Solar panel to offset alternator load

[silvermazda]

Cobb, your post was interesting.
Oldtamiya.., I am going in optimistic, this is one of the only mods that fits with my car, engine heater pending, peltier on radiator pending, partial grill block, pending. And half of the 100+ or 65 mpg mods dont work on my car or my car is broken from factory being a 4 cyl sporty car. Short gearing, gas was 1.50 back then, convertable ruins aero, ect. And to a degree I dont want to change the qualities of my car because it makes a joy to drive vs the family 4spd wide geared auto, which is quite comfortable, but boring on occasion (its probs the transmission and engine tuning, modifiable, but not easy or cheap).

I have to disclose that from the factory I had a 20.8lbs battery and replaced it with a 7lbs motorcycle 12V, which is great, still cranks over enough times in a winter morning. MPG didnt change and a slight bump when new.

[oldtamiyaphile]

Aero mod it!



I keep looking for a nice MX5 to do this to.

[oil pan 4]

Some time ago I figured for every 100 watts of accessory load I could remove (not alternator watts) from my suburban I would see about a 0.1mpg increase.
For a car, you would see about twice that for every 100w removed.

[oldtamiyaphile]

Originally Posted by oil pan 4

Some time ago I figured for every 100 watts of accessory load I could remove (not alternator watts) from my suburban I would see about a 0.1mpg increase.
For a car, you would see about twice that for every 100w removed.

When I turn the headlights (in round figures let's call that 100W, it has LED's where possible) on in my Jeep at idle, my LPH jumps up by 0.3. Since my average speed is 50km/h that's 0.6l per 100km. That's nearly 1MPG.

In a city driven car like my T5 with an AVG speed of 27km/h, that would be ~1.6MPG per 100W.

[order99]

Quick question-since Silverhonda wants to use peltier coolers on the radiator to reclaim power...any idea how many coolers it would take to just run the cooling fans directly, bypassing the other electrics and removing the parasitic load? Just curious-I think playing around with my recent Bicycle designs have me considering multiple self-powered autonomous subsystems of late...

While we're talking about power reclamation-did any of those 'shock-absorber generators' ever make it out of the labs, or did they prove impractical?

[silvermazda]

oldtamiya you forgot the back lights in that calc. I dont usually see a drop in mileage with the lights on. Hm.....food for thought, but I dont got a scangauge.

order99, I dont know maybe 5-12amps while running. Not accurate numbers.

oilpan4, do you think it will work in reverse? Would loading 100W burn as much gas as removing it?

[mort]

Originally Posted by silvermazda

...
I recently found about peltier coolers, but those dont generate much. I though about hooking up 10 to the top of the radiator, enough heat (~180*F), though I am not sure if it will work with out a heat sink on the other side, will it? ...

Hi silvermazda,
No. No huge number of junctions or huge heat sinks will help. I can show you the math if you like, but the bottom line is that if your car needs 10 hp to cruise, and you replace the radiator with a vast number of reversed peltiers the best you can do is about 15 watts of electric power at cruise. And approximately no electric power at idle.

-mort

[oldtamiyaphile]

Originally Posted by silvermazda

oldtamiya you forgot the back lights in that calc.

I didn't, I have LED tail lights on all my cars they draw about 1W, I haven't yet converted all my dash lights to LED, but there's only about 5W there, either way you'll never be able to measure the impact of draws like that except maybe in a very accurate lab situation.

If you've never noticed the FE effect of headlights, the effect of fitting a solar panel will only be 1/3 of that (ie you won't notice it). An SG2 will save you much more than a solar panel.

Realisitcally, if you're concerned about alt. load, reducing it is the first place to start. LED's throughout if done carefully, will improve safety, last forever and save fuel.

[serialk11r]

silvermazda I think you're looking in the wrong places for improvements. With a stock electrical system, you're still drawing way more power than the panel can provide, plus when the car is off the panel is only good for topping off the battery, not saving any fuel. The efficiency of lead acid batteries is pretty bad.

I think solar panels are a good idea, but just for topping off the battery while it's parked instead of using a trickle charger, which isn't an option for people who park in shared garages and on the street.

Peltiers on the radiator will also fail to reclaim much power. Consider that you need a 60mm 300C rated Peltier to generate 15W from a 200C temperature differential. You're working off <100C (probably more like 50C) temperature differential with the radiator, so you'd get 3W if you're lucky per 60mm x 60mm unit, probably less with air cooling.

If you stick 20 of those on the exhaust, and have them share the engine coolant loop, you'll be able to get rid of most of the load on the alternator, but you'll also be out over 1k in Peltiers plus whatever your heat exchanger costs you to make or buy. With currently available ones (300C max temp) you'd also need a way to control the temperature under heavy engine load so they don't fry.

Maybe in the near future we'll have silicon based thermoelectric generators that can tolerate higher temperatures and be more cost effective, but it's not feasible now. With 700C capable units and similar Z we would be able to generate more like 30-50W per unit.

[elhigh]

I always thought the smart place to put TE generators would be on the exhaust. MUCH hotter.

Billet aluminum machined to matching outside tube radius downstream of the catalytic converter, with a flat mounting surface for the TE, and then probably any stock extruded heat sink for the cold side. All of this projects slightly beyond a belly pan and Bob's your uncle. Series or parallel wiring as necessary for the appropriate voltage.

[edit] Whoops! Serial got there before me. Ah well.