Car Roof Solar

J1000

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I saw this today while driving around no joke :ROFLMAO:

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rover67

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Good point out golf cart has one panel and it gets decent range out of one days charge
 

satchel

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Toyota seems to think roof solar is a good idea for their new ev. Says it generates enough to go 1100 miles a year, which is what, maybe $50 in electricity? What a gimmick.

 

DanS

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Toyota seems to think roof solar is a good idea for their new ev. Says it generates enough to go 1100 miles a year, which is what, maybe $50 in electricity? What a gimmick.

Laugh all you want.

I want a truck with a rooftop panel. As in: that's probably a huge bonus for me.

Why? Not because I think it will power the truck. It's that I drive to the airport, and park there for 1-2 weeks, and then drive home. Give me something that can at least maintain the battery while its parked there, so I don't have to worry about it draining over 2 weeks. Last thing I want at the end of a 2 week trip is to do anything other than just go home.

Dan
 

DaveInDenver

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Toyota seems to think roof solar is a good idea for their new ev. Says it generates enough to go 1100 miles a year, which is what, maybe $50 in electricity? What a gimmick.

There's no reason not to cover every top surface with panels, it's free energy, of course.

To put numbers to things. It takes about 9 sq-inches to generate one watt of power with the best real panels. So what's the roof size here? I'd guess maybe 40" wide by 60"? So 2,400 sq-in and thus can generate around 250 watts peak.

Call it ideal sunlight for 8 hours a day, so 250 watts x 8 hours = 2kW-hr per day.

Off the top of my head I think a Telsa Model 3 battery is 50 kW-hr to get you a claimed 200 miles or 250 watt-hours per mile.

So sitting in the parking lot all day this hypothetical gets you 8 miles, assuming perfect conditions for all 8 hours - no clouds, no rain and the sun is directly overhead all day.

In reality you get about 50% of the rating from a panel over a typical sunny day if for no other reason than the sun travels in an arc and you don't get a ideal incidence. So realistically this theoretical probably generates about 4 miles per day sitting in the parking lot on a sunny day.

The exact numbers are kind of immaterial, it's good enough to know we're talking on the order of a couple to a few miles of free energy on a small commuter car-sized roof thus how Toyota probably arrived at the claim of 1,100 miles annually (car parked in the lot 200 working days x 5 miles = 1,000 "free" miles).

Yeah, my snarky reply was hyperbolic. Just don't expect miracles if you start thinking a panel on the roof is going to solve all of the range issues. It's supplementary, a nice bonus each day, but you can't use all 1,100 miles at once or anything. And in the real world you have rain, snow, clouds, daylight savings, bird poop, leaves falling that will mean a drop in actual performance.

Oh, and in the case of the Leaf in that photo, how badly do you imagine that messes up the aerodynamics? EVs don't have marginal power to play with. I bet at any decent speed that overhanging panel drops miles per kW-hr by a ton. I'd be completely guessing but I wouldn't be surprised if the net gain in range is offset by lost efficiency. That would not be a problem in that Toyota since the panel is molded into the body, of course.

It's like having a refinery on your roof giving you an ounce or two of gasoline every day. So you could do the White Rim over a span of two weeks or whatever. Actually, that would be perfect to sag a MTB trip, though. Anyway, you still need a prime mover source to go significant distances.

So annually in this theoretical panel generating 1,100 miles at 250 watt-hr per mile means it generated 275 kW-hr, which at our Tier 1 Xcel rate of $0.05461 per kW-hr is roughly $15 in free electricity.
 
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DouglasVB

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rover67

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yeah BUT.... say its a Tesla I think people talk about them loosing 1-3% each day sitting there... and more in winter. a solar roof could offset that and Dan could park it in the lot and not have to worry about coming back to a battery that has been discharged past a certain point maybe.

If it's a leaf like the one pictured above, maybe its 500w worth of panels... so 8 miles per day(dave's calcs), 112 miles in two weeks. that equals a free ride home for the bargain basement price of a few shitty panels.

We have a 300w panel on the golf cart and I haven't plugged it in to charge it in like 4 years. We drive it around a decent amount, do wheelies daily, and use it as a beer fun machine. Its pretty neat having a perpetual motion machine..
 

gungriffin

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So maybe someone can help me with this question. I just bought a house and I would like to install solar with no battery for now. Am I allowed to do the install myself or do I have to use one of these companies to do a grid tied system? Xcel won't show me any of the bills from before I moved in, how do I get the 12 month rolling usage number that I need to calculate the watts of solar that I am able to install?
 

DaveInDenver

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yeah BUT.... say its a Tesla I think people talk about them loosing 1-3% each day sitting there... and more in winter. a solar roof could offset that and Dan could park it in the lot and not have to worry about coming back to a battery that has been discharged past a certain point maybe.
Yeah, I can see the definite benefit case for that. It's like a 10 watt panel you throw on your dash when you leave your truck at airport.
If it's a leaf like the one pictured above, maybe its 500w worth of panels... so 8 miles per day(dave's calcs), 112 miles in two weeks. that equals a free ride home for the bargain basement price of a few shitty panels.
So you gotta drive a butt ugly econobox EV with a roof full of panels. If it gets them off our backs about driving old Toyotas, alright, fine.
We have a 300w panel on the golf cart and I haven't plugged it in to charge it in like 4 years. We drive it around a decent amount, do wheelies daily, and use it as a beer fun machine. Its pretty neat having a perpetual motion machine..
I got yur perpetual motion fun hog right here, buddy. If I may further jack the thread, a party pig sidecar on an e-mini bike! Should one attempt to be a passenger he or she should wear goggles, you know, for safety.

