Saturday, September 14, 2013

Drum roll please


I can't describe how good it is to be able to walk up a flight of stairs rather than climb a ladder!

Friday, September 13, 2013

Trapeze lighting

Before I began building the rammed earth walls in the garage, I read a lot about peoples' experiences with the method and one thing which kept being mentioned was the importance of embedding conduit in the walls so that electrical services can be run later. A good idea and very sensible, but in my case I didn't think it would be necessary as I didn't plan to run any wires through the walls.

That was before I came to plan the lighting for the "clean room" behind the rammed earth.

Even with my 3D model of the building in Sketchup, I failed to take into account the fact that this room would need lighting. Being underneath the suspended slab above and nestled between the buried retaining wall and the rammed earth, there's no natural light and so of course, lighting is going to be necessary.

Except I didn't run any conduit, anywhere...

The ceilings in here are the coolroom sandwich panels - polystyrene clad with colourbond steel. There's very little chance I could bore conduit into the styrene and in any case, I have nowhere to mount a switch without chasing ugly trenches into the rammed earth or running conduit over the surface. So, a little lateral thinking is in order.

Since I intend to implement a fair amount of home automation in the building (using one or more Ninja Blocks and LIFX LED lighting, more about that later) I've decided to attack the lighting problem in here in the same way. I'm starting with a single string of low-voltage trapeze lighting - the same sort of thing you often see in trendy restaurants - which neatly solves the problem of running power to the lights. But how to switch them?

That turned out to be easier than I expected. You can now buy remote controlled power points, which are intended to help you minimise the amount of standby power that appliances use by switching them off at the wall, using a remote control. Well it turns out that these all operate in the 433MHz band (I think that's right, my memory isn't the best) and are interoperable. So I can use a remote power switch to turn on the transformer, and just stick the remote to the rammed earth wall at the entrance to the room.

(Even better - once I get my home automation up and running I'll be able to control the lighting centrally, or from my phone!)

A grinding we shall go

It's taken a few months to get them onsite, but finally the floor grinders are here! Actually that's not strictly true - they did show up unannounced a month ago or so, and were unable to get their equipment into the building so gave up, and drove back to Shepparton!

But they're here now, and so with a little assistance with the bobcat we've got their gear inside and they're getting stuck into the floor.

Who took this photo!? Focus!!
A couple of hours and about 4 passes with 60 grit stones later, and there's still very little aggregate showing yet. What is coming through is very fine, as if the mix was a grout using 7mm rock - but I've checked the records, and it was definitely 32MPa mix with 20mm aggregate, so it's in there somewhere!

Rather than spend all day grinding with the finer stones, they've switched to the heavy duty stuff and now we're getting somewhere! These ones are leaving some pretty impressive scratches in the surface, but they're eating away and the aggregate is starting to show itself.

Another couple of passes and one more with the finer stones and I think we're there.

I'm pretty happy with the result - it's taken a while (and the job is only half done) - but I think we'll have a pretty nice concrete floor at the end of the job.

The grinders are coming back on Monday to give it one more pass to get rid of the coarse scratches, then it gets grouted to fill in the little air bubbles and cracks, and a coat of epoxy goes on. Then I can get stuck into the wall lining, and once that's finished they'll come back for a final polish and seal.

Monday, September 9, 2013

Solar performance

While researching our solar installation I came across a website, PVOutput which records the solar output of thousands of (mostly grid-tied) installations all across the world. Basically, owners of solar PV installations configure their systems to send generation data to PVOutput, and there it's logged, graphed and analysed a thousand different ways.

Being the nerd that I am, I knew that I'd have to hook our system up once I got it operational, if only so that I can keep tabs on it remotely when I'm not there. But the first problem is, how to get the place on the Internet?

As it turns out, we have fantastic 3G mobile coverage with Telstra, and I've been using one of their 4G USB dongles on site for some time with my laptop. But we're on a power budget, so how to maintain an Internet connection without running a full size, power hungry PC?

I found the answer in one of these.  They're an Intel-compatible PC (running a 1.6GHz Atom processor) but only use .. get this .. 5W of power idle, and 8W flat out! And they're tiny, about the size (and as it turns out, the contents) of my wallet.

On it I'm running a Linux operating system (CentOS 6.4 to be exact) and I'm using a little application called SMA-Bluetooth, which connects to our Sunny Boy inverter using .. you guessed it, Bluetooth, reads off the power generation data and uploads it to PVOutput.

The result is pretty amazing :) Click the pictures for the live graphs - you can even see what power is being generated every 15 minutes (during the daytime, of course ;) ). We live in the future!

