Solar waterheater for 0.3L water

We have a very cold winter here in europe right now..

I have some animals outside, with a small 0.3L water bowl. In under 20min the bowl is frozen so they can't drink from it.

I have searched and searched for a already built solution, that can keep the water thawed.

Any ideas for a cheap solution, that don't requires more power that I can make from a solar panel?
The water should not be heated to more than just over freezing point - So it's not very much power required?

Yes Sir,
To make a solar water heater is easy and cheap! You could even use a couple of meters kitchen Al foils to make one. Lots of Do it yourselfs are available on the net. Please search.
**broken link removed**
Make a Solar Water Heater for Under $5 : TreeHugger
**broken link removed**
DIY SMALL SOLAR HOT WATER HEATER DEMONSTRATION - FAST COLD TO HOT! WITH STEAM AND FLOW! Pt. 2 - YouTube

what is the average sunlight duration perday at your place?

in addition to your idea of heating with solarpanel , can it be done with your exhaust heat of your roomheater(or fireplace) which will be available for all day and night?

this came to my mind , so it is just a suggestion.
you can thinkover and reply.

srizbf said:

what is the average sunlight duration perday at your place?

Click to expand...

Yes, It is very important
Other Ideas,

1. Purchase a pan heater + galvanized poultry waterer. This will conduct heat better than a plastic one.

2. Use small sized aquarium heater with thermostat. They look like a sealed small test tube with attached electric cord.

---------- Post added at 22:11 ---------- Previous post was at 21:54 ----------

Another idea----------

To make a pan heater you can invert a ceramic flower pot or metal pan or bucket (at least a couple of inches high) and place a 60 watt incandescent light bulb attached to an electrical cord underneath . Plug in or turn on your water heater. Make sure the heat source is reflecting upward toward the top of the flower pot, bucket or pan.
Place your waterer on top of the overturned flower pot, bucket or pan.
Make sure it's stable before you fill it.
Having the warming base wider than the waterer is ideal.
If you want more -----Attach a timer to your warmer's electrical cord if you'd like.

---------- Post added at 22:15 ---------- Previous post was at 22:11 ----------

If you want even more, you could add a microcontroller based thermo meter. please see edaboard's microcontroller section.

Anyway, what kind of animals you are having? We could have given you better ideas if it were known to us.

Thanks for your links, but none of them apply to my needs, as they requires some sort of pump or other things.

The most important thing, is that there is no power/electricity at the place where this should be used - So it has to be 100% self powered.

We have around 8 hours of bright sunlite every day at the moment.

Research the thermosyphon effect to circulate the water

with the available sunlight you can have a small solar water heater
built.
instead of letting out the hot water , it can be used for heating your 300ml bowl , keeping it from frozen.

ie, the hot water heats the bowl(preferably a suitable material for the bowl with hot water tubes wound around it tightly.)

for recirculation , the panel should be at ground level in opensapce . Using thermosyphon effect it can be continuously circulated..

so a secondary heater (heat transfer tubes) principle is suggested.

Yes, it is more efficient to use the solar power that comes from putting the water tank in the sun.

Paint the upper part of the tank black, so it will absorb more heat. Paint the bottom half white (or silver), to retain the heat.

As to how to arrange a trough for animals to drink from, that will be difficult. Water in the trough is not necessarily in contact with heated water in the black tank.

This diagram may provide some ideas.



The tank may be metal or plastic. The water dish probably ought to consist of a basin indented into the tank. That way it will always stay in contact with the warm antifreeze in the tank.

In fact, it may be sufficient to use a simple water dish, painted black to pick up heat from the sun. Large enough to pick up enough heat. And made of metal to conduct the heat to a small basin area, which holds water.

BradtheRad said:

Yes, it is more efficient to use the solar power that comes from putting the water tank in the sun.

Paint the upper part of the tank black, so it will absorb more heat. Paint the bottom half white (or silver), to retain the heat.

As to how to arrange a trough for animals to drink from, that will be difficult. Water in the trough is not necessarily in contact with heated water in the black tank.

This diagram may provide some ideas.

The tank may be metal or plastic. The water dish probably ought to consist of a basin indented into the tank. That way it will always stay in contact with the warm antifreeze in the tank.

