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Battery capacity is so it will last 4 days, and the cost is $.15/W-hr. A smaller pack would wear out sooner. Plus these aren't fancy batteries.
Taking a battery to 25% depth of discharge versus 100% will help it last longer, but at 4x the cost, and neither 4x the lifespan nor 4x the utility.
If you plan on regular use, 4 days' reserve capacity on a New Mexico solar system is ridiculous; even the most drab winter day will put close to half an average day's worth of sunlight into the battery. That would explain up to 1 day. You're better off investing that money into more panels, allowing a smaller battery to recharge in less time.
(Oversizing the battery is kinda like splurging for extra jerrycans in your jeep rather than repairing the engine which is getting half its proper gas mileage).
On a cloudy day you might get 10% of the energy you would when the sun is shining. It is nil. And like I said, I don't have any backup, so would like to minimize the amount of time I spend without electricity. I played around with getting more panels and fewer batteries, but the difference was in the noise. If I want to weather a few cloudy days in a row, I need the batteries anyway.
On a cloudy day you might get 10% of the energy you would when the sun is shining. It is nil.
Baloney. Ever taken a meter to it? I have.
Just because your eye perceives it as dim and 10% doesn't mean the solar panel will. Plus, it's usually cold when it's cloudy here and that further boosts cell efficiency.
Germany's dim and cloudy and yet they have more solar installed than the US does.
Having trouble making sense of your spreadsheet (could try reposting in Courier or another monospaced font).
That's why I always space things out with '......'s - as needed.
Quote:
Originally Posted by rruff
I played around with getting more panels and fewer batteries, but the difference was in the noise.
Why not play around with a generator and some gasoline? It's still the most energy-dense fuel around ( not counting nuclear ).
Quote:
Originally Posted by Zoidberg
Plus, it's usually cold when it's cloudy here and that further boosts cell efficiency.
I didn't know that. Does that mean that all things being equal, you get more out of a cell here, in a
New Mexico winter day than they are getting out of those same cells in Phoenix when it is 118 deg?
The bottom line is that you are making a really really long-term investment to save a relatively
measly amount of money. There are plenty of people around who want to do it to make a
statement, have something fun to play with or whatever. Again, it's like buying a hybrid car.
Most people don't even contribute to a 401k or an IRA - even if it is available to them. The idea that those people
will ever do a solar installation is nuts - even when it ( someday ) becomes 50% cheaper ( than PNM ) without a subsidy.
I bet the ratio of Power Ball players who have a solar installation is way lower than
for people who wouldn't dream of playing that lottery who have a solar installation.
Perhaps a better use for my roof would be for the utility company to pay me to use the space - rather
than coat another jillion acres of beautiful open land with solar panels. I just got done parking in the nice
shade of the solar panels on the roof of the ABQ parking lot. If they did that at the malls and such, people
would likely drop a quarter or two in a box to park in the shade of a revenue-generating solar panel - a two-fer.
I think focusing on residental use is, relatively speaking, a loser.
I didn't know that. Does that mean that all things being equal, you get more out of a cell here,
in New Mexico than they are getting out of those same cells in Phoenix when it is 118 deg?
Assuming equivalent light, absolutely.
Interestingly enough, occasionally a poorly-thought-out system will blow out its inverter on a crisp subfreezing winter morning, because the voltage is higher than the inverter is designed to handle. That's why you'll often see complete solar kits with a heading "tropical use only" or "warm weather use only". Their inverters can't handle the cold weather voltage spike (and they don't need to if it never gets cold where they're going).
I lived off grid with a solar electric for many years. I didn't have a watt-meter, but I monitored voltage and the amount going in on cloudy days was tiny... determined by measuring voltage drop with the panel connected vs disconnected.
Does that mean that all things being equal, you get more out of a cell here, in a New Mexico winter day than they are getting out of those same cells in Phoenix when it is 118 deg?
If they are hooked to batteries, then the voltage will be ~12V... sight up from there and see how much a difference in temperature makes. Doesn't matter much until the panel temperature gets ~75C (167F)... which can happen on calm hot sunny days.
I lived off grid with a solar electric for many years. I didn't have a watt-meter, but I monitored voltage and the amount going in on cloudy days was tiny... determined by measuring voltage drop with the panel connected vs disconnected.
Yeah.. voltage has very little to do with the amount of incident light (though a meter will show it going to close to zero if you eliminate all light because of internal resistance in the meter and lead wires); you should have been measuring short-circuit current, which has everything to do with the amount of incident light.
One, you live in the sunny part.
Two, that map is for concentrated solar power. There is a huge difference when it comes to low light conditions.
Three, they used a wattmeter and they understood why they needed to use it.
Quote:
Germany doesn't have a lot of panels because they are in a good solar environment. It's because their government subsidizes it heavily.
Although their government subsidizes it, it's because their power is expensive more than because of any subsidy. Our government puts forth a similar subsidy but we have cheap power and much less adoption; hence, it can't be because of the subsidy alone.
Does that mean that all things being equal, you get more out of a cell here, in a New Mexico
winter day than they are getting out of those same cells in Phoenix when it is 118 deg?
Better to just look things up: - cite -
Your chart isn't very useful in light of my question. 25 degrees is considerably higher than NM winter temperatures.
Besides, all I was looking for was a 'yes' or a 'no' and I would bet money that Zoidberg would be back and answer the question.
I had another thought:
I wonder if PNM were paying for solar ( "clean" ) energy based on its value to them, would they pay more for energy when they were getting
capacity-constrained? That is; power produced at solar noon ( sun due South ), doesn't have the same value as power produced at peak load
times like 5 pm or therabouts on a summer day. Most home, rooftop solar arrays only have a tllt function and not a azimuth function. Orienting
the panels to produce maximum output at peak load might be worth more than orienting them to produce maximum power over the course of a day.
Right now, they just pay a flat rate, but that's not how they charge for it.
Your chart isn't very useful in light of my question. 25 degrees is considerably higher than NM winter temperatures.
Probably about right for the *panel* temperature during the day though.
If you look at how much the change is between 25C and 50C it will give you an idea of why they don't bother showing lower temperatures.
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