Help, dog water bowl heater ran by solar thermal energy...

[Nmeeker]

Hi guys,

First let me apologize if this has been posted elsewhere, I've been researching like crazy abd cant seem to find the information I really need, so as I've learned through my past DIY excursions, ask the pros with the Passion for such.

Here's the situation, I am constantly traveling in the nortern states and Canada with my dogs Bella and lucey, and as you know it gets cold out there, I work outside and have problems with my dogs water becoming frozen.

Here's what I would like to do . I would like to build a system and create a pad that would heat by solar power, as I am away from AC power to use a conventional pad. It needs to be able to hold a temperature above the waters freezing point (32f) throughout the day and night.

Now I thought this would be easy and has proven to be quite the obstacle. But I assume I would need a solar panel large enough (size undetermined ??). That connects to a cord with positive and negative connected to a solar battery system, that then runs to some.sort of pad. My next issue and largest I would imagine, is creating a pad. I've read tha you can use wire (the sort from a toaster) in a small guage to create heat, or even use a series of resistors.

I know I lack the education in this field but I imagine this project is barely a step towards some of the large scale projects otherwise mentioned in this forum.

Guys any help would be much appreciated,

Thanks.
Nate

[Sunking]

Nate in theory it could be done but are you willing to carry a couple of hundred pounds of junk while you travel, and spend a considerable amount of money?

To design such a system would first require daily energy requirement in watt hours, location, and time of year use.

OK first you do not have to make any kind of heater, for $8 you can buy a portable Trucker coffee heater like this one. It will do what you want and is the easy inexpensive part. It uses roughly 40 watts of power.

Now the fun part is determining the panel wattage, charge controller, and battery size. Your location is absolutely horrible for solar, especially in winter as you get at best 1 to 2 hours of Sun each day in winter months. The heater does not need to be on all day, just enough to keep the water from freezing. Educated guess is the heater will need to run at least 6 to 8 hours each day. That means 40 watts x 6 hours = 240 watt hours to 40 watts x 8 hours = 320 wh. That may not sound like much energy and is not from conventional sources but quite a bit for a portable solar system. To account for system losses the panels need to make 480 to 640 watt hours each day to run the heater.

The solar panel size is 480 wh / 2 Sun hours = 240 watts to 620 wh / 2 hours = 310 watts. That will require two very large solar panels of 150 watts each and cost you around $500 to $600 for the panels.

As for the battery will be a 12 volt battery and the size in Amp Hours will be around [300 wh x 5] / 12 volts = 125 AH @ 12 volts. So you are looking at a battery that weighs around 100 pounds and cost around $250 to $300 for a good AGM battery as it will be needed for the extreme cold and portability.

The last piece of equipment is the charge controller. It will require a 20 amp PWM controller. Those cost around $80 to $100.

All in all once you buy all the equipment and material you are looking at around $1000 USD and 200 pounds of crap to carry around to keep you dogs water from freezing.

Personally if it were me I would just use the vehicle alternator with an auxiliary battery installed.

[Kurtk]

thermal mass

Do you have the capability of heating something every few hours? I'm thinking a far simpler solution would be to give the bowl a a larger thermal mass (a couple inches of concrete - or heat stones in a "bag" the dog bowl sits on.) If you can heat the stones every few hours (or less often depending on air temp) it should keep the water from freezing.

Escentially, have the dog bowl placed on top of a sack of hot rocks. The rocks placed on top of some insulating material so the heat doesn't go into the ground.

I know some winter campers will throw some non-river rocks (don't want water in the rocks as it could explode) in their campfire then bundle them in newspaper or such to insult them and end up putting them in their sleeping bags for night. I'm just thinking something along that idea is far simpler than batteries and panels.

[Naptown]

Do you have the capability of heating something every few hours? I'm thinking a far simpler solution would be to give the bowl a a larger thermal mass (a couple inches of concrete - or heat stones in a "bag" the dog bowl sits on.) If you can heat the stones every few hours (or less often depending on air temp) it should keep the water from freezing.

Escentially, have the dog bowl placed on top of a sack of hot rocks. The rocks placed on top of some insulating material so the heat doesn't go into the ground.

I know some winter campers will throw some non-river rocks (don't want water in the rocks as it could explode) in their campfire then bundle them in newspaper or such to insult them and end up putting them in their sleeping bags for night. I'm just thinking something along that idea is far simpler than batteries and panels.

I wasn't aware that rocks were sensitive? I would imagine it take more than wrapping them in newspaper to insult them.

Just messing with you I know what you meant

[Naptown]

yes ！ i agree the gay said upper . its too weight , i heard someone said there is an solar shower bag , i think its easy to carry so i suggest you can try

I don't know where to begin with this?
What are you trying to say?

[Nmeeker]

thanks sunking

I appreciate the taste of how this works. However you raise great points, too heavy, too expensive not really a good option. Now i see how you calculated power needs through light hours and watts per hour needed. I was hoping to bring the cost down a bit more into the hundreds and weight down more as well. So if i could ask a few questions.. now normally I'm in Michigan and get around 6 hours of sunlight minimum give or take. Which would dramastically bring down solar demands according to your calculation. 240/6 is 40 watts @320/6 is 60.. also with the truckers coffee heater, at 40 watts per hour , I was looking into tying together a series of 5 watt resistors to bring heat down and hopefully power requirements. Also, because the winters here are not too harsh lately and the wewthers been a little on the warmer side the last few years I was curious if tying in a thermometer was an option in order to save power ? Maybe with these different factors I have a bettet chance ? Thanks sunking


Nate

[Naptown]

A thermostat in the bowl would be the most cost effective way of reducing power. Only heat when temp goes down to 34 and off at 40.
The problem with Michigan is you will not get 6 hours of sun during the winter when you need the heater. Maybe 2.
Look up the insolation values for the area you are in.

