Can a car cary enough solar panels / Can solar panels carry enough to charge an electric car?

[Richard808]

The DC fast charge power is 50 kW... forget doing that with solar.

That's pretty crazy. Thanks for the info. That is HOT.

[jflorey2]

Meantime, I think I'm going to go ahead and plug in just my car to the roof.

And how do you figure you will do that? (Not at a high level; I mean where do you think you will attach wires to your car to charge it?)

I'm a long way above my paygrade on the biophysics and material science being tossed around in that sentence; but it sounds to me -- and its just my opinion --- that what's going on there is apples and oranges.

At a high level, yes; photosynthesis produces oxygen and carbohydrates from water and carbon dioxide in the presence of light, whereas solar panels simply generate current. However at a low level the process is remarkably similar. In both cases you are pushing electrons (or their complement) across a potential gradient with photons, and that transforms the energy in the photon into potential energy in the electron.

[Richard808]

And how do you figure you will do that? (Not at a high level; I mean where do you think you will attach wires to your car to charge it?)

At a high level, yes; photosynthesis produces oxygen and carbohydrates from water and carbon dioxide in the presence of light, whereas solar panels simply generate current. However at a low level the process is remarkably similar. In both cases you are pushing electrons (or their complement) across a potential gradient with photons, and that transforms the energy in the photon into potential energy in the electron.

Here's how I figure I will do that: I think I shall attach a source of 240vDC power to the big round hatch with a J1722 jack that Chevrolet carved into the driver's side front quarter panel of my SparkEV. It's an electric car.

Now, as to the photosynthesis/PV panel comparison: An apples to apples, or oranges to oranges, comparison would have us comparing the energy captured per photon into chemical bonds, for photosynthesis; vs energy captured per photon into batteries charged, for typical solar power installations; making that a ratio of photons whose energy is captured to photons whose energy got away. Not that many photons get away from the plants; they're pretty efficient. But like you say there, we -- us humans -- are in the 20% range nowadays. What percentage are the plants -- the living cells of plants, with their thylakoid membranes and chloroplasts? Jeeez, I don't even really know. I"ll go read up on it again. It's a lot more than 20% ; but you'll have to go ask Dr Barker of the Berkeley Biochemistry Dept to explain it to you if you want an explanation of that. Electron tunneling in the fast reaction of photosynthesis is still one of those mysteries of Life, fast and efficient just about beyond comprehension. We use lasers in the lab to try and figure it out but it ain't quite figured out yet.

[jflorey2]

Here's how I figure I will do that: I think I shall attach a source of 240vDC power to the big round hatch with a J1722 jack that Chevrolet carved into the driver's side front quarter panel of my SparkEV. It's an electric car.

Nothing will happen. The J1772 connector requires a pilot signal that handshakes with the car. The pilot signal tells the system things like how much current it can draw and whether it needs ventilation or not. Without it nothing will happen.

(Which is good; if you managed to succeed in connecting 200-280 VDC to a 240 VAC charger, what would happen next would range from nothing, to nothing plus a $900 repair bill, to smoke and flame. Most likely the former.)

Now, as to the photosynthesis/PV panel comparison: An apples to apples, or oranges to oranges, comparison would have us comparing the energy captured per photon into chemical bonds, for photosynthesis; vs energy captured per photon into batteries charged, for typical solar power installations; making that a ratio of photons whose energy is captured to photons whose energy got away.

A few issues here.
One, capturing a photon does not mean it is converted to energy. Black paint captures photons quite efficiently but doesn't do anything with the energy (other than get warmer.) Two, even if it is turned into energy, often much of that energy is wasted. In a typical single-junction panel, for example, the extra energy in higher-energy photons (like the energy in blue light) is lost; only lower energy photons (near red) are fully utilized.

Not that many photons get away from the plants; they're pretty efficient. But like you say there, we -- us humans -- are in the 20% range nowadays. What percentage are the plants -- the living cells of plants, with their thylakoid membranes and chloroplasts?

About 2%. You can calculate it by comparing the energy inherent in the products of the reaction to the energy inherent in the inputs. However, sunlight is free; even a low efficiency is plenty for plants.

