How do you deal with freezing rain, or crusty snow that can't be brushed off?

[FilterGuy]

C or F ?

-30

-40 C is the same as -40F. -30C is not too different than -30F and Both are way below cold!

 

[Supervstech]

-40 C is the same as -40F. -30C is not too different than -30F and Both are way below cold!

Cold is true... but -20.4F (-30C) is significantly warmer than -30F...
Truly, anything below -10F is crazy cold...

Throw wind and precipitation in and forget it.

 

[Red Squirrel]

C in my case.

 

[FilterGuy]

Funny, I did the calculation from the other way: -30F = -34.44C . Either way, when you spit it may bounce!

 

[JeepHammer]

I don't care which scale, ice is still frozen down like concrete and takes a jack-hammer to get off!

AND...
I'm an old white guy, some of the parts that sag at this age I DO NOT want frozen off!

 

[Barb]

I do not know anything about living in those kind of conditions but couldnt you spray them with the windshield washer stuff that has anti freze in it?
or some biodegradable antifreeze mixed with water. Just thinking out loud

Spray or pour on a mixture of 2 parts rubbing alcohol and 1 part water. It works on icy windshields to my firsthand knowledge.

 

[FilterGuy]

I won't try to sell this as a home game, your batteries have to be fairly closely matched with your panels,
But I bypass the charge controller blocking diodes and allow batteries to heat the panels and the crap will come off fairly easily.
The panels become a 'Load' and warm up, you only have to get above freezing to get a layer of water between panels & ice and the ice comes off fairly easily, sometimes just slides off if the angle is vertical enough.

An interesting solution!!

So here is a question: Can a single panel handle a sustained short circuit? If so, could a short circuit help speed up the melt?
Granted, if there is no current being generated because of too much snow, nothing would happen. However, if there is a little current, it seems that it would heat up the panel and accelerate the melt.

Even if they can't sustain a short, if there is a load on them and they are creating current, it seems that the current would help warm up the panel. Correct?? If so, then when your battery is full, finding an alternate 'dump' for the power would help keep the panels de-iced.

 

[JeepHammer]

An interesting solution!!

So here is a question: Can a single panel handle a sustained short circuit? If so, could a short circuit help speed up the melt?
Granted, if there is no current being generated because of too much snow, nothing would happen. However, if there is a little current, it seems that it would heat up the panel and accelerate the melt.

Even if they can't sustain a short, if there is a load on them and they are creating current, it seems that the current would help warm up the panel. Correct?? If so, then when your battery is full, finding an alternate 'dump' for the power would help keep the panels de-iced.

Depends on how well balanced the system is, but keep in mind without blocking diodes the panels will suck the batteries dry.
All I'm doing is bypassing the blocking diodes in the charge controller.

If you are way over paneled less chance of doing harm, energy spread out over larger surface.
A resistor would solve the issue if you were over battery and under paneled.

3.12 BTU to the Watt, doesn't take long to melt the worst ice loose.
I'm sure some people won't be able to do the math, others will think it's too 'Dangerous', others won't want to risk panels, like I said, I can't sell it as a home game but I do it myself and have for nearly 20 years.

*IF* you decide to try it,
You might want to try a NAPA/ECHLIN p/n HC6144 Rheostat (about $20) and one of those $5 volt/amp meters off eBay so you know what your sending to any given panel/panel string.
The Rheostat is even marked 'Heat' and has an open circuit (off) setting.



Once you figure out what it takes to get the ice melted loose in about 10 minutes, check resistance with a multimeter and install resistors, or just mark the dial face so you don't crank it up too far.

I told you guys I wasn't wired the same as everybody else...

 

[TheDroidsYouAreLookingFor]

Simple solution is to orient the panels to vertical or a few degrees negitive while still facing the sun. Reflection from snow and super low temps should mean they almost produce the same amount if not more if the sun is actually out! Common thing for high altitude cabins here that get FEET of snow that lasts until Feb-March. It might get some caked on snow or ice but it falls right off after it warms at all since its vertical. Panels under snow get nearly nothing so you win without the work.

 

[JeepHammer]

Simple solution is to orient the panels to vertical or a few degrees negitive while still facing the sun. Reflection from snow and super low temps should mean they almost produce the same amount if not more if the sun is actually out! Common thing for high altitude cabins here that get FEET of snow that lasts until Feb-March. It might get some caked on snow or ice but it falls right off after it warms at all since its vertical. Panels under snow get nearly nothing so you win without the work.

I run a business off my panels, up LONG before the sun in winter, and have to have things ready to produce when the sun FINALLY makes an appearance so we can continue to work.

I *Think* the next round of upgrades for the post & pipe sun tracking mounts will have more rotation.
Now they rotate east/west about 90-100°, but it wouldn't be that hard to do about 180° so they can be vertical in snow...

