Solar electric car charging

[muffildy]

So, i have an idea thats only really worthwhile for people who work/are out and about when its darker out:

Buy cheap solar panels, wire them to a MPPT charge controller, hook that charge controller up to your car during the best solar energy hours. Size the system according to how big your car battery is.

This sort of system would use most of the solar panels ability to produce solar energy, and you wouldnt need to purchase extremely expensive inverters/grid tie in stuff or even talk to the power company.

Example:
Car with 10kwh battery; depleted on average to 30% leaves 7kwh needed to charge.
In florida, theres about 4.5 hours of useful sun, so i would need 7/4.5 = 1555w of solar panels PTC rate (usually around 87-94% of STC rate): So translated.... I would need most likely 10 185w solar panels & a charge controller capable of accepting around 250v...For example these:
Sun 185 Watt Solar Panel
Midnite, Classic 250, MPPT Charge Controller
So cost:
221*10 panels
721*1 controller
mounting brackets for the panels..not sure probably ??
combiner box + fuses, another ??
4/0 wire as needed ??
interconnecting wires as needed ??
So cost is 2931 + misc; probably adds up to 3.5k or so.

Estimated pay off:
3500$/{(7kw/day)*(13c/kwh)*250days/year} = 15.4 years

So it pays for itself a little bit faster than if i did a grid tie in system which typically pay off themselves in 20-25 years.

[ProDarwin]

Sounds like a cool concept, although the payoff is pretty long. I've heard that photovoltaic cells can put out more energy if you focus more light on them - linearly - as long as you can dissipate the extra heat. What about focusing a bunch of mirrors on a single panel to increase your efficiency for less $$?


I always thought it would be cool to get panels like these:

Amazon.com: HQRP 30W Flexible Solar Panel Power 30 Watt 12V Mono-crystalline PV Module w/ 4 Stainless Grommets for RV Boat Yacht plus HQRP UV Chain / UV Radiation Health Tester: Patio, Lawn & Garden

At 30 watts/495 sq-in, its 1 watt per 16.5 sq-in. If you could find other flexible solar material with a similar watt density and laminate the top surfaces of your car with it...

I figure on the average mid-size car, you could get maybe 20 x 50 inches of area on the trunk, 40 x 50 on the hood/fenders, and 60x50 on the roof - that's 6000/16.5 = 360 watts of power (max). That's power that's always charging the car, anytime its in the sun. Wherever you park it, or even if you are driving.

[Ryland]

Originally Posted by muffildy

Estimated pay off:
3500$/{(7kw/day)*(13c/kwh)*250days/year} = 15.4 years

So it pays for itself a little bit faster than if i did a grid tie in system which typically pay off themselves in 20-25 years.

In your math you show 250 days in a year, not 365... so a pay back of 10.5 years if your electric rates never go up, if you do this as a grid tie system then you are getting every bit of that power being used instead of it being lost as soon as you unhook your car and if you use micro inverters then you get the MPPT optimized for each panel so each panel is putting out it's peek, often above rated out put and extending the sun hours in a day because of how MPPT works, so less then 10 years if you don't have shading on your site.
Now the question is, what is the pay back on that gasoline that you bought over the last ten years? because charging with solar brakes even after 8 years or less compared to buying gasoline and that is even after hiring someone else to install them!

[muffildy]

yes i calculated using 250 days because the average person works 5 days a week 50 weeks of the year. That leaves 115 days where there would be extra power generated that isnt used. The problem with trying to use that extra power is the cost of a grid tie inverter is typically 2-3k$. So you would be almost doubling the cost of the system in order to get that 115 days. You also have to form a paralleling agreement with your power company, which they have a minimum charge for - my area the service charge minimum is 76$ and im paying only on average 100$ a month average right now so its not really worth connecting to the grid as i would need to produce 176/.13 = 1353kwh per month to make that zero. which means the system size would need to be 6 times as large (10000w in panels) to produce that.


So since a grid-tie inverter would cost a fortune to implement because of the minimum service charge, i could go with an off-grid which would be hooked up to the appliances. The inverter would pay for itself in:
1049$/{(7kw/day)*(13c/kwh)*115days/year} = 10 years.