[Richard808]

Nothing will happen. The J1772 connector requires a pilot signal that handshakes with the car. The pilot signal tells the system things like how much current it can draw and whether it needs ventilation or not. Without it nothing will happen.

(Which is good; if you managed to succeed in connecting 200-280 VDC to a 240 VAC charger, what would happen next would range from nothing, to nothing plus a $900 repair bill, to smoke and flame. Most likely the former.)


A few issues here.
One, capturing a photon does not mean it is converted to energy. Black paint captures photons quite efficiently but doesn't do anything with the energy (other than get warmer.) Two, even if it is turned into energy, often much of that energy is wasted. In a typical single-junction panel, for example, the extra energy in higher-energy photons (like the energy in blue light) is lost; only lower energy photons (near red) are fully utilized.


About 2%. You can calculate it by comparing the energy inherent in the products of the reaction to the energy inherent in the inputs. However, sunlight is free; even a low efficiency is plenty for plants.

The J1772 is at the end of a $500 Clipper Creek Electric Vehicle Charge Station cable, a very smart cable indeed. You can spend $2500 for the equivalent cable from Bosch, but with the blessings of GM/Chevrolet. It shakes hands very well with Sparky out there. The cable is 25 feet long and goes nicely from the inside of the garage to the outside driveway where Sparky parks, to receive his daily dose of electicity. I doubt very much that the Clipper Creek cable cares very much where his 240 vDC comes from, as long as it's got a pleasing waveform and a nice hefty regulated voltage. (If not it just flashes a few red lights and cuts out.)

I'm going to bow out of the efficiency discussion; like I said, it's above my paygrade and over my head. Sort of. I'm just a simple biophysicist. Suffice to say, though, that electron transfer in chloroplasts, much like in mitochondria, is --- evidently -- way over everybody's paygrade. I'll leave you with this, though --- a few years from now, we'll be discussing this in terms of quantum effects --- electrons are in the quantum realm, even if electricity is not discussed that way much, eg solar powered electricity -- and we'll be milking those photons for all they're worth.

[jflorey2]

The J1772 is at the end of a $500 Clipper Creek Electric Vehicle Charge Station cable, a very smart cable indeed. You can spend $2500 for the equivalent cable from Bosch, but with the blessings of GM/Chevrolet. It shakes hands very well with Sparky out there.

Right. And if you feed it 240 volts DC rather than the 240 volts AC it is expecting (which BTW is 320 volts peak to peak) it will either 1) blow up, 2) die quietly or 3) do nothing.

The cable is 25 feet long and goes nicely from the inside of the garage to the outside driveway where Sparky parks, to receive his daily dose of electicity. I doubt very much that the Clipper Creek cable cares very much where his 240 vDC comes from, as long as it's got a pleasing waveform and a nice hefty regulated voltage.

DC will not have a "pleasing waveform" and the output of a solar array is not a "nice regulated voltage."

But don't take my word for it; try it for yourself. You can get a new EVSE for a few hundred and a new EV charger for a few thousand, so go for it. Just have extinguishers on hand rated for electrical fires.

[ulrich]

[..] Is it possible today, let's say you have a 10 kwH solar system and you leave it collecting energy for about 8-9 hours [...] then when you come back home, you charge your electric car until the inverters run out of juice it had been supplied from the sun throughout the day.

I think the conversation digressed a little bit from this original question, and I'm not sure if the answer to this was clear to you. (Several posters addressed this issue, but perhaps not directly enough for the answer to be clear).

So to be clear: No, what you describe is not possible. Neither the solar panels nor the inverter is capable of storing any energy. If the car is not plugged in at the very moment that the solar panels collect the energy, the energy will be lost.

If you want to charge the car at a different time than the panels are generating the electricity, you will need to either store the energy in a battery until you're ready to use it, or sell it to the grid and then buy energy back from the grid at the time you want to charge your car.

[inMichigan]

Okay so this has been bothering my mind lately. I am a lover of electric cars and solar panels. I think of them going together like peanut butter and jelly. I constantly think of charging electric cars with solar panels.