[Sunking]

now normally I'm in Michigan and get around 6 hours of sunlight minimum give or take. Which would dramastically bring down solar demands according to your calculation. 240/6 is 40 watts @320/6 is 60.. also with the truckers coffee heater, at 40 watts per hour

No Sir you do not get 6 Sun Hours, only June and July. You are confusing daylight hours with Sun Hours. They are not the same thing and a common mistake people make. Using Detroit as a point of reference:

Nov = 1.7 Hours,
December = 1.3 Sun Hours
Jan = 1.6 Sun Hours
June = 6.1 Sun Hours
July = 6.0 Sun Hours

This forces you to use 1.3 Sun Hours which make the panel wattage even higher and more cost.

[Nmeeker]

I see what you're saying and yes i definitely had the sun hours and daylight hours mixed. So that creates an issue. So question, if i get 1.3 sun hours a day in december, and a panel gets 10w, I'm only going to generate 13 or so watts in a day ?

And if I use the nichrome wire I can bring temp up on two linear feet at a thin guage for between 3-5 watts per hour. But with that I would only get three hours or so of run time ag full strain. Hmm.. but thats in worst weather. If i had a thermometer attached it wouldn't need to run unless the temp dropped to where it kicked on , and could store on average enough to run for for a few hours each day ?

Thanks again guys

[Naptown]

I see what you're saying and yes i definitely had the sun hours and daylight hours mixed. So that creates an issue. So question, if i get 1.3 sun hours a day in december, and a panel gets 10w, I'm only going to generate 13 or so watts in a day ? Correct

And if I use the nichrome wire I can bring temp up on two linear feet at a thin guage for between 3-5 watts per hour. But with that I would only get three hours or so of run time ag full strain. Hmm.. but thats in worst weather. If i had a thermometer attached it wouldn't need to run unless the temp dropped to where it kicked on , and could store on average enough to run for for a few hours each day ?
You will still need a larger panel

Thanks again guys

Comments in red.

[Sunking]

I see what you're saying and yes i definitely had the sun hours and daylight hours mixed. So that creates an issue. So question, if i get 1.3 sun hours a day in December, and a panel gets 10w, I'm only going to generate 13 or so watts in a day ?

Close but no cigar. A 10 watt panel with 1.3 Sun Hours will generate 13 watt hours at the panel terminals, not 13 watts as you stated. However due to system losses of about 50% efficiency around 6.5 watt hours is useable at the battery.

And if I use the nichrome wire I can bring temp up on two linear feet at a thin guage

You cannot just go submerging nichrome wire or resistors in water. The water will short out the circuit. It ihas to be insulated like any direct electric heating element. Very doubtful you stand a chance at making one. At least not as cheap as $6 to $10 just buying one.

As you can begin to see using solar PV and batteries to heat water is pointless and way to expensive.

[john p]

You cannot just go submerging nichrome wire or resistors in water. The water will short out the circuit. It ihas to be insulated like any direct electric heating element. TOTALLY NOT TRUE. I was using nichrome wire wound around a ceramic former in a bucket of water for power testing 200 and 300w amplifiers for over 20 years . I also made an electric jug to run of the 12v battery in my 4wd for camping . it was used for years.IT WORKED PERFECTLY EVEN IF A BIT SLOW
Obviously it was a theory of his ,not ever tested in real.

[Sunking]

You cannot just go submerging nichrome wire or resistors in water. The water will short out the circuit. It ihas to be insulated like any direct electric heating element. TOTALLY NOT TRUE.

It is true and you know it. Water is conductive period, and you know it. If it worked it is because the current flowing through the water was heated. Some current would flow through the wire but it is in parallel with a lower resistance of the water.

[john p]

its not true and I and everyone elso doesnt know it either. Open wire jug elements were made for about 60 years and were made in the millions. The jugs were porcelain and had replaceable elements...FACT believe it or not.
If your statement was true how would cold water get hot using an open wire element in the COLD water? IF there really was a short circuit it would not be heating the water.
And at 12v dc the amount of loss between 2 electrodes(wire) in water would be miniscule compared to the current flowing in the heater(nichrome wire) element.

[Kurtk]

Pure water is actually a pretty poor conductor - might even call it an insulator. However, if you have impurities in the water it quickly becomes a conductor. When I first got my panels, I connected wire leads with several inches of bare copper to one panel and stuck them in a bowl of water. Very little current... I poured in salt and the amps increased greatly! (ps... this is also a cool way to make small quantities of hydrogen and oxygen gas as you're literally breaking apart the water molecules) If you catch the bubbles in a cup (fill it w/ water upside down and let the bubbles displace the water 'til you have a full plastic cup of gas stick a smoldering match in there and it'll ignite w/ a sudden "pop". (Watch the hairs on your hand.)

This is one of many fun experiments to do w/ kids.