factors in solar harvest: Oregon coast vs. NW Nevada / PITA

Carson City, NV is only ~500mi SSE of Yachats, OR but the solar situation couldn’t be more different.  Carson City is about 5,000’ ASL, cold (in the 20s this morning), clear skies.  Yachats was sea level, cool, and overcast.  

In Yachats the most power I made all day was 55w (10.5% of rated). Here in Carson City I was making 164.81w at 0925 local time, or 28.6% of rated.

No doubt the clear skies made the biggest difference, but let’s look the other factors that contribute to the 109.81w difference.


The difference between temperature derating at 10C (-7.8%) and -3.89C (-1.13%) is about 6.5 percentage points.  This would be ~7.14W of the difference between cool Yachats and cold Carson City. 


I had to do some digging, but it appears irradiance is increased by ~8% per 3000m of elevation.  This would be ~3.9% difference between sea level Yachats and ~4,800’ Carson City, or 4.28w.

For your amusement:  one might point out that we are technically closer to the sun at higher elevation, but that would make less than 1/93millionth of a percent difference.  The distance between the earth and sun changes by about 10,500 miles/day due to our elliptical orbit, dwarfing the earthly altitude factor in distance to the sun.

atmospheric clarity

Here I chiefly mean local weather, though there was surely some of that 2.5micron smoke crud in the air in Oregon.

If we chalk up the remaining difference to weather and other atmospheric losses (“atmospheric depletion”) it would be 89.6% of the observed difference, or 98.39w out of 109.81w.

Yes, overcast weather can occur anywhere but it is more likely on the coast than in the desert.  

pain in the ass

I actually started this post yesterday but stopped just before the math.  I was felled by crippling pain in the left hip joint / buttock area.  How/why could a butt hurt like that?  

Allow me to introduce the piriformis muscle:

It’s buried under the glutes and can get injured or cramp.  These cramps can last a long time;  one medical site referred to piriformis cramps as “relentless”.    Mine was cramped for about 20 hours, and wasn’t as much fun as it sounds. 

As if the direct pain weren’t enough, you can see the sciatic nerve (blue in the pic) runs under (or sometimes even through) the piriformis, so when the muscle acts up you can get sciatica symptoms.  That’s a nice little bonus, although I wasn’t affected much that way (see below).

 This stretch is the one that seemed to target the muscle most directly:

Screenshot 2020-10-23 at 11.24.53

[Screenshot from a YT video I can’t recall because I was operating on 3 functioning brain cells at the time.]

You can read “target the muscle” as “me moaning/cussing even louder and wishing for the sweet, inky blackness of unconsciousness”.

It was getting dark and I had been unable to walk the dog.  I couldn’t release her to go on her own because of the abandoned mines.  I found some Tylenol #3 left over from my dental adventures and ate half a tab.  After about 1/2 hour the pain was reduced from paralyzing to bad so I could walk enough steps (20?) to let the dog pee.  She is fiercely housetrained and will not willingly pee on her tie-out.

The painkiller also let me sleep.  When I woke up the muscle cramp had released and I could stand and walk again.   There is some soreness from the cramping and hobbling but it is a welcome relief overall.  

Lucky for me, the sciatic symptoms are limited to foot numbness/tingling – no leg or foot pain at all.  So this morning I only have the mild tingling.  I assume that will fade as pressure on the sciatic is reduced. I’ll walk a bit more carefully until it fades. 

I suspect this cramping was caused by my sitting position on a wooden barstool I like for its narrow build.  I’d noticed discomfort in the area before after long sitting sessions, but at those times I could alternate sitting and standing and it would fade. 

I’ve been standing all day today and will figure out some other arrangement.  I have a gardening pad I can use on the stool.  I might try that with a modified position and see if that works.  Or I might shorten the legs, or replace the stool. I definitely don’t want a repeat of yesterday.  Not ever.