A step toward completely off grid! - Fuel Economy, Hypermiling, EcoModding News and Forum

MPaulHolmes · 05-07-2013, 02:14 AM

Hello! We just purchased 5.6kW of solar panels for our place in Arizona. They are B quality panels, but still test at full power. It's 20 of them at 280watts each. I'm also basically done with the inverter. I just need to bolt it all together and try it out. I'm also going to get grid tie working. gasp... Oh no, not that. LOL. Sorry, the solar power forums are very "the proletariate shant discuss such things. Far to complicated! You are banned!!!" I'm not sure a good way to test it out yet, but I don't think it'll be very hard.

So, here's the plan! First, get them mounted on the ground. I've got lots of space in my back yard, and no obstructions for the sun. I could do it on the roof, but I don't want to alter it at all. I'm going to hook them up to power my shop at first, and then run a 110v extension cord to power a few isolated things at the house. Then, once I figure out the dang laws, which are not at all easy to understand in my area, We'll try to go off grid completely. My electric company charges like $30/month just to have it turned on, even if I don't use it. I'll be sure to take lots of pictures of the process.

NachtRitter · 05-07-2013, 02:47 PM

Awesome! Looking forward to seeing your progress!

cRiPpLe_rOoStEr · 05-07-2013, 10:41 PM

Sometimes I also get the willing to get off-grid, but living in an apartment makes the whole thing harder.

MPaulHolmes · 05-16-2013, 02:35 PM

The 20 panels are arriving today!! Also, I'm picking up the unistrut and some treated 4x4 lumber and cement bags tomorrow from the home crack ho (depot). haha.

I'm doing sort of a hybrid of these 2 approaches:

4KW grid-tied battery backup system - Page 2 - EcoRenovator

http://www.builditsolar.com/Projects...ideViewDim.jpg

thingstodo · 05-20-2013, 02:58 AM

Quote:

Originally Posted by MPaulHolmes

... I'm also going to get grid tie working. gasp... Oh no, not that. LOL. Sorry, the solar power forums are very "the proletariate shant discuss such things. Far to complicated! You are banned!!!" I'm not sure a good way to test it out yet, but I don't think it'll be very hard...

If you have a 120V generator you can set up your own 'grid' and do some testing with your inverter syncing to that. Some of the small generators don't regulate very well, particularly with no load ... so you may have to put a load onto the generator, like a hot plate, so that the frequency stabilizes and your inverter can synchronize to it.

Using a 220V generator would be a better test, but it is harder to keep the loads relatively balanced on both 120V 'phases'.

AND you can test that the output of the inverter shuts itself off when the 'grid' goes down (turn off the generator or trip the output breaker) ... so your inverter does not try to power up your whole neighborhood when a power company breaker trips.

One step further would test the load regulation on the inverter by adding a hair dryer load to your isolated little grid and see if the load on the generator gets higher (easy to tell by the sound of the motor) or if your inverter picks up all of the additional load. Turn off the dryer ... again, which one dropped the load? Generator or inverter?

Another INSPIRING project. I'm EAGER to read all about it!

MPaulHolmes · 05-20-2013, 07:53 AM

Thanks, Thingstodo!!!! That's a very good idea. I don't have a generator, but I'll be sure to get one for testing. Here's some progress pictures:

Unistrut from Home Depot

One of 4 of the wood parts that the unistrut will be connected to.

My son was a huge help.

It's getting there! But officially too dark to see what the heck I'm doing.

MPaulHolmes · 05-20-2013, 08:29 AM

I was thinking that MPPT was so complicated, until I realized, it's just a regular old buck charger! All you do (during the bulk charging phase) is adjust the PWM duty to maximize the output current! You don't need to maximize the product of the input current and input voltage (input power)! Just the output current! LEM Hass to the rescue! I think I'll sample current at a particular pwm duty.... Say, 0%. haha. I bet that will have a small output current. Then I'll just chase the higher output current by incrementing or decrementing the pwm duty to see if I need to hunt to the left or right for the global maximum. One problem with this is that I heard that there can be local maximums if panels aren't matched well. It's probably good enough to sweep through the whole range of 0-100% duty, and then assume that the global max you found can be kept in your sights by chasing it with the "increment/decrement pwm duty, and go in the direction of larger output current" method. haha that's a long name.

Ryland · 05-20-2013, 11:42 AM

Quote:

Originally Posted by MPaulHolmes

Also, I'm picking up the unistrut and some treated 4x4 lumber

Most people recommend not using wood at all in the structure to support the panels, unless it's well protected, like in the form of a house, but you are in a really dry area, right? reason for this is that your solar panels are going to outlive you, when your son is old there is a good chance that he will have to figure out who he wants to leave them to in his Will, you don't want to support them with something that will only last 20 years, but then again in Arizona you might be fine.

MPaulHolmes · 05-20-2013, 12:03 PM

I hadn't thought of that. We won't be here for 20 years though. Also, It rains around 0.1" per year around here. I'm already baking in the fires of heck and darn-nation, and it's 8:02am. Plus, before I die, I want to shoot the panels with a shotgun, and throw some off a big cliff to see them shatter, since that would look awesome. Also, in a couple years I'll get bored, tear the whole thing down, and make a solar tracker.