In fact, it may be sufficient to use a simple water dish, painted black to pick up heat from the sun. Large enough to pick up enough heat. And made of metal to conduct the heat to a small basin area, which holds water.

Click to expand...

Sounds good. A good solution for similar problems.

I think it's a little overkill - was more thinking in using a solar cell panel that made some few volts, and some device in the other end, that I could put in the bowl, for heating the water.

Torbenc said:

I think it's a little overkill - was more thinking in using a solar cell panel that made some few volts, and some device in the other end, that I could put in the bowl, for heating the water.

Click to expand...

Somewhere there is a formula. So many watts of photovoltaic cells will provide so many calories (or BTU's) of heat to a bowl of water.

I'm thinking how a resistor carrying 1 watt of electrical power, will become too hot to hold between my fingers. Now picture that heat distributed through a dish of water in freezing temperatures. Is it enough to keep the water liquid?

One watt does not seem enough. A better estimate is 12 watts worth of heat.

A 12V car battery (or marine battery, deep-cycle battery) has sufficient capacity to last for several hours, if you only draw an amp. That makes 12W. This is no worse than leaving the dome light on. And a dome light gets pretty hot. That sounds like enough to distribute through a bowl of water, to keep it liquid in freezing temperatures.

Or a 12W (a square foot or two) solar panel. I say this because a PV panel of a given area cannot possibly give you more heat than the sun's heating effect on an equal area of black-painted water dish.

The heating element can be:

Several inches (maybe several feet) of nichrome wire, obtained from an electric blanket, or therapeutic hot pad, or toaster.

Several resistors soldered into a loop. This shape will distribute the heat throughout the water. (Because you probably don't want to have the heat in one spot.) You can have each resistor be 1 ohm. If you string 12 together, that will make 12 ohms. They'll draw 1 amp at 12V. Heat generated will be 12W.

Since you are using low voltage, there is no danger if you simply drop the heating element in the bowl.

It isn't a good idea to submerge an incandescent lamp in water. (Although a large percentage of its output is in the form of heat). If the water freezes it will break the glass.

First order model : on the earth the sun generate 1000 W per square meter. The efficiency of PV cells are 13%

For the time being you can use a few D cells to power a resistor loop. Alkalines will not freeze.

Or you can use rechargeable D cells. Nicads or NIMH. Charge them indoors at night. Several dollars each.

No matter what the PV cells are rated, you'll probably need twice as much. In Europe's latitudes the winter sun doesn't get high in the sky. That reduces the solar illumination.

You can add a little salt to the water. This lowers the temperature at which the solution freezes. It may or may not suit your animals as to their taste or their health.

This is interesting, are there any body try this?

I forgot to mention, that the waterbowl not reach any sunlight.
It's placed in the hen house (that is isolated)

Futurlec.com has some cheap 12v solarcells for $11 each with 15% efficiency.
With my calculations, they should, they should produce 12W each in full sunlite. Solar Cell

Woulden't 2 of them, connected to eg. a resistor loop, be enough?

Torbenc said:

I forgot to mention, that the waterbowl not reach any sunlight.
It's placed in the hen house (that is isolated)

Futurlec.com has some cheap 12v solarcells for $11 each with 15% efficiency.
With my calculations, they should, they should produce 12W each in full sunlite. Solar Cell

Woulden't 2 of them, connected to eg. a resistor loop, be enough?

Click to expand...

It's okay to start with. 11.52V at .08 amps.

Makes 0.92 watts. That's how much the resistors can draw from 1 panel.
1.84 W from 2 panels.

I think you should not wire the panels in series. That will produce 24V or more. When put in contact with water, that's a high enough voltage that it will probably be detected by the animals. They may refuse to put their mouths in the water.

You can try it yourself and see if you feel a tingle when you touch your tongue to the water. You may find you must insulate all electrical components from the drinking water.

To get the most power from the panels, the total resistance will add up to 72 ohms (give or take).

You can choose any combination of resistors.

You can use five 15 ohm. Each will dissipate 368 mW. So each can have power rating of 1/2 W.

Or seven 10 ohm. Each will dissipate 263 mW.

Or ten 6.8 ohm. Each will dissipate 184 mW. Each can have power rating of 1/4 W.

Etc.

If two panels are not sufficient to keep the water liquid, then you'll need more.

This becomes expensive as you can see. It may be just as practical to use batteries. Recharge in the house each night.