sends it back into the container to continue to heat the metal and medium inside.

Proper design is the key to get the best performance from the panel, I tilt my panel toward the lowest location of the sun, and directly south as can be, so as to accomplish the best results during the coldest period of time, I also found this placement to work just as well right up to summer time during which the stored heat loss is less.

Along with proper alignment is the efficiency of the produced heat to rise, rather than decrease the size of the connecting pipe which would decrease the amount of heated water allowed to rise, I increase the size of the pipe going to the storage container and return also, this will increase the efficiency of the entire system.

Here is the panel and tank above before connection, i've since moved it over and upwards from its current location.

I then set out to design the hot water storage tank above the panel, the hot water enters on the sides and toward the bottom of the tank so as to heat the water above. I then drill a hole in the middle of the bottom of the tank so as to allow for the return of the less heated water, it then branches in two to return to the bottom of the panel to be reheated.

After insulating the back and connecting the return piping I filled up the panel with water and did this temp test so here it is.

I then cut and fit the metal first before soldering it, soldered as many pieces together as possible, then soldered the panel connection and rubber gasketed the pipe going into the tanks welded connection, I then insulated it and tested the performance, on good sunny cool days, it would take 2 solid days to heat 50 gallons to 150 degrees, and I would lose 10 degrees at night, it would go slightly higher, but the drop off at night was greater too.

My strategy is to heat 30 gallons to 170 and then circulate that 170 into the domestic hot water tanks 30 gallons, with the idea that on a good stretch of sunny days i'll have 60 gallons of 150 on average depending on how much is used, and how cold is the water you are domestically heating. Those tests will be forth coming and posted on the site as clickable updates

From here I had make a custom domestic hot water tank, it would circulate this hot water in and out and use the domestic pressured cold water to be heated. It can't leak or the pressured domestic water will go into the circulated hot water system, this would mostly be a problem if too much hot water was lost, or you were diluting the treated water in winter, if you used anti freeze.

I currently have a plug to release the water if it gets cold enough and just refill it again a day or two later until all is perfected.

It took me quite a number of tries before I had a successful pressure test, I bought the hot water storage tank for $50 and to buy something of the likes that I have made, costs about $2000.

Here is the domestic hot water container pressure test video.

I was back and forth on this next stage, do I switch the circulation pump say by solar panel only working during the day when the water is hot, or do I circulate all the time assuming a, no loss during transportation or storage of the water circulation system.

Now since I have a back up electric hot water heated tank already in use, and i'm not sure how many days and under what conditions i'll be able to stretch out the useable hot water, i'm going to test the system before I introduce it into the domestic pressurized system, this has yet to be done but shall be updated once known.

So here are the insulated tank and transportation system in place, i'll circulate the water all the time with this battery and solar panel charger, and run some tests, I have just now upgraded the bottom end of the solar panel return piping. So here are some of those.

From here I run two insulated lines into the soon to be insulated domestic hot water tank, if no issues need to be addressed first.

And the domestic hot water tank below before being introduced to the pressurized system and completely insulated.

This is 50 gallons of max temp reach.

With this being in constant circulation and once working I can then run some temp tests and durations w/o full sun.

Updates will be found on the home page panel section.

This concludes the first part of the hot water solar panel uses, the domestic hot water tank, now to the second best use of the panel, the room heater. It starts with a passive and electrical solar panel on the roof.

Now I have to tighten up on the efficiency angle and that going to take a year to determine, plus the direction is not nearly square nor is the direction of the panel in the right angle, but i'm going to see just how much heat I can derive and then do some things during the off season to upgrade the efficiency, I guessing 50% efficient and as the sun rises this shall improve, its dec 21st.

So the concept is too take the panel and place it as best you can to get the heat where it is needed, at least to get started, then pipe that heated water to some device (a cast iron hot water heater say) and once the heat is given off, send the cooler water to be reheated, so this will take a pump, and the pump will take electricity, I chose the 24v dc solar option.

For inside the house I had to be cost conscious and after a number of tries I settled on a car oil cooler and fan unit for $50 a piece, I got two of them. But I soon dropped the fans and instead got some different 24v slower moving air ones. Here are some videos,

So far everything works ok, suggestions going forward would be to use as few quick connects as possible as anything but straight does have a possible negative effect of leaking, and I would use as few piping pieces as possible too. As the sun angle rises and gets closer to direct coverage, the heat added over the course of the day is at least as good as the front side so an adjustment should make this panel and design work very well for the cold side of rooms.

The only other issue was burping out the air pockets I had to go up and down on the roof many times to accomplish this, part of that was on my design side, I'm going to look into swinging that around a little by next season. I pumped the water in from the high side, and out into the bottom of the panel, and the electrical switch work is just standard series and parallel to pump or fan wired independently so once activated then accumulate depending on how many devices are operational.

This ends this part of the hot water solar panel room heater, possible updates or even something more depending on.

I've completed the assembly of the bottom end piping system, this is before soldering.

Here is the final design of this system, the holding pipe was required for easy priming, and I had to take the pressure off the shark bites so a 90 degree bend was added, so now no leaks and I dont have to go up on the roof but once or twice to prime the air out of these radiators.

After doing some tests on the domestic hot water production, i'm finding that I'm heating a lot of material that doesn't hold it heat through the night. So I thought I'd try to only heat the domestic hot water tank from the panel on the far left above, and pump that super heated water to the tank and back in an attempt to heat just the domestic hot water to say 170 in just one good solid day of sun.

This will take a pumped straight from panel to domestic hot water tank heated via the heated element. The hot water is tapped off the top and then sent back from the domestic tank to the bottom of the panel, one bottom end is capped off while the other top opening is used to hold water should evaporation remove some of the circulated water below its threshold of operation.

Do what ever you have to do to make bleeding air out of the system, it will make life easier to work out the bugs.

Here is the new buried transport system, it has yet to be attached but this was majority of the hard work.

For those who want to use the heated tank water for hot water showers, you have to use all stainless steel metal to prevent the water from rusting and turning brown.

bottom of page