But more importantly, is it a reality? Is it possible today, let's say you have a 10 kwH solar system and you leave it collecting energy for about 8-9 hours, and this on a typical day, so even though it's 10 kwH I expect to collect around 3 to 4 kwH on a typical cloudy day, and then when you come back home, you charge your electric car until the inverters run out of juice it had been supplied from the sun throughout the day.

So basically, you let your solar panels collect energy when you're at work and then when you come back home, the inverters charge your car until it runs out of juice.

Is this practically possible today, or no? Oh and to be region specific, let's say around the Midwestern United States.

Reading through the posts, I see a couple of up front questions that would have reigned in the responses. Plus a potential misunderstanding or two...
It isn't how many hours of sun you see shining, the quality of sun is important too. I'm in Michigan. I get a yearly average of ~4 hours of perfect sun per day. I have 14 kw of panels on the roof so that I get a daily average of 43 kWh. You mentioned 10 kwH, did you mean putting 10 kw of PV panels or did you mean enough panels that give you 10 kWh on average or on a typical winter day?

Another important piece of information is how many times you do a full charge per week? Unless you are driving a lot, all the hardware you going to have to buy will never have enough miles to spread the fixed costs.

Here, the power company offers various deals of lower cost power for car chargers. If yours does, with cheaper power, your break even time gets long and longer. Are you want to use solar as a cost savings, or for feel-good reasons?

inMichigan

[Richard808]

Another important piece of information is how many times you do a full charge per week? Unless you are driving a lot, all the hardware you going to have to buy will never have enough miles to spread the fixed costs.

Read the whole thread. Electric cars don't have to go to a gas station; a lot of EV owners plug in every time they drive in the driveway; top it up; no hassle. "Full charge" is not the right way to approach it. The whole thing ends up being somewhere in that vast and forgiving space between deep cycle and tricklecharge. The car doesn't care. It will take whatever it can get.

One reason to ask the question is to find out what the minimum hardware would be. PV home systems are always quoted to me including all the hardware to hook it up to the grid AND to the rest of the house. Just the car.

BTW there's no rule that says you can only have one car getting juice from that rooftop. If I charge mine today and get my fill, maybe my neighbor would like to take my parking space and charge up her Volt. (Who knows , she might even chip in for a few of those chips.)

[ulrich]

One reason to ask the question is to find out what the minimum hardware would be. PV home systems are always quoted to me including all the hardware to hook it up to the grid AND to the rest of the house. Just the car.

I think you're finding (in people's explanations in this thread) why hooking up to the grid and house, even for your minimum requirements, is a reasonable thing. The solar panels (or rather the inverters that sell the most) are designed to power your house and be grid connected, and your car is designed to be plugged into your house's power (and, in some sense, also to be grid-connected). You're trying to swim upstream by eliminating the grid.

If you're worried about expense, one other thing to consider is that you will not be able to get your 30% tax credit for a setup that's designed to charge a car. That credit is reserved for solar that powers houses:
from http://energy.gov/savings/residentia...rgy-tax-credit (emphasis is mine)

A taxpayer may claim a credit of 30% of qualified expenditures for a system that serves a dwelling unit located in the United States that is owned and used as a residence by the taxpayer.

I think by the time you figure out everything necessary, you'll see the grid is actually a real cost-saving complement to a solar electric system, especially if you're trying to draw electricity in quantities and at times that are independent of generation.

[DerGiLLster]

Extra clarification

GUYS, I don't care if I will charge with solar panels all the time. Just some of the time. I don't expect to charge the full battery with solar panels, just enough for a day's trip.

Is it too much to ask for an inverter being 15-20 KW at MAX just so it can charge around 40-50 miles for me? Could it be with multiple smaller inverters?

I don't care if some days I use panels while some I will use from the grid. I just want to have some charging for free and for environmental reasons.

[Richard808]

I think you're finding (in people's explanations in this thread) why hooking up to the grid and house, even for your minimum requirements, is a reasonable thing. The solar panels (or rather the inverters that sell the most) are designed to power your house and be grid connected, and your car is designed to be plugged into your house's power (and, in some sense, also to be grid-connected). You're trying to swim upstream by eliminating the grid.

