Rough solar payout calx for just panels (the new stuff)

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The usual. As I have two large solar PV systems here, and my lab assistant just put one in, and others are interested in things like this, here's where that stuff goes. This is mostly for things that work now, not "gee someday a fusor will do this" -- we know that, but it's not someday yet.
The hope is to save anyone embarking on this sort of thing a lot of wasted time and money, as at least I have been off the grid since 1980 and have had a lot of practice (and made mistakes you won't have to).

Rough solar payout calx for just panels (the new stuff)

Postby Doug Coulter » Mon Feb 24, 2014 4:42 pm

I am showing just 1800 kWh out of one rack-set of 6 panels in nine months. Working the math, that's $234 worth of electricity at the local rates, or about the price of one of those 6 panels, for a 5.4 year payout per rack, considering *only* the panel costs, but also - I don't use all I get, the system sits around in "float" quite a lot - so if I was more agressive about using all I can, I'd have a quicker effective payout.

When I started this. way back in the day, it was calculated at 30 years+, and people thought I was nuts. The thing is, electricity was cheaper then - 9c a kWh instead of the current 13c, and panels have become WAY cheaper per watt.

I'll just have to start using more power, I suppose. What a terrible situation to be in! In fact, today, I'm actually using solar power to -electrically- heat my home since I "have it to burn and it's wasted falling on the ground if I don't". Honestly, I never thought I'd see that day. Sure, I'll have to turn off the couple of 1.5kw heaters at some point this afternoon, but by then the place will be "too warm" and I won't have to start a fire or turn on a propane heater till around 9pm, which will take me to the morning again.

Makes me kinda wish the Volt had a larger battery to charge with this - It's full and no place to put more power right now, I'm just making heat with it...it's toasty in here now, and as a skinny guy, by the time I'm comfortable, most people are sweating.

I'm very happy with how this lashup is working. While I don't have any panels that move to track the sun, what I did was have some optimized for winter, and some for summer, with one rack of each sort in parallel on the same controller. Theoretically, this would exceed the controller's ratings, but actually it doesn't since one set is near-vertical and the other near-horizontal, there is actually no way both racks/controller are putting out all they can - either both are more or less half, or one is maxed out and the other doing very little.

Since we only finished this just ahead of winter, we don't have a year's worth of data yet...more to come, but there's hardly any chance that summer will be worse.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Rough solar payout calx for just panels (the new stuff)

Postby solar_dave » Sun Mar 09, 2014 9:17 am

Yes it certainly looks like you are now in a sweet spot if you can burn the excess with heating, usually the worst and most wasteful use of solar electric.

I am thinking about adding some panels for my system to replace the VFD pool pump consumption by possibly going with a direct drive DC pump setup driven directly from the panels. Still some research required. One advantage is I don't need the utility involved but probably still need permitting from the city.

The utility has come around and added a smart meter to my solar production so they can now remote read the thing, this puts a crimp in expanding the AC system with out the permitting and buy off from them. Just one more Big Brother protecting you (them). :D Plus I think the utility will deny me anyway for a whole list of reasons as they now have taken up a campaign to stop solar in AZ. http://dontkillsolar.com/site/

We are now thinking on how to reduce the vampire loads without a change in life style, mostly for the wife as she has no desire to manually perform the needed switching steps. A few of those low watt Pi computers with a relay setup Might be the ticket. Ah more research needed. I also have a years worth of TED data in raw format that I need to analyze to determine what TOU plan is most advantageous. Currently we are load shifting to put stuff online during our on-peak period to consume the excess instead of getting "compensated" from the utility. They reduced the payback to about $0.0289 per kWh from $0.0659 per kWh. Big favor huh! they are actively selling that excess to my neighbors for up to $0.259 per kWh. We had 1604 kWh at year end for a grand total credit of $46, I would rather put it to work here or decrease my purchase of off-peak power.
Dave Shiels

My TED 5000 power monitoring
http://phx-solar.no-ip.info:8081/Footprints.html
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Re: Rough solar payout calx for just panels (the new stuff)

Postby Doug Coulter » Sun Mar 09, 2014 3:56 pm

I'd look at "surplus center of nebraska" for some good 90 or 180v DC permanent magnet motors and speed controllers. Now and then some excercise treadmill makes goes out of business and floods the market with 1-2 hp motors dirt cheap.
http://www.surpluscenter.com/

Being surplus, you might have to wait for the right moment such that they have stock on what you want. They are real decent motors, very efficient. The new prices (say, McMaster-Carr) are breathtaking, but surplus, I've gotten a few for $30.
You should be able to direct-drive these off DC panels, hooked in series-parallel till you match the load well. No other controllers required, though it might be nice.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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