RE: Re: Solar PV ?

[Marcus Warrington <marcus.warrington@xxxxxxxxxx>]

Lee,

> The thing you need to keep in mind, the that with a 3KW (or even 2KW)
> immersion heater, the solar PV needs to be running pretty much flat
out t=
o
> cover your houses base load plus the immersion heater.
> How often does this happen? Not that often judging from my graphs...

I think he is only using a 2Kw immersion heater and has a 3.8KWh array
that=
is southerly facing. Even so I do take your point that he is highly unlike=
ly to have it diverting energy to the immersion most of the time. But even
=
a few hours a day probably makes it worth while to him.

> Using an OWL to measure the consumption DOESN'T WORK when you have
solar
> PV. The OWL (or other meter) DOESN'TKNOW which way the current is
flowing=
.
>Eg.
>Base load 1Kw solar PV 1Kw =3D Owl reading 0Kw
>Base load 1Kw solar PV 2Kw =3D Owl reading 1Kw
>Base load 1Kw solar PV 0Kw =3D Owl reading 1Kw

Is that still the case when the OWL clamp is only on the AC cable from the
=
Inverter to the consumer unit ?
In other words, I think he had 2 OWL units one to monitor SolarArray
produc=
tion and one to monitor house usage.



=D8  Which leads me to the "Open Energy Monitor" project, using
an Arduino =
with a

Looks like an interesting project, but my soldering skills are pretty
limit=
ed :( Is anyone selling ready assembled devices ?


Marcus

From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf Of V=
argster
Sent: 20 July 2011 09:52
To: ukha_d@xxxxxxx
Subject: Re: [ukha_d] Re: Solar PV ?



More...

> I was speaking to my installer about my concerns on the Bluetooth's
range
> and he says that they can log into the inverter and up the gain on the
> transmitter from the standard 14dB to the maximum 20db. He recons at
20dB=
it
> should be good for 100M, if your supplier hasn't done this already it
may=
be
> worth asking them to do it for you.
>
> There is an add-on antenna for the SMA bluetooth piggyback, to boost
it's
range.

=D8 1. Is his IP switched socket a homebrew thing or are there commercially
> available units?
>
> It's a commercial unit although I'm not sure exactly which one, but
> something like this ;
> http://www.ambery.com/reposw.html
> If you google "IP controlled Power Strip" you'll get lots of
hits. I'm no=
t
> sured how much he paid for his but I don't think it was cheap (~=A3300
?)
>
> The thing you need to keep in mind, the that with a 3KW (or even 2KW)
immersion heater, the solar PV needs to be running pretty much flat out to
cover your houses base load plus the immersion heater.
How often does this happen? Not that often judging from my graphs...

> I would have thought that "we" could do something very
similar (and much
> cheaper) using a cheap radio controlled remote socket (byebye
standbye?) =
and
> a RFXCom tramsitter on the PC http://www.rfxcom.com/transmitters.htm
>
> I think he was getting the consumption figures using the now defunct
Goog=
le
> PowerMeter. In my case I'm already using an OWL clamp + transmitter
and h=
ave
> already writtem a VB application to grab this data using the "OWL
Connect=
"
> usb receiver (=A38 from eBay) , and am then transmitting my usage via
xAP=
to
> other machines in the house. It should be releatively straight forward
to
> have an program listen for the usage xAP message, compare it against
the
> inverters current generation figure and then have it send a suitable
on/o=
ff
> signal via the RFXCom device.
>
> Of course, ideally, I'd like to junk the OWL (which isn't that
accurate)
> and get my electricty company to put in a smart meter than I could
then g=
et
> more accurate figures from, but when I asked them about it they
wouldn't =
do
> it for free and wanted silly money to do it :(
>
> Using an OWL to measure the consumption DOESN'T WORK when you have
solar
PV. The OWL (or other meter) DOESN'TKNOW which way the current is flowing.
Eg.
Base load 1Kw solar PV 1Kw =3D Owl reading 0Kw
Base load 1Kw solar PV 2Kw =3D Owl reading 1Kw
Base load 1Kw solar PV 0Kw =3D Owl reading 1Kw

Automating this will result in problems...
There is the "Wattson Solar" which has two clamps, and does the
job
correctly, even has USB to connect to a computer. BUT it's still
inaccurate=
,
due to it's guessing of the voltage like the Owl.

Which leads me to the "Open Energy Monitor" project, using an
Arduino with =
a
small shield pcb, AND 9v AC adapter to do the maths properly, with USB to
get the data out (though some are using wireless/bluetooth/etc).
I haven't built one yet (the parts are on the bench), but apparently 99%
accurate.

Lee

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