Black Locust Post

Maximizing access to the sun’s radiant energy.

That was one of my first thoughts after making the decision to power the bioshelter with the sun, vs. grid electricity.

And for our site this meant placing the photovoltaic (pv) electric generating panel at or above the hight of the bioshelter. This realization was due to the limiting factor of winter sun access. The neighbors’ house casts it’s long shadow over our bioshelter for 6 weeks in winter.

I didn’t want to block any more of the sun then I had to with the panel. Which meant not attaching it to the front of the greenhouse structure itself. So it seemed that the only option was to put the panel on it’s own pole. And it had to be at least an 11 foot pole to get it to the top of the greenhouse.

With a low budget bioshelter design in mind, the pole should be low cost to purchase and install. This excludes expensive cemented steel or aluminum poles. What about wood?

Eric had already installed four black locust posts on the kiwi vine arbor. Could I use a longer black locust post for the solar pv panel?

Why black locust?

Black locust, Robinia pseudoacacia, is a native North American tree. It fixes nitrogen and is very adaptable to many soil types. It was brought north to New England many years ago to stabilize disturbed soil. Unfortunately the tree is now listed as an “invasive” species in Massachusetts. Even though it is illegal to grow or sell here, black locust has some wonderful qualities that make it a jewel for permaculturists.

Black locust is super rot resistent, has edible flowers, can be used as livestock forage, is fast growing, makes excellent fire wood, and honey bees like it.

Because it is a “weed” where I live, I felt obligated to do my duty, and visit some public land and chop down one of these “terrible invaders”. So, that is what I did.

IMG_5065Here I am harvesting the fifteen foot black locust post from a weedy urban lot down the street (make sure you wear your safety gear). As you can see I’m cutting the tree down with a bow saw without gasoline. I was on a hill, and the straightest length was at the bottom of the tree. So, here I am trying to cut at ankle level, not easy to do. And by the way, if you’ve never worked with locust before, it is as hard as stone!

Eli, an intern, and I lugged the tree out of the woods and strapped it to the top of my truck to take it home. Once it was in the back yard I measure to about fifteen feet and cut the extra off the top. The post needed to be 15 feet, so once in the ground 3 feet, it would stick up above the height of the bioshelter. I also drilled a hole through the top of the post to secure the solar panel.

IMG_0248While the post was on the ground, the 100 watt solar panel was installed, then Eric and I tipped the post into it’s hole (no cement). So far this winter, the solar panel has received enough sun to keep the battery charged to run a 25 watt water pump, set to run 6 hours a day, in the aquaponics tanks.

Although the post’s longevity in the ground was not a concern to me, black locust equalling pressure treated wood in rot resistance, it’s wind resistance is. It just so happened that within months after installation, the post got two tests. First hurricane Sandy passed over. Then a week later a Nor’easter, with even stronger winds made it’s way through. The post was unscathed during both wind events.

I hope you enjoyed my blog POST about a locust POST 🙂

Come back and read about the bioshelter’s solar electric system next time!

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2 thoughts on “Black Locust Post

  1. This sounds like an awesome idea. Since this posting in late 2012, how has the structure held up? Is it still sturdy?

    I ask partially because I’m thinking about constructing a similar structure in Western MA, but wind is a concern for me as well. I think it’d be neat to design it in such a way that you could angle the panels between 3 positions (e.g. 24°, 47.9°, and 70.4°) and thus have them sync’ed up with a particular location’s sun angles. Those angles sync up for Ashfield, btw!

    • Hello Greg,
      It is time for an update, isn’t it… thanks for asking! Overall the bioshelter is doing very well. As for the post and panel. They have seen many a harsh weather. We’ve had feet of snow, hurricane force winds, Noreasters, and lots of wind in general. I haven’t done exact calculations at our location, but based on local conditions during these storms we’ve easily reached over 40 to 50 mph gusts. One of the beauties of the post I think is that, like a tree, the post sways with the wind. Whereas a steal post in concrete wouldn’t have any give, setting up opportunity for breakage. I hope this helped. Good luck with your project. We do consult on greenhouses so let me know if you are interested.

      P.S. Here is a bioshelter I am helping with in Greenfield, MA
      greenfield bioshelter april

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