 

[Red Squirrel]

Depends on how well balanced the system is, but keep in mind without blocking diodes the panels will suck the batteries dry.
All I'm doing is bypassing the blocking diodes in the charge controller.

So how many volts are you sending to the panels? I might experiment with that. Like say, two 12v nominal 100w panels in series (so 24v nominal at 200w), what would you set the voltage to when sending to that? I imagine it's the current that matters but I presume there is a max voltage too. I could build a boost converter that measures current and then just slowly ramps up the voltage until it gets to the desired current. I'm assuming anything under the panel's rated wattage is safe? (ex: whatever volts you're sending, times the amps it's drawing).

With some relays I could setup a switch that disconnects the charge controller then connects the power supply straight to the panels. I would of course have to figure out how long I need to have it connected for, and size my battery bank accordingly. The whole thing could essentially be automated where if I see ice on the panels I hit a button and it runs for a couple hours or whatever time it takes then I come back and sweep the rest off. Could even put temp sensors on the panels and it tapers down when it reaches a certain temp then holds it for a while.

But yeah I think easiest is to just see if I can set the panels up to be vertical. Stuff may still stick, but perhaps not as much. could try the silicone or other chemical coatings suggested too.

 

[FilterGuy]

@JeepHammer
Could you provide a diagram of the set-up?

 

[JeepHammer]

Just a bypass from battery power (positive battery connection), through the rheostat, switch or resistor, and to the panel positive terminal of the charge controller.

If you have external blocking diodes (Isolated/Combiner Boxes) to the panel side of those diodes.
You simply jump batteries to panels, the panels NOT producing are the load, and current flows 'Backwards' to battery negative, heating the panels in the process.

And AGAIN, I'm NOT trying to sell this as a 'Home Game', if you don't understand the Volts/Amps your panels are capable of handling, or if you don't understand the function of Blocking Diodes, DO NOT attempt this.
Batteries contain Several Hours of full sunlight production power, and CAN over power the panels, cause damage.

==============

Diodes used for blocking first, and they are found in your charge controller,
OR, if you have ISOLATION blocks in your panel strings.
*MOST* small systems DO NOT have isolators in the panel strings.

Diodes used for 'Bypass' in panels ARE NOT blocking Diodes,
They are to bypass current flow around shaded or damaged CELLS/Cell Strings.
Anyone that tells you the diodes IN PANELS are Blocking Diodes doesn't understand what they are for or how they are connected.



When production is backed up, Voc shoots to the moon, and resistance heating in the damaged or shaded cells can be overcome by backup.
Bypass diodes simply give a path for that energy to BYPASS the effected areas.



How Bypass Diodes installed in modern panels are actually wired, and what they actually look like.



With Solar Cells Strings 'Center Tapped', there is a reason the Bypass Diodes are mounted in the center of the panel...



Since these diodes are INACTIVE when there isn't something wrong with the cells/cell strings,
AND since there is direct connection around the diodes when current flows the other direction (Backwards of Intended Travel Path)
Bypass diodes are invisible to REVERSION in electrical current from the battery.

==================================================

DIODES USED FOR BLOCKING...
Same component (Diode) but used in a different position for different application,
And the small system charge controllers, there is a set built into the charge controllers first thing when Positive Voc hits the panel input terminal...

If you have larger strings that are combined, depending on how those panels are wired, they MAY have blocking diodes external the charge controller.
If you didn't add them they aren't there...



Since the panels are quite capable of sucking your battery dry at night, one of the things a charge controller does is stop the panels from sucking your battery dry,
In this SIMPLE example, there is no charge controller so I can show how this happens, and how to stop it.

While some people call this 'Reverse Polarity', nothing 'Reverses Polarity',
In full production (Sunny) the panel has higher than battery voltage, the voltage flows the lesser (Called Voltage Differential).
Without the panel producing, it's no longer a 'Source', so now it becomes a 'Load'.
With higher than battery voltage, the Positive finds a Negative Path, and that's through the conductive traces in the panel.

With a Diode in the right position, it simply stops, or BLOCKS the reversion, but allows panel to feed battery in sunlight.
A Diode is an electrical 'One Way Valve'.



------------------------------------------------------------

With No Isolation Diodes in the system, I simply Jump the charge controller terminals with a Rheostat.



The Rheostat allows me to pass only the current from batteries needed to melt a layer of ice next to the panel.
I crank up a little each time they are iced over so they melt off in about 10-15 minutes and mark the Rheostat.

