Our solar production

[garygid]

Looks like a great way to energize your new year!

 

[DaveEV]

You can see graphing on my Sunnyportal site:

http://www.sunnyportal.com/Templates/PublicPageOverview.aspx?page=eb178848-3d09-431d-a9aa-d94379403702&plant=0f19afd5-0303-427c-9ef4-934a64228dde&splang=en-US

You should put a link to that in your sig and OP for easy reference.

 

[Gonewild]

We had a lot of rain yesterday and cooler temp's got 24.3kwh for winter that good.

 

[mwalsh]

You should put a link to that in your sig and OP for easy reference.

I can do a link in the OP, but my SIG is maxed out - you can only have 255 characters.

 

[Jimmydreams]

Yesterday was a great day for December solar.... 25.69kWh generation yesterday is a great pull for these short days!! (6.7kW system)

 

[mwalsh]

Yesterday was a great day for December solar.... 25.69kWh generation yesterday is a great pull for these short days!! (6.7kW system)

And today too! I'm already at 13kWh. Of course, that won't hold up....I get some pretty nasty afternoon shadowing from the neighbors chimney in winter.

 

[Boomer23]

Yesterday was a great day for December solar.... 25.69kWh generation yesterday is a great pull for these short days!! (6.7kW system)

And today too! I'm already at 13kWh. Of course, that won't hold up....I get some pretty nasty afternoon shadowing from the neighbors chimney in winter.

Wow, I didn't realize that you had some shading. That makes your generation numbers even more impressive. You'll do really well in summer.

If you "remedy" the neighbor's chimney shading problem, do you think they'd be able to trace the damage to you? :lol:

 

[Gonewild]

Cut your neighbor chimney down in the middle of the night. :lol:

I think mine put out more power because of the rain washed the dirt off the panels.

 

[mwalsh]

The chimney I can't do much about, but the palm trees they planted in about 10 years time......

Actually, if I'm completely honest, I'm not massively enthusiastic about laying the CA Solar Act on them. I mean, it's not their fault they neglected to consider that I might be installing solar in 10 years when they first planted them. We may just see how much impact they have - the are south east of my roof line, so really only the potential to be a problem on winter mornings.

 

[Boomer23]

The chimney I can't do much about, but the palm trees they planted in about 10 years time......

Actually, if I'm completely honest, I'm not massively enthusiastic about laying the CA Solar Act on them. I mean, it's not their fault they neglected to consider that I might be installing solar in 10 years when they first planted them. We may just see how much impact they have - the are south east of my roof line, so really only the potential to be a problem on winter mornings.

Sounds like minimal impact, mwalsh.

That said, it turns out that shading has a much bigger impact on PV array output than the percentage of the surface area shaded. A single panel shaded 10% might have an output 50% or 60% less than the same panel without shading (I'm guessing at the percentages, but I've played around with panels and I've seen the impact of shading). I think I also read that multiple panels on a single inverter can have their output compromised if a single panel is shaded. Others with more knowledge might correct me on that last part.

Still, if it's only on winter mornings, minimal impact.

 

[Jimmydreams]

Sounds like minimal impact, mwalsh.

That said, it turns out that shading has a much bigger impact on PV array output than the percentage of the surface area shaded. A single panel shaded 10% might have an output 50% or 60% less than the same panel without shading (I'm guessing at the percentages, but I've played around with panels and I've seen the impact of shading). I think I also read that multiple panels on a single inverter can have their output compromised if a single panel is shaded. Others with more knowledge might correct me on that last part.

Still, if it's only on winter mornings, minimal impact.

You're right about one panel being shaded bringing the whole string down. That's why people are starting to switch to micro-inverters on the back of each panel. That way, if 1 panel is shaded, only THAT panel sees a degraded output....all the others chug along at whatever rate they can. Also, the power coming all the way down from the roof is now A/C power vs D/C (since it was converted at each panel via the micro-inverter).....I believe A/C power has less transmission loss over a given distance, but I'm not positive. So depending on your circumstances, micro-inverters can make solar work better in places with some shading. But they're a bit more expensive. AND, there are more points-of-failure that your system might have but can endure. If my 1 inverter goes out, my whole solar is useless....if I had 30 micro-inverters, I could lose one and not worry much while a new one was being shipped.

 

[TomT]

With series connected DC PV arrays, one panel being shaded acts like a big resistor and inhibits the current flow of the whole string. With each one being separate and parallel via a AC micro-inverter, it is not an issue. It is technically possible to run a DC array in parallel too but the amperage would be so high because of the low voltage that the wiring would become impractical.

Actually, DC current transmission is more efficient than AC, everything else being equal. Edison was right about that and Westinghouse was wrong. The big problem with DC has always been that it is more difficult to convert it to different voltages and from DC to AC and vica-versa.

