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T O P I C     R E V I E W
The Famous Druid
Member # 1769
 - posted April 16, 2015 07:43
So our new solar panels went online last week, and I've been reviewing the statistics.
In an Autumn week with one clear sunny day, 2 dull overcast days, and the rest somewhere in between, we produced 2.5% less than our average weekly consumption (based on a years worth of electricity bills).
I'm quite pleased.
 
Snaggy
Member # 123
 - posted April 16, 2015 11:38
Wow, nice! [Applause]

Are there grants and subsidies to help pay, or do you have to go it alone?

Pics where the Sun do shine!
 
The Famous Druid
Member # 1769
 - posted April 17, 2015 00:41
quote:
Originally posted by Snaggy:
Are there grants and subsidies

Oh yes, I'm generously subsidizing the electricity company. [Frown]

It's a grid-connected system, excess energy generated during the day feeds into the grid, and I draw from the grid at night.

There's a charge of some hundreds of dollars to connect a solar system to the grid, plus the usual monthly charge everyone pays, and they sell me electricity at 4 times the price they pay for my exports, then sell my exports at a premium price to others as 'Green Power'.

Have I mentioned how much I hate our current climate-change-denying government?
 
Ashitaka
Member # 4924
 - posted April 17, 2015 05:53
Everyone her seems to be goisolar, the only problem for me is ther are no subsidies for going solar, despite the fact my country does not produce more energy than we use. It is all the rage for farmers with huge barns in the middle of fields. they are making a profit on selling their alectricity without any subsidies ( except the protectionist international agrarian policies my country uses)
 
The Famous Druid
Member # 1769
 - posted April 17, 2015 09:56
Autumn.
Heavy overcast all morning, rain most of the afternoon, still produced 1/2 of our average useage.
 
TheMoMan
Member # 1659
 - posted April 18, 2015 09:07
So what form of Photo Voltaic are you using on the roof?

How many Square feet or Meters?

Output watts?

Time to recover upfront costs?
 
The Famous Druid
Member # 1769
 - posted April 19, 2015 00:24
It's nominally a 4kW PV system, (16 x 250W panels , 1.5 m^2 (15 sq ft) each), but we'll never get that, because of the way the panels are arranged.

Basically, to get maximum total output from the system, you'd point all of the panels North, but that results in maximum power output around noon, with far less produced in the morning and late afternoon, which is when our daytime demand is highest.

Also, the way our house is laid out (with most of the roof surfaces facing East or West) would make it difficult to have very many North facing panels.

So, making a virtue of necessity, we've put 7 panels on the East facing side of the roof, and 9 on the West. Total power output over the day will be less, but it'll be a flatter output curve, with more available at the times we use it.

Looking at the stats, on a sunny Autumn day we get over 1 kW from about 8:30am - 4:30pm (sun rise/set times are currently about 7am/6pm) and over 2kW between about 10:30-2:30 (solar noon's about 12:30 here). For about 1/2 an hour around solar noon it might even edge over 3 kW.

So far, our best day has been 16.2 kWh, our worst 3.8 kWh, the average is 10.9 kWh, a little less that our average use of 12 kWh/day (although I'm expecting that to drop, our washing machine died a few weeks ago, and the new one is far more energy efficient, plus I bought a big box of LED lights)

As for recovering upfront costs, that's hard to say. The current government is very hostile, they dropped the feed-in payment by 25% between when we signed the contract and when it went online, so the future's anyone's guess. I did my sums on it halving our electricity bills, on that basis the payoff time will be about 6 years. I'll have a better idea of the real savings when we get our next electricity bill, and an even better idea when I see a full years bills.
 
TheMoMan
Member # 1659
 - posted April 19, 2015 13:36
I had to get out my atlas, you are closer to the Equator than we are, therefore your payoff is quicker. When we had this house sited I wanted the long axis E/W to slow down the solar absorption during the summer, and hopefully the Southern side would absorb during the winter.

Wind mills would be the better choice here but the wind while gusty does not blow steady enough, too many long periods of no winds.

I am still looking at stored solar (thermal) using phase change salts. How big of a tank would it take to store a Trillion BTUs, in a salt solution. I built a small scale tank many years ago using a mix of Na and K/ Cl salts in a saturated solution. It was an excellent fly killer, they would attempt to land but the surface tension would not support them and then sudden death.
 
