Solar Coop

early winter chicken coopFor the more pleasant parts of the year, our chicken coop functions quite well without electricity.  We can get the coop locked up before sundown or, if we are running late, we can use a flash light.  Our old coop, at our previous house, had electricity; the coop was attached to our garage and running power into it was quite easy.  Our coop in St. Paul, however, is not attached to any out-buildings.  In a former life, our coop was a dog house.

Without electricity, the coop has a distinct disadvantage during the winter months: the chicken’s water freezes.  We have used, at the depths of winter, a power inverter attached to a deep cycle marine battery.  It has worked well enough, but it too has a disadvantage – the battery is heavy and needs recharging now and again.  With the winters in the east-central part of Minnesota (where we now reside) milder than our previous locale, carrying fresh, warm water out to the coop each morning is usually not a problem.  The only time it proves to be an issue is when we need to be away from the house for an extended period of time.  Friends and family tend to be willing to drive out to our house, but we really wanted an option that would let us be away from the house for several days without having to burden those friends or family with chicken-maintenance.

Solar Panel Rick
My father-in-law, Rick, helping with the panel installation

Our original plans for the coop that we submitted to the city of St. Paul, included solar power as an option for providing a small amount of electricity to the coop.  I really had no idea how many panels we would need, or how much initial capital would be need to get something viable up and running.  I waited…a couple years.  After getting a bit more serious with the idea over the summer; I did some back-of-a-napkin math with how many watts would likely be needed to power a heated waterer, as well as having a small light in the coop.   I came up with a minimum of 200 watts.  Heated waterers run between 100 watts to 125 watts (and heat elements exist, too, if you were trying to keep a livestock tank free of ice).

Solar panels on the coop roof
Solar panels on the coop roof

Nearly all of the chicken waterers I looked at use alternating current (AC), e.g. they have a two prong plugin like a toaster or hairdryer; using AC power means a power inverter is needed to change the direct current (DC) from the solar panels and battery into AC power for the waterer.

In a perfect world with perfect balance, the battery recharge and power consumption and generation would be something like, [consumption] 100 watts per hour for the waterer; [generation] 200 watts per hour being generated by the solar panels; ½ that amount would go to the waterer and the other ½ would go to recharge the battery.  It should also be noted that inverters, on average, 95% efficient; e.g. 200 watts DC will result in 190 watts AC.  An amount of power would be consumed at night that is less than the amount of power that was regenerated the during the day.

There are variables that complicate the situation – persistent cloud cover, snow, freezing rain, and, as we enter winter on December 21, St. Paul receives less than nine hours of daylight.  And, so far, during the first part of meteorological winter, we have had fits and starts of abnormally warm weather.  A day, two days or even three-day stretches of above freezing temperatures.  This simply means we need to be smart about how we use the power; use of a thermostatically controller outlet, for example, maybe helpful.  The above freezing temperatures along with the thermostatic outlet would also allow the battery to regain charge quicker without having to warm the waterer.

Solar Charge Controller
Solar Charge Controller (without leads to battery)

So, what is needed to put solar panels on your own chicken coop?  A weekend, a bit of time, some handyman-(or woman)-type-skills, tools, and a bit of money. First, unless you buy used panels or are able to repurpose existing panels you might have and maybe patch to together bits of heavy gauge wire, the whole setup is not necessarily inexpensive.  This, of course, also excludes any of the indirect costs, too, of the power tools that were used – like an impact driver, angle grinder (I have two of these, actually), a drill, wrenches, a small propane torch for soldering, pliers, screwdrivers, hammer and, likely, sundry tools that I am forgetting.

Here is an almost-complete list of the things (and prices) for this project:

Renogy Solar Panel Bundle, 200 Watt $324.99
BESTEK 1000w/1200w 12v to 110v Inverter Power Supply MRI10011-1 $65.99
Terminal Ring, 12-10 AWG, Stud Size 8-10, Yellow (50 pk) $6.64
Terminal Ring, 6-10 AWG, Stud Size 3/8″, Blue (8 pk) $6.64
Solar Panel Cable 6 Ft – Mc4 Pv Extension (2x) $12.09
Keep It Clean FHC10 10 Gauge ATC Fuse Holder with Cover (2x) $16.72
10 Gauge, Strand, Black- Copper Wire – 50 feet $16.16
10 Gauge, Strand, Red – Copper Wire – 50 feet $16.16
Heat Shrink 1/4″ Tubing $1.97
4.1/2″ Metal Cutoff Blade $5.94
8′ Angle Steel – 1.1/2″ (2x) $37.98
5′ Angle Steel – 1.1/2 $13.78
Carriage Bolts – 3/4″ x 5/16″ – bag, count 39 (2x) $7.56
5/16″ Washers – bag, count 90 $2.28
1/4″ Fender washers $3.49
5/16 Nylon nuts – bag, count 90 $3.49
1.1/2″ Self-tapping polebarn screws $5.29
Electrical 40% tin/60% lead Solder $7.65
Blue 15 Amp ATC Blade Fuse, (Pack of 25) $7.99

Coop Roof and Solar Panel Angle CalculationThe angle steel was used to construct supports for the panels so they could be angled toward the sun.  The supports are two, 18″ pieces at the top of each panel, and two, 8″ pieces at the bottom.

