RE: A different approach to saving power with solar panels.

["Neil Wrightson" <neilw@xxxxxxxxxx>]

Hi Simon,

In option 1, I'm talking about switching the 240V AC power prior to it
going
in to the UPS.
The UPS would see the mains lost during the change over period (seconds)
and
then restored again.
So it would not need to be a full online UPS.

As an example of a sunny day.
Midnight to say 9AM in the morning. The UPS (and thus Node0) is being
powered by the coal power, Power Stations.
At 9AM the sun is bright enough for the panels to make enough 12V power to
feed a 240VAC inverter.
A change over relay (driven by some smart electronics) changes the power
feed from the power stations to the solar panel. (10 second change over)
At 3PM we start to run out of sunlight, the inverter output is dropping to
200VAC.
A change over relay (driven by some smart electronics) changes the power
feed from the inverter back to the power stations.

So during a 24Hr period, the UPS batteries only see a total runtime of 20
seconds.

The Node0 is driven by the sun for 6hrs of the day.


The draw back with option 2, is that the PC's could not be run from the
~12V
supply.
I have standard styles of PC's with big switch mode power supplies, with
heaps of different voltage taps.
The PC's are the biggest power users.

As you mention, the advantage with option 2 is that there are less losses
incurred converting from the native 12/24VDC panel output to 240VAC back
down to 12/5VDC/whatever.


Regards,

Neil Wrightson.
N.W.Electronics
ABN 76 768 513 867
Embedded Controllers and Home Automation Products
Skype : Neil_Wrightson
Web     : www.nwe.net.au




_____

From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf Of
Simon Haslam
Sent: Monday, 31 May 2010 8:21 PM
To: ukha_d@xxxxxxx
Subject: Re: [ukha_d] A different approach to saving power with solar
panels.




I had a similar kind of debate a while back on the navitron.org.uk forum.
Apparently "common" UPS's (from APC etc) operate in a
"direct" mode whereby
under normal conditions the AC is used to power the equipment directly
(albeit with some mains conditioning), and not via the 12V batteries. You
can get "indirect" UPS's where mains is converted to 12V (or
whatever) and
then converted back to 220/240V. Also there were debates about whether a
normal UPS would be capable of running for long periods on batteries
without
early component failure (as compared to solar inverters which are designed
for the task). Finally working inside the UPS with high voltages would mean
you'd need to be very careful about safety.

Your second approach sounds easier and more efficient (as it saves the
conversion from 12V to 220/240V to 5V or whatever). It would just be a
solar
installation charging a battery bank which has been tried and tested for
years. You'd need to work out what devices you could most easily make power
supplies for (ideally choose several of the same DC input voltage). I
haven't looked this up, but can imagine some green people will have done
this kind of thing before.

Simon

--- On Mon, 31/5/10, Neil Wrightson <neilw@xxxxxxx
<mailto:neilw%40nwe.net.au> >
wrote:

From: Neil Wrightson <neilw@xxxxxxx <mailto:neilw%40nwe.net.au> >
Subject: [ukha_d] A different approach to saving power with solar panels.
To: ukha_d@xxxxxxx <mailto:ukha_d%40yahoogroups.com>
Date: Monday, 31 May, 2010, 10:44



Hi All,

Here in Australia the government is encouraging us to install solar systems

either electrical and or hot water.

To this end they are subsidizing the cost but it is still quite a large
some

of money.

I.e. $10,000 over ten years. By then the cells are probably cactus and you

put your hand into your pocket and start again.

These systems use inverters that feed straight back into the electrical

grid. So no batteries are used.

I'm very much a handyman, so I have no problems in installing my own solar

panels (that I can buy at wholesale prices) but trying to get the rebate on

these and having a licensed electrician connect it to the grid, could be a

problem.

So how could I save a few electrical dollars and satisfy my geeky urge to

have something like this. Hmmm.

I, like many of you have a Node0. Mine has the usual array of UPS's
servers,

switches, video overlays, I/O, callerid, cameras etc etc.

So basically, what I was thinking was putting some solar panels onto the

roof and at least power my Node0 for some of the day.

Make me feel warm inside that I'm doing my green bit ;-) (Switching half

of it OFF would be greener but not as much fun)

Option 1

So considering that Node0 has a 1000VA UPS with additional battery packs.

I thought I could monitor the solar panels and when there is enough power

available switch the incoming mains power to the UPS off and feed the UPS

from the Solar panel inverter.

When the light starts to fail, say mid afternoon and the panels don't work

as well, switch the incoming UPS back to mains power.

Twice a day the UPS would see the power turned ON/OFF/ON for say a 30
second

change over period.

Apart from that, Node0 equipment would know no differently.

Option 2

Feed the 12/24VDC connection from the solar panels to a battery and
directly

power the lower voltage stuff in Node0.

Has anybody thought of trying to do this kind of thing?

Regards,

Neil Wrightson.

N.W.Electronics

ABN 76 768 513 867

Embedded Controllers and Home Automation Products

Skype : Neil_Wrightson

Web : www.nwe.net.au

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