Mains switchover to battery (newbie)

[vodzurk]

Hey guys!

I've been pondering on this for a few weeks now, and have just purchased my first property (in the UK).  It has a large floor-to-ceiling window, which I'm thinking of covering with sliding vertical blinds with 8 of these panels (removed from their 4-way frame) fixed to the outside...

http://www.maplin.co.uk/Module.aspx?ModuleNo=223250.

Then hooking up an inverter to the batteries so I can power (some of) my household 240v devices.

However, what I'd really like is for the system to somehow know when the battery is at say 70% charge, and flip the plug socket I draw from, uninterrupted to mains until it reaches 90% charge.

Daft drawing attached... my issue is... do the switches and capacitors exist already in electronics store, by a name i don't know?  I'd really prefer to buy a product off the shelf for this, as doing otherwise would likely invalidate my home insurance (and possibly cost lives if the place burns down!)

[ghurd]

The capacitor must go.
They cover a bit of switching time with DC, but act as a short with AC (the way you are thinking about it).

The panels will be indoors?  And vertical? 
That's not very good, or economical.  Especially if there is any shading such as the main window being made of several smaller framed pieces of glass.
Behind window glass, vertical, with partial shading, will limit their output to nearly nothing.

The switch has a lot of complicated issues.
Best to shut off everything on the circuit, then manually throw the switch.

The 10% and 80% numbers are not very good.  The 70% and 90% are better.  Important detail, but it can be sorted out later.
G-

[Ungrounded Lightning Rod]

Switching a running motor from one AC source to another is an invitation to disaster.  Switching a transformer-powered electronic device from one AC source to another, while live, can create damaging transients.  Etc.

You either turn power off from the grid and on from the inverter, use a UPS-style system, or use a grid-tie capable inverter.

UPS-style systems are designed mainly around keeping some important grid-powered load alive during outages.  They're built on the assumption that the load is important enough that it's worth paying extra for electricity to keep it alive.  So they tend to be pretty inefficient.  That means they're a poor match for a mixed line-RE system:  They're likely to burn all your precious RE power with their inefficiency, or at least force you to buy extra panels or whatever, at big bux.

Grid-tie capability in an RE inverter adds a considerable cost (even if it doesn't have a "sell" feature - and at least a couple grand or so with the latter).

So you'll probably want to do the "turn it off, wait five seconds for the motors to stop, turn it on the other way" dance.

[vodzurk]

Hi guys, looks like the idea is void, but hey, it was an interesting thought.

Why would the panels be less effective behind glass?  And vertical?  And with some having partial shading?

And the uninterrupted switching... maybe I could have my computer UPS plugged into it, rather than appliances, and draw from that instead?  But like you say, i'd imagine a UPS being incredibly inefficient... passing charge from one set of batteries to the next.  Though it'd still be nice for it to have an auto switch-over when the solar charged batteries hit 70% / 90%, without frying my appliances.

[ghurd]

"Why would the panels be less effective behind glass?"
Not all the light comes through window glass.  Less intense light greatly reduces the output.

"And vertical?"
Output is directly related to how much sun it can catch.
The larger the shadow of the panel, the more sun it is catching.  Vertical has a small shodow.
It can not catch much sun when vertical.

"And with some having partial shading?"
Shading a cell (or stripe on amorphous panels) makes that cell produce less current.  All the cells are in series (in a row), so the output is what the lowest cell is producing.
The effect is greater if the thing making the shadow is closer, and wood frames in the window will be close.

A single one of those panels properly mounted outdoors will make more power than 8 mounted on the blinds.
And one of those panels does not make much power even when properly mounted.

I doubt 8 in the window would make enough peak power amps at high noon to supply what a small UPS uses simply being turned on.
G-

[vodzurk]

One word.

Bugger.

[DamonHD]

Note: vertical wouldn't be too bad (60 to 70 degrees is roughly optimal) in a UK winter for a south facing window.

Try the calculator here setting a south-facing aspect and fiddle with the slope at 90 degrees down to 60 to see what you lose.  You may not care about maximising year-round collection.

I'd like to do the blinds or equivalent myself some day, but probably not in this house!

Rgds

Damon