Sunset from the rim of Crater Lake Oregon

Dry Camping twelve days on solar

Dry Camping twelve days on solar. Great Smoky Mountain National Park. Here are the results. Did our solar work for an extended camping period in the Great Smoky Mountain National Park?

This is a numbers post — if you want the story about our wonderful visit to the Smoky Mountain National Park area here is the link to the articles.

The first part is the raw data followed by analysis and conclusions.

Solar Energy data points:

  • Solar Array = 1800 watts, no attempt to orient the panels to the sun or track the sun path. The campsite was in full sun from 9 am (solar time) until 5 pm. (8 hours)
  • Charge controller maximum amperage at 50 each — two controllers. 100 amps per hour maximum combined. Observed occasional production at 100 amps/hour. Typically energy flow into the battery at above 90 amps per hour.
  • Typical voltage from solar panel to charge controller was 55 volts at 12.5 amps. Typical PV max voltage was 66 volts. Peak voltage observed at 70.98.
  • Typical observed watts per hour at 1,300. Typical array conversion 72% of rated 1,800 ideal output.
  •   Peak watts per hour observed at 1,476. Maximum array conversion 82% of rated 1,800 ideal output.
  • Typical battery voltage 13.5 static no charge or discharge.  Peak battery voltage when charging 14.62. Minimum battery voltage observed 12.91.
  • Typical battery temperature 72F. Peak battery temperature 90F. Maximum outside air temperature 90F.
  • Sunny days seven, cloudy days 3.
  • Energy produced from solar and consumed during our eleven night — 12-day stay. 53,210 watts full-days with no partial days included, thus average solar yield was 5.32 Kwh/day (including three overcast cloudy days). 
  • Maximum energy gained in one day was 6.93 Kwh. Minimum energy gained on a cloudy day was 2.95 Kwh.
  • Average energy produced during cloudy days, with some periods of light rain was 3.51 Kwh per day.
  • Typical battery state of charge 90%. Battery state of charge range 62 – 100%.

Appliances used from the battery power

  • Air Conditioner, one day two hours
  • Clothes Dryer, one day, one half hour
  • Microwave, everyday
  • Instant pot, three days
  • Computers (two) everyday
  • Televisions (zero) no internet or over the air signal

Analysis Solar

The three cloudy days, with two in a row, was exactly the test I was hoping for and was a key design consideration of 1,800 watts of panels limited by two controllers. During the cloudy days, we produced almost half as much energy as during the sunny days.  Had the array size been limited to thumb rules that are standard in the industry, production during cloudy days would have been cut by an additional 30%. 

Solar Array output from the passenger side of our RV. The passenger side is producing 728 watts and the total network power is 1366 watts.
Solar Array output from the passenger side of our RV. The passenger side is producing 728 watts and the total network power is 1366 watts. This means that at the time of this screen-capture the driver’s side array was producing 638 watts.
Screen Capture of four days of solar production including two cloudy/rainy days.
Screen Capture of four days of solar production including two cloudy/rainy days.

Analysis Battery State of Charge

Our battery bank varied between 62 and 100%.  On a clear sky day, the battery state of charge was typically 100% by solar noon. (Solar noon is not the same thing as daylight savings time noon.)  Battery low state of charge at 62% was a combination of using our air conditioner at the end of one day dropping the state of charge from 100% to 82% followed by two cloudy days. By the morning of the second cloudy day, the battery state of charge was at 62% and by the end of the second cloudy day battery state of charge was at 88%. Although the state of charge dropped to 72% overnight the next day was sunny and a full charge was achieved in the early afternoon.

Battery screen capture showing 84% charge and power (minus power being currently used) at 926 watts.
Battery screen capture showing 84% charge and power (minus power being currently used) at 926 watts.

Conclusions

Our experience shows that assuming we don’t need air conditioning or the clothes dryer we should be able to operate without outside electricity all summer or winter. Not only do the results of dry camping twelve days on solar prove our solar design we have the data to prove our electrical independence — without running our generator.

Predictions

The cloudy day data should be an accurate predictor of wintertime, limited daylight, less than ideal orientation, energy production.  With our current 1800 watt solar array, we may be able to operate without limitations, except for air conditioning and clothes dryer, in a mild climate, in the winter indefinitely.  If this doesn’t work out, I still have more room on the roof for more solar panels.

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