How insane/unlikely would it be to ad pv cells?

[GWAR]

Attaching them to the hood and roof wouldn't be to hard, but, initially the obstacles would be adaption and conversion of the energy, and setting up and somehow controlling how much and when you use the electric motor(not really possible, short of serious hacking, I'm thinking).
The idea started when I was thinking of the possibility of charging while at work after using primarily batteries on the way here.
I have almost no electrical or mechanical knowledge( ), and now the brains can tear the idea to pieces. But at least it's a good idea...

[Insightful Trekker]

Hi GWAR and welcome to the forum

Originally Posted by GWAR

<snip>
I have almost no electrical or mechanical knowledge( ), and now the brains can tear the idea to pieces. But at least it's a good idea...

OK you asked.

And its been asked and answered before, but its been awhile. Use the forum search feature if your interested.

In addition the problems you clearly understand what your missing is the _VERY_ small amount of energy that you could capture with even the most efficient PV's. Shooting from the hip (so please forgive all the unqualified generalizations) you could replenish a "dead" IMA pack once a week or so. And its equivalent energy stored can move the Insight down the road a mile or so. :/

So you can see its a HUGE expense and undertaking for VERY little in return.

Remember the _best_ MPG in an Insight comes from driving will little or no use of the IMA assist at all.

Sincerely,

[james]

The thing is, you'd be really under-utilizing those expensive solar cells by mounting them on your car - think of all the times they'd be in the shade, or facing away from the sun. If you have the money to buy a PV array, it'd MUCH more efficient to mount them on your roof or some such place, let them spend all day making energy that you feed into the grid.

Then there's the additional weight and drag to be considered, too.

[jtmco]

As a follow-up to John’s post, let me throw out a few numbers.

One square meter (1 m^2) of sunlight is about 1000 Watts (W) of energy. A good commercially available solar cell of crystalline silicon (the blue panels you see on the highway which have over 90% of the market) is about 15% efficient. That means that a 1 m^2 silicon solar panel produces about 150 W of electricity under direct sunlight.

If we assume that the hood and the roof of the Insight have 4 m^2 of area (generous, I think), that means that you could generate 600 W of electricity in direct sunlight. Remember, this is less than half the power used by a modern hair dryer. Since 746 W = 1 hp, you get an extra 0.8 hp (600/746) worth of electricity when the sun is shining. Depending on where you live, you could probably count on this for 4 hours per day.

If memory serves, the Insight batteries are rated for 6 Amp-hours and a total of 144 V. That means that the batteries store about 864 W-hours or electricity. At 600 W, it would take (864 /600 = 1.44 hours) about 1.5 hours to charge the batteries at full blast. This would, of course, probably overheat them.

This also means that the Insight batteries can provide 1.16 hp (864 / 746) for one hour. If you want 10 hp, you get about 6 minutes. If you want 20 hp (which you probably need to maintain 60 mph) then you get 3 minutes. So you go 3 miles. This ignores accelerating up to the speed.

Bottom line, John is right. The charge on the batteries is worth about 1 mile. At the very best, it would take 1.5 hours to charge the batteries and probably much longer if you aren’t going to kill them.

How much would it cost? The solar cells mentioned above dominate the market. You can buy more efficient (up to 30%) Gallium Arsenide (and MUCH more expensive) or less efficient (about 6-8%) amorphous silicon, but crystalline silicon is currently the leader until the next generation, low cost polymer or dye-sensitized solar cells are improved (they are currently are at 5% efficiency and need to reach about 10% to truly impact the market). Crystalline silicon solar cells cost $3.00-$3.50 per Watt. So, 600 W * $3.00 / W = $1800 for the solar panels alone. This does not include controllers or electronics of any kind, even the kind necessary to connect to a bank of lead acid batteries, let alone the Insight pack.