We decided to go with a fixed angle setup.  Fancier installations can have step motors and a pair of light dependent resistors with the panel support structure mounted on turntable of sorts to automatically track the sun laterally intra-day, as well as adjusting the angle of inclination as the sun tracks higher above the horizon during the summer and lower in the winter.

2014-12-06 at 12-56-35Following the calculations found at SolarPanelTilt.com, the correct angle for our latitude, near 44.9°, the formula is latitude, times 0.76, plus 3.1°.  This turns out to be 37.2°.  I am not sure of reasoning behind the use of 0.76 as a multiplier and then addition of 3.1°, but I will go with it for now.

The roof of the coop is angled at roughly 11°, leaving the panel support angle at 26°.   A bit of dusting off my trigonometric & algebra skills and I calculated the opposite side from the angle to be 28″ from perpendicular to the horizon.  Cutting the triangle with the 11° roof angle and a bit of subtraction, the vertical supports come out to be about 21″ tall.  I ended up going a little shorter than 21″ – due to a transposition of two numbers.  The angle is shallower than ideal for the winter months, but would be great for summer (which would be a pointless time to run a freeze-free waterer).

Renogy - 200W Solar
Instructions for wiring panels + battery + controller + inverter

With the panels mounted on the roof, the wiring fed through into the coop, I got to work connecting the panels’ wire to the charge controller, the charge controller to the battery, as well as connecting the inverter.  The panels are connected in parallel as each panel generates 12 volts and there is only one 12 volt battery.

Following the instructions on wiring, there are several fuses used in the setup.  There is a calculation to get an idea of what size fuses you will need; these two panels needed two, 15 amp fuses; the third fuse is actually built into the inverter.  Check your inverter specs to see if you need to install a fuse before your inverter or if there already is one as part of the inverter.  The first 15 amp fuse is installed between the solar panels and the charge controller.  The second 15 amp fuse is installed between the charge controller and the battery.   Checkout the instructions (above) and consult with friend who is an electrical engineer, if needed.

To the keen observer, a few questions may come to mind; why 10 gauge wire with 15 amp fuses?  It is a bit overkill, I will admit, but the fuses are changable.  If we added two more panels, the only things that would need to changed to handle the 27 amps would be the fuses.

Another question might revolve around the massive 1000 watt inverter.  I mostly settled on the unit I did buy because it had threaded terminal posts as well as a thermo/load-sensor for controlling the cooling fan.  Simple, light loads will not cause the fan to turn on allowing you to stretch a little more out of your battery.

Mouse in the Chicken HouseFinally, and possibly the elephant or mouse in the room, the cost-question.  Around $500 to keep water for a small flock of chickens from freezing.  I look at it as an experiment with a bit of usefulness thrown in. The experiment is that I have never worked with solar on this scale.  It is still small compared to a utility company’s solar array, but it is quite a bit larger than that solar powered set of christmas lights you may have seen at the hardware store.  The experiment part also comes into play for us on two fronts; first, on the family-land north of Hibbing, the nearest electrical pole is a couple miles to the north.  If the coop works out well for us, we could think of solar as an option for when and if we build a cabin.  The second front is closer to home here in St. Paul.  We have tossed around the idea of putting a small array on the house once we put new shingles on the house.  Both of the situations would require more in depth cost analysis to determine the return on investment, e.g. how long would it take to recover the upfront cost of an array.

The final bit of usefulness for us is that we now have a small amount of power at an outbuilding that would otherwise be much more expensive to bring power out to than this project cost.  I won’t be able to lug the 50 amp, 240 volt arc welder out there, but powering a trouble light or recharging the drill and driver batteries is definitely within reason.

We will give give our new setup a trial run on the coop, and we will likely post, again, with what we find.

Night Lights in the Coop

Alex Jokela

programmeranalyst with a flair for horticulture // I build data tools // ♥ data // assistant-overlord of a small poultry flock

4 thoughts on “Solar Coop

  • December 11, 2014 at 07:47
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    I think a sesame street song warned us about the evil ” transposition” didn’t it?!? 🙂

  • December 10, 2014 at 23:05
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    Sweet! I look forward to hearing how this progresses!

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