Cleaning Solar Panels - Will it make much difference?

[Nifty]

As I posted earlier, we just got solar power on the house.

We have fantastic visibility into how each module is reporting. I can even export second by second output data on each and every module!

Well, I just noticed yesterday that they have a bit of a dusty haze / layer on them (the joys of living on a dirt road).

I've cleaned them 2 times so far but with the significant fluctuations day to day it is hard for me to get an accurate baseline. I figure even if cleaning makes a 5 - 10% difference I don't know if I'd be able to attribute it to cleaning.

Even without the data proof I figured I'll probably still spray them down from time to time to get off the visible layer of dust.

Well, I woke up this morning realizing that it doesnt have to be all or nothing. My plan was to do the following:

1. Export all my data to excel for the past 2 weeks
2. Determine which 4 panels have the closest power output
3. All are equally dirty, so cleaning a controlled set of 2 should help me see if there is any difference.
4. Check the results

If I wanted to get really anal I could fine 6 panels:
2 keep dirty
2 wash once
2 wash weekly

I just did an export of my data, (every 15 minutes) over the past 30 days. I discovered:

Modules A1 and A2 have only a 0.03% difference from a months worth of data!

Modules A7 and A8 have 0.06% difference!

A1 and A7 are both in line with one another and easier to reach, so Ill clean both of them and then clean A1 more frequently.

If I notice an immediate difference between A1 and A2 I may clean all panels except A8 and A2

YAY controlled experiments and data!!!

Any suggestions before I embark? Ill probably clean them in an hour once the sun has been off them for a bit for cooldown.

 

[SKR8PN]

Nifty....we need to find you a real job..........

 

[Nifty]

Come on... this is the kind of stuff that keeps my mind sharp!

 

[xpc]

I've read a 5% reduction as a worst case scenario too. You can do what we did in the north on satellite dishes, get yourself a super soaker squirt gun as they are dual purpose and fill with windshield washing fluid with the rainx additive. It not only washes the surface but treats it so dirt doesn't stick as easy. The better guns have a 30 foot range so you can have some fun with the local wild life too.

We used it for melting snow off the dishes when a slippery iced roof would be too hazardous to climb.

 

[Nifty]

Google's even more data anal than I am. On their non-tilted panels the output DOUBLED overnight when they cleaned them. The tilted ones... not so much.

http://googleblog.blogspot.com/2009/07/should-you-spring-clean-your-solar.html

 

[Nifty]

Ok, I cleaned two of them at 7:20 PST... we'll see if anything happens (honestly, they really weren't all that dirty).

 

[SKR8PN]

Nifty......on your solar install, did you ever figure out a way to keep your solar power switched on and feeding your batteries, when the grid goes down? Reason I am asking, is we have a automatic "transfer switch" wired in for our backup generator. When the power from the grid goes out, the transfer switch starts the generator and only lets it supply power to our box. The power from the generator can't get backfed to the grid. I was wondering if you could use something like that in your solar setup.

 

[Nifty]

We don't get a lot of power outages around here so while the thought of being up during a short or long blackout (ack Armageddon) is cool, I ended up deciding it wasn't worth the cost and hassle.

Mostly the hassle since I'm sure the solar company, PG&E, and the local city codes (permits) wouldn't be too happy about it... especially since it doesn't seem like I can find anybody doing this.

I'll have to do some deeper Googling to see if anybody has attempted to get a grid tied system to function without using batteries. If I had the time and the money I'd be tempted to blaze the trail.

 

[SKR8PN]

Even on a short blackout, it would be nice to be able to use your solar supply to keep your refrigerator/freezer or a furnace going. Our main concerns are the sump pumps during a heavy rain. If we lose those, we lose our finished basement and its contents, including our pantry. That is NOT an option for us.

 

[xpc]

The first thing you will need is a "sunny island inverter", about $4000 or so then another $4000 in batteries, chargers, and cabling. You are right about the poco wanting complete line isolation and may cancel the netmeter contract.

Your current inverter synchronizes with the poco sine wave before turning on to give the juice. A sunny island does not.