Solar Panel Ice

[boB]

but to heat the panel up would you not need reverse flow?

The question is, what do you mean by reverse flow ?

If you mean reverse "polarity",  it is not the case.  The bypass diode will not conduct for snow melting.

boB

[Westbranch]

boB, I will rephrase the question, since I now have no idea as to how a panel can be heated up:

How can a panel be heated to melt snow and ice on the panel, (without any solar insolation)?

Just a Forester lost in the woods...

[boB]

boB, I will rephrase the question, since I now have no idea as to how a panel can be heated up:

How can a panel be heated to melt snow and ice on the panel, (without any solar insolation)?

Just a Forester lost in the woods...

Feed the panel enough voltage and current.  Current times voltage is the amount of Watts that turns into heat.
A few hundred Watts per module is generally possible, but, you can only raise the temperature so much...   If it's too cold out, you may not be able to melt the ice or snow.

You must be careful how much you feed the panels so that aspect must be understood and done properly.

boB

[Brad00]

I have been using a window washing squeege mounted on end of 10 foot piece of plastic electrical conduit. My panels are pole mount and it takes the whole 10 foot to get top modules on rack. Thought of a new idea and wondering if anyone thinks it might work. What about using a leaf blower to blow off the snow? I don,t have one or I would try it. I hate to buy one and find it won,t work. Has anyone else tryed it or want too.    8)solarvic

I always refer SqueegeesWindowCleaning's service but last time them didnt work well, does you know correct way to use your Ettore scrapers?

[terrence35]

I am thinking of adding a solar panel for my fish house this year.Do you want to give any suggestions???

[boB]

but to heat the panel up would you not need reverse flow?

Yes.  The power and energy goes from/to the opposite direction than it normally would if you were charging batteries from solar PV.

The power goes from the low voltage side, through the Classic, up to a higher voltage, and then the power is dissipated in the panels which melts the snow and/or ice  (hopefully)...      Rather than FROM the panels, through the Classic and out to the battery/low voltage side.

boB

[niel]

I am thinking of adding a solar panel for my fish house this year.Do you want to give any suggestions???

ok, i'll bite. what's a fish house?

[Kent0]

boB,

Will the Classic be reporting on how much energy is consumed by the ice melting process? While only enough ice has to be melted to get it to slide off, it does take a lot of energy to melt ice. You've already mentioned that if it is too cold, it won't work. Seems like even on days that it will work, the energy invested may not yield any energy returns. It would be a pity to spend half the day melting snow, possibly get less solar energy than the energy used to melt the snow, only to have more snow the next day. Not to say that it would always be a looser, but some way to evaluate seems pertinent.

[boB]

boB,

Will the Classic be reporting on how much energy is consumed by the ice melting process? While only enough ice has to be melted to get it to slide off, it does take a lot of energy to melt ice. You've already mentioned that if it is too cold, it won't work. Seems like even on days that it will work, the energy invested may not yield any energy returns. It would be a pity to spend half the day melting snow, possibly get less solar energy than the energy used to melt the snow, only to have more snow the next day. Not to say that it would always be a looser, but some way to evaluate seems pertinent.

You're correct, Kent...  However, if a "site"  is running a generator 24/7 and cannot use the PV resource, then there's usually so much energy being wasted anyway by just running the generator  (unless it's maxed out).    If the snow melt was successful, then the generator might be able to be turned off.
That's where the gain is.   If it's going to snow again in another, say, couple of days, then the site has just saved some fuel.  In a case like that, they probably won't gain back the energy from the lost solar by itself...  Just fuel savings.

What da ya think ?

boB

[Kent0]

I'm thinking of the PV array as a black box. Normally we get energy out of it, but not when there is snow on the array. When melting is performed, we are dumping energy into it in hopes that we can get the PV array back into the energy production mode. If the melt uses the equivalent of three days energy production, it possible the next storm will have dumped more snow on the PV array before the energy is regained. This is a procedure that needs to be considered carefully, or the user may be a loser.

