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Plug and play solar backup

DIY solar diagram
We still think that plug and play is the way to go for our cheap solar backup, but we've tweaked the specific components a bit.  We wanted to find a powerpack that we could pick up at a physical store since powerpacks bought online have often been stored in warehouses for years and have dubious longevity.  We figure that by picking one up locally, we can easily return it if it turns out to be old.

Back of the Harbor Freight 5-in-1 Power packThe 5-in-1 power pack at Harbor Freight is the best we could find at a physical store --- it's only two thirds as voluminous as the Duracell 600 watt power pack, holding 216 watt-hours of energy, but the price commensurate.  And the reviews are quite good --- one user notes that his powerpack is only starting to lose its gumption after five years of use.

The 45 watt solar panel kit is really too big for our system, but it's irresistible at the current sale price ($170 on Harbor Freight's website --- print out the price page to use as a coupon at local stores.)  Since we've oversized our solar panel, we have to throw in a $26 charge controller, bringing the total cost to just under $300 for the entire backup system.

On a sunny, summer day, our 45 watt solar panel will probably be wasting quite a bit of juice, since it should pull in 135 watt-hours of energy a day even in the dead of winter.  I suspect that there will be a way to capture that excess, perhaps by plugging an inverter directly into the included power center to run electronics while also charging the powerpack.  Or, better yet, we might buy a (roughly) $100 grid tie inverter, which would allow us to plug our solar panel directly into an electric socket in the house and sell power back to the grid --- no muss, no fuss, and easily detachable to plug the solar panel into an inverter when the power goes out.

We'll update you as we experiment, but Mark is currently on his way to pick up our components, so this phase of the project is now set in stone.

Our homemade chicken waterer is an even simpler DIY project to make your homestead more self-sufficient.


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which would allow us to plug our solar panel directly into an electric socket in the house and sell money back to the grid

Technically, you'd be selling power back to the grid, in exchange for money. :^)

This is awesome, though!

Comment by irilyth [livejournal.com] Wed Aug 18 08:37:34 2010
You are so right. Edited to correct that (although the visual of selling money to the power company is pleasant. "Here's $5, I want $10 back.")
Comment by anna Wed Aug 18 08:59:10 2010

For putting electricity back into the grid you'll also need an inverter and an MPP tracker. And you might need a different meter. Check your your local power company.

Make sure to put the panel up at the correct angle and pointed to the south. The angle between the panel and the horizontal should be equal to your latitude.

I'm assuming that the charge controller includes an MPP tracker, but you might want to check on that.

If you have energy to spare in the summer, why not e.g. run a small pump to keep your water tank topped up?

Comment by Roland_Smith Wed Aug 18 12:53:14 2010

From what I understand, the grid tie inverter is all I would need to put electricity back into the grid. We do have the right kind of meter, but thinking about it this morning, I wonder if you'd even need to have that as long as you were using more energy than you were making? My very vague understanding of electricity makes me think that if you plug the grid tie inverter into a household electric socket the way the inverters are designed to be used, the electricity produced by the solar panel would be used first by the household and would just make us draw a bit less juice from the grid. Or is that too simplistic of an understanding?

Mark's going to put some thought into where to put the panel. Clearly, more research has to be done! :-)

Comment by anna Wed Aug 18 14:31:29 2010

I hate electricity:-0, been hit one tooooooo many times. Let me start of by saying I know nothing about Solar Power. But here goes a train of thought.

One concern being tied into the grid should be for the safety of those working on the line in the event of a downed power line. Just like hooking up generators here in Fl, you have to make sure that no power will go back up the line and hurt someone working on the other end when power lines are down. Something to talk over with the power guys.

You guys are going to be totally off grid before you know it, way to go. GOOD LUCK, Yall are in our Prayers, oneoldchief

Comment by oneoldchief Sat Aug 21 09:07:47 2010
You're totally right. I've got a post coming up tomorrow with more information on this, but the short version is that I decided tying into the grid wasn't worth it (even though the potential is enticing.)
Comment by anna Sat Aug 21 09:47:40 2010