solar on the car roof

[JoeS]

PV1, I admire your tenacity pursuing this subject, even though the math perhaps by now should have shown you the negligible benefits relative to the cost and effort; nevertheless, I thought you might enjoy the following two photos of a solar-assisted Solectria Force which were posted a few days ago on our local Electric Auto Association mail list. No information available about this contraption. BTW, I assume you're planning on solar-->regulator-->?Vbattery-->inverter-->EVSE-->J1772, or were you thinking of adapting to CHAdeMO? So, what's the latest with having a simple 120vac outlet at work and save yourself lots of time and $$$? When are you going to get an iMiEV?

 

[iMiEVNZ7]

Grin JoeS,
The solution would give good power but is a bit wind prone for the iMiEV ! I think PV1's idea of the thin film ones is best, and we plan to do the same too. I think, even if it turns out to be no good for recharging the main battery it would be easily useful for running a fan to cool the car during hot days, where no shelter is possible like in a large carpark, and for recharging a 2 Kw get me home battery pack to recharge via an inverter to EVSE to the main battery.

Update on our purchase.. still waiting for approval from the boss, we have one month hire sorted, and another client is doing a test drive of a dealer car today, and if all works well, that will give us another month hire, when we get three months hire sorted, we are good to go, if finance works well.

 

[Don]

. . . . I thought you might enjoy the following two photos of a solar-assisted Solectria Force which were posted a few days ago on our local Electric Auto Association mail list. No information available about this contraption.

Well, he accomplished three things for sure! 1.) He's got enough panels to make a difference, 2.) He's got them tilted enough so that whenever he parks the car facing south (or north if he lives Down Under) they'll probably give him more than 50% of their rated output, and 3.) His car is in the shade most of the time so he won't be needing nearly so much A/C. On the downside, he's really hurt his top speed and the energy required to drive more than just a few miles per hour has gone up . . . . but now everyone knows he's driving a 'solar car'!!

BTW, I assume you're planning on solar-->regulator-->?Vbattery-->inverter-->EVSE-->J1772

One other BIG plus for his 'contraption' - I'm betting that this car is a homebrew conversion running off 96 volts, and that these are 24 volt panels, so he's charging the traction pack directly rather than using the very inefficient method of charging an intermediate battery and then using an inverter to charge the main battery. For our car we would ideally need teeny-tiny solar cells so that 350 volts worth would fit on the roof - A very small amount of current, but the roof could charge the traction pack directly. I suspect this is how it works on the Fisker Karma, which is probably why it cost them $5K to do

Don

 

[jray3]

Sorry Don, as JoeS said, this is a Solectria Force from the mid 90's.
http://en.wikipedia.org/wiki/Solectria_Force
AC drive, but still only 156 volts, easy to charge thru an inverter or perhaps directly from those big panels.
Of course, the array is comical and counterproductive.

 

[Don]

Well shoot - But as I said earlier, empherical evidence beats all kinds of theoretical guesses

I suppose he could still charge the traction pack directly with some sort of automatic switching relay - Charge 1/2 of the pack for 10 or 15 minutes, connect to the other half for 10 or 15 and repeat . . . . endlessly. That wouldn't be terribly hard to rig up - Still beats charging an intermediate battery and all the associated losses that brings

Comical for sure and maybe not terribly productive but I'll bet he feels just like PV-1 . . . . at least he's doing something even if it isn't terribly practical

Don

 

[JoeS]

This solar-powered Solectria Force might be a contraption, but let's see just how practical it might be. Simply eyeballing them, say those panels combined produce 600W peak (dunno what these are, but I would use the highly-efficient SunPower panels in this application). So, let's say if they're properly pointed into the sun they're averaging 400W output over a sunny nine-hour workday (preumably he/she goes out at lunchtime and moves it). That's 3.6kWhr. Say there's a dc-dc converter with a wide input voltage range that feeds the 156V battery pack directly and let's assume a 85% converter efficiency, which means he/she feeds 3kWh into the traction pack during the workday.