There needs to be a way for the user to evaluate the cost/benefit.  Perhaps the Classic could keep track of the energy used in the melt say, -12 kWh, then, as energy is recovered, integrate up to zero again so the user knows when the energy has been recovered.  After getting a feel for how long it takes, a person could think about how long it is until the next storm.

I'm thinking about the generator issue still.  When charging batteries, the last two or three hours the generator is operating at light load.  We normally tell customers to do as many required tasked as possible at that time because it is more efficient to operate loads generator direct than it is to charge batteries then power a load.  Obviously, the generator is more efficient too.  Does it make sense to melt snow at this time?  Not if we are dumping more energy into the melt than is recovered in solar energy.

[boB]

I'm thinking about the generator issue still.  When charging batteries, the last two or three hours the generator is operating at light load.  We normally tell customers to do as many required tasked as possible at that time because it is more efficient to operate loads generator direct than it is to charge batteries then power a load.  Obviously, the generator is more efficient too.  Does it make sense to melt snow at this time?  Not if we are dumping more energy into the melt than is recovered in solar energy.

Sure, we'll run the odometer backwards.  (kW-Hours)  That will be a good thing to do.

Does it make sense to use stored battery energy, is what I think you are asking ?  We just don't know yet.  Maybe some times it will make sense.  I would say it might if the energy required for the temperature rise isn't very much, say just a few degrees, and there isn't a huge pile of ice and/or snow, then that would be ideal.   That would be one scenario.

The other scenario would be when you are running the generator because you have to, like would be the case at a remote repeater site and you don't care if you break even or not.  Like doing the laundry because you have the generator running is the key in that situation.  If the generator is over-sized at all, I believe it even makes sense to use it even in bulk charge. That is assuming there isn't just snow clouds hovering overhead and snow melting was in vain.  That's when we blame the weatherman, right ?  If he/she were right all the time, then she/he wouldn't have to come to work every day.

Melting snow is terribly inefficient. For the 125 Watt Kyocera panel where I melted snow in my front yard, (although it was sitting IN the snow rather than on a pole), it took about 1 kW-Hour of energy. It took about 3 hours or so, so that's about right if it was done while in Absorb charge mode.  Experimentation would definitely be required to get a good feel for this in different installations.
I think you live in a good area (eastern Oregon) to play with this.

BUT !!   Who cares if it's REALLY great in all situations !  It will be fun to play with !  Possibly another "toy" a lot of the time ?  We'll see.

boB

[niel]

i think the decision on the melt and for how long is one for the individual to make. if you wish to chance losing a little to gain back more it will be your choice. how well you judge is up to you.

now as there are various arrays i think to properly gauge the power to be exported to the arrays should include a little calculator of sorts, aka program, so one can judge how much to send to the array. i don't know if it would matter if you have a 12v battery bank being fed from say 72v pv strings or if they are 12v pvs paralleled or other various configurations. i admit i don't know what all it is you have in mind with the power being sent back up to the pvs, but i think you get the gist of what i'm saying as it could be meant as a rough guide on it and some rough guide would be needed. even to the point of cautions and good practices that they don't want to melt 1ft of snow from their pvs if they can give it a head start by brushing the bulk of that snow off first.

[Kent0]

In Eastern Oregon we do get lots of opportunity to play in the snow  The average amount of sun is a little over 2 sun hours for December and January, so the KC125 would have to work almost 4 "average" days to recover the 1 kWh used to melt the snow in your 3-hour test.  Averages aren't necessarily a good gauge - a clear winter day will probably have 2.5 times the sunlight of an "average" day.  There is a lot to be learned about this yet.

[boB]

In Eastern Oregon we do get lots of opportunity to play in the snow  The average amount of sun is a little over 2 sun hours for December and January, so the KC125 would have to work almost 4 "average" days to recover the 1 kWh used to melt the snow in your 3-hour test.  Averages aren't necessarily a good gauge - a clear winter day will probably have 2.5 times the sunlight of an "average" day.  There is a lot to be learned about this yet.

Yes, there certainly is a lot to learn about this !

If you had to run your generator 24/7 because there was an inch of snow covering your modules and you had to run an extra kW-Hour per KC125 to be able to turn off the generator for a few days, would that be worth it for less gen run time and fuel usage ??

boB