Cleaning Solar Panels

Never. We let the rain clean them (or melting snow).
I would check your manual, but I would think many types of soap or cleaners could leave a residue which would lead to lower power generation.
Now, our oldest panels are about 20 months old, so long term we may need to do something, but they were just inspected (when we added some more last month, and the panels had no dust or dirt on them.

 

Cody,

Panels degrade but not that fast! Most panels have a warranty that guarantees 80% of original rated output at 25 years.

How much of a dip have you seen? Solar input variability is probably what you're measuring, not panel degradation.

Where is Pleasanton? I think I've asked you this before, but it slips me mind.

 

1) Am I harming my panels by using soapy water, sponge/terry head?
No. You are only touching the glass surface and the aluminum frame. You can do anything to solar panels that you can do to windows.

2) How big a concern is hard water build up on the panels?
Probably a slightly bigger concern than the dust that might build up on them. The dust will wash off with precipitation. The hard water spots won't. Neither will effect the output very much, however.

3) Is every other month not frequent enough? (my manual says once or twice a year...no way I'd let them go that long). I need to balance the cleaning frequency with the cost of cleaning (soap, di cartridges).
Every other month is about 6x more often than I clean mine here in Davis.

4) It seems like I'm not getting the production that I was getting last year when the panels were new, is there a drop-off in production as panels age? I really won't know for sure until next August and we get to see what the production numbers are.
PV panels fade with time, yes. But you won't notice a drop in production from one year to the next. Maybe comparing year five to year one, but not year to year. Don't sweat it. PV is one of those "almost zero maintenance" devices. Enjoy it. Worry less.

 

just saw an episode of "living with ed" where bill Neigh invented a brush/mop to either dry clean or wash the panels.

 

I have had my 7.5kW system online for since Aug 04, and I have to wash my system once a week. Simple rinse, lottsa dusty dirt!! I have a Black and Decker electric 10 foot long power scrubber with a soft rotary brush that every other month I use instead of a hosing off and that breaks up the sulphur drops and birdcrap that a simple rinse misses.

Every time I clean I check the computer monitor system and I regain between 600 - 800 watts back. loosing that much power due to dirt is unacceptable to me and its worth the minor effort to do this.

I plumbed 1/2 copper along side of the conduit on the roof that goes to each bank of panels and have a hose bib with a quick disconnect at each bank of panels, I have 5 seperate locations on my roof (flat) that the panels are located. I use a 10 ft hose and can acomplish the cleaning in about 20 min every Sat morning. The power scrubbing takes about 40 minutes.

Still very much worth the effort since I still pay approx $300.00 a YEAR for my power!!

73 de Pat KK6PD

 

Wow. 600-800 W after a week's exposure? Madness...

 

Sadly, not madness, just a simple fact of life in my neighborhood. too many leaf blowers, Freeway's, neighbors dirt driveway.
Still, sweat equity is good for the soul, as well as the wallet!!!

Thank god I have a flat roof and was able to plumb the copper back when a 10 ft stick was 7.99 at Home Depot!!!!!! Now its around $30 a stick

73 de Pat KK6PD

 

Never,, or almost never.

A couple of things to remember, both of which may be counterintuitive.

First, PV panel output goes down with increased panel temperature. Output goes up, significantly with DECREASE in panel temperature. If memory serves, most panels are rated with standard test conditions (stc) of 77f. My panels put out more than their rated capacity at -30f, but only about 90% at 90f. Also haze, humidity has a very detrimental effect. Cold weather and reflection off of snow can up my output to ~125-150% on rare occasions.

Second, ANY partial shading on a panel string that is wired in series will reduce the output of that string to almost zero. Most large arrays are made up of series strings, wired into larger parallel strings. For a test, look at your output meter on a good sunny day, then shade one panel in the string with just a broom handle, and watch the meter. You will be amazed at the drop (assuming your panels are wired in series). Even a simple telephone wire can have a huge effect on output.

Some of the increase that KK6PD may be seeing is the cooling effect of washing them, in addition to the clearing effect.

You certainly aren't going to hurt them by washing them, although I would avoid high pressure power was on the panel edges, or harsh chemicals. The top of the panel is nothing but standard tempered glass, just like a patio door.

Icarus

 

Absolutely correct, I have a computer monitoring the 3 inverters 24/7,and if temp were playing a large factor as I cleaned, I would notice a large change from winter to summer. The net cleaning gain is always about 750. Winter or Summer. My best output is right after a shower and the air is washed clean and that sun is blazing through a hole in the clouds, at that point I get every watt of that 7.5 kW I paid for, other wise with haze and smog about 6.5 kW is normal for me During the Los Angeles summers I do however always see a System derating due to High Temps on the roof!

Again Absolutely correct, I have a Antenna Tower that at various times during the year shades a bit of the panel system, it does knock about 500 watts off that string and inverter!

Yes there may be a bit, especially in summer, but I usually clean early in AM when the sun has had a couple of hours to turn the system on and stabilize the system, and the heat of the day is just thinking about starting to build, usually around 10am every Sat . I have the light hose off routine down to about 20 min tops!!
So the amount of Sun azimuth difference is small, and what clouds!! This is L.A.

Simple garden hose at 65 PSI and a good nozzle is usually all I need to blast even the most nasty Bird Poop off the panels. I use the scrubber and some dish soap to clean every 8th weekend! It gets the tuff stuff off!

My panels are not glass but a 1/4" thick Lexan, or some other strong plastic covering! Not exactly sure which one, but I am sure its not glass.

Icarus, Good points all. OK now the rest of you, GO SOLAR. even a 2.5 kW system would make a huge diff, but take up a small footprint!!

