Cleaning solar panels

[inetdog]

what are your thoughts on a hog hair brush?

Personally, I would say that a hog bristle (usually not thought of as hair....) brush will be firm but not scratching as long as there are no abrasive particles (dirt, dust, or otherwise) under it.
It would not scratch glass by itself but I would be concerned about plastic covered panels.

Any brush can scratch if there is abrasive on the glass but softer bristle brushes are less likely to exert enough localized pressure on the grit to cause scratches.

[Volusiano]

what are your thoughts on a hog hair brush?

For the purpose of having a firm brush so that it doesn't collapse on its weight for solar panel cleaning (or when you do higher than 4 story windows), you'll need to be able to design/control the firmness of the brush. It's easier to do this with a nylon brush because you can control the thickness hence firmness of the bristles. You can't control how firm hog hair is, with it being a natural material.

The other thing is that hog hair brush tends to be very dense, which is desirable in the situation where you want to maximize the agitation efficiency like with soft and flagged trim brushes (the tips are all flagged/frayed into smaller fibers, maximizing the contact area). This will tend to cause the dirt to get trapped in and a potential for it to be redeposited later on. So on solar panels, the brush needs to be "self cleaning", so the density of the brush needs to be very low (beside being firm) to allow water and hence dirt to escape if it's too heavy to lift up the brush to rinse.

[Volusiano]

I like where the operator gets the heavy pole & brush about 10" up, and something gives way, and it smashes down on the panel.

Yeah, even if you have a high end light weight firm carbon fiber pole, the physics of the pole being fairly flat along the solar panels instead of vertical makes it virtually impossible to lift and rinse. The last thing you want is to try to lift it up to rinse only to have it smash down on the panel again. Just get a firm thin brush, leave it on the panels at all time, and maybe have a higher flow of water and spend more time agitating the surface until the water washes all the dirt away.

If you can be real close to the panels (standing on the roof) to lift the brush off easily, then of course rinse away. But if you're at the bottom pushing the pole up at a 20 degree pitch, you can forget about lifting the brush up.

[inetdog]

Since the weight of the water on the brush adds a variable but large weight load, I propose building a "hovercraft" brush which floats above the panel with most of its weight borne by the water pressure under its skirt. Any brushes also under the skirt would have a limited compression, limiting the force they could exert.

[russ]

Since the weight of the water on the brush adds a variable but large weight load, I propose building a "hovercraft" brush which floats above the panel with most of its weight borne by the water pressure under its skirt. Any brushes also under the skirt would have a limited compression, limiting the force they could exert.

Sounds like a job for a specialized drone helicopter!

[Robert1234]

Exactly what wavelength(s) of light do you think are being impeded by each of the cleaning technologies you believe you are superior to?

I'm calling BS on this "special, zero TDS" cleaning method having a significant impact over just regular old standard cleaning methods, so I will repeat my request. Exactly what wavelength(s) of light do you think are being impeded by each of the cleaning technologies you believe you are superior to?

(Heads up... I've got really nice "toys" and am measuring reflectance, transmission of light every day right now on my projects like the attached. Quite easy to look at the transmission through glass panes cleaned a couple different ways.)

Color Trans.jpg

[paulcheung]

What kind water is rain and snow? after you clean it with whatever water you think is good for the panels, then rain water come and wash it again. does that leave and residue?

Lucky thing I have my panels on my flat concrete roof that I can stand right in front or behind or at the side to wipe them clean with cloth or any brush.

[J.P.M.]

I'm calling BS on this "special, zero TDS" cleaning method having a significant impact over just regular old standard cleaning methods, so I will repeat my request. Exactly what wavelength(s) of light do you think are being impeded by each of the cleaning technologies you believe you are superior to?

(Heads up... I've got really nice "toys" and am measuring reflectance, transmission of light every day right now on my projects like the attached. Quite easy to look at the transmission through glass panes cleaned a couple different ways.)

[ATTACH=CONFIG]3863[/ATTACH]

What type of instrument(s) are you using ?

[Ian S]

What kind water is rain and snow? after you clean it with whatever water you think is good for the panels, then rain water come and wash it again. does that leave and residue?

Lucky thing I have my panels on my flat concrete roof that I can stand right in front or behind or at the side to wipe them clean with cloth or any brush.

Rain will pick up contaminants from the atmosphere - dust, pollen, acidic gases, etc. - after it forms and some of these can leave residue when the rain dries on a surface. Obviously, the amount of impurities will vary with location. Still, there will be substantially less mineral contamination than there is in groundwater so I suspect the residues would also be less. I would think that because it is in solid form and cold, snow would pick up less in the way of impurities as it passed through the atmosphere but a quick google didn't reveal any actual analyses to support that beyond the slightly higher pH (lower acid content) of acid snow compared to acid rain.

[JC1]

I'm calling BS on this "special, zero TDS" cleaning method having a significant impact over just regular old standard cleaning methods, so I will repeat my request. Exactly what wavelength(s) of light do you think are being impeded by each of the cleaning technologies you believe you are superior to?

