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Old 10-09-2019, 02:03 PM   #51 (permalink)
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Quote:
Originally Posted by kmccune
Get an EV and setup a "Totem" system, which uses an ICE to run a generator and catches the waste heat for domestic water heating, that way you can be sure your fuel is being utilized in an efficient manner, you can do this with gas,diesel or natural gas even propane.
I've read about the [legendary] stationary Lister Diesel engine. They're reproduced in India today, but apparently you have to special order the good bearings, etc.

http://www.wikihow.com/Cook-Food-on-Your-Car's-Engine

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Old 10-10-2019, 08:34 AM   #52 (permalink)
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You could use an auto engine for this purpose or a 'China-Diesel"
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Old 10-10-2019, 12:49 PM   #53 (permalink)
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Where to do the thermal storage?

First thing I can think of is how to store the heat energy from a car in such a way it can both be captured without leaking heat and will not weigh so much (think: huge seal and outer foam insulated water container) it would kill the car's fuel economy, thus largely defeating the point.

The other thing is how does running a car engine for heat compare to running, say, an heat exchanger / A/C in reverse for heating?

One idea, wind some sort of water filled coil around the area near the pistons/explosions and exhaust and use that to drive a steam engine that charges a battery and then have the gas recondense on part of the coil that hangs outside the car in the cold. Maybe even have it directly recharge the 12v battery, reducing the amount of power the alternator needs to take from the engine to run accessories.

Then again, I own all electric vehicles that have no such heat loss and, in the greater scheme of things, would recommend just dumping all the complexity and getting a solar charged EV setup like I have at home or, depending on the location, perhaps hydrothermal, wind, or another non-wood based renewable energy source and skip the initial problem altogether. And/or at least just plain old build, say, such a steam engine generator into remaining natural gas electricity generation plants, if they don't have such already, and power the EV through those as a second option as they don't have the thermal storage mass issues a car would for such a setup.
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Old 10-10-2019, 01:36 PM   #54 (permalink)
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Some of the better heat pumps can deliver 4-6x as much heat as they use in electricity in most climates.
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Old 10-10-2019, 02:55 PM   #55 (permalink)
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Well, ground-source heat pump is ideal, but carries with it a higher cost to install and difficult repair should a break develop.
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Old 10-10-2019, 06:33 PM   #56 (permalink)
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Stop the presses, we'll need to rethink everything from batteries to heat exchangers based on this: https://phys.org/news/2018-08-schwar...fullerene.html

Quote:
The discovery of buckyballs surprised and delighted chemists in the 1980s, nanotubes jazzed physicists in the 1990s, and graphene charged up materials scientists in the 2000s, but one nanoscale carbon structure—a negatively curved surface called a schwarzite—has eluded everyone. Until now.
[snip]
The new structures were built inside the pores of zeolites, crystalline forms of silicon dioxide—sand—more commonly used as water softeners in laundry detergents and to catalytically crack petroleum into gasoline. Called zeolite-templated carbons (ZTC), the structures were being investigated for possible interesting properties, though the creators were unaware of their identity as schwarzites, which theoretical chemists have worked on for decades.
This structure divides any arbitrary volume into two with a minimal* surface area separating them. On the macroscale an air-to-air heat exchanger could be 3D printed from copper or even an thin insulator like paper.

Exhaust air to intake air or vice versa.

*Then again, maybe I meant maximal. A flat plane would be minimal.
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Old 10-10-2019, 08:10 PM   #57 (permalink)
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Quote:
Originally Posted by Bicycle Bob View Post
In heat engines, efficiency is totally dependent on temperature difference. That's why jet engines use such expensive high-temperature materials, and diesels still beat them by letting ordinary metal cool off between thermal peaks.

Not to mention jets, turboprops/turbofans and turboshafts usually fitted to helicopters and stationary powerplants are more prone to FOD than a Diesel. