Solar panel/cell info

[ron-travisano]

Is the rate of charging from the onboard solar cells the same while actually in motion as apposed to parked with the Aptera off?

• This reply was modified 1 year, 10 months ago by  Wyatt Andrews.
• This reply was modified 1 year, 9 months ago by  Gabriel Kemeny.
• This reply was modified 1 year, 7 months ago by  Gabriel Kemeny.

[len]

Like everything… TBC but they said to think of it as a trickle charger where the sun properly exposed to the panels will produce the range

The Gamma should have solar more solar panels and I assume the solar advances they have been working on.

They said they few more spots for a couple more solar cells.

I believe originally a full solar was 180 solar cells

[ron-travisano]

Sure, trickle charging. I’m just curious if I’m in full sun on the highway is it the same trickle as if in full sun parked. Not sure if the act of engaging the batteries for driving will slow the rate of charging.

[harry-parker]

The solar panels add to the power coming from the batteries as you drive down the road.

As Paul mentioned, the rate of energy production from the panels may be even higher when you’re moving due to air cooling effects. However, except when you’re braking or going downhill, the motors are usually drawing more power than the solar panels are generating.

So, the solar panels will just provide part of the power the Aptera needs while its moving, except at very slow speeds and decelerating, reducing the energy drain on the battery but not eliminating it.

The full solar option is rated at 700 watts. Since 1000 watts-hours will take Aptera 10 miles, 700 watt-hours will take Aptera 7 miles. So the power of the full Sun alone is enough to push the Aptera at about 7 miles per hour (not counting a few percent lost from inefficiencies in the power conversion electronics). Driving slower than that average speed and you would be charging the batteries while you drive in the sunlight!

[Qiang]

Since 10mile/kwh is EPA at much higher speed than 7 mile/hour, I would expect Aptera can go more than 7 mile/hour constant speed assuming getting full 700w from sun.

[harry-parker]

Yes. That’s a good point. The question is, how much is the drag reduced at those lower speeds?

I’ve read that the EPA average speed is about 45 mph, but drag is nonlinear with speed, and some power is used even when the car is stopped, running the electronics.

Of course other factors make a big difference, such as incline and wind speed and whether heat or cooling energy is being used. At 7 mph, the wind speed could easily be faster than the car is going, doubling or reducing to zero the relative air speed depending on its direction.

[georg-matt]

In the June webinar at about 38:00 minutes, they mention that they squeezed 4 extra panels on the hood and alluded to additional panels elsewhere on the vehicle. Has there been any more discussion of this? Anybody know exactly where and how this was done?

[Fran]

Watch Aptera Owners Club video channel. Steve examined carefully the Gama mock-up and found that the Aptera was stretched in its mid section which made room for one more row (6) of solar cells on the roof. The rear hatch appears to be unchanged even though the total length of the Aptera was increased by 4 inches. Six cells added on roof, four added on the hood but two taken away on the dash where the bottom/front door “hinge” goes into the body.

[kerbe2705]

@Georg Matt – also keep in mind that the individual units are “cells” and the combination of many cells together makes up a “panel.” Aptera’s dashboard is one panel and the roof is another panel, as are the hood (bonnet) and the hatch. The six cells on the rear of the body comprise the final solar panel on the vehicle.

[OkieKev]

I’ve been curious as to the decision to place the cells in an Argyle pattern verses square pattern, similar to the Lightyear. I would think you could fit more cells in each panel by one full row. The tail section looks like there is room for a full row clear across plus 2 partial rows in front of that. I wonder if it is because of aesthetics or some kind of efficiency that I am not aware of. Just one of those things that make me go “Hmm”.🤔

Something else I’ve puzzled about, not just with Aptera, but solar cells in general. Do they HAVE to be square or rectangle?

• This reply was modified 1 year, 10 months ago by  Kevin Bradbury.

[Sam]

Is there any particular reason why there aren’t any panels on the sides? It’s not like the sun never shines there. Some may leave doors open for extended periods as well. As I understand it, these panels are inexpensive and lightweight. Every little bit counts, right?

• This reply was modified 1 year, 10 months ago by  Sam Adams.
• This reply was modified 1 year, 10 months ago by  Sam Adams.

[erick-vega]

What I am more interested about is the circuitry used to charge the batteries during driving. Is this actually occurring or are you bypassing “charging” and using solar panel wattage directly to the motor during driving.

Also, will we be allowed to purchase and mount more solar panels and connect to the charging system for even more range or will we be software locked to a certain Solar wattage?

[harry-parker]

The Aptera solar charging circuit is very similar to a home battery charging circuit. Nothing is preventing the power from the solar panels going out to power the car and charging the battery at the same time, depending on the car’s power demands that instant. If the car is going at highway speeds the motors will draw more power than the panels can deliver so that solar power will be added to power from the battery. However, as soon as you start slowing down, the motors won’t need the solar power so the batteries will recharge using sunlight and what’s produced by regenerative braking.

Re. extra solar panels: the CEOs have confirmed in a video that they will provide a connector for external panels, but have not provided specs on what range of voltage, current and power those panels must be. Perhaps up to another 700 watts? However I picture those as camping panels placed on the ground rather than mounted on the car.

