rainy weather, solar harvest, and propane relo

how I ran my bank down

Most of the year I can cook with excess power from solar. In winter I usually have reduced my electric cooking partially or go to propane exclusively.

This year I use 100% electric cooking until quite late in November. There are a few components to this intentional decision, but now I have to deal with it.

1. I used electric too late into winter because…
2. I didn’t know how much I had in the bulk tank…
3. and refilling it would be complicated…
4. because I am carrying the scooter on the receiver hitch
5. which prevents direct access to the bulk tank.

rain pushes the issue

It’s been rainy overcast the past few days and no real sunny is forecast for the next few days. I decided this was the time to act.

moving the tank

I offloaded the scooter to get access to the tank. I relocated it from the rear storage (where it used to be easily accessible) to underneath the galley bench. I can access the valve easier for driving, and can also easily pull the tank for refill.

While moving it around it felt like I had about half a tank left.

putting out the portables

Since I’d overdrawn the bank even before the rain took its toll on solar, I put out the 200w portable array at about 1030 today. They were able to add ~310Wh to the kitty.

tilt vs flat in overcast weather

I’ve talked about it before but will beat the dead horse for those who haven’t heard it before: tilt is great in the winter when you have direct sun. In overcast conditions flat vs tilted makes very little difference. The reason for this is under overcast skies the light is coming from many directions.

But there’s no reason not to set the portables up at optimal tilt so I did so. For this week it was ~60° from horizontal (~30° from vertical). I used the Sungres app for both tilt data and fr the inbuilt level function.

In direct sun the optimally tilted portables made about 84.5% of their rated wattage. At that same moment the main flat array made about 58.5% of rated. Good, right?

But the sun wasn’t out for long. When it was full overcast again the titled portables made 31% of rated and the flat array 29.5% of rated. This is when tilt has minimal effect and why we must use tools like PVwatts to predict harvest with tilt.
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Total harvest for the rainy day was 1.63kWh (1.32 + 0.31).

Update: the next day was sunny most of the time, bucking the forecast. Combined harvest was 3.6kWh and the bank got to about 90%.