73 de Pat KK6PD

 

That's precisely what we're planning to do. We've committed to staying in our house long term so now I'm looking at my options. I'm chuffed that the $2000 cap on res installs was removed in the "bailout" bill. Silly place for it, but I'll take it. The first thing we need to do is replace our pig 20 year old refrigerator. That thing uses loads of energy. Once we've done that, a 2.5 kW system would probably cover 80% of our energy needs. Maybe more (I haven't done the math yet).

 

Tripp -

My advice is to shoot low on the system (2.5 sounds great!) and then chip away at everything with the goal of getting to parity with the annual output.

 

To more points,, on important, the other only interesting.

The interesting on first. KK6PD mentions his highest output "while the sun is burning a hole in the clouds". The highest output possible is from what we call "edge of cloud" events. The combination of reflection from the clouds can and does have a dramatic effect (very short however) on output. I get close to 150% of output in winter with reflection off the snow, coupled with edge of cloud event. Way cool to watch the meter pin!

The important point. While I strongly encourage PV solar, it should only come after a exhaustive (VERY EXHAUSTIVE!) plan to reduce demand on a personal level. Conservation is your cheapest energy dollar, and that every dollar spent on conservation reduces the cost of PV by about ten. Spend a lot of time looking at your loads, and do everything you can to reduce them. Simple things first, expensive ones next. Even something as simple as unplugging the satellite receiver saves ~30 watts. Take that 30 watts over an 18 hour day, times 2 receivers in the house and you reduce the need for ~200 watts of capacity! Do this for everything in the house from CFL's to power bricks, to phantom loads and most people can find hundreds of watts to turn off.

Icarus

 

I will 2nd what Icarus said, decrease the load and demand, then buy to pay the remaining bill! Its amazing to see what you can do. What I would really like to see is the elimination of a majority of "Power Vampires", you know that VCR thats always draws power, but is in the "Stand-by Mode" the TV that has to be plugged in to retain channel memory, those little buggers add up quickly in kWh consumed. Manufacturers need to make units with non volatile RAM to retain system memory!. Off should be OFF!!! NO CURRENT DRAW! What a waste of power!. With everything off in the house, lights etc TV's it takes 1.1 kW to make my meter stand dead still. I call that the "Station Keeping Point" The power it takes to run the power vampires, Refrigerator, and the other items that really have to be powered on. I figure that 1/3 third of that 1.1 kW Station Keeping wattage I mentioned is really necessary, the Refidge, Water bed, Aquarium, Clocks, Phones, however a line powered phone would really be the ticket! Let Telco pay for the power!. If I could reclaim the other 2.3'rds of the "Vampires consumption, Which are all the other Wall Warts, VCR's TV's Things that don't need to be on when they are supposed to be "OFF" I would be saving a lot more cash!! And thats always a good thing!

But by all means put in a system!!!

73 de Pat KK6PD

 

We use power strips to kill the ghost loads. We used 264 kWh in October and ~95 kWh were the fridge. I'm thinking that I can easily cut 50 kWh/mo off our consumption by replacing that one applicance. We've got CFLs throughout the house and we do a pretty good job of keeping the lights off when not in use. We don't run our computers all day. The next big one is the dryer. Perhaps we'll break out the clothsline next spring.

 

KK6PD,

Let the telco pay the power,,, use a corded phone!

On the other hand, I use voip so I pay it anyway.

I power down my house to almost nothing every night. All IT hardware is on outlet strips, scanner, printer etc. The modem, router and voip box stay lit for the phone. The satellite receivers go off, even though they take a few minutes to reboot. The lap tops un-plug, cell phone charges unplug. The only thing left lit is the fridge, freezer, solar water heat controller, demand water heat controller and gas space heater digital controls. (the last 3 draw ~5 watts together!)

In our remote cabin, where we live ~6 months a year, we use ~500 watt/hours/day, all from solar. This is with a Propane fridge, and no TV. We do run the shop on a generator as needed using perhaps 1 gallon of gasoline per week. Wood heat, propane demand hot water, wood fired hot tub!

At the "real house" we use ~10kwh/day. This includes the 24/7 superinsulated hot tub, two shops, and the occasional dryer. Wood heat, solar water/demand gas heat, propane space heat.

We haven't invested in PV because the payback in NW Washington is very hard to justify. What with paying $.09kwh for "green power" from Puget Power, long amounts of grey, the calculated payback exceeds the life expectancy of the system. If we were almost anywhere else in N. America I would do it in a heartbeat!

Icarus

 

Here in CO we get a $3.50/W rebate (used to be $4.50, but Xcel chopped a dollar off). So between that and the 30% fed credit we can save a lot. What's the going rate per watt (installed) these days. I thought I heard $7-8/W. It used to be $9/W if I recall. Icarus, does that sound about right?

 

Tripp,

I always use $10watt as a nice round number. I think you can get that down to under $8 if you try, and considerably less if you are willing to shop and do a bunch of your work yourself. This is for grid tie systems. I just do off grid systems and you can double these numbers depending on your battery configuration. When it gets right down to it, the grid is a bargain, as well as being a great "battery" to dump you excess PV into, and then to draw from.

For those that are interested, the following link takes you to a great site, filled with very sharp, learned folks who have forgotten more about Pv than most of us will know! Solar Electric Discussion Forum - Powered by vBulletin

Icarus

 

Icarus, Dude I like your style. You get it!!! I discovered the same things as I continue to evolve usage wise! Our next improvement is in 2 weeks when we get a energy star 95% efficient furnace that takes half the gas and 1/5 the AC to run. The new compressor has equal savings stats with a SEER of 14.
Ka-Ching more money I wont have to pay for power or gas!!!

KK6PD