I’ve done all this from memory and late at night, so if I’ve typed a wrong number, my apologies. And I’ve tried to use typical numbers. Phoenix might be better, Seattle might be worse. Nonetheless, you get the idea. If you spend well over $1800 (I would guess well over $3000), you can add the equivalent of 0.8 hp to your Insight (during the daylight hours ) or you can save that energy in IMA battery pack for most of the day and go an extra 1 - 2 miles at night. If gas is $3.00/gal, you can buy (1800 /$3.00 - 600) 600 gallons of gas so you could drive about (600 gals * 60 miles / gal =) 36000 miles on that money. Since you get maybe 2 miles per day out of the solar panels it will only take you 18,000 days of sunlight (49.3 years) to drive the same distance for the dollar.

This could go on forever (maybe it has!).

I love solar, but it isn't a good solution for direct installation on a car.

Jim

[VinceDee]

Excellent, concise, and logical analysis, Jim. You did all the work I'd have a heck of a time figuring out how to do to tell us just whether it would be worth it or not.

I think it's safe to say it's not.

[IamIan]

I agree with most of what has already been said.... Solar cells to the car as it is provide very little benefit per cost.... unless cost means nothing to you....

If you got a MIMA system at least then you could use the power you stored when you want it without useing more gas.... up to the ~10 or so HP the IMA motor will give you....

If you added a booster battery like mike is doing... then at least you can get above the stock battery capacity 6.5Ah battery rated... but only uses ~4Ah of that so only ~576Watt Hours of usable energy from the stock battery... with a additional booster battery that can store 10Ah or more then at least with a MIMA you are getting to the point where more agressive use of the IMA motor is a benefit .... Now that you have a MIMA and a Booster battery of some kind... Most of the time You would probably charge the booster battery from home.... and solar cells would work best when angeled and such for the most direct perpendicular effect, at home....

If you were going to put them on the car itself I can think of 2 good possibilities... asuming you already installed MIMA and a booster battery of some kind like mike is doing..... and 1 option without MIMA....

#1> the flexable solar cells they have lower efficincies like 6%ish but since they are flexable you could mold them to the contours of the car and thus not mess up the cd of the car too much, which if you did would hurt you more above 40 MPH than you could get back.... now this will add some weight to the car and such... so you will lose some MPG but would gain some from the solar energy that they provide during the day when you are out and about after you leave home but before you get back home to fully charge up the battery from the home power solar or grid.... exactly when this breaks on what you lose vs what you gain I don't know but either way you would have several thousand dollars most likely invested.... you could also bring along with you a tent or tarp / car cover type of thing made from these flexable solar cells and such cover the car when you get out of it... but that won't help while you are driving around...

#2> solar cells are fabricated the shapes and such they are for cost effectiveness in the facotry .... solar cells even the crystaline types could be made in almost any shape .... and on a wide variety of backings... so if you thought the flexable solar cells and such would be expensive... try now entering the billion dollar car market to create body panels and such for the car that are specificly shaped and designed for you.... they should be able to be made just as light or lighter than current body panels and have no effect on cd.... no weight gain means only the increase in energy... oh and the little matter of at least several million dollars...

#3> the last option and the only one that doesn't include MIMA would be to replace the starter motor in the car with one that still fits and can still act as a starter but can also handel continuous use as you drive around.... this is no small task itself... and I doubt you would be able to get more than 2 or 3 HP from such a hybrid starter motor... you then need a seperate 2nd 12V battery to charge via solar and such and to power the hybrid starter motor as you go down the road... and a charge controller for the 12 V battery to prevent it from being over discharged or over charged.... and a 12V motor controller for the hybrid starter... and then solar power as said above in #1 or #2

[clett]

Ah, one of my favourite topics returns to the forum! This subject has stimulated much past debate.

I am in the pro-solar camp!

Solar on a vehicle has been tried before, just ask Peter Perkins (who posts on this forum) for his views on this as he runs a solar EV. A Prius has also been converted to solar, though not with aerodynamic flexible cells - it's not pretty, but it catches a lot of light!

(See Steve Lapp's solar Prius here)

The average incident sunlight in the US is 5 kWh per m2. This is the US-wide average, it's higher in the sunnier states and obviously more in the summer months, less in winter. If you managed to cover the car with 4 m2 of cells, that's a total of 20 kWh per day of incident energy.

