Some new information on the non-US bound solar roof

Discussion in 'Prime Technical Discussion' started by Tideland Prius, Jun 19, 2016.

  1. Tideland Prius

    Tideland Prius Moderator of the North
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    [​IMG]

    (1). The DC-DC unit does the energy management from the solar roof to each of the batteries. (Yes, it can charge both a 2nd NiMH battery and the 12V battery.)

    (2) This acts as a temporary storage for the energy generated (by the solar panel). [Note: Nickel Metal Hydride battery]

    (3) The solar panel will generate a world's highest maximum output of 180W *internal measurements

    [​IMG]

    The picture on the left depicts the solar panel charging the NiMH battery while the car is parked. This is the temporary storage unit.

    The picture on the right explains how the solar panel charges the 12V battery while the car is in motion.


    Also, a quote from Chief Engineer Koji Toyoshima:
    So there's hope that it'll eventually be offered.
     
    #1 Tideland Prius, Jun 19, 2016
    Last edited: Jun 19, 2016
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  2. drash

    drash Senior Member

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    The NiMH battery is in addition to the Lithium battery? This is the Prime? That would be odd. That separate NiMH battery looks like its right where the middle seat should be.

    Kind of neat that Toyota's uses the solar panels to charge the 12V while the car is in motion. Takes a little stress off of the main battery so it can be mainly used for motive power.
     
  3. Tideland Prius

    Tideland Prius Moderator of the North
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    I've edited for clarity.

    Yeah it looks like it's charging a separate NiMH battery and not the Li-Ion traction battery directly. This is interesting.

    I wonder what the additional weight is. I assume the miles gained must offset the additional weight.
     
  4. drash

    drash Senior Member

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    Probably in the reinforced glass roof designed for the solar panels and the extra NiMH battery. I don't think they'll lose much weight when they eventually switch to the laminated glass for the US to meet US safety requirements.

    Regardless 180 watts is pretty impressive. Now I have only a few more questions, ha ha!
     
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  5. Jan Treur

    Jan Treur Active Member

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    Let me do some calculations, now we know the Wattpeak of the solar panels. I estimate you can produce 1 kWh per day using such a 180 Wp solar roof. I assume during driving the temporary NiMH storage is used for traction (or at least to save energy from the traction battery that otherwise is used for non traction processes), maybe through charging the 8.8 battery as soon as it gets space.

    Then after a day of charging (for example, driving home after work) actually you can start with 1 kWh + 0.7*8.8 kWh = 7 kWh on board. Currently I get an annual average of 7 km/kWh (4.4 mi/kWh), so this 7 kWh will provide 49 km (31 mi) of EV range as an annual average.

    Maybe there is some efficiency gain, and the factor 0.7 of the usable part of the traction battery might be a bit higher. If there is 10% gain in efficiency and the factor 0.7 is set on 0.8 it becomes 1 kWh + 0.8*8.8 kWh = 8 kWh, and 7.7* 8= 62 km (39 mi) annual average EV range. But there also may be some losses if the NiMH battery is not directly used for driving but for charging the traction battery during the driving.
     
    #5 Jan Treur, Jun 19, 2016
    Last edited: Jun 19, 2016
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  6. Tideland Prius

    Tideland Prius Moderator of the North
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    Interesting. There was another article (There's a slew of them from last week about the Prime's solar roof) that quoted Koji stating a 1,000km average of EV driving on solar-panel-generated electricity. Using your fuel efficiency of 7km/kWh, that's 7km*1kWh*364 days = 2,548km of solar electric driving per annum if it's sunny every day.

    The average Canadian driving distance is 15,000km/year, so using the conservative 1,000km, 6.7% of driving is done with solar-generated power.
     
  7. Jan Treur

    Jan Treur Active Member

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    Whether you can get the 1 kWh per sunny day depends on your region and the season. In my region I know from my own solar panels with similar flat orientation that during the period March or April to October this is well possible, but not in November, December, January and February. For regions that are more south, such as CA for example, I expect it will be a longer period.

    By the way, this dedicated battery for temporary storage, is that the same as in the P4, wasn't it 1.2 kWh which is 100% usable?
     
  8. 3PriusMike

    3PriusMike Prius owner since 2000, Tesla M3 2018

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    Even if this is true, I'd wager that the extra cost of the system far outweighs the value of electricity produced. Much better to just collect the money, aggregate for many people and install a solar farm in a desert somewhere. Then send the owners a utility gift card every year for X number of kwh.

