Featured You're wrong about the Aptera

There is some evidence that the long held data on mounting angles might be irrelevant and other angles might perform better depending on your climate

for what it’s worth antique bifacial panels might solve the duck curve, maybe solendria was onto something just leaving them pipe shaped

 

I don't have typical roof heating contribution figures, but will remind that even PV modules mounted on open-air racks will get very significantly hotter than the ambient air.

Checking a spec sheet from the same product line as my PVs, it lists a maximum power point temperature coefficient of -0.41%/℃. Don't confuse this with the Voc tempco of -0.30%/℃.

That varies by maker. Mine is stated as guaranteed to be no more than 0.7% per annum, for 25 years. These are also SolarWorld, but pre-date the improved warranty listed by 3PriusMike.

Numerous others allow greater loss.

Wind storm resistance. Panels mounted higher can experience greater lift, which is not something anybody actually wants of their PV modules. Especially in hurricane zones.

 

Have we been doing Solar wrong all along? - Undecided with Matt Ferrell

 

Interesting. Thanks.

 

spoiler the conclusion is maybe for highway sound control or age land use, otherwise its more expensive and less practical than traditional solar panels.

 

No doubt. My question remains though, does the warmer temperatures on a shingle roof contribute to the lower efficiency?
If it were solely due to the heat generated by the panels, the efficiency loss would be constant and not increase in the summer.

As such, my hypothesis is that both ambient temperatures and self generated heat contribute to the efficiency loss.
I just need to find data now that will support, or blow up the hypothesis.

 

Efficiency is a function of absolute semiconductor junction temperature, which determines what is known as a "bandgap voltage", an important element of the efficiency calculation. As temperature rises, this voltage decreases by a set equation. Ambient and all heat and other sources contribute. Most of the 'self generated heat' is from the high solar flux beating down on and getting absorbed by the dark non-reflecting surface, similar to any other black body, not from external electric current flowing through the cells. (Freed charge carriers re-combining within the cells before they can be harvested, are a different matter internally, but functionally no different than simple blackbody absorption.)

Differences in roofing temperatures and module ventilation certainly do contribute to the final semiconductor junction temperature.

 

"To get the maximum returns on your solar panels, the general rule of thumb is to set them to the same degree as your latitude. For example, I live in New England, my latitude is about 42 degrees, so my solar panels, ideally, should be set to about 42 degrees."

As I pointed out here more than a decade ago (timestamped a couple years before building my own system), this general rule of thumb is not correct for those of us in the seasonally cloudy mid-latitudes. A shallower tilt, sacrificing some weak sun on those short cloudy winter days in order to collect more strong sun on the longer clearer summer days, produces greater annual output. Extracting estimates from NREL's PVWatts calculator of that era, I plotted this chart for a south-facing panel:


img_5958_48224.jpg | PriusChat

I would hope that the TNO folks who did the calculations described in this article, adjusted their reference-tilted PV modules similarly, but the article doesn't present enough detail to betray an answer.

For large scale production in various regions, the timing factors described in this article may well become important. And vertical arrays on building walls could also be a very useful added solar resource at various facilities, beyond the horizontal arrays on their roofs.

But for me personally, on a small scale with a strictly net-zero metering plan, total annual production is what matters most. For my hydropower-rich region, every bit of energy I produce is water saved from a hydro reservoir or river flow. Plus, boosting summer dry-season production, at the expense of winter wet season production, better complements the local hydro resource's seasonal capacity. So I'll keep my tilted horizontal arrays.

 

I hope this car comes to fruition. Wonder what will happen w the law that requires 2/3 wheel vehicle operators to have MCY licenses...

 

Thinking of how infrequent one sees a trike motorcycle in town or on the open road, it's going to really be a niche market ... if it does ever go into production.
It's been over 15 years now since Google gave them $24 million to get things running. Of course CEO's do need to have a hefty income ... so I guess it didn't take long (few months) for them to blow through that chunk of change. Heck, it does cost a lot to send your kids to college.
This is one person that feels fortunate to get back their $500 deposit in 2009.
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I see them occasionally on nice days. It likely indicates that they are a occasional vehicle, and I see a lot more 2 wheeled motorcycles, scooters, and e-bikes. I'm sure there are some countries where this would make sense (India and the philopenas come to mind) but the aptera design is wrong for them as they would want a more narrow, less expensive vehicle.

 

The trikes currently on the market aren't exactly for every day driving. The ones I see are open cockpit.

Aptera went trike cause the US doesn't have a quadricycle or kei car classification.

 

and .... trikes - being in the motorcycle class are not required to go through rigorous crash tests the way 4-wheel cars are, so they save a boat load (R&D) not having to do that.

 

looked up the electric trike I saw recently, it was about $8K, 3kw motor 74 mph top speed, 32 mile range, open air. I have never seen one in bad weather. It looked good. We will see if the aptera sells more than the mirai.

 

That would be funny ... not sure though ... maybe sad, or hilarious.

 

How can I be wrong about something I haven’t heard of?
What about cleaning the solar panels, don’t they have to be clean to maintain efficiency?

 

"have to"? They don't have to - anymore than you have to wash dishes or change your shorts. It's just that people do because it's kind of - sort of better

I'd guess most people don't ever worry about dirty panels but I would go up once or twice a year to clean off our 8kW worth - just so I'd get a few hundred extra watts. It's a hassle ... & not everybody is OCD.
.

 

They have to be clean to maintain efficiency, nothing there about the owner having to do it.

 

In our region the rain and snow keep the panels clean enough.
I have not noticed any loss of efficiency.

In some areas, the amount of dust can build up much quicker, and/or the precipitation is much less frequent.

 

nothing but being thrifty & still agile enough to negotiate a 3 & 12 roof pitch w/ long handle water brusher & squeegee in hand without fear of falling off a 2 story house.