Of course you can't have all of that 20 kWh, you can only really convert 20% of that into electricity if using good cells (like SunPower's 20.4% efficient A300s), so that adds up to 4 kWh per day on average (more in summer, less in winter).

This is WAY more than the little Insight battery can store, so you would need an additional battery to store the excess. (Lithium-ion could store 5 kWh in 25 kg.)

So assuming you can collect 4 kWh per day, which sounds like a tiny amount of electricity (only ~30 cents worth), you need to figure out how many miles that would reduce from your gasoline usage, by pumping the energy through the IMA.

The answer is that typical EVs, like the Solectria Force, get about 4-5 miles per kWh. An Insight would probably manage about 7 miles per kWh, so your 4 kWh would give you up to 28 miles per day of solar energy, reduced from your gasoline bill.

Over a year that's about 10,000 miles of sunshine-powered motoring. A big reduction in your gasoline bill. But, as mentioned above, it's going to be a LOT cheaper just to plug your Insight into the mains or put the cells on your house!

Further discussion and information on my point of view on this subject here.

[IamIan]

clett I agree and am also in the pro solar camp.. it is on my long list of thing to do to my Insight.... I also agree that there is some solar energy to be had if done carefully...

but the 7miles per Kwh number you gave I think is for a Pure EV Insight ... with the pumping losses of the current design we would be likely only to see ~15 miles per Day .... added to a 60MPG stock insight this isn't much....

but the best way I like to think about Solar is over the year... ~15 Miles a Day worth of Virtually free travel over 5 days a week is 60 Miles per Week or about 1 free gallon per week over 50 Weeks out of the year and you get 3,000 extra Miles of transportation or about 50 less gallons of gas for the year even for the gas sipping Insight ....

Can it power the Car out right... no ... can it help ... yes.... how much will it cost... Thousands to tens of thousands of dollars.... You could buy a second insight for the cost of adding the extra battery and solar cells.....

That having been said... I am still a fan of it and it is on my long list... Got my MIMA... Now saving up for and making plans for my eventual Booster PHEV Battery.... then I can add Solar to it.. .... long way off for me though.... At the rate Mike is going already up and running with a EV-Mode and a Booster Battery he is making great progresss... especially for 1 guy.

I personally don't want to give the cd of the Insight ... so for me as it stands now the flexable solar cells are my target... even though they do put out 1/2 to 1/3 the power of others.... unless something drastic happens so I could use the higher power ones and not give up the cd of the Insight.

Time will tell.... Although I suspect to see someone else with a solar PHEV Insight before I am ready to do it myself.

[Insightful Trekker]

Looks like my fancy shootin inspired the sharpshooters of the forum.

Thanks jtmco (and clett and Ian) for your in depth expansion on the subject. I've added this thread to my personal bookmarks and included it in my IC FAQ folder too. I'll use the link in reply for future similar questions in the forums.

Sincerely,

[retepsnikrep]

Ah!! I see my name mentioned so better post a reply

I would like to see a solar boosted Insight, but it would have to be very carefuly done.

I would not sacrifce any aerodynamics or shaping, so cells would have to be perfectly mounted/blended into/onto the roof/bonnet to be acceptable to me. The car would have to look exactly the same after the mod except that you could see it had cells attached, but not where they joined! or how they were mounted!

They would have to be 20%+ effciency or it would not be worth bothering.

Then you have to store the energy in the IMA or a boost pack of some sort and integrate that with the car. Not easy at all.

My van does have some low <10% effciency cells on the roof, and they do make a useful contribution. It's outside in all weathers with a big battery pack, and it can safely absorb the 150v 1ah (150w) charging current the cells produce. If I lived in Arizona with say 8 hours sun a day, call it 1kwh, I could go about 5miles. In the Northern UK I get a couple of miles a day free. But it is relentless, so 2 miles a day x 365, call it 700 miles a year, x 30 year life of cells = 21,000 miles in UK. In Arizona or some other sunny climate with say 20% effciency cells, 2kwh or 10miles free a day could be possible. 3650 miles a year. etc etc.

We need some nice high effciency flexible thin light cells (like wall paper!)and then these dreams may become reality.

Regards Peter