This model for example would work:
5000 Watt Pure Sine 24 Volt Inverter by AIMS Power
Then the problem is that it runs on 24v and the car battery is probably running at much higher than that, so you would need a dc-dc converter as well, not sure where you can get a 5000w dc to dc converter.

[NeilBlanchard]

You can get solar PV panels put on your roof for virtually $0 down, from several different companies. And you pay less than half of what you pay for electricity now. Two of my nephews are working for one solar PV installer, called Astrum Solar. They are hiring, by the way.

[jamesqf]

Originally Posted by muffildy

You also have to form a paralleling agreement with your power company, which they have a minimum charge for - my area the service charge minimum is 76$ and im paying only on average 100$ a month average right now...

But that's just the policy of YOUR power company, not a universal. My local utility even offers a certain number of partial rebates for the cost of home solar installations. (There's apparently enough demand that they had to set up a lottery to decide which applicants will get the rebate each year.)

Second, you seem to think $2-3K for a grid-tie inverter is too much, but how much does it cost to buy an electric car? Anywhere from $35K for a Leaf to $110K for a Tesla, so worrying about the cost of the inverter seems to fit the "penny wise, pound foolish" paradigm.

[rs14smith]

Originally Posted by ProDarwin

Sounds like a cool concept, although the payoff is pretty long. I've heard that photovoltaic cells can put out more energy if you focus more light on them - linearly - as long as you can dissipate the extra heat. What about focusing a bunch of mirrors on a single panel to increase your efficiency for less $$?

Using mirrors is not recommended what so ever. Solar panel manufactures will void your solar panel's warranty if you use mirrors. Using mirror/s usually heats up the panel quicker thus decreasing the efficiency.

[Ryland]

Originally Posted by muffildy

my area the service charge minimum is 76$ and im paying only on average 100$ a month average

To me that $76 per month connection fee would be enough to go 100% off grid! you are paying $1,200 a year for $300 worth of electricity! most of the time it's not cost effective to have a battery based system but for you it sounds like it is, that you could easily get a system to pay for it's self in 5 years or so then make it large enough to charge your electric car too and you could take out a 10 year loan and pay less per month then you are paying right now for gasoline and electricity, after that ten years is up you enjoy free electricity and transportation fuel for the rest of your life, just make sure to put your solar panels in your will for your grand children!

[muffildy]

Their website is very confusing instead of just putting all the the facts at a glance they spread it out everyplace...
So, i assume my rate schedule would be Cogeneration, as available purchase:
https://www.progress-energy.com/asse...savailable.pdf
Which seems to indicate that big monthly minimum fee at the bottom...maybe im not interpreting their rules correctly though? i wish they would just put it all in a straightforward FAQ for solar home generation...

So my current power bills minimum monthly fee is the non-interconnect version and a bit less than 10$.
So, im actually paying 90$ average a month for electricity.
I would need a solar system capable of about 700kwh/month.
So at a minimum i would need a 6000w system.
typical cost for an off-grid system is 4$/w, so cost 24,000$ monthly taking 20 years to pay off...

The cost of an electric car is out of the question for a production vehicle, the only way they are cost effective is a DIY project costing 14000$ or so which would pay for itself in 10 years at current gas prices for me.

*edit addition*
there is a 30% federal tax credit for solar installions, but im not entirely sure how it works.
First time homebuyers were sent a check; i got sent 8000$ for example...
Lets say i spend 24000$, 30% of that is 7200$ - would the gov be sending me a check in that amount? Or is this credit just a reduction in what i owe to the goverment?
If its a reduction in what i owe, what if what i owe/year is small? i typically owe 0$ a year (in fact most years they pay me). So would there by any benefit from the program in this case?

[SwamiSalami]

Originally Posted by ProDarwin

Sounds like a cool concept, although the payoff is pretty long.

I don't understand why everyone thinks that these investments have to pay for themselves. Isn't the enjoyment enough? Does a corvette pay for itself? No, but many indulgent people could still be heard saying "Is this going to pay for itself?" Maybe it will, maybe it will be a close call, but we know one thing for sure, a Hummer or a Jet Boat or a house that's too big, or my favorite--a nice lawn, will NEVER pay for themselves.

We have to squash this conditioned stigma that every investment that's not flashy has to "payoff".