Being an off-grid installation and we're not yet using much (if any) power, the system has the batteries fully charged and so we're basically only generating around 100W of power during the day, which serves to power the inverters (about 40W) and trickle charge the batteries. The spike in the morning serves to replenish what the inverters (and my little 5W PC!) has used overnight.

Sunday, September 8, 2013

Stairs update

With very little left to do downstairs in the garage, I'm beginning to turn my attention to the wall lining upstairs in the unit. However, before I can do that I need to get the staircase finished - I'll be damned if I'm carrying the plywood around the building to get up there! I'm hoping to have the floor grinders in next week to grind back and polish the concrete floor, after which I can get stuck into the lining full speed ahead. So this weekend I really need to break the back of these stairs!

About half way there. Looking good, but that last step is a killer!
With seven treads in place, I've been looking at the slabs I have remaining and even my optimism isn't going to produce seven more treads from two slabs. At their narrowest these slabs are about 500mm wide, while the treads are 260mm each and so obviously I can't cut two side-by-side. Likewise, the slabs are just short of three treads long at 2.5m - each tread is just shy of 900mm, so it looks like I'm going to have to compromise and laminate a few treads to get them to size.

This is what I'm working with:

I don't know what species the timber is, but I'd love to know. If anyone can tell from the photos, drop me a note in the comments! The wood is quite hard but my rebuilt Triton saw cuts it easily with a 60 tooth blade, and the cut surfaces are absolutely beautiful and smooth. The corners are so crisp you could almost shave with them!

The slabs originally looked quite blonde off the chainsaw, but the sawdust is almost pink. I had originally thought it might be grey ironbark or box, but now I'm not so sure. The tree was slabbed over near Bendigo, but I don't know what species are indigenous that area...

I'm leaving the chainsaw finish on the treads, and just sealing them with linseed oil diluted 50:50 with mineral turps for penetration. This is giving them an absolutely gorgeous deep reddish-brown finish which is a fantastic contrast to the blonde of the plywood and rammed earth walls. I plan to fill in the risers with the ply as well, which should look a treat.

This is where the trouble begins, I think. This is my first laminated tread, made up of one piece 200mm wide and another off cut at 60mm. I've glued the pieces together with regular ol' PVA, and clamped them together and down to the workbench to (hopefully) create a flat surface on top. While they're clamped I've also bored about 40mm into the narrow (back) piece and screwed the two together using 100mm bugle-head batten screws to keep it all together when the clamps come off.

This is the final product. I attempted to match the two pieces for colour and chainsaw grain as closely as possible, but obviously there's a mismatch and so to minimise this, I'm distressing the joint with a chisel to mimic the chainsaw cuts, to give some continuity across the joint and mask it somewhat.

It's nowhere near perfect (not that I'm expecting that) but I'm happy enough with the end result.

Apparently there's more of this tree still over near Bendigo, so if I get dissatisfied with the laminated treads (or if they're not durable) then I can wrangle Steve and his Alaskan chainsaw mill and go cut a few more slabs.

The first laminated tread, oiled and in position.
So I have four more treads to go, two of which I can cut whole out of the remaining slab. At least now I can use a short step ladder to reach the first tread, so once they're dry we have a serviceable staircase :)

Friday, September 6, 2013

Last concrete for a while

Today we poured what I hope will be the last concrete for a while. There are three jobs:

  1. The slab outside the dwelling and onto the shipping container;
  2. An extension to the little slab next to the pump room entrance, upon which the slimline 2kL rainwater tank will sit; and
  3. A cap on top of the retaining wall to bring it up to roof height.
The weather has been looking a little dodgy until this morning, but the Bureau is forecasting a 40% chance of up to 1mm which with any luck will translate into no rain at all. So my first job this morning was to race around and remeasure the slabs to confirm the concrete volume with the supplier - and a good thing I did, because I'd ordered 3.2m3 and it turns out we'll need closer to 3.4m3.

But while running around the place I spotted this:

There's no sign that anyone has been around the place - nothing disturbed, no food scraps, wrappers, cigarette butts, footprints even ... but someone has clearly built themselves a tiny little fire (the scar is about a foot in diameter) and cooked something over the reinforcing steel. Part of me is a little apprehensive about it, but the other part rather likes the idea that there's someone around living lightly on the land.

Anyway, back to the concreting!

So with the concrete confirmed and paid for, and the reinforcing steel finished off we waited for the concrete to arrive - "we" being myself, Shackles (a local concreter and all-round good bloke), my mate Steve and his partner Amy, and Peter the builder and architect.

