Solar Power in the Chicken House

[Scott]

Quote:
Hmmm, getting too complicated for me again. The more components that are hooked up, the more power it will zap. I think I'd be ahead to hook it up only when I know we have below zero temps. That way the only device needed is the heat strip. Then again, the auto feature of the thermostat would be very nice.

 

[Scott]

Does anyone have the actual equation for figuring this thing? Surely a 20 watt solar panel connect to a 12v battery will power a 10watt heat strip. I know there are a lot of variables involved, like hours of direct sunlight, but their has to be a general equation that will help you figure exactly what you need in solar wattage. I found a basic equation the other day that assumed a 20 watt solar panel hooked to a 12v battery and 5 hours of sunlight. It led me to believe that this particular system would run a 7.5 watt heat strip. My solar panel and solar controller should be here any day. I'm really thrilled about the dc heat strip. I'm going to order that heat strip tonight. I'm going to rig it up as soon as they get here... hopefully, we get some below zero temps soon.

 

[goodegg2010]

I think your batteries will have an amp hour listed on them. Then I think you can take that number and that is your capacity. So if you are running 12V heat strips and you know the wattage, then you get the amps. You add up all your amperage loads on the system and divide that into your amp hours and you should know how long your system will run.

This is my very simplistic view but in general I think it is how it works.

 

[NorthernOntario]

Quote:
You're right, there are a lot of variables. Solar (photovoltaic) panels aren't super efficient, and that 20w rating is likely going to max out around 15-17.5w. Then there is a small loss when that power gets pushed into the battery (generates heat during the chemical reaction).

So lets assume you get 5 hours of sunlight at 17.5w... thats 1.325amps/hour (assuming 13.2v)... so you've stored 1.33x5=6.63amp/hrs. Now, during a full 24hr day, you run a 7.5w heater... 7.5w @13.2v = 0.568Ax24=13.64 amp/hrs.

You stored 6.63amp/hrs, and you used 13.64amp/hrs... so your battery lost ~7amp/hrs.

Next day, same thing... you're at a deficit. Following day, cloudy, so there isn't as much power produced... so even larger deficit.

Your battery should have an amp/hrs rating. For a regular car battery, you shouldn't go beyond 50% of this value... if you pull a car battery down below ~12-12.2V, sulfate crystals (from the sulphuric acid) start to form on the lead plates, resulting in a less efficient battery. For a deep cycle battery, you can drain more from it, but you still need to be sure to bring it back to full charge, and sulfate buildup can still occur. Battery maintenance and desulfation is a whole other can of worms... there are forums out there devoted to just that stuff!

Now a solar water heater captures much more of the energy from the sun's rays. Light is converted into heat much more readily than light is converted into electricity. You could also look into solar air heaters; insulate the coop, the use the sun to heat the air in the coop.

There are equations out there for calculating heat loss... you could (if you really felt like learning) calculate the difference in temp that you need to achieve (air temp is below freezing, you want water temp to be above freezing)... based on heat transfer through convection and conduction, you can calculate how quickly the water loses it's heat energy... which will tell you how much energy you much input to overcome the loss. But that's a couple months of college classes!

I will eventually have to deal with frozen water too; I'm in Northern Ontario (obviously), and our average winter temps are in the -20C to -30C. Hardiness Zone 3B. We are getting our chicks this spring, and I figure I'm insulating the heck out of my coop... min. R12 walls, R6 floor, R20 ceiling... controlled ventilation to minimize moisture but eliminate cold drafts on the chickens... then I may incorporate solar water heating as a small project to help keep the water warm.

 

[Scott]

Quote:
You're right, there are a lot of variables. Solar (photovoltaic) panels aren't super efficient, and that 20w rating is likely going to max out around 15-17.5w. Then there is a small loss when that power gets pushed into the battery (generates heat during the chemical reaction).

So lets assume you get 5 hours of sunlight at 17.5w... thats 1.325amps/hour (assuming 13.2v)... so you've stored 1.33x5=6.63amp/hrs. Now, during a full 24hr day, you run a 7.5w heater... 7.5w @13.2v = 0.568Ax24=13.64 amp/hrs.

You stored 6.63amp/hrs, and you used 13.64amp/hrs... so your battery lost ~7amp/hrs.

Next day, same thing... you're at a deficit. Following day, cloudy, so there isn't as much power produced... so even larger deficit.

Your battery should have an amp/hrs rating. For a regular car battery, you shouldn't go beyond 50% of this value... if you pull a car battery down below ~12-12.2V, sulfate crystals (from the sulphuric acid) start to form on the lead plates, resulting in a less efficient battery. For a deep cycle battery, you can drain more from it, but you still need to be sure to bring it back to full charge, and sulfate buildup can still occur. Battery maintenance and desulfation is a whole other can of worms... there are forums out there devoted to just that stuff!

Now a solar water heater captures much more of the energy from the sun's rays. Light is converted into heat much more readily than light is converted into electricity. You could also look into solar air heaters; insulate the coop, the use the sun to heat the air in the coop.

There are equations out there for calculating heat loss... you could (if you really felt like learning) calculate the difference in temp that you need to achieve (air temp is below freezing, you want water temp to be above freezing)... based on heat transfer through convection and conduction, you can calculate how quickly the water loses it's heat energy... which will tell you how much energy you much input to overcome the loss. But that's a couple months of college classes!