If it was feeding my iMiEV which has a lifetime history of 4.2miles/kWh then I'd be getting 12.6 miles daily off these panels. Unfortunately, my iMiEV would no longer be getting 4.2mils/kWhr with all this stuff plastered on it, so that's yet another issue. This whole discussion is aimed at the commuter who has a 40-mile one-way commute in the iMiEV and cannot recharge at work. This additional 12.6-mile range increase would still not solve the problem, even if the iMiEV's efficiency was unaffected. For that scenario, I would think you'd need to add at least 20 miles additional range if this is going to be a serious commuting solution. Say, nicely-contoured flexible solar panels are employed, their relative inefficiency and surface area still wouldn't solve the problem, IMO. In any case, a cloudy/rainy day would mean you sleep at work that night. :roll:

If it was me, I would try really hard to find a place to simply plug into 120vac while at work. How about working out a deal and parking in back of a nearby gas station? :lol:

 

[iMiEVNZ7]

Hi JoeS,
Maybe one could carry an extra battery pack in the car boot and use solar too. For the same weight as 2 back seat passengers, assuming 85 Kg people, for a total of 170 Kg, one could have a 40 Kg inverter, and at 30 Kg per battery, say 4 Batteries.

That would give approx 4 Kw extra, and with say another 1. 7 Kw per day from the solar panels, a extra if needed, range of
5. 7 Kw or say 5 Kw , and @ 160 watts/ hr per Km, that would give another 31 km.

So say a round trip to work is 100 Kms, using most or all of the 16 Kw main battery and with no at work charging available, with the 300 watts of thin film solar providing say, 200 watts over the 8 hours, it would give a buffer of 31 Km if a unplanned trip was needed on the way to work or on the way home.

A timer or circuit could be used to prevent too deep a discharge on the extra battery pack on days the extra range was not all needed if one knew ahead of time.

For our longer trips, we are.. cough, taking two honda or similar, 2000i petrol generators to recharge via a 3.3 Kw EVSE.

The cost of the petrol for the generators, even for a full charge is less than running our petrol car for the same distance. $ 15 compared to $ 24.

 

[Don]

So say a round trip to work is 100 Kms, using most or all of the 16 Kw main battery and with no at work charging available, with the 300 watts of thin film solar providing say, 200 watts over the 8 hours, it would give a buffer of 31 Km if a unplanned trip was needed on the way to work or on the way home

You're probably never going to get 66% efficiency from solar panels glued flat on the roof which you can't aim at the sun and then (as Joe mentioned) you're left high and dry on cloudy days - Not a practical solution

Rather than a series of expensive modifications which might work most of the time, if I needed transportation beyond the range the i can provide, I would buy another car. If it's marginal now, think what it will be like in a couple years when our 16 Kw battery is only 80% efficient, or when it's cold out and your 80% battery can only deliver 65%, or when you need heat for that 100 Km drive

Don

 

[PV1]

Nice. Hopefully thin films are lower profile, . I was thinking of using the panels from eBay. I could fit 6 on the roof, 2 wide and 3 long. Which 50 watt'ers were you talking about?

I might be getting an i next February or March. The setup I was imagining was:
Panels --> MPPT --> 48 volt LiFePO4 battery --> inverter --> EVSE --> J1772.

The battery pack would be made up of 200 ah cells, wired in series for 51.2 volts nominal, giving me 10 kWh of storage, plus a kWh from solar, good for 11 hours on level 1.

Since I'm stuck in the middle of the natural gas boom geographically, having an EV powered by solar that's on the roof would make a statement that would get people thinking outside of fossil fuels.

 

[NeilBlanchard]

Those panels would add a LOT of aerodynamic drag -- probably like 3 or 4 more "car's worth"?

Here's a car that can drive using just the power from the (very high efficiency) PV panels -- they have about 830W output:

The SolarWorld GT car built by Bochum University is about 800 pounds and it has a Cd of just 0.14. It has extremely efficient motors in the hubs of the front wheels. It can go about 31mph in full sun. It consumes about 35Wh/mile -- compare this to the i MiEV!

 

[JoeS]

Davide never plugs in this lithium-powered Sparrow - all the panels fold up into a package as a front bumper:

 

[PV1]

Help it! It's getting attacked by a Prius! Pretty neat setup it has, though.

I was reading on pluginamerica.com and it showed an extended range battery pack for the LEAF that fits in the floor of the trunk. It has its own charger that grabs some juice from the J1772 plug, and feeds in battery power on the DC side of the onboard charger. Could something like this be done for the i? Possibly have it connect on the high voltage side of the dc-dc converter, so power input/output looks like the 12 volt system to the car? Use a PV controller with boost for 330 volt and charge this battery with solar, that way there's extended range and solar power available while driving. If the dc-dc converter is on while the car is plugged in (meaning HV available because of a closed contactor), a second contactor could be installed for the second battery and close with the dc-dc contactor, so both batteries charge on plug-in with power going to the second battery looking like 12 volt usage to the car.

