Solar panel and heating element to combat condensation ?

sarabande

sarabande

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Another thread on overwinter condensation raises questions.


I have seen on Amazon and ebay some silicon 12v heating pads.

Amazon.co.uk : 12v heating pad

If on a boat not connected to the mains one set up a couple of, say, 100W solar panels orientated SE-ish and SW-ish, and connected them to a number of these pads glued perhaps to the engine or base of an internal locker, so that heat was absorbed and released relatively gradually, could that be of use in helping moisture evaporate and be ducted out of the cabin to the outside ?

Boat cabin is about 12 ft by 9ft by 6ft.

TIA
 
I think you would struggle to get much out of the heating pads from your panels over winter, we have 240 watts on board and over the last week have generated 22 watts in total over the 7 days with yesterday 15 watts for 30 minutes as part of that
 
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I would (have) run a very small dehumidifier on a timer instead. Far more effective. Something like this, run on 12V. Peltier effect. Around here, snow blocks the panels for a few weeks here and there.

That said, the idea of going from solar, to electric, and back to heat sounds very inefficient. I wonder if there is not some direct (greenhouse effect) heating process that would work better. The problem is, if there is cycling of the heat output (not the same thing as temperature cycling) the condensation may actually be worse.

Either ventilate or run a very small dehumidifier.
 
The problem with OP idea is one of getting the max power out of the solar PV into the heating element.
What you need to do is match the solar PV panel internal resistance with the resistance of the heating element. (Assuming full or decent sunlight on panel)
So a 12v heating element might be 12 watts ie 1 amp at 12v. Resistance of 12 ohms. Now a 50 w solar PV produces at 15 volts about 2.5 amps so internal or source resistance is 6 ohms. The heating element will only use half of available power. In this case something like 30 w heating element will have a resistance of 5 and a bit ohms which will more closely match and use all of solar PV power.
So to calculate required resistance of heating pad. Take solar PV wattage divide by 20 gives amps. (or check max PV current on data plate. Divide 15v typical loaded PV volts by current to get a resistance figure. This is the total resistance needed for your heating pad.
Resistance of the heating pad is calculated from rated wattage divided by rated volts. Pads can then be connected in parallel to reduce resistance or in series to increase resistance. Or you could make your own heating element from stainless steel or nichrome wire, light bulbs or even set up a string of 5w resistors.
However all the calculations on solar PV panels are calculated on full sun. Even then in UK summer derate by 20% and in winter perhaps 50 or more %. This is the reason why MPPT (max power point tracking) is used in any serious PV system.
Would it actually raise temp of cabin? probably not but you could try it. ol'will
 
I'd start off by increasing the ventilation, as Thin suggests, maybe solar fans (I've never seen them let alone used them).

My thought is - if you find a way of increasing the temperature in the cabin all you will do is increase the humidity and that humidity will condense somewhere - unless you can remove the humid air. So - first up find a way to increase ventilation.

If the yacht is on a swing mooring its easier as you then know you need to design a ventilation system extracting at the stern.

Jonathan
 
I have seen the orange heating pads for sale direct from China for a few pennies.
Others have pooh poohed the idea (sort of), but if you have solar doing nothing else then fitting the pads and a computer fan to blow the heated wet air out sounds like an experiment worth trying for hardly any money.
If your solar charges batteries then using any excess energy from the solar panels to heat the pads and blow the fans sounds like a good plan. Fitting a device that stops the batteries giving out energy once they drop to a specific voltage seems sensible too . I tried it but the electronic device I bought that stopped my batteries going flat used a lot of electricity and actually flattened the batteries but I may have bought a dodgy device.
I like the idea. I have always been on a swinging mooring.
Dessicant packs that change colour when wet can be bought cheaply too, to add to the heating and fan system.
 
William_H said:
Would it actually raise temp of cabin? probably not but you could try it. ol'will
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It was very sunny in Southern England yesterday, for the first time in what feels like months. With 600w of solar we managed just 77Wh. Just like the Inuit, we will have to wait for the sun to return at the end of March before solar does anything worth recording.
 
sarabande said:
Another thread on overwinter condensation raises questions.


I have seen on Amazon and ebay some silicon 12v heating pads.

Amazon.co.uk : 12v heating pad

If on a boat not connected to the mains one set up a couple of, say, 100W solar panels orientated SE-ish and SW-ish, and connected them to a number of these pads glued perhaps to the engine or base of an internal locker, so that heat was absorbed and released relatively gradually, could that be of use in helping moisture evaporate and be ducted out of the cabin to the outside ?

