Amp Draw of a Water Heater

no kidding. just use a fluid panel(s)with a pump and a differential switch o activate the circulation cycle when the panel gets hot enough it fires up the pump....the fluid circulates and picks up the available heat in the panel and the fluid returns to a storage area....as the panel gains more heat the cycle starts all ovwer again

You can't get much simpler than the tank shown in your first link.

Drew K--

General Electric tried selling these around the late 70's but it was not successful. Too many technical problems with them. They finally sold the whole operation,,, located in/near Gettysburg, PA, to an entrepreneur located in Orange, NJ. Several years later, after no success he sold it to the Chinese. Problems were in breakage of the one-way mirrored vacuum sealed glass tubes (similar to long thin thermos bottle tubes), imperfect parts, brazing of the tubing, holding the frames together, operation of the manufacturing process, quality control, problems with the deposition system for applying the mirror finish and several others.

Operating problems included:

1) what do you do with the heat during the summer? Too cumbersome to take units down for the summer. Heat of the components would cause breakage. Some customers ended up adding baseboard heaters under decks, etc. to dissipate the excess heat;

2) Breakage of the glass one way reflective tubes. Without these the system will be very inefficient by a factor of about 8-10. The tubes can be broken by random stones, sea gulls dropping clams, target shooters, or any other projectile and that's for roof mounted units!

3) integrity of the pumping system. The tubes should be smaller diameter (no more than 1/4-.3/8" i.d. to get the most heat out per pound of water circulated. This requires more head capability for the pump due to the friction resistance.

4) the pump and controls are electric, where will you get this from? If by PV solar panels why not make it all PV panels?

5) Water solar panels emit heat into the "black of night" during dark periods. This results in a negative operation and thus less useable heat, especially if a storage tank is being used. Hot tank in the evening, cold tank in the morning. The only way to prevent this is to put a black "window shade" over them during the night.

6) An ethylene glycol/water mix must be used if the ambient temperatures go anywhere near freezing. This increases the cost and maintenance, especially if there is a leak somewhere in the system.

7) An expansion tank must be used to compensate for surges and pressure changes, due to heat. This is a pressurized system therefore safeties become involved.

8) a plain system with a pump circulating water from a water drink tank up to a solar panel and back down again to the drink tank will be very inefficient since it won't pick up enough heat from the solar panel. Also very inefficient due to the large amount of electricity you have to put in to get the heat out.

From the knowledge I have gained from these water based solar panels, it sounds good and economical but it has too many problems and expensive to fix problems. You would probably end up making all your parts yourself if you could not find a commercially unit available and with readily available parts.

In summary, you have provided some good links but the end result is probably glamorized by the authors. If I had my choices of systems, knowing what I do now, this type of system would be my last choice.

I agree it would be a nice way to go but it is too expensive, high maintenance and not economical to fabricate or run.

Good Luck, Old Salt

Most of the homes and farms out in the country (and houses in the villages and cities) in Turkey have a solar hot water collector on the roof. They are incredibly common.

Most of them do not have circulating pumps, they are designed with a storage tank above the tubes and work of off simple convection. Hot water rises into the tank and pushes the water there down into the house (cattle tank).

Yes, you need an anti-freeze solution in the winter and it should be covered in the summer.

The problem is that these units are not as redily available in the states because energy is cheap compared to income...doesn't mean it is smarter. In many 'uncivilized' parts of the world they buy their hot water instead of paying for it; they pay for the unit once and then don't have to pay for the heating of the water. Calculate how much you pay for a gas or electric hot water heater then how much you pay for the water and tell me if it is cheaper than a solar system...then calculate in running fuel or power to a remote location.

I have given serious consideration to starting a business that would install systems like this in my neighborhood.

Drew K

Drew K-

Your points are well taken. I used to share a fishing cabin with some guys and we had solar heat. It consisted of a small PV solar powered pump getting water from a shallow well. Next the water was stored in a water tank painted black on the roof so that it could absorb the heat of the sun. From there it was directly piped to the sink and the shower. As everyone who used the cabin will agree, that system was extremely inefficient as determined by the number of cold showers that were taken. First guy happy, 2nd guy ok, third guy a bit too cool, all others burrrrrrrrrr. These were also 3 minute Navy showers! Since that time I have always considered that type of system as inefficient.

