Solar
- Thread starter stuart-t6
- Start date
In a word, "Yes".
The manufacturer almost certainly measures the power output when the sun is at right angles to the panel. The power generated by the panel decreases as the light source moves away from this ideal position and is zero when the light shines in from the edge of the panel. At the moment (12 November), the highest elevation the sun reaches is about 20 deg. Assuming that your panel is fitted flat on the roof of your van, the output power then will only be 35% of its nominal rating and clouds will further reduce the power generated.
I hope that I have not made any mistakes. If in doubt, please check. I used the NOAA Solar Calculator [1] to find the maximum solar elevation for London (20.72 deg) on the 12 November and hence the cosine of the solar zenith angle (0.3539).
[1] NOAA Solar Position Calculator
The manufacturer almost certainly measures the power output when the sun is at right angles to the panel. The power generated by the panel decreases as the light source moves away from this ideal position and is zero when the light shines in from the edge of the panel. At the moment (12 November), the highest elevation the sun reaches is about 20 deg. Assuming that your panel is fitted flat on the roof of your van, the output power then will only be 35% of its nominal rating and clouds will further reduce the power generated.
I hope that I have not made any mistakes. If in doubt, please check. I used the NOAA Solar Calculator [1] to find the maximum solar elevation for London (20.72 deg) on the 12 November and hence the cosine of the solar zenith angle (0.3539).
[1] NOAA Solar Position Calculator
Prior to camping this weekend our van had been sat on the drive for 3 weeks without the engine being started or being plugged in to the mains. During this time we have had the fridge running all the time, via our 75ah leisure battery, without problem. So, whilst I can’t say if your 10w yesterday is good or bad from a 100w panel, I can say that the weather over the last 3 weeks has provided sufficient solar via my 100w panel to keep my fridge (Waeco crx65) running without problem.
Thank you. This is just the sort of observation that stuart-t6 and I are glad that you've shared because it is difficult to work out what will happen in practice if one only has the manufacturer's specification [1]. Although it is expected to draw (on average) 12V x 1.6A = 19.2W at 25°C, I doubt whether the temperature in the van has reached this in the last three weeks even when the sun has been shining. At night the temp will probably have dropped below 10°C, giving the compressor very little work to do. As you see, too many unknowns to make a confident guess.
[1] From: Waeco Coolmatic CRX 65 Caravan and Campervan Fridge
Current Consumption (12 volts DC):
1.6 Ah/h at +25°C ambient temperature,
1.9 Ah/h at +32°C ambient temperature,
both at +5°C interior temperature and -18°C in the freezer compartment
[1] From: Waeco Coolmatic CRX 65 Caravan and Campervan Fridge
Current Consumption (12 volts DC):
1.6 Ah/h at +25°C ambient temperature,
1.9 Ah/h at +32°C ambient temperature,
both at +5°C interior temperature and -18°C in the freezer compartment
Totally agree, lots of variables to consider and I know what you are saying about ambient temperature having a massive affect on how hard the fridge has to work (when the temperature overnight gets much below 8c the ice box defrosts suggesting that the compressor has not been running overnight). The flip side of this is that I had similar periods of running the fridge over the summer.
Ultimately the solar panel is doing what I wanted and providing the ability to keep the fridge running 24/7 year round and enables me to run off grid with addition of lighting and heater for a few days when required.
All I have to monitor battery state is a simple red/amber/green dial together with a battery charge state indicator on the charge controller; over the last 3 weeks I have not seen either go out of the green and for most of the time the charge controller is flashing suggesting fully charged.
Also worth saying that our drive faces North East so the solar panel is in shade of the house from around noon at the moment.
For info: Panel is a 100w PV Logic flexible and charge controller is standard Solar Technology one:- 100 Watt Panel Kit
Ultimately the solar panel is doing what I wanted and providing the ability to keep the fridge running 24/7 year round and enables me to run off grid with addition of lighting and heater for a few days when required.
All I have to monitor battery state is a simple red/amber/green dial together with a battery charge state indicator on the charge controller; over the last 3 weeks I have not seen either go out of the green and for most of the time the charge controller is flashing suggesting fully charged.
Also worth saying that our drive faces North East so the solar panel is in shade of the house from around noon at the moment.
For info: Panel is a 100w PV Logic flexible and charge controller is standard Solar Technology one:- 100 Watt Panel Kit
If anybody is in the market for a solar panel, I have just had an email from Solar Technology International advising they have 15% everything tomorrow (so called Black Friday). Use code "15BF" at the checkout.
SWB with front opening SCA - panel at the back. I think it makes sense to have the panels and/or cable exit at the lowest end of the pop top to minimise the length of cable that has to hang down unsupported and fold up with the roof - the alternatives would be to run the cable the length of the roof to the low point before dropping down.
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