Right on time the truck arrived and everyone swung into action - myself, Peter and Steve on wheelbarrows, Shackles on the screed and Amy with the vibrator.

Steve supervising, enjoying a refreshing beverage while Shackles does the real work.

The finished product. This will a nice little spot to sit and watch the countryside :)

I don't have pics, but in addition to this slab we also topped off the retaining wall and extended the water tank slab. And would you believe it, we used three-point-four cubit metres of concrete exactly. None wasted, none short. Win!

Thursday, September 5, 2013

Whatever will they think of next!?

Can you believe it? A flushing toilet! What a good idea...

No more poo-ing in a bucket for me! :)

Mmm, stairs

The new armature assembly arrived for my Triton circular saw last week, and so with a new set of bearings it's back together and stronger than ever. So without delay, it's into the stairs!

I've decided that the chainsaw finish on the treads is so good, and being that these are stair treads and could do with a little texture for grip, that I'm not going to sand or plane them at all. All I've done is given them a coat of linseed oil thinned with turps for penetration, and voila!

How good to they look!? :)

Ultimately I think I'll enclose the treads, as they currently only just meet the requirement that a 125mm ball not pass between them, and I'm sure there'll be the odd one or two that fail that test by a millimetre or two. So I'll use offcuts from my wall ply and fill in the risers, which should give a nice contrast to the rich red of the timber.

A bit slow on the update

I really have no excuse, aside from just being slack with the updates! So on with the show.

After the power went on everything seemed to be working fine - the Sunny Boy panel inverter producing power, and the Sunny Island charging up the batteries.

Everything however was not quite right.

The Sunny Boy is a grid-tied panel inverter, which in 99% of cases is used in installations which have access to the electricity grid, and the power generated by the panels is fed into the grid. In this mode there's no throttling - every watt of energy produced is fed into the grid and this is how the inverter was configured out of the box.

In our installation we have no access to the grid, so we have to balance our energy production against our energy use. Power we don't use directly is used to charge the batteries, but once they're fully charged we simply have to stop generating electricity as we have no "dump loads" (basically heating elements which turn excess power into heat). The Sunny Island inverter/charger controls our "grid", and signals to the Sunny Boy that it should throttle back by raising the frequency of the grid slightly from its nominal 50Hz. Conversely, when it needs solar power to serve loads or charge the battery it drops the frequency slightly.

Because I hadn't configured the Sunny Boy for off-grid operation, it was blindly ignoring the "hints" from the Sunny Island until the frequency exceeded 55Hz, at which point it disconnected with a "grid fault" error. This served to effectively modulate the power produced, but was extremely coarse and if left, would likely cause the batteries to be over-charged.

Once I configured the Sunny Boy in "island" mode, the two inverters talk politely and the grid frequency remains between about 49.5Hz (when solar power is required) and 52.0Hz, when it's not. Perfect.

Except it's not.

When Nenad was onsite during the week to diagnose an earth fault causing one of the RCDs (safety switch) to trip, he noticed that occasionally the power would drop out completely for a second, then come straight back on. This seemed to happen in concert with the panels receiving full sun for a little while, then being shaded by cloud. I spent half the day last Friday poring over the settings of both inverters to try and sort this out, to no avail. Sure enough, in solid overcast the system worked reliably but when the panels lost full sun, the power would drop out for about a second and then return.

Even more curiously, this only happened when I had about 1kW of load present. Odd.

Unable to solve this myself I ended up calling SMA Australia for assistance. While talking them through the problem and describing the symptoms, the power dropped out again and I noticed that the word "search" flashed up on the remote control very briefly at the time the power went out. This proved to be a strong clue to the cause - the Sunny Island has a power saving "search" mode whereby it detects how much load is present on the inverter and if it's lower than a configurable threshold, it goes into "sleep" mode to save power. What was happening was that although there was plenty of load (1kW) present, when the Sunny Boy fed in a couple of kW as it got sun on the panels, the system transitioned between the Sunny Island supplying the loads from the battery, and the Sunny Boy taking over. When the sun disappeared again, we got the same transition but it seems the Sunny Island detected this as a zero nett load for a short period and decided to go into sleep mode. Once the feed in from the Sunny Boy dropped below that of the loads, the Sunny Island detected the loads again and powered back up.

SMA think this is a bug in the software (I agree) and are working with Germany to sort it out. In the meantime, I've got the system stable by simply turning off this "search" power-saving mode.

In other news, Peter and I began setting up the little concrete slab which will cover the void in front of  and above the shipping container, and underneath the large window of the unit. This will be a nice spot for a shade sail and outdoor furniture :)

The aim is to pour the concrete here on the 6th of September.