Charging directly from solar panels

[Newton]

I sent a tweet at elon and tesla. Saying it would be badass to have external panels able to connect for when I'm out in the forest. I suggest others send some if they want this.

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[ajdelange]

Coming at this thread from a slightly different direction it occurs to me that the CT isn't going to fit into my garage and considerations of SS in the sun aside I don't want the sun beating down on the truck because it eventually plays havoc with the interior materials, the heat isn't good for the electronics etc. So I thought I'd build some sort of structure to shade it. Since the sun is beating down on the roof of this structure that roof might as well be covered with solar panels and that energy from which I am trying to shield that truck might as well be used to charge it. How many panels should I install?

The panels I have on the roof of the main house are Hanwa 315W (DC) panels. Each of these with an Enphase IQ7 inverter mounted on it (what my supplier would install were he doing the job today) delivers 250 W at 240 VAC at full sunshine. I'm here in Virginia for the winter months. Between October and Jun last year I got an average of 2.78 hours of full sunshine per day. Assuming the CT to consume 350 Wh/mi each of these panels would deliver 2.6 miles per day on average. I probably drive 800 miles per month or so which is 25.8 miles per day to which I would add the 5 miles lost to phantom drain per day for a total of 30.8 so I'd need a dozen panels based on average requirements. In two rows of 6 that would require a roof area of 31.1 feet by 6.6 feet (217 square feet). A 12 panel system would be considered a 3 kW system based on its peak AC output in full sunshine and obviously wouldn't, even in maximum sunshine, charge the truck very fast (8.6 mi/h).

The system would need a buffer battery for days like 6 Jun (posted above) and the obvious choice is a PowerWall as the app evidently now has features that make management of charging in a missing grid situation more feasible e.g. it will sense that the PowerWall is getting low and command the car to stop charging until it is full to some level set by the user.. One PW holds 13 kWh (37 miles) and can deliver energy at up to 6 kW continuous so that it would carry the charging through a 2 hour cloudy period if the battery were completely charged.

In the months of December and January I average 1.74 hr of full sun per day. In order to be able to work within that I will probably install 24 panels (3 rows of 8; a 6 kW system) and 2 Powerwalls. This would give me 1.74*6000/350 = 30 miles per day even on these dark days.

As usual the hope here is that people will look at these numbers, scale them to their own requirements and, at least, disabuse themselves of the notion that they will be operating their CT exclusively from a toneau cover PV array.

 

[TyPope]

Coming at this thread from a slightly different direction it occurs to me that the CT isn't going to fit into my garage and considerations of SS in the sun aside I don't want the sun beating down on the truck because it eventually plays havoc with the interior materials, the heat isn't good for the electronics etc. So I thought I'd build some sort of structure to shade it. Since the sun is beating down on the roof of this structure that roof might as well be covered with solar panels and that energy from which I am trying to shield that truck might as well be used to charge it. How many panels should I install?

The panels I have on the roof of the main house are Hanwa 315W (DC) panels. Each of these with an Enphase IQ7 inverter mounted on it (what my supplier would install were he doing the job today) delivers 250 W at 240 VAC at full sunshine. I'm here in Virginia for the winter months. Between October and Jun last year I got an average of 2.78 hours of full sunshine per day. Assuming the CT to consume 350 Wh/mi each of these panels would deliver 2.6 miles per day on average. I probably drive 800 miles per month or so which is 25.8 miles per day to which I would add the 5 miles lost to phantom drain per day for a total of 30.8 so I'd need a dozen panels based on average requirements. In two rows of 6 that would require a roof area of 31.1 feet by 6.6 feet (217 square feet). A 12 panel system would be considered a 3 kW system based on its peak AC output in full sunshine and obviously wouldn't, even in maximum sunshine, charge the truck very fast (8.6 mi/h).

The system would need a buffer battery for days like 6 Jun (posted above) and the obvious choice is a PowerWall as the app evidently now has features that make management of charging in a missing grid situation more feasible e.g. it will sense that the PowerWall is getting low and command the car to stop charging until it is full to some level set by the user.. One PW holds 13 kWh (37 miles) and can deliver energy at up to 6 kW continuous so that it would carry the charging through a 2 hour cloudy period if the battery were completely charged.

In the months of December and January I average 1.74 hr of full sun per day. In order to be able to work within that I will probably install 24 panels (3 rows of 8; a 6 kW system) and 2 Powerwalls. This would give me 1.74*6000/350 = 30 miles per day even on these dark days.

As usual the hope here is that people will look at these numbers, scale them to their own requirements and, at least, disabuse themselves of the notion that they will be operating their CT exclusively from a toneau cover PV array.

