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Thread: (Partially) Solar Powered Motorhome

  1. #111
    Senior Member Starjots's Avatar
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    Narrowing the Solution Space

    What design concept to pursue? So far I've explored the solution space and not so much the solution, and at this point I want to pick one and drill down.

    There are four basic classes of 'how to do it' that I see:
    1. Take a promising motorhome and modify it into an all electric motorhome
    2. Take an electric car/truck and build a motorhome on it (this is how motorhomes are built today)
    3. Take an electric car and build an electric trailer (to live in) to be towed
    4. Build a motorhome FROM SCRATCH

    When working myself up to actually doing something I usually spend a long time figuring out how I would go about the task and then see if I can manage it.

    Spoiler: Back of Envelope Analysis

    TECHNIQUE ......................Work (1-10) Cost (1-10) Error (1-10) Meets Goals (1-10) Sum
    **For all numbers, LOWER is better**
    **Don't overthink it, this is back of the envelope**

    Modify Ultravan.................. 3............... 6 ..............3.................... 5 ........................17
    Modify Vixen...................... 3 ...............7.............. 3.................... 5........................ 18
    Leaf or Bolt pulling trailer..... 4.............. 5 ..............5 ....................7......................... 22
    Tesla X pulling trailer ...........3 ..............10 .............3................... 3......................... 19
    Build on Chevy Bolt............. 5 ...............7.............. 6................... 5......................... 23
    Build on Leaf ......................5............... 6............. 6..................... 7......................... 24
    Build on Tesla S, X ..............5.............. 10............. 5.................... 4......................... 24
    From Scratch - Composite Bent. 8........... 8 ...............6 ...................5 .........................27
    From Scratch - 3D Printed ........7.......... 10 ..............4................... 7......................... 28
    From Scratch - Boat Building.... 9............ 8.............. 5 ...................6 .........................28
    From Scratch Carbon over Foam 10 ........10.............. 6................... 4 ........................30

    Control: Buy a 24' Diesel............0..........6..............0..... ...............5..........................11
    Control: Chinook uber alles........0...........2...............0........ ...........7..........................9


    So a couple of things become obvious. First, I should chuck the entire idea. In a sense, I have since I've got a running RV and can go places and do things. But there's something in the human spirit (being dumb perhaps?) that drives us to do shit that doesn't always make sense.

    So in the project area, two solutions rise to the top in terms of feasibility today:
    -Modifying an existing motorhome, Vixen or Ultravan or
    -Build a trailer designed to be pulled by a Tesla Model X.

  2. #112
    Senior Member Starjots's Avatar
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    Time moves on - in the last three years my energy/money has been going into houses with three purchased and two major renovations and a kitchen renovation in that time. Our old school RV (a 1995 Chinook) has been upgraded with a nice solar/battery bank I designed and put in myself for the experience and is really great except the 11-12 mpg. The plan is to 'use it up' and to that end we've put 20,000 miles on it in two years which is pretty good for an RV. At this rate it should easily last another five years or so, so no hurry there.

    I'm watching the development of electric trucks at the moment as a base. Several companies are looking like more than vaporware - Workhorse coming out of the gate the strongest so far with many others major players making their intentions known.

    The main reason I'm posting today though is my favorite Dutch team, Eindhoven has just revealed their third generation Stella solar car. I got misty eyed looking at the pictures. It has a 1000 km range on a sunny day like gen 2 Stella Lux despite having 1 square meter less solar cells (they keep f'ing with the rules for the World Solar Challenge) and a smaller battery.

    Here's my very rough design from three years ago.

    Here's Stella Vie unveiled today.


    and some other shots showing important aerodynamic details:






    The evolution in their designs continue to serve as a strong inspiration.

  3. #113
    Senior Member Starjots's Avatar
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    An interesting development:



    The popular RV company Dethleffs has its new “e.home” on display at this year’s Caravan Salon Düsseldorf 2017 through Sept. 3. The unveiling comes just in time to steal the thunder from Volkswagen’s Kombi van announcement.

    Keeping a motorhome and all its components powered up requires an extensive amount of energy. To meet that requirement, Dethleffs has covered virtually every inch of the e.home with solar panels, similar to the European school with solar panels slathered on all its exterior walls. The RV is built on the company’s Iveco Daily Electric chassis with a 107-horsepower electric motor. The motorhome would have a range just shy of 100 miles if it wasn’t covered in solar panels, but it is. Those babies can make up to 3,000 watts of electricity for its 228-Ah battery. In other words, you’re all good to just keep on going.
    Since this is all European a chassis seems to be available - looks like a delivery van sort of thing. Information on the chassis website is sparse, I think the primary battery clocks in around 60kwh which would match a 100 mile range for something of that weight and form factor.

    The interior is Euro styled. The big plus I see is thick walls implying good insulation, something that you really need if you are relying on electricity for climate control. One of the websites mentions some creative heating and cooling and that's an issues I've thought about but not mentioned here. For my conventional RV when boondocking I have to run the old gas generator to run the AC more than I like because the insulation is little to none. Camping in mountains or parking under a tree is the best solution I have right now in the summer. Keeping an RV cool in the summer and warm in the winter is a big deal problem.

    The exterior shape and weight is old school all the way. The cab overhang (Class C RV in US parlance) gives you a nice sleeping area but is decidedly terrible for aerodynamic drag. Conventional Class C motorhomes sport the worst gas mileage for this very reason, often clocking in at 8-9 miles per gallon vs 10-12 when you lose the overhang.

    The stated 3000 watt charging power is probably calculated on using every inch of exterior space, at least 1/3 of which will not be getting sun at any given time (the opposite walls). The solar cells look like they are derives from Sun Power which are made in the US and are high efficiency at around 22% - which is good. The guts of the electrical system are Victron (Swiss company) which is very good quality stuff and expensive - I'm guessing the inverter is $3000 by itself. I don't get what they are talking about with a 228 ah battery - for 12 volts that's nothing (I have 450 AH in my RV under a couch) unless the voltage is much higher or this is a secondary battery bank devoted to internal power supply needs.

    Regarding range etc., just back of the envelope extrapolations - assuming 2kw/hour charge with 6 hours effective daylight gives 12 kwh/day which is 1/5th estimated battery bank capacity or 20 miles of range/day. If you lived in a densely populated area like Europe you could ease around in this thing using plugins to recharge fairly often. I don't think this is practicable for the western US where distances between destinations are often hundreds of miles.

    However, a more aerodynamic shell and lighter weight materials could significantly extend range with a concomitant decrease in internal living space and increase in price.

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