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Building A Passive Solar Stock Tank For Sheep In Winter

Facing the challenge of keeping a remotely situated stock tank unfrozen, this shepherd tasked her son with building a passive solar solution. Here's what happened.

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by Jana WilsonDecember 7, 2020
PHOTO: Jana Wilson

As cold weather started to set in, we separated our flock into two pastures. The older ewes and a young ram are staying up near the house in hopes of a spring lambing season. They have a nice stock tank water heater that we could plug in when the weather starts freezing,

The 8-month-old lambs got moved to a pasture about an 1/8 of a mile from our house, just off our large field that we use for herding practice with our border collies. It’s got a farm pump right there, so water hasn’t been an issue … until now!

The problem? There is no electrical source in the far pasture. And it’s too far to run an extension cord. But the lambs need to have fresh water and I was not looking forward to hauling fresh water down to that pasture a couple of times a day if the temperatures got really cold.


If You Build It…

I challenged my son Ryan, a recently graduated engineering student, to see if he could figure something out that would not require electricity to keep the water from being frozen.

He took the challenge!

passive solar stock water tank
Jana Wilson

After doing a pretty thorough Google search, he found the same links I did–which are not many–about creating a solar-heated stock tank. I was surprised that you couldn’t buy something like this, but maybe I didn’t look hard enough,

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At any rate, my son decided to follow plans for a solar stock tank from Mother Earth News. We had looked at that link before and honestly it seemed like the only one out there that would suit our needs.


Read more: Solar thermal systems heat your water with the sun.


Material Matters

Now one thing about our farm is that we use found materials whenever possible–rather than going out and buying new. So some of our projects look a little odd. But if they work, that’s great!

Ryan as well was determined to use materials only found at our place.

First of all, we collect wood pallets that others are going to throw out. So that seemed like the natural casing for our 40-gallon black rubber water tank.

Ryan also used a few pieces of foam insulation that we had available to go around the tank. But we didn’t have enough to complete the job.

Then I remembered that we had a couple of bags of extra wool we had stored from last spring’s shearing! What better way to insulate than with wool?

passive solar stock water tank
Jana Wilson

The insulation was finished off with plastic feed bags from sheep and chicken feed. Ryan stapled the bags along the outer edge of the pallet “tank holder” and filled it with the various types of insulation.

He and my husband then moved the tank in its casing to the south side of the lamb shed. There, it would be protected and get as much light as possible during the winter months.

So here’s the verdict:

The Downside

The tank ended up behind higher off the ground because he set it on a wood pallet. Not being a livestock owner, my son did not think about the fact that this flock is composed of half-grown lambs that might not be tall enough to reach the tank.

(I don’t think the full-size sheep would have a problem).

So using his engineering ingenuity, he added a stable log step at each end of the tank.

We have watched for a couple of days and the lambs are actually getting up on the log and drinking!


Read more: Sustainable farming and solar solutions power this Kentucky couple’s dreams.


The Upside

I went out yesterday morning, when the temperature was at about 24 degrees F, to check on both watering tanks. I first went down to the newly built passive solar stock tank (which we are also covering at night to keep any heat in) and found that there was a thin veneer of ice over the top that broke easily when I touched it.

Great news!

Then I came up to the pasture near our house that has an electric stock tank heater placed in the water tank. The electric stock tank heater was frozen into a couple of inches of solid ice that I couldn’t break up at all.

Hmm, I thought. Not good news.

So I followed the extension cord back to the plug and found that my husband had plugged in the wrong cord. I exchanged plugs and the water thawed within a few hours.

So we shall see how my passive solar water heating tank works throughout the winter. If anyone else has tried this and has had some success, I’d love to hear about it!

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