Wow, slack on the updates. The last pieces of the device are being put together now, I'll have media once there's something interesting to photograph.

This is a design I sort of threw together one afternoon thinking about the absolute easiest and cheapest way to make a greenhouse, ideally for farming in cities and favella type environments.

It's just three tripods together in a triangle, wrapped in some ultra cheap plastic such as transparent mulch film, which some farmers throw literally kilometres of away each year.


It's arbitrarily scalable, the one pictured would have a 110 m2 footprint, giving about 320 m2 growing area. It'd also tie in well with aquaponics and similar.

I'll have a look at getting a working group together here in Perth, leave most of the work with them while I get on with the solar thing.

It'll largely come down to what land can be found, but as the thing will be somewhat moveable, getting kicked out won't be such a big issue.

Updates on this will appear on http://urbangreenhouse.blogspot.com/

A few components still missing and a bit hacked together, but pretty much working.

Cute, no?

Unnecessary distractions 2: The Spoon Fork.

In Malaga my wallet was stolen at a market where I was wanting to, interestingly, buy a new wallet. (But then couldn't because I no longer had any money).

They made off with €50 and a couple of cards, but what I missed the most was a little folding plastic spoon I'd got with an icecream in Australia.

How one is meant to travel without a spoon remains unclear.

So, finally, I got around to making myself a replacement. Hence:

the spoon fork.


(Not a spork!)

Unnecessary distractions 1: The Solar Shower.

There were a couple of reasons for building a solar powered shower at the Traumschule when I showed up for the skill sharing camp in March; it'd been something I'd wanted to learn for a while, the only existing shower they had was a cold hose in the basement, and it was the north of Germany, in March.
Generally if the only way to get clean involves water slightly above freezing, I just won't get clean. The other people there didn't seem to mind too much, but Germans, like Scandinavians, are insane.

Most of what you see here was built in about two weeks, but wasn't actually finished until October, and not by me. I had an epic struggle with first the bends for the copper tubing (below) and then the water tank, which simply would not stop exploding, often spectacularly.

(I wasn't aware the water pressure was 5 bar, or twice that of a car tyre. That kind of psi simply will not be contained.)

In the end we went with a non-pressurised system using a toilet cistern. It worked pretty good and we still got a good rate of flow from the shower head.

It all works off a simple thermosyphon principle, where the water circulates itself through the heating panel due to the fact that hot things rise.


The actual metal panel we ended up using was donated to us, but not before I'd spent longer than intended trying to make this one. We had a bunch of old copper pipe, but I had massive problems joining it together.

The proper way is to get copper elbows and solder the whole thing, but we didn't have the money or soldering setup for that, so I had to try to make do with plastic hose, which kept going soft and collapsing when it got hot.













Finally the solution was to use two types of hose, one inside that other. The outer hose is the right diameter to fit snugly over the copper, with ridged washing machine hose inside to keep it strong and evenly curved.
However, shortly after coming to this I decided I really had to get back to the solarflower, and then we were donated the other panel anyway, so it never got finished.

But it's a good way of doing it.

Then a month later we discovered a full industrial grade water heating panel just laying around in the basement which made all of this unnecessary in the first place.

Inside the shower.

It was a fatal accident waiting to happen, but I was quite proud of that little structure.
The inwardly sloped roof is so you can shower in the rain. Didn't really work, but looks pretty.


You can click on all these images for larger versions, and if you want any extra details on the shower's design and construction, just ask.
It's very simple and worked surprisingly well.

The device has entered a vaguely quantum state of being both finished and not finished, working and not working, simultaneously.
Which is to say, the heat engine works and I got a correction out of the thing, but it took about a quarter hour where it should be six minutes at the absolute most.
This, I'm thinking it's safe to say, is largely due to the fact that I'm trying to extract useful amounts of solar energy from Germany's north in October.

If I was attempting a design based on oppressive grey and misery I could probably power the entire god forsaken region.

As it happens, however, this is not a problem, as in about three weeks I'll be back in Australia, where I can more realistically expect blue skies, 40º, and ozone depletion.
Roll on summer!

Again!

Things are circling some kind of belated conclusion in a sum-to-infinity style equation; as in, when one draws perpetually closer to something without ever reaching it.

The design has entered a state of flux, what little scraps of direct sunlight I'm able to gather from the formidable Saxon weather are scrambled frenetically about in, testing what's been made and discarding all the things that turn out not to work. The little micro-updates have been appearing on the Facebook page, but once there's actually something to show, photos and jubilation will appear here.
Touch wood- I think it's not unrealistic to expect something very soon.

A litany of failures, part one: liquid core light pipe.

The original idea I had for transporting the energy once collected, and we're going back more than a year here, was a liquid core light pipe. Essentially a fat, squishy fibre optic cable.

This works through the principle of total internal reflection, whereby light bounces without loss off the barrier between two materials of reasonably different levels of refraction. Such as glass and plastic, or water and air, or in this case: silicon and mineral oil.




The latter being pretty ideal, as it's easy to get, very refractive, has a high boiling point, and optically clear.

The former is what killed it. Silicone isn't particularly ubiquitous, cheap or clear, but the thing that really makes it inappropriate for this is that due to it's micro-surface texture, it scatters the light too much. What you really want here is something nice and smooth, like Teflon FEP or AF.