Here's the link to the LEAF's battery:
http://www.pluginamerica.org/accessories/enginer-auxiliary-battery-pack

 

[JoeS]

Hey, PV1, have you bought your iMiEV yet?

At the Green Drive Expo there were two companies showing off their add-on plug-in battery packs for hybrids. Same concept certainly applies to EVs. Enginer's is a 48v pack feeding a dc-dc converter feeding the HV traction pack. Plug-In Supply's output voltage matches the vehicle's traction pack.

If this output is properly current-limited and diode-isolated and fed in at the motor controller battery connection while the battery pack and the vehicle are both turned on, I think that the iMiEV's BMS would simply treat this it like regeneration. No technical reason why this shouldn't work that I can think of. As well as plugging it in, one can recharge the auxiliary pack using solar.

Is the concept of an integrated onboard solar-recharged auxiliary battery pack time, cost, volume, and weight effective for our little iMiEV? You can do that analysis yourself, if you wish.

 

[PV1]

Nope, not yet, but getting closer every week. I'm looking mid-March.

I priced cells to match the traction pack voltage and store 20 Ah. It was about $3,000 with BMS and connectors. The solar is another $1,000, but I'd need to find a dc-dc converter to get to traction voltage.

As to how the car treats the extra electrons, that's why I thought to put it on the 12 volt converter circuit so the pack is only connected during driving and charging, and so that the power is accounted for. I guess the controller input would work, too. You just can't hook it directly to the traction pack terminals or else coulomb counting and SOC reports would be seriously miscalibrated. It has to be metered by the car somewhere, and that's where the motor controller or converter come into play.

I remember seeing a solar-powered Prius that had the same setup we're talking about. It treated the power as regen. Greg Johanson made it.

 

[JoeS]

Hey, PV1, for a long time you were concerned about charging at work. Here's a solution:
http://www.greencarreports.com/news...a-portable-affordable-solar-charging-solution

 

[PV1]

Reminds me of Icarus:

And the man behind it:

(Elon Musk's unknown twin)


If anybody remembers way back when I was talking about a 73 mile commute without any destination charging at the apprenticeship (wasn't this thread), I swung by the place when I first got the car a little over a month ago. They now have a solar canopy with two level 2 chargers. I just come from a level 2 charger a few miles up the road when I stopped, so I was pretty close to full in this picture. The chargers had card readers on them anyways.

 

[JoeS]

PV1 has a penchant for solar-powering vehicles, so I thought I'd continue adding to this thread with this article on a solar4-powered VW bus conversion. Unfortunately, it's lacking in technical details…

http://www.bostonmagazine.com/news/blog/2014/11/14/vecna-cto-solar-powered-vw-bus/

Sorry, don't know how to reduce the image size for this photo linked directly to that site:

 

[Don]

Neat!

On a (semi) related note, I recently read that a 1955 23 window micro-bus with 6,500 original miles on it sold at auction in Germany for $235,000. They made hundreds of thousands of them but due to rust and hard use, originals in good condition have become quite rare and evidently very valuable!

Don

 

[LMT]

Hi all,

Just got my i 2010 model and looking for solar hack to charge main pack. Ive read and searched alot of the posts but coundnt find anything on how the regenerative braking system works, which is where i hope to add solar/battery input. are there any wiring diagrams of how it works?

I can only assume that when regen braking occurs thru D, E or B (love driving all the time in B and saving brake pads) the engine produces a DC output (anyone know the voltages and currents generated?) which is then returned/applied some how to the traction battery pack .

my current intention is to have:
solar panel 200+W > battery charger > battery > power diode > connection to regen system.
so battery chargers during day light hours and adds to regen when braking occurs in D, E or B.

i understand even if i can get it to work ill only be getting a couple of km extra a day but i think thats cool.

Cheers

 

[Don]

Max regen is on the order of 340 volts and 75 amps. You would need a BUNCH of very tiny solar cells to get you the needed 340 volts . . . . at 2.5 volts per cell, around 130 or 140 of them and they would be so small they probably wouldn't give you half an amp. As you've no doubt read, solar on the car roof is completely impractical. If the solar panels added to the Cd by even 5% or so, it would probably be a net loss - You'd lose more range by increasing the drag than you would gain

Don