(Heads up... I've got really nice "toys" and am measuring reflectance, transmission of light every day right now on my projects like the attached. Quite easy to look at the transmission through glass panes cleaned a couple different ways.)

[ATTACH=CONFIG]3863[/ATTACH]

Why are you calling BS in zero TDS? Typical water from a spigot will have ~20 PPM (in my area) and much more in other areas. Filtering water to zero TDS will mean it will dry clean because there are no particles left on the surface.

The wave length I am worried about is the one that is needed to make solar panels work.

The glass used on solar panels is different than the glass used for windows so whatever testing you are doing is not very helpful. Unless you are testing multiple solar panels, side by side, with different cleaning methods on each panel with equal exposure to the sun AND tracking the output of each panel independently, you are not getting info useful to this discussion.

[Robert1234]

What type of instrument(s) are you using ?

Used to be a MacBeth color-eye, but we've upgraded equipment recently so I'm not sure it's still GretagMacbeth. I'll look for the exact model as I'm getting ready to head that direction again in just a few moments. I still just call it a color eye Typically use a D65 light source.

We can do transmission, reflection, solids, liquids, gases, etc. I can run both in UV and visible on this unit. Have to go to a really special unit to do IR (but that's not needed on solar panel work as only visible light is used to knock the electrons off the semiconductors to generate current).

[Volusiano]

I'm calling BS on this "special, zero TDS" cleaning method having a significant impact over just regular old standard cleaning methods, so I will repeat my request. Exactly what wavelength(s) of light do you think are being impeded by each of the cleaning technologies you believe you are superior to?

The only reason you want to use the pure water cleaning approach is if you can only clean the panels from afar with a water fed pole because you cannot get close enough to the solar panels enough to allow you to use the traditional cleaning approach which requires to dry it with a squeegee by hand.

Even if you can get up on the roof to be close to the panels, you may still not be able to get to the middle panels to hand squeegee them dry if they're all laid out in a big slab like in my case (I have 44 panels laid out in 4 rows of 11 panels altogether, and the rows have the panels laid out length wise in the up/down direction -> a slab of 20x33 sqft).

The advantage of the water fed pole approach is that you can now reach the panels safely from afar. The catch is that you can't squeegee dry with a water fed pole. So the solution to this is to clean and rinse with pure water so that when the water dries out, no stain/spot of mineral impurities is left behind.

It's no BS. Water fed pole using pure water is taking window cleaning and solar panel cleaning by storm because it's much safer (no ladder most of the times, not walking on roof) and faster than the traditional cleaning approach with a squeegee. You can clean windows that are 5, 6, 7 story high with a water fed pole from the ground with ease.

[russ]

Why are you calling BS in zero TDS? Typical water from a spigot will have ~20 PPM (in my area) and much more in other areas. Filtering water to zero TDS will mean it will dry clean because there are no particles left on the surface.

The wave length I am worried about is the one that is needed to make solar panels work.

The glass used on solar panels is different than the glass used for windows so whatever testing you are doing is not very helpful. Unless you are testing multiple solar panels, side by side, with different cleaning methods on each panel with equal exposure to the sun AND tracking the output of each panel independently, you are not getting info useful to this discussion.

You get zero TDS by filtering only? Never heard of anyone managing that - maybe in the NASA/DARPA/military world but not for civılians - ypu don,t have such a thing.

One wave length only is required for solar?

Who tells you this garbage? Or did you figure it out all by yourself?

[Volusiano]

Typical water from a spigot will have ~20 PPM (in my area) and much more in other areas. Filtering water to zero TDS will mean it will dry clean because there are no particles left on the surface.

You're very lucky that you have 20ppm water in your area. That's very low by the way. Most areas have TDS in the 100-400ppm range. In my area, it's 750ppm!!!

I think with regular window cleaning using water fed pole, sometimes you can get away with TDS as high as 50ppm and still dry spot free if the glass is hydrophilic and the water doesn't bead up too much. In this case, if the RO can deliver 50 TDS, you may not even need the DI resin to take it down further. But solar panels will probably require lower TDS to dry spot free because they're placed more horizontal than vertical, so it's not as easy for the water to cascade down and it's easier for it to bead up on the glass.

[Volusiano]

You get zero TDS by filtering only? Never heard of anyone managing that - maybe in the NASA/DARPA/military world but not for civılians - ypu don,t have such a thing.

Yes, it's possible to get 0 TDS by filtering only. For areas with low enough TDS, using DI resin can get it down to 0ppm TDS. But DI resin is fairly expensive. So in areas with higher TDS, RO is used in the first phase as a lower cost option to take the TDS reading down low enough (RO membranes usually has 90+% rejection ratio), then that gets fed into a DI resin cartridge to take it down to 0ppm TDS.

Sometimes if there's silicates in the water, neither the RO nor the DI will be able to filter out silicates (they're not ionically charged so DI can't trap non-ionic particles), then you can't always get down to 0ppm TDS. But if there's no silicates, it's possible to get to 0 TDS. I actually just bought an RO/DI filtering system recently and last weekend, I was able to get 0 TDS out of the system from tap source as high as 750ppm. In the water-fed-pole window cleaning world, 0ppm TDS happens every day.