*IF* production starts happening, the Rheostat limits the panel production to batteries so batteries don't get full voltage potential.
The charge controller is often less resistance than the Rheostat, so most of the current will take that path.
You MUST remember to turn the Rheostat OFF! And never use it in full sunlight production.
A safety switch in the circuit would make using it a 2 (easy) step process,
And a mechanical timer would automatically limit the time it was bypassing the charge controller.



,

 

[FilterGuy]

Just a bypass from battery power (positive battery connection), through the rheostat, switch or resistor, and to the panel positive terminal of the charge controller.

If you have external blocking diodes (Isolated/Combiner Boxes) to the panel side of those diodes.
You simply jump batteries to panels, the panels NOT producing are the load, and current flows 'Backwards' to battery negative, heating the panels in the process.

And AGAIN, I'm NOT trying to sell this as a 'Home Game', if you don't understand the Volts/Amps your panels are capable of handling, or if you don't understand the function of Blocking Diodes, DO NOT attempt this.
Batteries contain Several Hours of full sunlight production power, and CAN over power the panels, cause damage.

==============

Diodes used for blocking first, and they are found in your charge controller,
OR, if you have ISOLATION blocks in your panel strings.
*MOST* small systems DO NOT have isolators in the panel strings.

Diodes used for 'Bypass' in panels ARE NOT blocking Diodes,
They are to bypass current flow around shaded or damaged CELLS/Cell Strings.
Anyone that tells you the diodes IN PANELS are Blocking Diodes doesn't understand what they are for or how they are connected.

View attachment 4474

When production is backed up, Voc shoots to the moon, and resistance heating in the damaged or shaded cells can be overcome by backup.
Bypass diodes simply give a path for that energy to BYPASS the effected areas.

View attachment 4475

How Bypass Diodes installed in modern panels are actually wired, and what they actually look like.

View attachment 4476

With Solar Cells Strings 'Center Tapped', there is a reason the Bypass Diodes are mounted in the center of the panel...

View attachment 4477

Since these diodes are INACTIVE when there isn't something wrong with the cells/cell strings,
AND since there is direct connection around the diodes when current flows the other direction (Backwards of Intended Travel Path)
Bypass diodes are invisible to REVERSION in electrical current from the battery.

==================================================

DIODES USED FOR BLOCKING...
Same component (Diode) but used in a different position for different application,
And the small system charge controllers, there is a set built into the charge controllers first thing when Positive Voc hits the panel input terminal...

If you have larger strings that are combined, depending on how those panels are wired, they MAY have blocking diodes external the charge controller.
If you didn't add them they aren't there...

View attachment 4473

Since the panels are quite capable of sucking your battery dry at night, one of the things a charge controller does is stop the panels from sucking your battery dry,
In this SIMPLE example, there is no charge controller so I can show how this happens, and how to stop it.

While some people call this 'Reverse Polarity', nothing 'Reverses Polarity',
In full production (Sunny) the panel has higher than battery voltage, the voltage flows the lesser (Called Voltage Differential).
Without the panel producing, it's no longer a 'Source', so now it becomes a 'Load'.
With higher than battery voltage, the Positive finds a Negative Path, and that's through the conductive traces in the panel.

With a Diode in the right position, it simply stops, or BLOCKS the reversion, but allows panel to feed battery in sunlight.
A Diode is an electrical 'One Way Valve'.

View attachment 4478

------------------------------------------------------------

With No Isolation Diodes in the system, I simply Jump the charge controller terminals with a Rheostat.

View attachment 4482

The Rheostat allows me to pass only the current from batteries needed to melt a layer of ice next to the panel.
I crank up a little each time they are iced over so they melt off in about 10-15 minutes and mark the Rheostat.

*IF* production starts happening, the Rheostat limits the panel production to batteries so batteries don't get full voltage potential.
The charge controller is often less resistance than the Rheostat, so most of the current will take that path.
You MUST remember to turn the Rheostat OFF! And never use it in full sunlight production.
A safety switch in the circuit would make using it a 2 (easy) step process,
And a mechanical timer would automatically limit the time it was bypassing the charge controller.

View attachment 4483

,

OK that makes sense.


What you are doing is forward biasing the diode component of the equivalent circuit and that is generating the heat on the Rs portion of the equivalent circuit. Cool! (pun intended). Rsh is going to be pretty large so it probably does not contribute much to the heating.

I don't know how much current the cell can handle but 1) it is large so there is a lot of silicon to dissipate the heat and 2) by definition, it is starting out very cold when this is happening. My guess is that current can be quite high..... probably as high as the short circuit rating.... maybe higher.

Have you ever measured the current you are driving when you do this?

 

[JeepHammer]

So how many volts are you sending to the panels? I might experiment with that. Like say, two 12v nominal 100w panels in series (so 24v nominal at 200w), what would you set the voltage to when sending to that? I imagine it's the current that matters but I presume there is a max voltage too. I could build a boost converter that measures current and then just slowly ramps up the voltage until it gets to the desired current. I'm assuming anything under the panel's rated wattage is safe? (ex: whatever volts you're sending, times the amps it's drawing).

