Wasabii - cold house

I've been thinking of growing some Wasabii and have been following a thread on Backyard Aquaponics discussing things like the temperature it likes.

It seems it likes to grow in less than 10c water, and less than 25c air.

I'm about to get two solar panels for my epic solar boat adventure, so when they're are not powering the boat, I'll be using them to power my aquaponics system, and I've been thinking of ways to keep the system cool to extend the trout growing season, so perhaps I could use them for that as well.

I ran the problem through the invention engine, and it suggested running coils of hose through a container of water in a fridge as a heat exchange. And connecting the hose to my system. This would obviously cost a lot to run because each time the water went through the growbed, it would collect a stack of heat on a hot day.

But if I put a shade house over the top, I might be able to work something out.

Wasabii likes shade as well, so it should be easy enough to get a couple of layers of that grown up bubble wrap they use for pool covers, and make a tent. Wasabii doesn't grow very tall, so it should only need to be around half a metre high. Perhaps on hinges so it can be lifted when access is required.

I'd add a window so I wouldn't need to let all the heat in whenever I took a peek.

120 Things in 20 years is being told to finish the boat first.


  1. What is the ground-water temperature for you? One of the ideas up by me is to bury a deepish tank. This will help it from freezing during the winter, and keep it cooler during the summer.

    You could also do a 'cold' loop that cycled water just from the deep tank to the wasabi during the day, but involved more systems at night so the water heated up less.

    I also wonder if you could make a solar 'heater' that you run only at night, which will chill 10 degrees below ambient temps on clear nights. You have lots of clear nights when it's hot there, right?

    1. Sorry Mike, it looks like I never got to this. My water comes out of the tap at around 20c (from memory) in summer and I think 14c in winter. This is after running the water for quite a while so that it takes into account the fact that the plumbing is running along the side of the house out of the ground for 50m or so. I suspect our year round underground temperature is probably 18c. The pipe delivering the water is copper pressed against the brick wall of the outside of the house, so probably has quite a bit of influence. I commented somewhere to someone, that it might be a useful thing to actually run all your household water through your system to cool it for trout. My experiments with heat transfer and solar heating showed that even a short length of hose running through a space could add or remove a stack of heat. It would probably be a good way to regulate temps all year to something relatively consistent.

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