The water circulated solar heaters I described earlier seemed to be a good promise of efficiency for circulated water system. Regretfully, it turned out not to be. It also promised to be more capable of being like the hot water heater the OP posted than the system you have described. That is why I stated that a water circulated hot water solar panel system would be my last choice.

Good Luck, Old Salt

It doesn't take too much to keep cow drinking water from freezing, Old Salt, but showering a bunch of fishermen takes a lot more effort. The black tank on the roof had not enough surface area, a panel is necessary. Once the water is heated, it must be stored in an insulated tank. My favorite unit has the tank above the panel all on the roof, but can be mounted anywhere that has the most sun.

The black tank sounds like a very old system. Many of the modern ones can heat water as it passes through (hotter than you can handle in a shower). As long as the sun is shining you have hot water and for when the sun goes down you have to use an insulated storage tank.

The modern systems work significantly better than the system you describe.

Drew K

300/12 = 25 amps.

Everything else gets more complicated and very expensive from there.

If I recall, I think one of our members, Del the Cat did a direct solar project. Search CR4 comments, or PM Del.

Surely the cattle are not getting hot showers, so this is just drinking water that you don't want to freeze. I presume you are north enough for above ground water tanks to freeze, so you are also north enough to suffer days without sunlight, or sun strong enough to adequately heat a solar panel enough to make much difference.

My favorite solar heater has a 12 volt panel that feeds a 12 volt pump to circulate the heated water. When the sun shines, the water gets circulated. Even not heated much, circulated water is less likely to freeze.

Have you considered burying the tank, below the frost line, to use the heat of the Earth to keep the water from freezing? Just pump up enough water for the cows each day.

Unless you have some use other use for AC, converting from DC to AC is not required for heating water. But as others have said, far better to heat the water directly.

If you are convinced that you want AC to do this, then plan for 28 amps or so, to allow for losses in the inverter. If your battery is 200 AH, plan to use no more than 100AH routinely, to avoid damaging the battery. So a 200 AH battery could be used for about 3.6 hours after the sun goes down.

Depending upon where you are located and season, you might be able to plan on 4 hours a day of useful sun. So, to supply 4 hours of heating you could figure on about 300 watts of solar panels. Four hours of heating might be far less than you have in mind, however.

What about a simple bubbler? They use them here in Michigan all winter long to keep ice from docks, boats and ponds. I imagine this would be more economic then heating the water.

Below are links AC units, DC units and even solar. There are many links typing "winter water bubbler" into your favorite search engine.

http://www.thepondreport.com/dock-bubbler-deicer.shtml#.UhVjyV3D-M8

http://www.thepondreport.com/store/dc-air-pump

https://ecovantageenergy.com/catalog/items/item2178.html

Found a number of options....

"There are many options for winter watering including

commercially available "earth-heated" waterers, super

insulated "energy-free" waterers and water troughs that

rely on the heat stored in the water itself to keep it from

freezing, and propane-heated waterers. There are also

continuous water flow-through systems to prevent

freezing, frost-free animal-operated nose pumps as well as

solar and wind-powered pumping systems for winter use..."

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex11857/$file/400_716(c30).pdf?OpenElement

I say create large bladders that can be filled with water and strapped onto the cows. You could harness the energy from the cows body heat to keep the water from freezing, and with a properly trained cow you could run a flexible tube from the bladder to their mouth that can be used as a drinking straw.

It is a good bet to start with conservation and re-use first before employing other methods. This will make your solar investment more palatable and give you room financially to pick a system you can build and upgrade on with existing equipment. Insulation is cheap and easy to shop for to trap the most heat with the fewest headaches. If the tank must be outside, best to insulate well and place on the south facing side with minimal wind striking the tank. Placing a tank below the frostline will add pumping and service costs unless you have a hillside of soil immune to freezing. Then all you need to do is bury the tank in a deep enough recess with access to draining and refilling (cheap and less insulation needed). Combining this with solar heat can most likely become complicated and costly. But you may be interested to see what is done with Drake's Landing Solar Community's seasonal thermal storage as an example of combining the two technologies. [ By being on a farm, you most likely have tools available to do some digging/drilling and pay next to nothing the tank is a stand alone.

Sir: you said "the water heater element is 120V , 300 watt." Really only 300w ?

Must be very small! Is 300w correct?