With some relays I could setup a switch that disconnects the charge controller then connects the power supply straight to the panels. I would of course have to figure out how long I need to have it connected for, and size my battery bank accordingly. The whole thing could essentially be automated where if I see ice on the panels I hit a button and it runs for a couple hours or whatever time it takes then I come back and sweep the rest off. Could even put temp sensors on the panels and it tapers down when it reaches a certain temp then holds it for a while.

But yeah I think easiest is to just see if I can set the panels up to be vertical. Stuff may still stick, but perhaps not as much. could try the silicone or other chemical coatings suggested too.

Your Panels will NEVER be rated less voltage than your batteries.
2ea. 12 volts @ 24 volts to controller, with 12 or 24 volt battery, will still take the Vmp.
The size of the string will determine if the small Rheostat does the job or not.
I've not see a 12 Volt string that it won't work on, and unless it's just an Amp stupid Parallel string (Low resistance), it will do 24 volts just fine off a 12 Volt battery string.

The idea is to have the strings as resistance, Resistance makes heat, panels make a layer of water between themselves and ice.
I'm not talking about trying to heat a SAUNA with panels!
I'm turning Watts (Vmp) into Heat (BTU) at a rate of 3.12 BTU for every Watt.
And ONLY when the snow is frozen in place and normal daylight can't reach cells so they produce their own heat to melt things the rest of the way off...

The panels are only about 20% efficient at best,
Where do you think the other 80% if sun hitting them goes? HEAT!
Either light frequency shift heating the panel directly, or electrical resistance to producing current in the first place.
When no or little light gets to the cells, neither happens, and reversion is simply making the panels do what they normally do, turn energy into mostly heat...

A 100 Watt panel will (almost ironically), absorb 100 Watts of current from the Batteries without damage,
AND, it will Produce 312 BTUs of Heat doing so.

 

[TheDroidsYouAreLookingFor]

Sounds like it would work except that a rheostat deals with current like really inexpensive and inefficient dimmers or motor controls and a potentiometer deals with voltage for example for use in volume control knobs. Not sure which one would work better in this situation but voltage could still come through if it is usong a rheostat.

 

[JeepHammer]

Have you ever measured the current you are driving when you do this?

Not really, other than to watch the amp gauge to make sure I'm not moving enough amps to exceed what the panels normally produce.
Every panel, charge controller, battery string has a meter, volts/watts/amps MOVING.
The voltage will always be limited to what the battery can produce, and it's considerably less than the panels can handle, some panels can handle 1,000 volts, so no issue at all in my experience.
By controlling Amp flow I can regulate under what the panels can handle in full production when I really crank up the current.

Like I said, 'Sneak Up' the current so the panels melt off in a reasonable amount of time, if you want to keep current lower, just increase time for the conversion from current to heat to happen...

 

[Red Squirrel]

So if I take the + and - lead from the array, and connect it straight to the 12v battery (neg to neg, pos to pos), it will be safe for the panel, and it will turn the panels into a heater? If it matters, the way my setup is, I have two sets of 2x100w panels in parallel and those sets are in in series. So 400w at 24v nominal. (I get closer to like 44v out). I did this so the controller has a higher voltage to work from as it's overcast here most of the year. For now before I setup something better I could look at doing this so I can at least get the panels going again. If this works then what I may do is setup some contactors so I can essentially automate that switching. Could add a temp sensor on the panels too so I can regulate the switching. That combined with tilting them better might work.

 

[FilterGuy]

I am warming up to this idea. (sorry, I could not resist the pun).

An interesting side point to this is that in normal operation, they are generating heat when they are producing current to charge the battery.

Almost all charge controllers stop the current once the batteries are full. If a way to keep the current flowing through a dump load is implimented it will allow the panel to stay warmer.

 

[JeepHammer]

Sounds like it would work except that a rheostat deals with current like really inexpensive and inefficient dimmers or motor controls and a potentiometer deals with voltage for example for use in volume control knobs. Not sure which one would work better in this situation but voltage could still come through if it is usong a rheostat.

OK...
But how *EXACTLY* is BATTERY Voltage going to exceed what the panel strings can produce?
Panels produce ABOVE BATTERY VOLTAGE to charge the batteries in the first place?

How *EXACTLY* is Battery Amperage going to exceed what panels can handle with limiting resistance in the line?

*IF* you believe you will damage your system, Or you can't figure it out, then simply DON'T DO IT.

I'm not interested in another thread like what happened with fuses arcing over and no one could understand differential...
If you don't understand the principal, DON'T DO IT.