Saving gas with solar

Shadowcatcher
Shadowcatcher Solar Expert Posts: 228 ✭✭✭
I have to take our teardrop trailer in to the factory in Indiana to get the galley hatch door fixed and was thinking, I know dangerous, there is a line from the TV battery to the trailer battery and a 180W panel on the roof of the trailer. It will supply some of the power (not much) to run the car, the formula about 1 HP to generate 15A.

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Saving gas with solar

    :confused: Are you thinking of connecting the solar panel to the vehicle's electrical system to save gas?
    Don't waste your time: one electrical HP is 746 Watts. 180 Watts is an insignificant blip.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: Saving gas with solar
    It will supply some of the power (not much) to run the car, the formula about 1 HP to generate 15A.

    Remember, your solar panel is probably 17.5 VDC, and the 15 Amps is at 120 VAC 60 Hz:
    • 17.5 volts * 15 amps = 262 watts
    • 120 VAC * 15 amps * 0.67 typical power factor = 1,200 Watts
    • 1 HP ~ 746 Watts

    And your panel is only ~180 watts in ideal sun/conditions anyway...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Saving gas with solar

    Don't mean to be snarky, but why do you have move the trailer x miles just to fix the gally door? Why not remove the door repair it on site, or ship it back to the factory for repair,, or to the dealer?

    Tony
  • jagec
    jagec Solar Expert Posts: 157 ✭✭
    Re: Saving gas with solar

    Some fuel mileage fanatics do "alternator deletes", where they remove the alternator belt and run the car's electronics on deep-cycle batteries alone, recharging them at night. They see about a 10% gain in fuel efficiency, but it takes a lot of work to monitor the charging system while they drive, and plan their night trips carefully so that they don't drain the batteries fully and get stranded.

    You could do something like that, with the solar panel being used to keep the battery from draining during the day.

    It would be interesting, if impractical.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Saving gas with solar

    Do the math,, you ain't going to save 10% of the fuel to run a car with the alternator disconnected! Running watts of a car, with the lights on is maybe 300 watts. Unless y ou are driving a car with ~5 hp the savings is almost not calculable.

    Tony
  • offgrid me
    offgrid me Solar Expert Posts: 119 ✭✭
    Re: Saving gas with solar

    Some newer BMWs and Mercedes have clutched alternators that only come on when the battery gets below a certain threshold. They are saving a couple of percentage points in gas milage.
    Ned
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Saving gas with solar

    Install a magneto for the ignition, replace the fuel injection with a carburetor, switch to carbide lights and hand signals, and learn to sing.
    Problem solved. :p
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Saving gas with solar
    Install a magneto for the ignition, replace the fuel injection with a carburetor, switch to carbide lights and hand signals, and learn to sing.
    Problem solved. :p

    you forgot put a hole in the floor and run like fred flintstone.:p
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Saving gas with solar

    Reding out of curiosity the BMW profile, they suggest a 3% fuel economy improvement. My best guess is that BMw is going for this to improve acceleration as much as for fuel economy, since it shuts off the Alt upon acceleration, turns it on during decel. To me it is a solution in search of a problem. Best drive a bit slower, accelertor a bit slower and you would save the 3% and more! Not to mention, another (expensive) part to fail.

    Tony
  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Re: Saving gas with solar

    This is somewhat not understood correctly,and Its just not BMW/MB units.Mostly all finer Euro units use this system plus many other details I posted here once,

    The So called clutch is a sprag type of clutch , or one way clutch. This is used to to ease the belt load & noise of idling pulsations from the constant uneven idle revs. Slight from each cylinder fire. 4 cyls are worse to V12's they barely require a clutch.
    That is what the So called clutch is, Not like a Air conditioner clutch Electro-mechanical pull in type.

    HTH's
    YMMV

    VT
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Saving gas with solar

    Hmm. And to think I used to idle the old Borgward down to 400 RPM and watch the generator light glow. :p
  • Lee Dodge
    Lee Dodge Solar Expert Posts: 112 ✭✭
    Re: Saving gas with solar
    icarus wrote: »
    Do the math,, you ain't going to save 10% of the fuel to run a car with the alternator disconnected! Running watts of a car, with the lights on is maybe 300 watts. Unless y ou are driving a car with ~5 hp the savings is almost not calculable.

    Tony

    Road load on flat ground for most cars is roughly 5 to 15 HP. So 300 W would be 300/746 HP = 0.4 HP for a 100% efficient alternator. This would be about 3% to 8% of road load, so the electrical load would not be negligible.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Saving gas with solar

    The detail of this is, how often are you running on a flat road, no wind resistance etc. I would be surprised to see a 3% increase in the net. 1% maybe,,, at 30 mpg that is .3 mpg. I would be surprised. I drive with lights on all the time, and once in a while I monitor fuel mileage with the lights off,, and there is no measurable change in fuel mileage.

    Tony
  • Lee Dodge
    Lee Dodge Solar Expert Posts: 112 ✭✭
    Re: Saving gas with solar
    icarus wrote: »
    The detail of this is, how often are you running on a flat road, no wind resistance etc. I would be surprised to see a 3% increase in the net. 1% maybe,,, at 30 mpg that is .3 mpg. I would be surprised. I drive with lights on all the time, and once in a while I monitor fuel mileage with the lights off,, and there is no measurable change in fuel mileage.

    Tony

    The road load numbers do include wind resistance. Wind resistance is the main loss for a vehicle at a constant highway speed. To set up a vehicle dynamometer, there is a required coastdown test, and that coastdown test is also used to easily evaluate air resistance changes to vehicles. (The hyper-mileage guys often report their results this way for aero changes, e.g., http://www.gassavers.org/showthread.php?t=4419)

    I would not claim that the electrical load is huge, but it is large enough that engineers working on automotive fuel efficiency have to consider it. To make fuel efficient cars, there are a lot of small efficiency improvements that are required that add up to very significant improvements in total.

    Interestingly, operating automotive accessories electrically is sometimes more efficient that mechanically when all the losses are included, so in some cases mechanical drives are replaced with electric motors, increasing the overall electric load in a vehicle. I assume that is also required for hybrid cars which need accessories running when the engine is shut down.
  • jagec
    jagec Solar Expert Posts: 157 ✭✭
    Re: Saving gas with solar
    Lee Dodge wrote: »
    Road load on flat ground for most cars is roughly 5 to 15 HP. So 300 W would be 300/746 HP = 0.4 HP for a 100% efficient alternator. This would be about 3% to 8% of road load, so the electrical load would not be negligible.

    And the alternator is closer to 50-60% efficient, so make that 5-16% of road load.

    The people who go to enough trouble to actually remove the alternator are pretty serious about fuel mileage, so they probably operate their cars at minimal loads (which increases the savings from dropping the alternator) more often than most.

    Example link with some tests:
    http://www.metrompg.com/posts/alternator-optional.htm
  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: Saving gas with solar

    The purpose of the thread was to excite discussion, in reality very little is saved and I knew that. As a side note on the way back form Challenger Door I had an accident and the trailer became disconnected from the TV and ended up on its side. The manufactured had never adjusted the coupler for the two inch ball and when I hit a hard bump... no damage to the TV.
    The solar panel attached with VHB tape stayed in place and the Lifeline battery ended upside down with no damage, the Morningstar MPPT controller which was on top of the battery suffered a dent but works fine.