If you're worried about expense, one other thing to consider is that you will not be able to get your 30% tax credit for a setup that's designed to charge a car. That credit is reserved for solar that powers houses:
from http://energy.gov/savings/residentia...rgy-tax-credit (emphasis is mine)


I think by the time you figure out everything necessary, you'll see the grid is actually a real cost-saving complement to a solar electric system, especially if you're trying to draw electricity in quantities and at times that are independent of generation.

I am indeed already plugged into the grid. I'm a cardcarrying member of the Ratepayers of America; been paying my montly bill to Pacific Gas and Electric for fifty years now, give or take. Whatever I put on my roof, I can plug into the grid any time I want; or not, if I don't happen to like being an integral part of PG&E generation. I'll look into the inverters available and make sure that whatever I get to serve the Clipper Creek charging station J1722 cable is compatible with the utility; I'm gonna sell this place someday no doubt, don't want to create problems for the next guy. With inverters going for fifteen hundred bucks or so, one had better be scutinizing one's inverter very carefully.

Meantime, your point about not being able to take the 30% is wrong. Check it out. I'm permanently installing roofjacks, supports, panels, and electronics all in my residence, all in the United States of America; anybody wants to audit that can stop on over and I'll bring out a couple cold beers. I'm just about one hundred percent sure about all that because I did it before, long time ago, putting up all of the hardware for solar thermal, and taking that tax break. One just has to actually spend the money on the hardware and actually install it; the Govt never did care whether any of it worked or not; you never had to swear that you got it working, just so you had the receipts and you owned the home. Maybe things have changed, and this time I haven't read the legislation or the tax code; on the other hand, this time I haven't actually done anything about it yet.

BTW you oughta see the kind of subsidies and rebates you get on electric cars!!! We lease Sparky out there for two hundred bucks a month; with a substantial rebate on the upfront payment.

The interesting thing here is when you use the word "reasonable". Right off the top, it's not reasonable for me to be talking solar residential electric power; my electric bill is about forty-five bucks a month, total -- including the car! But the real reason it's not reasonable is that residential solar gets you electricity at around $3.50 per kwh , while even commercial solar is more like two bucks; utility solar is more like a dollar and a half and is genuinely competitive with quite a bit of the electric power on the grid; the natural gas portion, say.

Funny, whilst I was composing this Reply, the original Post-er, derGILLster, was back on the thread and he said everything I have to say better than I'm saying it.

[ulrich]

Meantime, your point about not being able to take the 30% is wrong. [...] One just has to actually spend the money on the hardware and actually install it; the Govt never did care whether any of it worked or not; you never had to swear that you got it working.

Well, the IRS code uses the phrase "placed in service" which means the system has to be operational.
You will certainly be able to claim the credit on your taxes, and chances are they'll never catch you (audit rates on individuals are around 1%, and lower if your income is less than $200,000), but I do believe that you'll be claiming the credit contrary to the law.

BTW you oughta see the kind of subsidies and rebates you get on electric cars!!! We lease Sparky out there for two hundred bucks a month; with a substantial rebate on the upfront payment.

Tell me about it - I'm getting close to pulling the trigger on a 36 month lease on a VW E-Golf SE. After incentives it'll be around $100/month with no money down.

[...] residential solar gets you electricity at around $3.50 per kwh [...]

I think you have your units confused. Residential solar costs about $3.50 per kW (no h at the end) if you have it installed commercially, so I suspect that's what you meant.

I'm using a non-profit vendor that uses volunteers for labor, and will be getting it for a little under $2.70 per kW before incentives (4.48 kW system). This system should generate something around 7200 kWh per year in my location. At the national average price of $0.12 per kWh for electricity, that's $864 per year, for a non-discounted payoff period of around 14 years. Add in the Federal tax credit, and payoff goes down to 10 years. Use the actual electricity rates here in CA (about $0.18 per kWh), and payoff is around 6 years.

[Mike90250]

Can solar panels carry enough to charge an electric car?

The proper question is,
Can the car carry enough panels to charge itself ?

Sometimes, just barely:

good aerodynamics, low rolling resistance, and sunny skies makes it work.

[Richard808]

good aerodynamics, low rolling resistance, and sunny skies makes it work.

Somewhere on the internet there's a picture of an airplane flying, just as far up as the Wright Brothers, covered in solar panels. Could be photoshop'd for all I know; never found it again.