Soot decays my power production faster than the boost from lengthening days in April

[sethland]

I just got rooftop solar on April 5. Where I live in California, soot is a slow and steady phenomenon. April 12th, April 13th, and April 14th, 3 identical cloudless days, I noticed my production was slightly decreasing day-over-day about 0.7% each day on average. But over these days, the amount of sunlight was increasing by 0.3% each day. Today I had time to go on the roof, experiment and wash 40% of my panels. They had a thin layer of soot on them. in the graphic, see if you can spot at what time I cleaned the panels. I'll clean all the panels to see what my total boost in production is.

 

[LydMekk]

Here i have the same with pollen and sand from Marokko.

 

[Ampster]

April 12th, April 13th, and April 14th, 3 identical cloudless days, I noticed my production was slightly decreasing day-over-day

Was the temperature identical? There is a reduciton in production as the temperature increases. Also, sometimes high cirrus clouds can create higher insolation. You may also need a larger sample size, which is going to be hard to find exact days of insolation as the days get longer and sun gets higher in the sky.
On April 13th I got 56.0 kWhs and April 14th I got 55.5 kWhs from a 9kW system. I am at 38.4 Latitude in Northern California and my azimuth, tilt and DC to AC ratio may not correspond to your system but am offering it as a rough benchmark

 

[HarryN]

On my vehicle solar panels, the decrease is pretty dramatic.

I wash them every two weeks. Not the vehicle - just the panels.

 

[400bird]

I just got rooftop solar on April 5. Where I live in California, soot is a slow and steady phenomenon.

I'll believe it, with the wildfires we've seen that soot build up. But, where about are you that soot is constant?!

 

[Zapper77]

Gravel pit about two miles upwind.

 

[400bird]

Ah, you say soot, I hear fire and smoke. Gravel plant dust makes more sense. I'm sure the cars are difficult to wash, I'll be the paint looks like nothing but scratches and swirls unless you are very careful.

 

[sethland]

Was the temperature identical? There is a reduciton in production as the temperature increases. Also, sometimes high cirrus clouds can create higher insolation. You may also need a larger sample size, which is going to be hard to find exact days of insolation as the days get longer and sun gets higher in the sky.
On April 13th I got 56.0 kWhs and April 14th I got 55.5 kWhs from a 9kW system. I am at 38.4 Latitude in Northern California and my azimuth, tilt and DC to AC ratio may not correspond to your system but am offering it as a rough benchmark

As identical as you can imagine. See the screenshot for the dates mentioned. I have carefully observed high cirrus clouds (that were absent those days). You can see the effect of cloud cover being more dramatic and would reflect in hourly fluccuations. Look no further than the morning of the 23rd screenshot above. A "pure" smooth waveform is indicative of cloudless conditions.

 

[sethland]

I'll believe it, with the wildfires we've seen that soot build up. But, where about are you that soot is constant?!I'

I'm in San Francisco. Most of the particulates are likely car exhaust, but some of it is dust from other sources. Despite our access to clean ocean breezes, when it's dry, we get a slow buildup as anyone who observes their window or their car parked outside can attest.

 

[Shimmy]

I just got rooftop solar on April 5. Where I live in California, soot is a slow and steady phenomenon.

I remember the joys of black soot from diesel exhaust from my time living in San Francisco. You will likely hit a limit on degradation after a few weeks. What angle are they mounted at?

 

[HarryN]

I'm in San Francisco. Most of the particulates are likely car exhaust, but some of it is dust from other sources. Despite our access to clean ocean breezes, when it's dry, we get a slow buildup as anyone who observes their window or their car parked outside can attest.

Actually most of the particulate here comes from:
- Ocean cargo ships
- Literally blown in by the trade winds from China

Car exhaust is a very small contribution any more.

It is astounding how much particulate comes in on the trade winds. If you look at sattellite photos, you can see this large smog coming off of China and blowing across Japan - and then it follows the winds up and around the ocean currents - down to SF.

 

[Shimmy]

Actually most of the particulate here comes from:
- Ocean cargo ships
- Literally blown in by the trade winds from China

Car exhaust is a very small contribution any more.

It is astounding how much particulate comes in on the trade winds. If you look at sattellite photos, you can see this large smog coming off of China and blowing across Japan - and then it follows the winds up and around the ocean currents - down to SF.

Interesting. It used to be primarily the busses.

 

[sethland]

I remember the joys of black soot from diesel exhaust from my time living in San Francisco. You will likely hit a limit on degradation after a few weeks. What angle are they mounted at?