I will eventually have to deal with frozen water too; I'm in Northern Ontario (obviously), and our average winter temps are in the -20C to -30C. Hardiness Zone 3B. We are getting our chicks this spring, and I figure I'm insulating the heck out of my coop... min. R12 walls, R6 floor, R20 ceiling... controlled ventilation to minimize moisture but eliminate cold drafts on the chickens... then I may incorporate solar water heating as a small project to help keep the water warm.

Thank you for all the information. Let me ask you this... if I were too bump up the power, where do i need it first? Do I need a larger solar panel? Or do I need to add an addition deep cycle battery, or both? My coop is double walled, but I've already decided that I am going to take down the inner wall this spring and install insulation throughout. Then, put new interior walls back up. Its the one regret I have with my chicken house... I wish I had have insulated. We aren't nearly as cold as you here in winter, but we get about 2 months worth of days at or under freezing per year.

Keep in mind, my goal isnt to warm the house with solar, but keep a 2-3 gallon waterer unfrozen during freezing tempatures. If that means a 60 or 80 watt solar panel, then I'm willing to invest in that. If the solar system works, it will save me 60 days plus of replacing frozen water each year.

 

[NorthernOntario]

I think you're just taking the wrong approach... lets say you invest in 40-60w of solar electric ($200-300+), plus batteries ($100+), then a heat strip which *might* have enough power to keep water warm... all the while you're dealing with conversion losses...

Seems you would be more efficient to go with 20w of solar and a good battery, PLUS a DIY solar water heater and a home-built storage tank. Use the battery and solar panel to run a low-power 12v pump to do the water circulation during the day to the solar water panel. Because it's set up to be temp-controlled, your pump won't run at night or on really cloudy days, so you won't be drawing battery power when the solar-electric panel isn't charging.

Then you just need to figure out a way to extract heat from the hot-water tank to keep your chicken's drinking water warm. Can be as simple as setting the waterer ontop of the hot water tank, and eliminating the insulation underneath. Or building a 'heat exchanger' out of copper/pex pipe... wrap it around the waterer, the plumb into the water storage tank... small 12v pump on a timer to run for 30min every 3 hours or something. You're trying to find a way to use the sun to heat a large mass (water tank), and then control the release of that heat to a specific area.


From some reading I did of cold-weather coops, a decently insulated coop, not too large (so the birds aren't heating a huge area), will hover around the freezing mark in the winter... add a bit of active solar heat (hot water in a storage tank), and you might just do it. To remain totally off-grid, you'll need some solar-electric to run pumps... but it'll take a lot less power than trying to run a heating element all day with high-losses through electric conversion.

Plus, a 12v battery setup would allow you to have some lighting out there if you needed to go out at night.

 

[cutlass1972]

Quote:
The thermostat idea is great, but they are intended to work in a refrigerator. You're not thinking that these can be put in the water, right? Bare with me, but this thing measures the ambient air temperature, so it would kick on the heating strip when the air temp drops below 35? How would you wire it? I mean, from the battery but then you would have to wire to the heat strip. How would you do that if it is only intended to plug into to one wire in a refrigerator.

Scott,
I just ordered one of the defrost tmep switches. I have no intention of putting it under water. I am going to mount ir to the side or bottom of my galvanized metal waterer. The actual temperature sensor on this type of switch is on the front of it, so if I put the front of the switch in direct contact with my metal waterer I will get good thermal transfer and a good reading of the temperature of the water.


Someone else here mentioned that your 20 watt solar panel will hardly ever put out 20 watts. They rate these things by the absolute best of conditions, just like the HO ratings of car engines. So on the very best of days you will more than likely see 17watts of power for the first few years you have the panels and it will degrade over time.

I see you are also asking how long your battery will run your little strip heater and someone is explaining amp hours, so you are on the right track.

You asked what to upgrade first, I recommend your panels. Adding more batteries will give you more capacity, which means you can store more electricity, but you have to have surplus electricity to store first, so you need way more power then you are currently using to stuff that extra into those batteries.

IMPORTANT: always remember you should never allow your batteries to drop down to below 75% charge. Below 75% and you start damaging them, and below 50% you start damaging them exponentially. So a long story short if you do not want to be buying a new battery twice a year keep them charged above 75% at all times.

 

[cutlass1972]

Quote:
Nah, a switch is a switch. it is a simple device that either connects a circuit or breaks it. All you really care about is whether it is designed to handle at least your working volatage and power. This particular switch is buit to handle WAY more power than we are talking about, so good to go.

 

[Scott]

Quote:
Nah, a switch is a switch. it is a simple device that either connects a circuit or breaks it. All you really care about is whether it is designed to handle at least your working volatage and power. This particular switch is buit to handle WAY more power than we are talking about, so good to go.

Or I could just go with a simple on/off switch... like a wall light switch. I recieved my solar panel and solar controller in the mail this past weekend. All I need now is the 12v battery and the heat strip... then, I will be able to begin experimenting.

 

[Intheswamp]

Quote:
Nah, a switch is a switch. it is a simple device that either connects a circuit or breaks it. All you really care about is whether it is designed to handle at least your working volatage and power. This particular switch is buit to handle WAY more power than we are talking about, so good to go.

Or I could just go with a simple on/off switch... like a wall light switch. I recieved my solar panel and solar controller in the mail this past weekend. All I need now is the 12v battery and the heat strip... then, I will be able to begin experimenting.

If you want to do it correctly you need to purchase a DC switch...standard house-type light switchs are designed for ac current, not dc. An ac switch used in a dc application can burn out due to arcing.

Ed

Edit: spelling