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I was measuring the voltage drop in the wiring between the panels and batteries... which is directly proportional to current and power.
The chart is not for concentrated solar... where did you get that? It's the amount of incident solar resource at those locations. Everyplace gets the same number of hours of daylight per year... the difference is how much makes it to the ground... ie cloudy places have much lower available solar energy... up to a 5X difference! So tell me again why clouds hardly matter. If you can find a any info to back up your claim that would be helpful.
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.
PNM has a number of considerations for what they need and what they charge- the state has mandated a renewable energy component to their energy mix, which in part they have taken care of with large-scale centralized PV plants (there's actually quite a big one just south of the Reeves power station at Paseo near Jefferson), and in part they've thrown a bone to homeowners.
Solar PV is not what they call dispatchable- you can't turn it on high or on low or off depending on what the grid needs. This lack of demand response will hinder its pricing because of its lack of ability to meet 5pm summer peak demand.
If we had no way of putting relatively cheap dispatchable power on the grid, there might could be a reason to tilt your panels for late afternoon peak, but we have plenty of natural gas peaker capacity, and natural gas is very cheap to run these days (particularly the equipment to burn it).
The other factor you run into is self-shading when you point your panels that low. What ends up being a pretty reasonable spacing for latitude tilt ends up being way too tight for 5pm peak.
I was measuring the voltage drop in the wiring between the panels and batteries... which is directly proportional to current and power.
Your battery is not an ohmic device- its voltage and its resistance changes as a matter of temperature, apparent load, and state of charge.
Your panel is not an ohmic device- its voltage, current, and power output changes as a matter of temperature, apparent load, and amount of illumination.
Think about it. When your battery is fully charged, it might run at about 14 volts. When it's near dead, about 11 volts. Take it up to 100° F and it'll gain a volt, but not gain any charge. Nothing directly proportional about any of that.
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The chart is not for concentrated solar... where did you get that?
Two places. One, the word "concentrator" in the upper left corner in nice big 18 point type. Second, the URL calls it "map_csp_us..". The "csp" stands for "concentrated solar power".
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It's the amount of incident solar resource at those locations. Everyplace gets the same number of hours of daylight per year... the difference is how much makes it to the ground... ie cloudy places have much lower available solar energy... up to a 5X difference! So tell me again why clouds hardly matter. If you can find a any info to back up your claim that would be helpful.
Here's the map that you meant to use: http://www.nrel.gov/gis/images/map_p...al_may2004.jpg
Notice this one is more of a 2X difference, and there's still plenty of light in cloudy places (there was plenty with your other map too but nobody in their right mind would set up a tracking PV concentrator in a cloudy place with today's economics).
I still don't see why this is important to you given that everybody in this discussion lives in New Mexico, which has plenty of sun for whatever purpose. Even in December.
Your battery is not an ohmic device- its voltage and its resistance changes as a matter of temperature, apparent load, and state of charge.
Your panel is not an ohmic device- its voltage, current, and power output changes as a matter of temperature, apparent load, and amount of illumination.
Apparently you don't even know Ohm's law. So you understand nothing about electricity.
V=I*R. The resistance in the wiring is fixed, so the voltage drop is directly proportional to the current flow and power.
So if I measure a drop of 0.8V on a sunny day and <0.1V on a cloudy day, then that means the power is <1/8th as much.
Here is another example. Some of the weather stations have solar radiation measurements. Below is the data for one on a mostly sunny summer day:
And here is the same station when clouds are introduced on a summer day. Notice that just before 2pm the radiation level drops to nearly zero:
So if you compare fixed panels the difference is only 3x? The reason why cloudy places get that much solar energy is because no place is cloudy all the time.
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I still don't see why this is important to you given that everybody in this discussion lives in New Mexico, which has plenty of sun for whatever purpose.
You may have forgotten, but the way this started was with me claiming that off-grid solar is very expensive electricity any way you do it. You said it wasn't that costly. I showed you my system. You said I didn't need 4 days of battery backup because you get plenty of energy even on cloudy days. I said that isn't true. So far you provided no info to make your case, while I've showed plenty that makes mine.
I'd really like to see your proposed off-grid solar system, that is significantly cheaper per KW-hr than mine.
The power dissipated in the wiring will be 1/64th as much, but the power supplied to the battery will be proportional to current.... or <1/8th. The full circuit voltage is ~12V in both cases.
You said I didn't need 4 days of battery backup because you get plenty of energy even on cloudy days. I said that isn't true.
Taking your cloudy day example (you sure that wasn't smoke from the 100% contained but still smoldering Whitewater-Baldy Complex fire?) and integrating over that, I show an approximate energy gain of 3 kWh/m2 over the course of that day (compared to about 7 kWh/m2 for the previous sunny day example).
3 kWh/m2 sure sounds like plenty of energy to me.
I definitely don't see why 15 kWh of storage would be necessary for a 4 kWh shortfall (which is uncommon). This is a bit like putting a 100 gallon gas tank in a car in order to save on gas.
Bear in mind this is for using a system at 100% its power potential; every day, without fail, using 7 kWh.
If you're using more than you're getting in sunlight on a daily basis, you'd deplete the battery no matter how big or small you made it. If 4/15 makes you nervous, doubling the size of the array would make it 1/15. Easily doable for less than that price range you put forth.
It wasn't a cloudy day... it was a typical summer day where clouds came up in the afternoon (check the temperature). In the winter the solar energy/day is considerably lower, and storms can come in and make it cloudy for several days in a row. Regardless, there will be times when the storage is inadequate.
Having a generator would be nice but I haven't seen any designed specifically for battery charging that are less than $5,000 shipped... which would blow my budget on a small system. Plus the additional hassle of noise, fueling, building a shed for it, maintenance, etc.
When I get a chance I'll look at sizing a larger system with a generator and see what the costs look like.
We have a solar array in Corrales, and have really enjoyed it.
We got a 1099-misc from the PNM stating that they reported the payments that we received on our array, basically to cover their behind.
Is this something that we are required to pay tax on, or is their some kind of exemption?
It's taxable income, since PNM is paying you for ur excess generation.
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Taxes????