I average 4.79 hours of peak sun year round here in Nebraska. I drive 16 miles a day.
4.79*6,000/350=82. miles per day. I only need 16 miles of range so I need maybe 6 panels to get my 16 miles, right? Between the vault cover and roof, I can only fit 4 panels like your Hanwas. Tesla also does solar panels and I would hope they could do better for fit though their current efficiency is only 19.4%. Anyway, that'd get me 13.33 miles on an average day since I happen to park outside during those 4.79 peak sun hours I get. During the Summer, we average 5.4 peak sun hours which would get me 15.43 miles with my 4 panels. Pretty close to what Elon said. Cool. This is quite possible.

SunPower makes a 400 Watt panel. It's 22.8% efficient. Using the same ratio you did with your 315 watt panel, the 400 watt panel should put out at least 317 watts. 5.4 peak sun hours * 317 watts * 4 panels / 350 Watts per mile = 19.56 miles worth of charge in the Summer and (4.38*317*4/350= 15.86) during the Winter. I'd average 17.71 miles per day for the year with that setup.

Thanks! I wasn't sure it would make sense but now, I can see it does. Now, maybe not for everyone but for those of us with good sun hours, it does. Heck, if it just managed half of my commute, that would be great!

 

[Sirfun]

I average 4.79 hours of peak sun year round here in Nebraska. I drive 16 miles a day.
4.79*6,000/350=82. miles per day. I only need 16 miles of range so I need maybe 6 panels to get my 16 miles, right? Between the vault cover and roof, I can only fit 4 panels like your Hanwas. Tesla also does solar panels and I would hope they could do better for fit though their current efficiency is only 19.4%. Anyway, that'd get me 13.33 miles on an average day since I happen to park outside during those 4.79 peak sun hours I get. During the Summer, we average 5.4 peak sun hours which would get me 15.43 miles with my 4 panels. Pretty close to what Elon said. Cool. This is quite possible.

SunPower makes a 400 Watt panel. It's 22.8% efficient. Using the same ratio you did with your 315 watt panel, the 400 watt panel should put out at least 317 watts. 5.4 peak sun hours * 317 watts * 4 panels / 350 Watts per mile = 19.56 miles worth of charge in the Summer and (4.38*317*4/350= 15.86) during the Winter. I'd average 17.71 miles per day for the year with that setup.

Thanks! I wasn't sure it would make sense but now, I can see it does. Now, maybe not for everyone but for those of us with good sun hours, it does. Heck, if it just managed half of my commute, that would be great!

I just saw this and grabbed it for you.

 

[ajdelange]

During the Summer, we average 5.4 peak sun hours which would get me 15.43 miles with my 4 panels. Pretty close to what Elon said. Cool. This is quite possible.

In summer your insolation is 7.00 hr/da (average between the equinoxes and assuming optimum panel elevation of 54°) but you only receive 5.4 which means clouds, haze, rain etc. are letting 5.4/7.0 = 77% through. In winter your average insolation is 4.7 hr/da on averaage (again, between the equinoxes). Applying the same ratio for the winter means that your effective average insolation for that period would go down to 3.61 hr/da. And in the dreary month of December insolation goes down to 3.6 hrs per day and, with the same 77% factor for weather, that leaves you 2.8. Thus yes, in summer it is quite possible. In winter the picture is less rosy. What I'm trying to get across is that you cannot count on the best conditions pertaining all the time. Although I must have said it a dozen times already here and elsewhere, in citing performance Elon isn't going to pick the worst case. He's going to pick the best case and maybe even boost what his engineers calculated for best case a wee bit.

Another thing you seem to overlook consistently is the vampire tax. In my X it seems to amount to about 5 miles per day.

In any case it is pretty clear you understand how to work the numbers. If you do so and are comfortable with the results then that's what counts.

 

[TyPope]

I know it's a best case scenario and besides, there's the weight penalty that you'd also have to bear continually. I'm only a proponent because it's a step in the right direction. Someday, they'll make panels efficient enough (even breaking that barrier we love so much) that it'll be worth the complexity and weight penalty. With today's tech, it'd just be great to have to roof covered in some kind of transparent sells that makes enough electricity to counter the vampire drain and maybe ventilate a hot car. For me, it really doesn't matter. I've got one charger installed in the garage and the wiring already run for a second one. My commute is almost nothing and I take long trips maybe twice a year. But, I'm all for efficiency and minimizing the need for external power where possible.

 

[CybertronUK]

Coming from a country with dismal sunlight hours, I considered wind generation. I live at a relatively high point where 150 years ago we had a windmill in our garden. The average wind speed for our area is 15 m/s but being right on top of the hill, and surrounded by fields I suspect we can achieve more.
I looked at this being unobtrusive and novel.

https://www.tesup.co.uk/product-pag...MI_JzQ56z96QIVQqQYCh0q8wZkEAQYDSABEgJKlvD_BwE

However being mechanical rather than electrical, my rudimentary conclusion was that it could certainly help the general home electricity at nominally 13kWh per day, but would be pretty useless to charge an EV. Unless I had rather a lot of them of course.

Thoughts.....

