Gone Solar

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  • #1
Chi Meson
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The panels are up. 7kW system will be 110% of our electrical needs. Grid intertie, no batteries, no pile of money up front: $109/month for the next 15 years.
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Plus dig the new deck I built last summer.

--Chi "Happy Homeowner" Meson
 

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  • #2
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Looks good. I have always wanted to put solar on our home.

You mentioned no batteries. What about night time?

Just curious, if you did not finance, what was the total cost?
 
  • #3
Astronuc
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I hope you monitor the electrical power output during the year to see how effective the system is, particularly during the winter, and particuarly with snow covering the panels, and only cloudy/rainy days.

So without batteries, one uses the grid at night? Does the system supply the grid when generation exceeds utilization?
 
  • #4
Chi Meson
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Batteries are not only unnecessary, they are "negatively beneficial" if talking 'bout environmental concerns OR financial concerns. The price of small inverters has come way the **** down, so it is much better to tie the solar output directly to the grid through the electric meter. When the panels crank out the kilowatts (mine is optimized for summer sun), the meter runs backward, and I get credit for the electricity I provide to the grid. At night, and in cloudy weather, the grid supplies electricity to me.

The thing is, rooftop panels will be at maximum production exactly when electric demand is highest: mid-day summer, when all the AC units in malls and businesses are cranking to achieve stupidly cold indoor climates. New incentives are working their way through state legislature where residents will be credited 3x the rate when they produce more than they use.

I chose the best incentive/financing plan available now: it's a "lease" of the system, where I pay about 90% of my usual monthly electric bill over the next 15 years. If I produce more than I use, a credit is set aside and used to pay for any repairs required along the way.

Next year, Connecticut will require that new systems get credited 55 cents per kWh when they produce, as opposed to 18 / kWh when they use. This will be an incentive to put the largest # of panels possible for an array. I can't get this deal until the lease runs out.
 
  • #5
Chi Meson
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I hope you monitor the electrical power output during the year to see how effective the system is, particularly during the winter, and particuarly with snow covering the panels, and only cloudy/rainy days.
There's an App for that! I'll be able to check production from anywhere. If you see the space above the panels over the garage, I'm putting in 4 skylights. One of these will be used as an access portal if I need to scrape some snow off.

They are 0% effective unless under direct sunlight, so even a light dusting of snow makes them useless

But as I mentioned, my grid is optimized for summer. Due to the pitch of the roof, I'll only get just under 3000 kW from November through February in the best conditions. From March through October, it should be 7000kW-ish, peaking over 9000kW in June/July.
 
  • #6
turbo
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Sweet setup, Chi! I'd love to do something like that, though are snow-loads are incredible in recent years, and I would fear for the physical viability of the panels.
 
  • #7
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Damn, what a nice, big house! I love the deck and congratulations on the solar!
 
  • #8
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Damn, what a nice, big house! I love the deck and congratulations on the solar!
Yeah. That's a sweet house Chi! Where do you live out of curiosity? New England?

EDIT: Just read your profile. I am waving from the next state over! :smile:
 
  • #9
Astronuc
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Speaking of the nice deck, is that TREX?

I need to replace my front porch because the cheap wood that the contractor used has weathered and the handrails have warped. I replaced the wood on the small backdoor deck with TREX, and it turned our really nice.
 
  • #10
dlgoff
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Sweet setup, Chi! I'd love to do something like that, though are snow-loads are incredible in recent years, and I would fear for the physical viability of the panels.
I can just imagine the damage caused by roof-rakes and snow-blowers.
 
  • #11
Ivan Seeking
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Most excellent, Chi. The fixed monthly cost makes this completely mangeable.

It's looking like solar may be viable here in Oregon pretty soon. But it has stiff competition with the low-cost hydro power we have locally. It may be another generation or two [of the technology] before it's worth doing here.
 
  • #12
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....The thing is, rooftop panels will be at maximum production exactly when electric demand is highest: mid-day summer, ..
Please don't shoot the messenger.

http://www.reuk.co.uk/Effect-of-Temperature-on-Solar-Panels.htm

Assuming the reflectivity of 5% of black panels and at say 30 degrees relative lattitude they absorb 0.95 * sine(45) * 1360 W/m2 = 911 W/m2 at noon. Stefan Boltzman transfers this to a temp of 356K or 83 degrees C, so the effectivity may drop 30% or something, due to the heat.

I guess it would be a double whammy if the panels were liquid cooled, the heat of the water being stored under ground.
 
