SWH project part 16 - up and running

It's going! I'll be leaving behind a short list of outstanding finishing touches, and a couple of suggestions for future improvements, but in the meantime it's working: preheating the water for the laundry so the geyser doesn't have to work so hard, and thus saves fuel.

Solar Water Heater opening ceremony.  The first overcast day in ages, but was
actually just as warm and twice as humid.  Sweaty.

Some of my main helpers.

Re-fitting the heat exchangers (see here for why)

Lid back on after much intricate wielding of the hacksaw.

The brazing chap from Lahore was back doing some other work in the hospital,
so I got him to attend to a minor leak.

One last piece of colourful frazzled copper.

Snug as a bug in a rug about to chug a mug of... hot chocolate?  Glug!

SolarBot doing his thing.

Modest temperatures on a cloudy morning.  In the middle of a clear day the
panels hit 80°C, and the tank gets to 65-70°C.

Again, on a clear day the output beats 50°C.  This could be improved by
lengthening the heat exchanger coils, or by moving to a pressurised tank
with no heat exchanger.  The latter is almost certainly worth doing.  When
someone gets round to it...

Finished system.  For a given value of "finished".

Tank insulated and roofed.  Among the final touches I'm
leaving for the workshop guys to do at some point is to stop
the rainwater collecting on the platform and soaking into the
bottom couple of inches of insulation.  Preferably before the
monsoon starts in earnest.

Thermal expansion coupled with cycles of thunderstorms
followed by hot clear days has done for these strips we used
to hold down the glazing.  They'll replace them with some-
thing better and redo the seals...

(This one's an extreme example - the other nine seem to be fine!)

...which should hopefully stop this happening.  They'll also put some metal
sheeting along the top edge of the panels.

SWH project part 13 - plumbing

Pipe-laying in the trench.  Since it was dug a few weeks ago
up to 3 feet of vegetation has sprung up along its edges.

Every joint requires you to cut 2 screw threads with this die, which is no mean
feat even when you're not trying to do it in the trench.

Cold line, sensor cable conduit, hot line (which needs some
attention with the tape...)

Coiling the heat exchangers.  Strangely, they coiled beautifully
 in this direction, but when we started trying to bend the ends
 upwards, it was threatening to kink at every opportunity.

So, how complicated can we make this?

Copper coils successfully installed, and due a little de-kinking with the pliers.

Exchangers connected up.  Incidentally, you should never
do what's been done here and connect the copper directly
to the galvanised pipe.  I predict corrosion before too long,
but there's only so many times you can tell your boss "We
should REALLY do it a different way".

Still, at least all the parts likely to suffer from galvanic
corrosion are cheap, on the outside, and easily replaceable.

This was a good bit. We're using that big black tank to provide
 the pressure to run the water to and from the SWH, but when
we came to disconnect it so that we could alter the pipework,
 we discovered that no one had thought to put a stop valve on
 the outlet.  Which means you can't work on the pipes down-
stream without 500 gallons of water coming out.  This is what
we call a DESIGN FLAW.  Solution:  just start unscrewing
the pipes (fast!), working backwards from the nearest union,
then quickly screw on a new valve, all the while being sprayed
by this forceful jet of water.  Refreshing on a hot day, mind
(we're up in the mid-to-high 30s these days).

We have water!

Data logger up and running.  Had a few short circuit problems to sort out when
I discovered a couple of the sensors weren't as waterproof as I might have liked.

I'm still in love with the colours of frazzled copper.

SWH project part 10 - temperature logging 2

Like I said yesterday, in the quiet patches between the bulk of the project making any headway, some progress has been made on my temperature monitoring system.  It all works happily enough on the desk; the next step is to get all the sensors mounted and wired up in a waterproof way and see if it still behaves out in the wet muddy real world.

Green and happy.
(no sensors plugged in just now, so values are nonsense.)

Nice and ordered in theory...

...a little more disorderly in real life.

Turning a 2D layout into a 3D structure and mounting it all in a tapering
cylindrical tub is an interesting challenge.

The multiplexer board will be mounted out at the panel site (in another
plastic tub), gathering together the inputs from 16 temperature sensors.
This means I only need 2 bits of wire 40m long instead of 16.

When panel overheat, SolarBot angry is!
He may even have a tantrum of irritating beeping noises until someone
does something about it.

SWH prototype project part 5 - temperature logging

A quick foray into some electronics, just for a change. The plan is to build a little data logger which will record the temperatures at various points in the panels and tank over the course of the day (or week, or month for that matter) - and thus save me having to take the lid off the tank and check a glass thermometer every hour!

This nifty little screen will eventually give an up-to-the-minute temperature display.



















For my fellow geeks, the red board is a Seeeduino Stalker microcontroller - an Arduino variant with onboard real-time clock and microSD slot for data logging purposes. I'll be connecting up a few MCP9700A thermistors in the next couple of days. In it's current state I have 6 inputs to play with - possibly expandable with a multiplexer at some later stage if I feel like it.

Time and part-availability* permitting I might think about adding a light sensor of some sort, and an alarm for if/when the panels get too hot in summer (so that someone can take some sort of action - probably just shading the panels. It'd be sweet to have some sort of canopy unfurl automatically, but I think that's probably a bit over-ambitious!)

(*a big problem - trade embargoes at the UK end mean RS orders take 6-8 weeks to arrive, after they've obtained an export certificate - I had to get our recent visitors to bring out the thermistors for me. On the other hand, the circuit boards arrived from Singapore without too much hassle...)



















The absence of breadboards means a whole lot of trying to solder ends of wires to each other - a bit messier than I'd like.

I think this soldering iron is designed for somewhat larger applications...