 

[ajdelange]

13 kWh is 13 kWh, equivalent to perhaps 37 miles of range in a CT, whether it came from solar, wind or the mains. A windmill based system is conceptually identical to a solar based one. It needs a controller/rectifier to make sure the maximum amount of energy is being extracted from the system however fast the wind is blowing, a battery to buffer the produced energy and an inverter and EVSE to interface the battery to the vehicle. If your daily needs are (including phantom loss) 37 miles or less a small windmill like the one you link to could provide all of that - of course provided that the wind cooperates.

 

[CybertronUK]

13 kWh is 13 kWh, equivalent to perhaps 37 miles of range in a CT, whether it came from solar, wind or the mains. A windmill based system is conceptually identical to a solar based one. It needs a controller/rectifier to make sure the maximum amount of energy is being extracted from the system however fast the wind is blowing, a battery to buffer the produced energy and an inverter and EVSE to interface the battery to the vehicle. If your daily needs are (including phantom loss) 37 miles or less a small windmill like the one you link to could provide all of that - of course provided that the wind cooperates.

Thank you.
13Kwh is approx how much my home needs to run each day. (We don’t have or need AC).
I don’t commute as go to sites all around the country so quite often do trips of 180 miles but some days it will sit at home all day too.
The wind cooperates far more than the sun here.

Conceptually anything I generate over 13KWh can top up the CT but the cost and capacity of powerwalls as I think I would need at least 2, makes the economics dubious to say the least.

I just liked the idea of having a windmill return after 150 years

 

[Newton]

Coming from a country with dismal sunlight hours, I considered wind generation. I live at a relatively high point where 150 years ago we had a windmill in our garden. The average wind speed for our area is 15 m/s but being right on top of the hill, and surrounded by fields I suspect we can achieve more.
I looked at this being unobtrusive and novel.

https://www.tesup.co.uk/product-pag...MI_JzQ56z96QIVQqQYCh0q8wZkEAQYDSABEgJKlvD_BwE

However being mechanical rather than electrical, my rudimentary conclusion was that it could certainly help the general home electricity at nominally 13kWh per day, but would be pretty useless to charge an EV. Unless I had rather a lot of them of course.

Thoughts.....

thats a nice wind generator and would be easy to put multiples near each other. Like AJ said whether its mechanical like a wind device, or water device , or pureish electrical like a solar panel, the energy generated is the same.
But that figure from the wind generator is only if you have consistantly strong wind all the time.
Also I agree about the power walls, way to expensive and I think only good if you have blackouts, or just alot of money and want something to do with it.

 

[ajdelange]

Conceptually anything I generate over 13KWh can top up the CT but the cost and capacity of powerwalls as I think I would need at least 2, makes the economics dubious to say the least.

I did say you would need a battery to buffer the windmill output but I definitely had Powerwalls on my mind when I said that. The utility makes a fine battery if they are in the mood to serve as one and in many places they want too and in most others they are forced to by the government. Your windmill/waterwheel/solarpanel contrtoller/inverter takes energy from your generating device and turns it into mains AC. This output is connected in parallel to your mains feed and panel. If the device isn't producing your appliances draw their energy from the utility. If the device is producing its energy goes to the appliances and to the grid if there is any left over. If your appliances aren't using any, then it all goes to the grid. If your utility has "net metering" anything you send to them runs the meter backwards offsetting charges drawn from the grid when your device isn't producing. In this way you get credit for anything you produce whether you use it or not at the time it is produced. Policies vary widely so if you are interested in this approach you should contact your supplier.

 

[CyberCop]

OMG ?,
This forum is a band of electrical geniuses.
I understood maybe 8 words in this thread.

 

[CybertronUK]

I did say you would need a battery to buffer the windmill output but I definitely had Powerwalls on my mind when I said that. The utility makes a fine battery if they are in the mood to serve as one and in many places they want too and in most others they are forced to by the government.

I hadn’t considered the utility ‘battery’ option. Especially as we have a peak and off peak tariff.

 

[Sirfun]

I hadn’t considered the utility ‘battery’ option. Especially as we have a peak and off peak tariff.

I've been looking into solar in California and that's how it works here. You send them your excess and they send power back to you when you need it, as long as your bank has credits.
The one problem with that, is any time the grid power goes down your system shuts down also. This to me is a perfect reason to use the large battery in a CT for backup storage. Way more capacity then a powerwall and you already have the CT. Yes you can use the outlets in the bed, but V2H would be even better.
BTW, I'm very limited on knowledge of how this would be feasible. But I'm wanting to learn.

 

[Crissa]

It's super-feasible, the DC pins are right there for your EVSE hookup.

Tesla hasn't done anything about it, but that's now standard equipment in Japan, for instance. Or rather, will be required from now for EVSEs, and Leafs of the last few years do it already. It's considered one of the three reasons Tesla has poor penetration in Japan (poor use of CHAdeMO, high cost are the others) so far.

-Crissa

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