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  • #13
Ivan Seeking
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Please don't shoot the messenger.

http://www.reuk.co.uk/Effect-of-Temperature-on-Solar-Panels.htm

Assuming the reflectivity of 5% of black panels and at say 30 degrees relative lattitude they absorb 0.95 * sine(45) * 1360 W/m2 = 911 W/m2 at noon. Stefan Boltzman transfers this to a temp of 356K or 83 degrees C, so the effectivity may drop 20% or something, due to the heat.

I guess it would be a double whammy if the panels were liquid cooled, the heat of the water being stored under ground.
You are assuming that 100% of the energy goes to heat.
 
  • #14
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No the sad lessons learned by my brother in law.
 
  • #15
Ivan Seeking
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No the sad lessons learned by my brother in law.
No, you took the total incident energy and assumed that it all heats the panel. That is incorrect. The panel is producing power.

Also, where did you get 1360 Watts. That seems too high even for the total incident power per sq meter.
 
  • #16
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No I did not

I merely looked at the graph in the link

Experiment Results - How Does Temperature Affect Solar Panel Power Output
solar-panel-power-temperature-relationship.gif


Note that 83 degrees C is off the scale

Also http://www.jsgregg.com/teaching/GEOG345/Assignments/Examples.pdf [Broken], so I was 10 W/m2 too low for the safe side.

But we have indeed to substract the energy which is converted to electricity. 6-12% and for 12% the numbers would be 802 W/m2 remaining absorbed energy gives 345 K or 72C
 
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  • #17
256bits
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But as I mentioned, my grid is optimized for summer. Due to the pitch of the roof, I'll only get just under 3000 kW from November through February in the best conditions. From March through October, it should be 7000kW-ish, peaking over 9000kW in June/July.
Where did you get the kW figures from as they seem a little high for the area of solar panel, guessing about 100 square meters. Would not 9000 sq meter be needed for 9000 kW?
 
  • #18
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It must be a local thing. My electric bill is $40 a month in the winter and $80 in the summer.
 
  • #19
Chi Meson
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It must be a local thing. My electric bill is $40 a month in the winter and $80 in the summer.
Is your stove gas? Hot water? In my previous home, we had all propane and my electric bill was mostly the monthly connect fee. This house had electric everything, plus we developed a family of five constantly wearing clothes. 90% of the lights are cf, I installed the thermal panels 5 years ago, and still we consume a ridiculous 18 kWh per day.
 
  • #20
Chi Meson
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Where did you get the kW figures from as they seem a little high for the area of solar panel, guessing about 100 square meters. Would not 9000 sq meter be needed for 9000 kW?
My error there (a little high indeed): Summer peak should be just over 8000W, not 9000 kW, ideally. And of course, I will be expecting ideal conditions. The Panels tested at 250W for 1000W/m2, so nominally I should get 7400 W. Around solstice, the sun will be near normal to the panels at noon, so I'll keep people posted as to what the actual output will be (watch it rain for 6 weeks next year!).

Oh, and it's not even connected yet! the electrician took a vacation. Switch happens next week.
 
  • #21
Evo
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My error there (a little high indeed): Summer peak should be just over 8000W, not 9000 kW, ideally. And of course, I will be expecting ideal conditions. The Panels tested at 250W for 1000W/m2, so nominally I should get 7400 W. Around solstice, the sun will be near normal to the panels at noon, so I'll keep people posted as to what the actual output will be (watch it rain for 6 weeks next year!).

Oh, and it's not even connected yet! the electrician took a vacation. Switch happens next week.
Lovely house Chi. Hope this works out for you.
 
  • #22
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Is your stove gas? Hot water?
Yeah, I forgot about that. The total gas and electric bill runs closer to about $110 a month.
 
  • #23
Chi Meson
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Sweet setup, Chi! I'd love to do something like that, though are snow-loads are incredible in recent years, and I would fear for the physical viability of the panels.
For higher latitudes, a ground-mount system with tracking would be a better option. If not full tracking, then a seasonally adjustable tilt. During winter, a 60 degree tilt will keep the snow off, however you need a large treeless swath of land. Nothing's easy.
 
  • #24
Drakkith
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I thought about going solar and hooking them up to the grid, however my electric company would charge upwards of 70+ dollars a month JUST to hook it up and the amount they would pay me per KWh would be terribly low.
 
  • #25
AlephZero
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No, you took the total incident energy and assumed that it all heats the panel. That is incorrect. The panel is producing power.

Also, where did you get 1360 Watts. That seems too high even for the total incident power per sq meter.
There seem to be several things wrong here. 1360W/m^2 is the solar radiation at the top of the atmosphere, not what reaches ground level. The temperature calculations seem to be assuming only radative heat transfer, not convection to the atmosphere. But considering the conversion efficiency to electricity is low (certainly less than 20% and possibly less than 10%) ignoring that is probably not the biggest error in the thermal calculation.
 

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