The Famous Druid
Member # 1769
 - posted April 21, 2015 20:03
quote:
Originally posted by TheMoMan:
I had to get out my atlas, you are closer to the Equator than we are, therefore your payoff is quicker.

That'll be part of it, but the bigger factor will be the higher electricity costs here, about twice what you pay. (which is a rant I'll have Some Other Time)

Distance from the equator doesn't make as much difference as you'd think, your panels would run cooler, (PV output drops about 1% per degree C) and for half the year your days are longer.
 
The Famous Druid
Member # 1769
 - posted June 22, 2015 06:08
Update:
Winter Solstice yesterday, i.e. the shortest day, worst angles, etc etc...

The solar panels generated 79% of our average daily electricity consumption.

Looking at the stats over the last 2 1/2 months, we've generated 70% of our average demand.

On those stats, I'm fairly sure we'll be net exporters during the summer months (when electricity demand is at its highest) and probably about break-even over the whole year.

I'm quite pleased.
 
Ugh, MightyClub
Member # 3112
 - posted June 22, 2015 13:40
Great to hear! So given the data you have so far, do you have a better idea for how long it will take to pay off the upfront costs? I'm also curious about the expected lifetime of your rig. And related, does the efficiency of the system degrade over time?

It would also be pretty neat to see how long it takes to "pay off" the carbon footprint (and other up front intangibles) from the manufacture, transport, and install of the system.

Speaking of intangible, has anyone else ever wondered what consequences solar, wind, wave, etc. power have that we haven't thought about yet? I mean, the energy in the universe is technically finite, right? So by soaking rays into a solar cell you're theoretically denying that energy to a plant. If you hook enough turbines up to waves, do you introduce enough resistance to screw up currents? Do you alter the rotation of the earth itself?
 
TheMoMan
Member # 1659
 - posted June 22, 2015 14:04
If a tree falls in the forest, it is still the mans fault.

Does water flowing downstream in a river weaken gravity? I have seen very few plants growing on roofs. Tides would seem to me to be the largest drag on rotation. Have sailboats changed the winds?
 
The Famous Druid
Member # 1769
 - posted June 23, 2015 04:18
quote:
Originally posted by Ugh, MightyClub:
Great to hear! So given the data you have so far, do you have a better idea for how long it will take to pay off the upfront costs?

Hard to say.
If we used all of the power generated, it'd be about 5 years, but we don't, and as noted earlier, the rate we get for our exports is only 1/4 of what we pay for imports.
So, the key factor is how much of our production we use.
So far, we're using about 2/3, but it's winter, the days are short, and most of Clan MacDruid are out for most of the day.

I'm hoping that during the summer months our imports will drop, because the sun will still be shining for much of the evening when the Clan are home.

quote:
I'm also curious about the expected lifetime of your rig. And related, does the efficiency of the system degrade over time?
Solar panels do degrade slowly, but they should be good for 25-30 years. So, by the time these panels are due to be replaced, I probably won't be thinking about such long-term investments.


quote:
It would also be pretty neat to see how long it takes to "pay off" the carbon footprint (and other up front intangibles) from the manufacture, transport, and install of the system.
Current gen panels about 3 years for manufacture, add a few months for transport and installation.

quote:
Speaking of intangible, has anyone else ever wondered what consequences solar, wind, wave, etc. power have that we haven't thought about yet?

I've wondered the same thing.
If I'm installing solar panels to do my bit fighting global warming, is 24 m^2 of black, non-reflective surface the best way to go?
Does the warming effect of the dark surface outweigh the benefit of reduced CO2?
Could I counter the effect by painting the rest of Roof Del Druid white?
Someone who knows what they're doing should crunch the numbers.
 
TheMoMan
Member # 1659
 - posted June 23, 2015 14:26
TFD, et all. The Univ.of Florida did some experiments with different colors on solar for thermal absorpsion. Comparing heat loss and adsorpsion, Elm Leaf Green had the best heat gain vs loss numbers of any color they tested. It seems that the middle towards the UV end of the visable spectrum has more energy. Remember all those pastel colored cars and the sun faded paint.
 




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