• This reply was modified 1 year, 10 months ago by  Harry Parker.
• This reply was modified 1 year, 9 months ago by  Gabriel Kemeny.
• This reply was modified 1 year, 7 months ago by  Gabriel Kemeny.
• This reply was modified 1 year, 7 months ago by  Gabriel Kemeny.

[FoggyOptic]

In my current vehicles I use a sun shade in the windshield to keep the cabin temps down and protect the interior. Something in that form factor with integrated solar charging might be an interesting dual-purpose option. It would potentially offer more surface area for solar cells, but may negate or eliminate the cells on the dashboard.

[kerbe2705]

@John Hermann Another option would be a solar shade that, instead of pressing against the windshield, attaches along the top of the windshield but then attaches to the dashboard on the interior side of the solar panel, hanging nearly vertically.

[kerbe2705]

@Harry Parker The phrase, “push Aptera down the road”, implies that the solar panels can generate enough current to turn Aptera’s motors without the intercession of a storage battery to accumulate the power the cells generate. What the panels can do is generate enough power to charge the battery so that it can push Aptera down the road but, even in full sunlight at the optimal angle to the cells, the panels can’t generate enough current to turn Aptera’s two or three fifty kW motors directly.

[harry-parker]

Kerbe, yes, that’s what I meant.

To be precise, solar panels are connected to a Maximum Power Point Tracking (MPPT) solar charge controller. That charge controller is connected to the battery. Also connected to the battery are the motor controllers. So is a DC to DC converter that provides a lower voltage to the other electronics such as the lights, displays and radios. With regenerative braking, the power can flow either way to and from those motor controllers.

Whether the battery is getting charged or discharged depends on whether the solar charge controller is putting out more or less power than the car needs at any instant in time.

Those 50 kW motors only draw those 50 kW each when you floor your Aptera. Going steady down the road they only use a small fraction of that. The Aptera uses 0.1 KWH to go 1 mile, at the average speed of the EPA test cycle, ~45 mph. So at a steady 45 mph on level ground the car is drawing about 4.5 KW, still much more than the 0.7 KW the solar panels produce.

In full Sun, when the panels are producing their 0.7 KW, the the car will draw about 4.5 – 0.7 = 3.8 KW from the battery at a steady 45 mph. At some lower steady speed the car will need only what solar panels provide. At even lower speeds the solar panels will charge the battery.

[alain-chuzel]

Properly engineered solar arrays will mitigate power reduction due to “mismatch” (partial “blocking”). Using multiple controllers is one way as well as the use of diodes configured in “bypass” mode (so-called bypass diodes).

My personal solar array at home, for example, consists of 12 series connected 255 watt (rated) panels. These are simply connected to a grid tie “string” MPPT/Inverter. Each panel has 3 bypass diodes in their junction boxes. If enough partial shading should occur on a given sub-string within a given panel, the sub-string would be “bypassed” (effectively shorted out) and the rest of the sub-strings in that panel and all the other 11 panels would operate as usual.

[curtis-cibinel]

At about 15 mph the draw per the physics is 33.9 wh/m. Combined with 200w for computers and screens and this accounts for the 700w solar generation. Admittedly this has assumptions but it matches range expectations and effectively models all ranges (very similar to those numbers by Aptera Owners club and motor matchup)

[dan-stevens]

Figure 40 miles of range from solar a day.
5 solar hours a day (average)
40 miles divided by 5 hours = 8 mph.

Definitely faster than 7. No land speed record being set here though.

[giedzinski]

Solar farm engineer here! Not sure if this info has been said, but the wattage rating of solar cells is based on Standard Test Conditions (irradiance of 1000 W/m^2, which simulates an average sunny day). The 700-watt rating from Aptera’s cells will differ a lot from real use. If you’re really lucky, you could get 1 kW of power or more sometimes, but to account for shade, cell angle, and climate conditions… I wouldn’t count on much more than 500 W for full solar most of the time, at least if we’re trying to make conservative calculations.

Hope this helps! Looking forward to the day when we can check all these numbers for real 🙂

[jonah-jorgenson]

Always nice to have a professional expert way in.

I agree the 700 watt rating is under the best conditions and marketing optimistic. I would not expect 700 watts even where I live in FL. Hence I think the reason Aptera added some extra cells.

[alain-chuzel]

Welcome.

While not in exactly the same terms, much of what you say has, indeed, been said but it’s always nice to get some additional experts weighing in. My expertise is in design/build of specialty solar panels/module and much of my work has been for vehicles with compound curve arrays (solar race cars).

[efra]

I wonder how much heat the solar panels themselves prevent. If a panel has a 20% efficiency, does that mean that only 80% of the light hitting that panel turns into heat?

[alain-chuzel]

It’s complicated….

In the case of a 20% efficient cell, only 80% of the incident power (light) is left. I’m all but certain that only SOME of that 80% is “absorbed” and turned into heat. How much? I’m afraid I don’t know but perhaps someone much more versed in the science of “heat transfer” could chime in.

From my personal experience working with solar cell, panels and arrays, cells can get pretty hot. Take a look at the following forum thread for more detail.

https://aptera.us/community/discussion/solar-cell-temperature/