Boat cabin is about 12 ft by 9ft by 6ft.

TIA
Click to expand...
Why on earth would you do that . . .The Amazon pads are DIY level, rubbish basically...Have a dehumidifier running off a decent power bank ie a jakkery for example....That way you do the job RIGHT FIRST TIME
 
I have a domestic Meaco dehumidifier which has a rated power of 650W.

I can put up 2 or 3 decent PVs at 400W each, and arrange for them to heat e.g. the engine block during the day, which then trickles the heat out overnight.

To use the Meaco, I need mains power. Using a "power bank" (do you mean panels plus an inverter plus batteries ?) means storage and conversion losses in the region of 10 - 20%. Using panels direct to heating pads is much less, virtually zero.

Try reading carefully the OP and subsequent posts and comments before wildly challenging the methodology, and issuing a childish mock-business motto.
 
sarabande said:
I have a domestic Meaco dehumidifier which has a rated power of 650W.

I can put up 2 or 3 decent PVs at 400W each, and arrange for them to heat e.g. the engine block during the day, which then trickles the heat out overnight.

To use the Meaco, I need mains power. Using a "power bank" (do you mean panels plus an inverter plus batteries ?) means storage and conversion losses in the region of 10 - 20%. Using panels direct to heating pads is much less, virtually zero.

Try reading carefully the OP and subsequent posts and comments before wildly challenging the methodology, and issuing a childish mock-business motto.
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Try reading what I said about Amazon DIY pads ,there dangerous and basically not made for the job plus the output would be nowhere as efficient as a dehumidifier .. Oh and please get your facts right regards to the conversion losses on a quality power bank, but then if you were looking at Amazon hand warmer pads to do the job then you were probably basing your pie in the sky efficiency figures on something you had out of a Christmas cracker
 
Sorry I forgot to mention the reason I know this is probably 20yrs as a qualified Electrical Engineer so as you can appreciate it's not really wildly challenging methods ... To be honest I've seen it all regards to Electrical jobs... It's one of the biggest causes of fires on boats that why I always say do it right first time
 
Dellquay13 said:
Solar fans are widely available, cheap so probably rubbish…

20W Solar Panel Powered Fan Mini Ventilator For Greenhouse Pet Dog Chicken House | eBay
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It may interest some - but Solar Vent Fans can be powered by other than Solar in the cowl ...

They work by supplying low voltage charge to a NiMh cell ... usually an AA or C cell size battery ...

In winter - these are pretty useless as sun power is reduced in hours and elevation ... BUT the answer is to parellel an alternative charge source .. a DC to DC power adaptor can be parallel wired in ....
 
My 100W solar panel is was doing nothing to keep aux battery charged when I went to boat a week ago despite bringing it up to 13.7v in early october. On that basis I wont expect much out of it till we launch at easter. So as a power supply for dehumidifiers or heater it would not be much use in the damper parts of the year.

Happily the boat is dryish and we have shore supply available if required in yard, but maintaining power for a 5W anchor light on the moorings and very occasional autobilge pump is not the same as giving regular 60w for drying use
 
oldmanofthehills said:
My 100W solar panel is was doing nothing to keep aux battery charged when I went to boat a week ago despite bringing it up to 13.7v in early october. On that basis I wont expect much out of it till we launch at easter. So as a power supply for dehumidifiers or heater it would not be much use in the damper parts of the year.

Happily the boat is dryish and we have shore supply available if required in yard, but maintaining power for a 5W anchor light on the moorings and very occasional autobilge pump is not the same as giving regular 60w for drying use
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At last !!

Sorry for your results .. but this is something that I have been commenting on too often.

Summer sunny climes - fine ... shitty winter climes - another ball game altogether.

Its why I asked ages ago about wind vs solar ...
 
A couple of boats moored need us both have wind gen and both tell me that they are taking them off as they get so little power not worth the effort and the noise when spinning is greater than you would expect, this is especially true for neighbouring boats.

they also say just because they are spinning dies not mean they are actually generating anything
 
Daverw said:
A couple of boats moored need us both have wind gen and both tell me that they are taking them off as they get so little power not worth the effort and the noise when spinning is greater than you would expect, this is especially true for neighbouring boats.

they also say just because they are spinning dies not mean they are actually generating anything
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Knowing a few installations - I can say that what your 'people' have must be pretty bad then ..

One boat ... HR42 ... pal of mine ... could tell me the wind speed based on the amps his wind was delivering ..
 
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