Solar Back-Up power project

[Xringer]

Here's the guts of one of the three circuits. (Only #3 is wired at this time).
We cut into the 120VAC house wiring, between the breaker box and the loads (outlets).

The NC (normally closed) contacts allow the power to pass normally.
But when the Inverter is on and the 15A breaker is closed, the relay coil is energized.

The relay disconnects the loads from the main breaker box (the grid),
and allows the inverter to feed those loads.

I have the time delay disabled, so power from the inverter turns on the relay instantly.


Here's what it looked like before the blizzard of 2011 hit us.


#3 box is finished.. But, the AC input from the inverter has not been wired into the little breaker box yet.
The inverter (and bank box) have not been moved into their final resting place yet.
I will likely use a 20' extension cord for testing..

[Xringer]

I installed a filter inside the breaker box.



"XPF 20A Wired-In Noise Filter"

XPF 20A Wired-In Noise Filter - X10 Pro

I want to see if the squarewave-like MSW waveform can be cleaned up a bit.
Maybe round off the sharp edges a bit..

I ran my 200w computer room load for a while and didn't hear any buzzing.
But I did hear buzz when I got close to the filter. Those iron cores are singing.

When the sun comes back out again (maybe Friday), I'll crank it up again
and see what the line looks like with the O-scope..

Neat thing happened. When I shut off the MSW inverter, the relay dropped out,
and re-connected the grid to my PC.. Did not re-boot!
And drop-out is a lot slower than energizing the relay (turning on the inverter).


Edit: 3/2/2011
The filter buzzed a little, and didn't round of the shoulders of the MSW very much.
Then, I saw it was loading down the inverter! The output of the inverter supplies the breakers.
With all the breakers open, I should have had about 70 ma of DC inverter load..
But, it was closer to 200 ma of DC current. I assume the high frequency component
of the waveform was seeing the caps as a load. So, the filter is out of the box..

My plan is to try a large DIY iron-core inductor in series with the inverter AC output.
It will be made from about 10 feet of #10 wire, coiled around
a one pound iron rod. (or maybe mild steel).

[strider3700]

sweet. Mind if I ask what this has run you? My constantly wasted 45 watts of panels would make me much happier if they charged a battery bank then the excess went to keeping a PC or the woodstove fan going.

[Xringer]

I don't keep track of what I spend on this stuff. It's not like I'm going to get a tax break on a back-up power supply.
But, you can Google the hardware and see who has the best prices..

If it's only 45w of PV, you should find a cheap charge controller and get a good battery,
and use that stored juice at night to run 20-30 watts of LED lighting.


I've got two 10W panels and finally put one of them to work running the LED reading
lamp on headboard in the master bedroom.
It's nice because it can run for days without sun. And if we have a power failure,
I want a good light working when I get out of bed. (and need to find my flashlights)!

I have not decided what to do with the second 10w unit, but I'm leaning
towards 5 or 10w LED lamp in the kitchen.

[Xringer]

Got them dug out and tweaked the up angle on the tracker. The sun is higher in the sky!!!



I now have a little path dug down to the panels. Still need the tall boots,
but now it doesn't take five minutes to slog though waist deep snow with a crust on top..

Yesterday, I got out there early and freed up the bottom panel on the tracker.
When the ice broke, it buzzed and started moving west! I got there just in time!
I'm not sure if the motor could have broken it free..

So, now we ready for another foot. But not two feet!
Loads of sun today. Some of hotwater heating from the 400w fixed
full bank charge from the 500w tracker..

[Xringer]

Yesterday, I used the MSW inverter with the batteries/tracker to run my PC and some other loads for about 8 hours.
In the evening, I still had about 12.75v(51v bank) on the batteries (no load).

When the sun came out fully this morning, my 500w tracking array was providing a full
500w of charging power into the bank (Bulk mode).
Which kinda makes me glad that I didn't spring for the MPPT charge controller.

Also checked on the Canadian twins, and they were pushing 412 watts into my hotwater storage..
Which I think is pretty dang good for early morning sun, on a non-tracking array..

[Xringer]

I built a small voltage sensor (12V) that will control an SSR, that controls the AC from the MSW inverter, to the load.

This should keep the inverter from discharging the bank below 48v.. I hope.
I'll be testing and tweaking this week.

The board is on the lower left. The SSR tray is upper right.


Wide view

[Daox]

How much power are you getting out of these panels on a regular/average basis?

[Xringer]

Since the weather has been pretty irregular lately, I don't even try to use the
backup system most of the time. Now that it's getting sunnier, I've started
using it to run my PC load (about 300w) until the sun goes down.
It's been on since I came home from work today (16:30) and I'm going to see
when the little circuit starts trying to turn off this evening.. (If it does)..

I'm not sure that I want to start logging the kwh numbers, since it's not
what I consider a good use of my spare time..

I've met my goal of creating a back-up supply that we can use during power failures.
I plan to use it lightly, just to keep the batteries in good shape. Make them last a while.

However, I don't like the idea of 500w of PV going to waste after the bank is charged..
So, I'm thinking of adding a 230vac inverter and running the Sanyo when
the bank is already charged.

Backed-up AC would be nice if the grid fails on a hot day this summer.
I can stay cool using the tracking array.. 500w will do the trick!

[osolemio]

Very interesting project! I will be grid connected, but I intend to eventually have a battery backup for several reasons.

One of them being that in case of a blackout, the inverter shuts down and PV production idles. This is where I can continue to use the DC directly to charge a set of batteries. Off these batteries I will run a USB bus, as well as 6, 12 and 24 volt. This enables me to run all these small DC gadgets directly, without using the supplied AC-DC power supplies for each unit - that is, without making solar PV DC into AC, then back into DC. The bus WILL run all the time, but normally it will be solar/grid powered, whereas during a blackout, it would be solar/battery powered.

If the main AC grid has a blackout, the inverter will have to shut down. If not, it would try to run the entire neighborhood electricity use, which is not possible - the inverter would snap instantly! So when a mains AC fault is detected, the inverter will switch to local mode (by a control system I will design - it is not that complicated really). Because of the inverter built-in protection logic, I need an AC current it can sync against. This is where a small battery operated inverter will feed a lead AC into the inverter (instead of the mains AC), to keep it running.

It will still need some further protection circuits, to make sure that demand does not exceed production. Since the battery pack will only supple the small controlling inverter and not the big one, the main AC users cannot be used when there is no sunlight. But the small inverter will keep the solar heat pumps and control running, as well as other essential - but low power - units. Maybe including the TV?

So the two main reasons for me to extend to battery backup are

1) To get the solar PV DC production directly into local DC gadgets, without going DC->AC->DC

and

2) To be able to sustain PV usage in the case of a grid blackout

Would I not feel stupid, if there was a blackout and my PVs cannot be used! That defeats the idea of producing your own electricity!