You're right about one panel being shaded bringing the whole string down. That's why people are starting to switch to micro-inverters on the back of each panel. That way, if 1 panel is shaded, only THAT panel sees a degraded output....all the others chug along at whatever rate they can. Also, the power coming all the way down from the roof is now A/C power vs D/C (since it was converted at each panel via the micro-inverter).....I believe A/C power has less transmission loss over a given distance, but I'm not positive. So depending on your circumstances, micro-inverters can make solar work better in places with some shading. But they're a bit more expensive. AND, there are more points-of-failure that your system might have but can endure. If my 1 inverter goes out, my whole solar is useless....if I had 30 micro-inverters, I could lose one and not worry much while a new one was being shipped.

 

[Smidge204]

Actually, DC current transmission is more efficient than AC, everything else being equal. Edison was right about that and Westinghouse was wrong. The big problem with DC has always been that it is more difficult to convert it to different voltages and from DC to AC and vica-versa.

Truth here. AC became popular for transmission because a simple set of coils (aka a transformer) can change voltage with relatively high efficiency. By jacking up voltages to tens or hundreds of thousands of volts, you can reduce your I-squared-R losses and come out ahead.

With the advent of efficient AC-DC conversion, High voltage DC has become popular for long distance transmission. Doubly so for superconducting transmission lines, where the capacitive and inductive properties of the cables at AC frequencies can cause additional problems.

I do love the microinverter concept, though. It greatly simplifies design and installation, especially for larger systems, though I have to look at it closer to see what, if any, cost benefits it offers and how that scales with system size.
=Smidge=

 

[TomT]

Another reason that Edison preferred DC over AC was, he stated, safety. It takes ten times the current through the body to stop the heart with DC as it does with AC. While this is certainly true, many think that Edison was simply be obstinate because he didn't like Westinghouse and AC was a competing system...

If you've ever heard the buzzing from a AC high voltage line and/or insulators, you've experienced one of the problems and lose sources with AC. It can also be a significant source of RFI (radio frequency interference) as it acts like an early 20th century spark gap radio transmitter.

 

[Azrich]

Great beginning of 2011 with 29.62 kWh produced on New Years Day. The high was only 44 degrees.

Do panels generally produce more in lower temperatures?

 

[Gonewild]

yes lower power temps over 70deg

 

[DaveEV]

Do panels generally produce more in lower temperatures?

Generally about 0.4% more for each degree C drop in panel temperature. The spec sheet for your panels will have the exact number, but 0.4% is pretty standard for standard silicon modules.

 

[wsbca]

Do panels generally produce more in lower temperatures?

No, they produce less power in higher temperatures

 

[Gonewild]

Do panels generally produce more in lower temperatures?

No, they produce less power in higher temperatures

That is what we both said.

 

[hill]

Here's a solar production fun fact, and a question. Our 7.1kwh AC rated system has yielded 2.6kwh average, for each hour that the inverters are 'active' over the last 24 months of opperaton. That's because:
1) during the LAST and 1st 1/2 hour or so of each day, there are only a few watts being generated.
2) the PV industry "rates" a system when panels are in their "ideal" position. That happens a couple days during the summer solstice, when (in our area) the sun is almost over head (azimuth appx 80 degrees), and presumes it's not cloudy on those days, and presumes it's not 90 or 100 degrees, which further reduces output. During the winter, when the sun's azimuth is only in the mid 30 degree range, and the days are shorter, and the weather is often more cloudy, raining and dark, output can be reduced to only 15% of the 7.1kwh "rating".

Ok, that was the fun fact. Here's the question (and I do have a guess at the answer). Since ultimately, PV's DC power has to run through inverters to be used in your home as AC ... and there is a given loss percentage that occurs, thus yielding a lower "AC" number ... why the heck is it that the PV industry is so desirous to advertise, and pass on to us, the DC number?

My guess? Because it SOUNDS better. When an installation company 'rates' a system, THEY know how long your winter, summer, and equinox days are ... they know the weather and temperature patterns in your area, often based on 50, 75 ... sometimes 100 years of history! So why don't the good people at REVCO, or Sunpower, or Aliso Electric or BP or whom ever ... why don't they tell their customer, "your system will average 2.6kwh for each waking hour your system is running" ... rather than 7.1kWh AC ... or an even more inflated sounding DC rating?

Any way:
Two year total Kwh production of our 2 inverters combined: 22,023 kWh.
Two year total of hours of (2) inverters in operation (averaged): 8,380 hrs

With the over 3,000kWh surplus,

that we've back fed onto the grid, our utility will have to pay us almost $500 for our good deed. Of course the Leaf, when ever it gets here, will make quick work of that 1,500kWh per year average surplus.