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Jenny Cruiser

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Do these minimize the issue of a shaded panel reducing all the panels in the string of panels? Other than efficiency, is there an advantage to having so many more inverters
Yes. They also handle less power than a single inverter and are arguably more reliable. You can also monitor each panel (enphase envoy) and if one goes down for whatever reason (shade/nacelle debris) you don't lose power from those panels that are unaffected. If there is a problem it is that you have to get up on your roof, or wherever, for repairs. They are more expensive as well. We'll be setting our arrays on the ground, so access won't be an issue. Cost hopefully won't be an issue for us because we don't plan on going with the most expensive panels/batteries available. That's one of the reasons we are waiting. The longer you wait, the cheaper and better panels and batteries become. We hope to have panels with actual output of at least 300 watts each. Our batteries are going to include static and mobile storage - ideally. The goal is to have 5kw of power between the arrays for ~$10,000 or less not including the batteries. My actual target is $7,000 plus batteries. We'll see.
 
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DaveInDenver

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Yes. They also handle less power than a single inverter and are arguably more reliable. You can also monitor each panel (enphase envoy) and if one goes down for whatever reason (shade/nacelle debris) you don't lose power from those panels that are unaffected. If there is a problem it is that you have to get up on your roof, or wherever, for repairs. They are more expensive as well. We'll be setting our arrays on the ground, so access won't be an issue. Cost hopefully won't be an issue for us because we don't plan on going with the most expensive panels/batteries available. That's one of the reasons we are waiting. The longer you wait, the cheaper and better panels and batteries become. We hope to have panels that put out at least 300 watts each. Our batteries are going to include static and mobile storage - ideally. The goal is to have 5kw of power between the arrays for ~$10,000 or less not including the batteries.
Another advantage to microinverters is one less level of safety devices. In a traditional configuration where you string several panels to feed a single (or least small number) of large inverters you would very likely need to have a high voltage DC rapid disconnect, which changed significantly in the 2017 NEC and would be required for a string over 80V (within the array) and 30V beyond 1 foot of the array boundary (the rule is 690.12).

The intention is to protect firefighters. They'll open the main disconnect to break power to a building but that doesn't stop solar panels from solar paneling on the DC side.

Since you'll need a way to initiate it on the 120/240 side either way it's usually a feature in the inverter itself. If you want to avoid needing HV DC protection by keeping the array under the voltage limit then you run into increasing losses, e.g. low voltage = high current = increased heating losses.

It's a solvable problem if you want to still use a central inverter. For example better inverters act as master controllers to slave contactors on their arrays to achieve this but the wiring (and troubleshooting) complexity increases with all the control wiring. In large installations this is fine but there's a break-even point in a residential situation where just putting an inverter on banks of panels is simpler.

Also this configuration is easier to expand capability later by just adding another "unit" of panels + microinverter. In the traditional sense you either oversize the wiring and inverter with the intention of expanding later or you have a more involved retrofit.
 
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DouglasVB

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So you gotta drive a butt ugly econobox EV with a roof full of panels

You're describing a 💩📦 which sounds a whole lot like the 💩📦 I drive minus getting rid of the ICE engine. I think you're threatening me with a good time 🤣🤣🤣🤣

(If I was even close to competent with GIMP, this is where I would throw together a crude image of my truck with a bunch of solar panels all over it and some lightning bolts)
 

Romer

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Isn't this thread on HOME SOLAR? Definitely a worthy topic, but could use its own thread. I am getting lost between the Home and vehicle posts.
 

satchel

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Isn't this thread on HOME SOLAR? Definitely a worthy topic, but could use its own thread. I am getting lost between the Home and vehicle posts.
Sounds like you've never had to live out of your car :).
 

DouglasVB

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Isn't this thread on HOME SOLAR? Definitely a worthy topic, but could use its own thread

Sounds like you've never had to live out of your car :).

I think we're getting close to #VanLifeSolar at this point 🤣 Although my friends stealth camping generally agree that a solar panel on the roof of a vehicle is a dead giveaway that someone's living in it.

But yeah home solar here. And I'm really interested in those mini inverters that are on a per-panel basis. Makes a ton of sense.

My parents are getting a bit closer to taking the solar/battery plunge. The things that will be annoying are 1) where to put the panels (the house roof isn't an option because my mom thinks it'll look bad), 2) need to upgrade the breaker panel to a 200 amp setup (currently 100 amps because reasons 🙄), 3) need to connect the outbuildings to the main panel (currently they're connected to the intermediate voltage transformer we use to do our own 1000+ ft run from where the utility company's transformer is located), 4) figure out where a battery bank would go (I think I'd like it in a separate outbuilding so if there ever is a thermal runaway, it wouldn't burn the house down -- CALFIRE response time, assuming someone is there to call it in, would be ~15-20 minutes), 5) find a company that can actually integrate solar, batteries, and a propane generator together (most just want to do solar and that's it because they make good money that way), 6) make sure it'll all work with a to-be-added A/C unit or heat pump.
 

J1000

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Sorry for the derailing. I left a note on the solar LEAFs windshield and the owner emailed me back. He gets about 13 miles per day in summer and the LEAF is an old one with badly degraded battery that only gets 50 miles maximum so this is a stop-gap measure to keep it useful. He's building net-zero housing in Denver as his normal job.

Sounds like you've never had to live out of your car :).
You can live in a car but you can't drive a house!! That's what I always say.
 
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