    Mike
     
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  9. Tideland Prius

    Tideland Prius Moderator of the North
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    In the US? Yeah probably. In Japan, this option is used for emergencies (like a strong earthquake with significant infrastructure damage).
     
  10. bisco

    bisco cookie crumbler

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    i wouldn't want to park in the sun just to use the roof. if i already did, that would be a different story.
     
  11. Jan Treur

    Jan Treur Active Member

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    Yes, parking in the sun regularly has a strong impact on battery degradation. You should have the possibility to leave all windows open, or an AC cooling system that becomes active before a too high temperature is reached.
     
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  12. iplug

    iplug Senior Member

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    Agree with others here. Kinda a gimmick. In addition to battery degradation from excess heat, the UV damage to the paint, upholstery, interior plastic...premature aging of the car... just to get a small charge from the solar roof and get into a hot car is not worth it.

    Green dollars are better spent elsewhere.
     
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  13. alanclarkeau

    alanclarkeau Senior Member

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    Lots of cars park in the sun all day Mon-Friday, and they'd benefit.

    My other question - would it be charging as the car is being driven? I'm thinking "SOLAR IMPULSE" around the world solar plane - which is charging its batteries during the day, and the "SOLAR CHALLENGE" race cars which charge while they're racing.
     
  14. Coast Cruiser

    Coast Cruiser Senior Member

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    I believe California has the most Prius owners/drivers? I'm surprised the Gen4 does not have a solar roof option. I would be interested in that.

    My cars have always been parked in the sun. My previous Toyota vehicles never had any paint degradation, or interior damage/fading. I hope my new Prius does just as well. It was 102 degrees yesterday. Even with white paint, and tinted windows, and "Heatshields" placed in the front & back windows I was shocked at how hot the interior got.

    I'm a Prius rookie. I'm curious to see how, (or if) this extreme heat affects the L-ion battery. While driving yesterday, I noticed the battery never gained a full charge. It only had about 3 or 4 bars on the meter. And the gas mileage dropped. (Yes, I had the AC on, but it's usually always on.) In "normal" temps, the battery was always near full capacity.
     
  15. Trollbait

    Trollbait It's a D&D thing

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    With the car on, the solar panels supply power to the 12 volt accessory system. Providing gains by lessening that load from the traction battery and ICE.
     
  16. fotomoto

    fotomoto Senior Member

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    Thinking the same thing. From May through Oct., I purposely go out of my way to park in shade so that both I and the battery are more comfortable. Even when I had the solar vent option, it was still WAY cooler to park in the shade than to use it in full sun. Now, park it in the sun and heat up the batts. through both interior heat and charging? For battery longevity, that doesn't sound like a great idea for folks in the south and southwest.
     
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  17. bisco

    bisco cookie crumbler

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    what they need is a deployable solar wings, like nasa uses.
     
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  18. fotomoto

    fotomoto Senior Member

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    A few years ago, Ford kicked around the solar roof idea and came up with an "outside the box" concept (pun intended) using a rigid box with a fresnel lens that would concentrate solar rays on to the roof top.


    "Ford's new concept plug-in hybrid model, called the C-MAX Solar Energi, will host an array of SunPower's X21 high-efficiency solar cells on the top. The cells on their own wouldn't provide enough electricity to recharge the car's battery in a timely fashion, however. So Ford turned to researchers at Georgia Tech, who developed an acrylic Fresnel lens integrated into a canopy structure that will concentrate the sun onto the cells.

    [​IMG]

    In Ford's vision, a driver would park the car under the canopy at work or in a public space. Sensors along the car would engage autonomous driving, moving the vehicle beneath the canopy to track the sun. Tinskey said that a six-hour charge could provide 21 miles of solar-based driving. " Are Ford and SunPower About to Make the Grid Irrelevant for EV Charging? | Greentech Media
     
  19. iplug

    iplug Senior Member

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    If one can garage a car at home and/or work this will do wonders to prevent paint fading and aging of interior materials. UV damage happens with every vehicle and is a function of degree of exposure and time. It may not be very noticeable in the first few years of a car left outside, but it happens to them all.

    If the price is right and there is no choice but to park in the sun, it may be worth it. But if it's a ~$1k option, that money is better applied to home or community solar.
     
  20. 3PriusMike

    3PriusMike Prius owner since 2000, Tesla M3 2018

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    Take the money for the solar option and instead install (probably 5x - 10x) as many panels on your home roof. Install a utility disconnect switch so that during an emergency you can disconnect from the grid and have one outlet available to charge your car. You'll charge much faster and have some useful power for other emergency uses as well. And you'll be saving money on your utility bill the 99.9% of the time there isn't an emergency
     
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