monitoring mains power usage with solar panels installed

[Ken]

For those who are interested in this stuff...

I just got off the phone with a guy from ETSA, (well, SA Power Networks) who answered my web query about my choices in power meter with solar panels.
There is none.  Single phase or 3 phase. That's it.  (I'm 3 phase.)

At present I have a mains power meter which flashes a LED at a rate set by power draw.
The new meter will not have that, just an LCD display with multiple choices of what to show.
I gather it doesn't even stop on a choice, but cycles through the different readings.

So...
With a solar feed-in, I have no way of programmatically reading the power being fed into the house by my supplier.
(I'll have a Bluetooth connection telling me what the solar panels are generating.)

I think that sucks.

If anyone can figure a way around this, please sing out.
(Preferable something easier than a webcam viewing and interpreting the LCD.)

There must be a market opportunity here.

When I get some time (at home), I'll have to do some serious googling on the subject.

Ken.

[Ken]

A workmate has told me of one possible solution.  fluksometer

Ken.

[Steve Roehrs]

Hi Ken

I started on Origin's "Solar Cities" time-of-use plan a few years ago - which means they install a smart meter with its own GSM and ZigBee interfaces.  It was free to join - I just have to go on their time of use plan.  I also started before I got my solar panels - it may be impossible to do it the other way around. (Whirlpool Green-tech forum has lots of info here)

The zigbee is locked down and only talks to its own "In Home Display" unit - which graphs import across the day (but not export - not in my firmware version)  and also shows instantaneous import. When I'm exporting it shows as 0.0 import which isn't that useful.

The GSM interface is polled by Metropolis Metering every night around 2am and I can download my 30-minute import/export data from their website the next morning.   I have a script that downloads it every morning (around 6am) and inserts it into a database, right alongside my solar generation data that I get from the inverter over bluetooth using the linux smatool package.  The downloaded data shows import and export in 30 minute blocks across the day.  I then use some PHP scripts to collate the data and show me a graph of import, self-consumption, and export throughout the day.  It also calculates total cost for the day (negative in weather like this!) and ROI.  I've got scripts that will upload my import/export data into PVOutput but I don't run them regularly, just in batch mode every month or two.  The solar generation data is uploaded every 5 minutes :)

I think there's a huge market for cheap energy monitoring - and for solar panel performance monitoring.  I treat my panels like an investment, and like any investment, I monitor their performance and try to get the best out of them, including things like load-shifting to evenings - which I was doing anyway on the time of use plan.

I've heard of fluksometer - it would give me realtime capability instead of the 'next day' capability that I have now.  There are also all sorts of DIN-rail mounted watt meters available with RS485 (Modbus) or similar interfaces that I want to look into too

cheers

Steve

Ken.

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[Kim Hawtin]

On Thu, Nov 8, 2012 at 3:47 PM, Ken <k...@waggies.net> wrote:

> For those who are interested in this stuff...

...

> There must be a market opportunity here.

All of the 3 phase power meters I've seen that do solar feed in have
either an RS485[1] or InfraRed port that you can interface to, to
"read" the current values.

Which model have you got installed or going to have installed?

cheers,

Kim
--
"Art without engineering is dreaming; engineering without art is
calculating." --SKR

[1] or other balanced/differential serial module

[Steve Roehrs]

Here's the graph I get from my scripts every morning.  Would be nice to have it updated in realtime during the day!

[Paul Schulz]

fluksometer for the win.. http://www.rowetel.com/blog/?p=2381

[Ken]

Not installed yet Kim, so I don't know what model it is.  -I just know I don't get a choice.

Steve, I intend to use sma-bluetooth on linux, but I haven't investigated it fully yet.

If I come up with anything useful, I'll document it and let hackerspace know.
Early days yet, I've had a quote from Zen, and a quote from Solar Wholesalers.  $3k difference!
(Guess which one I'm going for.)

Ken.

[Ken]

:)

I haven't investigated yet, Paul, but I'm told fluksometer works with two sets of current transformers, one on the incoming, one ofn the solar feed, basically subracting solar from incoming.
If that works, I'll probably go for it.
Just need to tell the installer electrician that I want the three solar feed wires split just before the meter, so I can put current transformer clamps on them.

Ken.

[Paul Schulz]

From the description, the V2 model supports a maximum of 3 current clamps, so

- 1 clamp for a home without PV

- 2 clamps for a single phase house with PV (as you described) allowing you to get PV power production readings.

- 3 clamps to monitor power usage on a 3 phase house (net power usage?).

You would need an additional unit to support 3-phase PV system.

[Ken]

I wonder if it would be too quick and dirty to feed in to the normal current clamp inputs on the fluksometer, a difference between current clamp voltages?

[Steve Roehrs]

+1 for Solar Wholesalers they did a great job on my 4kW SMA/Suntech system.   sma-bluetooth is a bit of a dogs breakfast, it's been forked a number of times, the original code is particularly ugly. Like lots of hacks though, once it's working you tend to forget about the trouble you had setting it up - until it breaks again!  What inverter are you looking at?

Steve

[Ken]

I'll get whatever invertor Solar Wholesalers install.  SMA 5000TL

[Christopher Yeoh]

On Thu, 8 Nov 2012 15:47:29 +1030
Ken <k...@waggies.net> wrote:
>
> I think that sucks.
>
> If anyone can figure a way around this, please sing out.
> (Preferable something easier than a webcam viewing and interpreting
> the LCD.)
>

> There *must* be a market opportunity here.

I've used a CurrentCost device (www.currentcost.com) for quite a while.
You can buy them now in Australia from http://www.smartnow.com.au/ -
though I haven't purchased through them myself.

By default they come with one clamp, but you can buy a couple of extra
clamps which plug into the transmitter to handle 3-phase situations (I
have 3-phase).

One problem with clamp solutions is they can't measure the phase so
they are inherently inaccurate depending on the load in your house.
Still, its better than nothing.

Chris
--
cbk...@gmail.com

[Tamsyn Michael]

Hey Ken,

I was checking out the Raspberry Pi Blog and came across this gem:
http://www.raspberrypi.org/archives/3562

Seems all the cool kids (I mean literally children) are using Raspberry
Pis to monitor their Electricity usage. There are some useful links
for you (and me too) in the comments.

[Ken]

Thanks Tamsyn.
I do have an electricity monitor I could reverse engineer. But electronics seems to have taken a back seat for me lately. On Saturday I leave on the motorbike for a month/8000km over east. Travelling to QLD via Alice. Maybe when I return I can fire up the soldering iron and DSO. A couple of IPcams (and a friend) will watch my house while I'm away.
Ken.
ps. My gustbook is spam free after two days from the rename.

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