Installer said 22 or 23 degrees. But I haven't taken my protractor out to measure.

 

[sethland]

Actually most of the particulate here comes from:
- Ocean cargo ships
- Literally blown in by the trade winds from China

Car exhaust is a very small contribution any more.

It is astounding how much particulate comes in on the trade winds. If you look at sattellite photos, you can see this large smog coming off of China and blowing across Japan - and then it follows the winds up and around the ocean currents - down to SF.

Scary if true. I'll take you at your word. When I lived next to the Bay Bridge, I do remember the particulate being a little more black though.

 

[sethland]

As a followup. I'm observing that lengthening days don't necessarily help a solar array at fixed, uniform orientation (South heading 180, 23 degree inclination). This is because the extra morning and evening sun is when it is ENE and WNW (let's say compass headings of 80 degrees and 280 respectively). The sun is high enough to still catch a very acute angle to my panels, but there is a point that it will sink below the plane of my panels (while still hitting my roof). Indirect light has a very low ability to produce electricity. For my 10 panel array, I'm wondering if it'd be advantageous to point 1-2 panels more westerly. Especially since our peak consumption is in the early evening (as well as peak prices).

 

[HarryN]

As a followup. I'm observing that lengthening days don't necessarily help a solar array at fixed, uniform orientation (South heading 180, 23 degree inclination). This is because the extra morning and evening sun is when it is ENE and WNW (let's say compass headings of 80 degrees and 280 respectively). The sun is high enough to still catch a very acute angle to my panels, but there is a point that it will sink below the plane of my panels (while still hitting my roof). Indirect light has a very low ability to produce electricity. For my 10 panel array, I'm wondering if it'd be advantageous to point 1-2 panels more westerly. Especially since our peak consumption is in the early evening (as well as peak prices).

I have a small off grid work shop in the east bay.

What I do is point them roughly 25% early morning, 25% mid day, 50% late afternoon.

The morning and late afternoon panels are literally vertical.

It is much closer to my actual power usage, and as you note - late afternoon power is 2 - 4x the price of the other times.

Actually within SF and that peninsula - mornings are tough. Might have to use something like a solar land poly for those.

__________

Out of curiosity, have you considered to put some water up there so that you don't need to climb on the roof to clean?

We have pretty hard water in the east bay, but SF / Hetch Hetchy water has much lower mineral levels so it "might" work.

 

[sethland]

I have a small off grid work shop in the east bay.

What I do is point them roughly 25% early morning, 25% mid day, 50% late afternoon.

The morning and late afternoon panels are literally vertical.

It is much closer to my actual power usage, and as you note - late afternoon power is 2 - 4x the price of the other times.

Actually within SF and that peninsula - mornings are tough. Might have to use something like a solar land poly for those.

__________

Out of curiosity, have you considered to put some water up there so that you don't need to climb on the roof to clean?

We have pretty hard water in the east bay, but SF / Hetch Hetchy water has much lower mineral levels so it "might" work.

Everything is an optimization calculation. Changing orientation to get a slightly better evening capture is free. I also bought a $7 closet mirror from Target that I'm going to experiment with and has already given me a little boost. I'm sure I could find a robo-window washing system to clean them off every week, but it wouldn't be worth it. Cleaning every 2-3 months manually might be. I am also wondering if I can get a spray (like for a windshield) that makes your panels super slick and helping to prevent the dry soot from accumulating on the surface. Any ideas welcome.

 

[HarryN]

Everything is an optimization calculation. Changing orientation to get a slightly better evening capture is free. I also bought a $7 closet mirror from Target that I'm going to experiment with and has already given me a little boost. I'm sure I could find a robo-window washing system to clean them off every week, but it wouldn't be worth it. Cleaning every 2-3 months manually might be. I am also wondering if I can get a spray (like for a windshield) that makes your panels super slick and helping to prevent the dry soot from accumulating on the surface. Any ideas welcome.

Sounds like an interesting idea. I am interested to hear how things come out - success or not.

From a PGE grid perspective, the bulk of renewable generation looks just like your curves.

The bulk of demand is essentially time shifted, centered on 6 pm when solar production is crashing - so it costs them a fortune to fire up quick start generators to deal with it. Or they pay for large battery banks to time shift it.

In this area - they want access to our air conditioners to turn them off at the hottest part of the day = "demand response". Tough to impose on the family when it is 110 - 115 F outside.

I am too cheap - so I just put as many solar panels as possible to face the sun at peak demand / 6 pm.