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Wed, Aug. 9th, 2006, 11:18 am

Something wechsler just said give me cause to wonder in an idle sort of fashion... I can fairly easily caluclate how long it'd take me at current electrical rates to "pay off" by offsetting electric bills (or even backfeeding if I had a big enough system) if I were to install enough photvoltaics and a big enough battery/inverter system to run my house. What'd be interesting to figure is how many years' electric-bill savings would it take to offset the total energy/materials/environmental cost of manufacturing the pV system in the first place? Hmmm...

suemac and I have actually talked about installing a whole-house pV system. One thing we certainly have plenty of here is sunlight and roof area, facing in all the appropriate directions. Plus, the power is unreliable enough in the summertime (all those thunderstorms and hurricanes, you see) that we're going to need some serious UPS capacity for all the computers we have and are getting. So we bounced around the idea of, why not go PV? And for cloudy days when we don't get enough juice from the 'cells, there's always getting power from the utiltiy. And we'd still have the generator if everything else were to tank.

Another potential moneysaver, especially in the summer, would be solar hot water, either as a primary system or as a supplemental system, feeding from and back to the water heater, to keep the water hot so the heater wouldn't cycle as often.

Then THAT brings up the notion of cooling system efficiency. Like most 70s era US houses, ours could stand a slew more insulation in the roof, and maybe even boring holes in the walls and blowing insulation inot the walls as well. The windows are old cheap single-pane aluminum frame units that really ought to be replaced - that's another potential energy savings.
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Wed, Aug. 9th, 2006 03:41 pm (UTC)
mrz80: Aaaaaahahahahaha! Crazy Harry plays with <b>electricity!!!</b>

So how big is your PV system? Are you ever in a position to backfeed, and if so, is your local utility *required* to pay for the power you put out?

And it'd be a fairly complicated set of design decisions, trying to design a load-sharing backfeeding PV system with an aux generator (for those pesky hurricanes were we get multiple days off-grid with no sunlight due to the 20,000 of clouds piled up overhead :-) ) that wouldn't glitch the load. It'd have to be a fulltime system with a fair amount of battery capacity, and the transfer switch would have to be on the input-supply side of the PV system. And there'd have to be some provision for locking out the PV system during extended generator runs, so that if the sun came out the PV wouldn't try to backfeed the generator... hmmm... this is gonna be more fun than I thought :-)
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Wed, Aug. 9th, 2006 04:34 pm (UTC)
mrz80: Re: Aaaaaahahahahaha! Crazy Harry plays with <b>electricity!!!</b>

I have a predicted first year electrical bill of -$94
Is that %94 per month, or in fact $94 for the whole year?!?!?!? COOL! Our utility bills are about $300 a month, of which 2/3 is electricity. Anything I can do to knock that down is a goood idea.

Wed, Aug. 9th, 2006 03:29 pm (UTC)
thesilia: my little sister...

my sister just had insulation blown into her attic. her house was built in the 40's and moved to its current location sometime in the 80's, so it sincerely needed the help. i think she paid around $600 for the insulation work, so that's something that'll pay for itself quite easily. as an amusing aside, she had an old mattress up in her attic that was left by the previous owners that she was dreading having to remove. her insulation installation dude said he could just spray the insulation over the top of it and make it a more or less permanently-sealed part of her attic insulation. so he did, and now she's just got a really THICK patch of insulation in that part of the attic. :)

this post of yours made my tree-hugging little heart go pitter-patter. :)

Wed, Aug. 9th, 2006 03:46 pm (UTC)
mrz80: Re: my little sister...

I just have this almost-fetish for systems engineering :-). We're also looking at having to re-plumb some or all of the water supply because it's so blocked up that you can only have one tap running at a time, e.g. turn on the kitchen sink or start the washing machine, and the shower loses all pressure, usually right as the person taking the shower is trying to rinse hair. I'm looking at using PEX tube and going through the attic (rather than relaying copper and digging up the slab in spots) because you can home-run each faucet to these really uberspiffy manifolds with individual valves for each run and it comes out looking like network cabling and it's just the niftiest looking stuff. Oh, that and it's incredibly strong, incredibly flexible, doesn't leach anything into the water to affect taste or cause a third eyeball to grow at the base of your throat or anything :-).

Wed, Aug. 9th, 2006 06:20 pm (UTC)
thesilia: Re: my little sister...

i happen to like the third eyeball option.

"no, i'm not being fresh with you."
"but you just winked at me..."
"don't mind that, it's just my third eyeball. she kinda has a mind of her own, and it's usually in the gutter."

Wed, Aug. 9th, 2006 06:26 pm (UTC)
mrz80: Re: my little sister...

Hmm... wouldn't it be versatile if, say, that third eyeball were oh, say, smack dab in the middle of your decolletage? That way you could still make eye contact with people who insist upon trying to cop a gaze down your shirt! You could glare at 'em even!

Wed, Aug. 9th, 2006 06:53 pm (UTC)

I priced out a system somthing that had enough inverter juice to keep lights running, power the fridge and kick the well over I was looking at around 20,000 even going the surplus route. I would need an inverter that would do 240/30 atleast

Thu, Aug. 10th, 2006 02:29 am (UTC)

Funny you should mention this now. Lisa happened to mention Just The Other Day (TM) that we should think about some sort of PV system, given that we have a roofline that faces due south with no trees in the way. A quick price-up at a few "package places" like Mr. Solar and a couple of others was in the 20-25K range, which is a bit much for right now.

My ideal system would be both grid-tied and have backup battery capacity to run the usual stuff for a few days, with an additional gizmo that would allow us to recharge the batteries from our generator if needed. My "reality system" would be modular, and I could add components as the budget allows. Meaning I'd start off with a PV panel, battery and jumper cables :-) and go from there.

Thu, Aug. 10th, 2006 12:38 pm (UTC)

Some kind of modular, pay-as-you-go Erector-set approach is what we're after. I'm still weighing the various options on how to configure it - where to put the generator and transfer switch relative to the PV, do I need multiple points or switching to move the PV and inverter from one spot in the scheme to another, etc etc etc

My biggest thing right now would be to have fulltime PV with densaer's "net metering", where when I'm not drawing from the utility I'm feeding *to* the utility. The utility bills are our single biggest non-mortgage expense, and at $200+ a month for electricity in the spring and summer, it really wouldn't take all that long to cost-justify a PV system.