Unfortunately, tho those would be perfect for the application in every way (AF 2400 has the lowest refractive index of any polymer, to the point that you can even use water as your core (trust me, that's impressive)), it's almost impossible to get your hands on. And expensive when you do.

As you can see the silicone pipe did basically function, but comprehensive transmissivity analysis (digital camera, laser pointer, piece of paper and photoshop's histogram function) showed that even over only a meter and without bends, only about 10% of light was making it out the other end. The rest being scattered through the pipe wall.

And I wanted to put hundreds of watts through the thing. I guess this is why most everyone told me this was not a likely idea.
But it's quite pretty. I capped it with glass beads and hose clamps, attached a small l.e.d. torch with reflective tape, and am now using it as a rather dim light for my room.

So, since this was not going to do what I wanted I went on to investigate heat pipes, which are actually very promising and worth future further inspection, but ultimately for simplicity's sake have opted for a heat transfer fluid thermosyphon. Like most everyone else.
More on this later.

I've had an interesting realisation.

At no point have I known for sure that what I'm trying to make here will actually succeed. From the start of all this, over a year ago, I would always end sentences on the matter with 'if the thing works', and then laugh nervously.

But it didn't work.
The first three or four basic designs for the solarflower simply didn't function, as it turns out, and it's current form is almost entirely unrelated to them. For the first nine or so months of this project I was pursuing designs which were doomed to failure; my most feared scenario set to transpire over and over again.

And yet it's taken me this long to even notice.
The design doesn't matter.
Only the function, and the consequence.
I've seen so many mechanisms and systems pass through this thing, some of them beautiful, only to be discarded or consumed. It's a good thing. It's evolutionary.
Every death signifies an improvement, an approachment on purity of function through form.

There is always a solution... there is always a solution... there is always a solution...

Returned from the festival a few days ago, pleased to discover that after ten days of rain and wind the device was still structurally sound and hadn't exploded even once.
However, as I was stripping the reflector to upgrade a bit of wood I made the potentially catastrophic discovery that mylar sucks.
Every single piece of dust, every spot where the metal mesh touched it, every spattering of guano had somehow eaten a tiny hole in the reflective surface, leaving only the clear plastic backing. Holding it up to the light the damnable thing resembles a starry night sky of disappointment.

The two days of internet research which followed would be best described as 'feverish'; due partly to the fact that my stress levels always elevate a bit towards the end of projects, but mainly because I knew full well that:
Mylar, my default option from day one, was now going to be completely unusable,
The list of alternatives was very small, possibly zero,
And the inability to locate one would pretty much kill this entire project.

As of this morning the list runs to just one item: aluminium kitchen foil.
I've always heard that this is about the worst thing you can use; it's a bastard to work with, scatters the light too much, and is poorly reflective. Early research on marijuana cultivation forums seemed to confirm it.
However, closer reading turned up that there's no real reason this should be the case, as aluminium is one of the most reflective metals, running about 85-95% reflective through white light and well into near infra-red.

Caught a train to town, got a roll of the most reflective looking stuff I could find in the supermarket, taped three lengths together and whacked it in the assembly.
The results are very interesting.

The focus is about half as tight as the mylar thermal blanket, ie 10-12 mm as opposed to 5ish. Still pretty good. However the amount of energy is (according to my incredibly precise method of sticking my hand in and seeing how much it hurts) a lot higher. Like, 50% higher, even at the half concentration.

This, I think, means two things.
The thermal blanket, as well as sucking at durability, also sucks at reflectance.
and
Aluminium foil is a lot more reflective than it's generally given credit for.

I'm really happy to have discovered this, as though it requirs a somewhat careful workflow to avoid tearing, foil is by far the most accessible and ubiquitous reflector material in the world. That it turns out to also be one of the most effective has a lot of ramifications for home made solar.
And, yes, I'm aware that I hardly discovered it. About 90% of projects I've seen have used kitchen foil, but pretty much all of them have made what looks to be the mistake of gluing the foil to a backing material. It desperately wants to crinkle, and it's the crinkling which makes it almost useless. -You've got to stretch it-.
It also loves to tear, but taping the edges and any holes seems (touching wood) to resolve this. If it doesn't hold up in the field I'll just cover the entire back with stickytape. It's cheap enough.

So, if Google led you here because you're researching reflector materials, know this: aluminium foil rocks. Use it.
(There's pretty much no other affordable option.)

So you know how I insisted that I wouldn't be leaving here until the prototype was working? Lies. Tomorrow I'm heading for the Ecotopia festival for a week.
There are three reasons why this is necessary.
First, I really need a break. I haven't officially shunned the project for more than three days since I was last in Edinburgh, in November.
Second, it's set to rain, and as the next step is plugging the tracking system together and seeing if it works, I'll be needing some sun.
Thirdly I've mounted up the collector and want to leave it for a while to see if it blows over/blows up/rips in half or gets messed around by the weather.


All plugged together it's still on about 20 grams to turn it, which is about a quarter what I was expecting.
So that's good news.

Wobbles like a bastard tho, haven't managed yet to devise a decent couple for attaching the collector to the main shaft. That'll get done when I'm back.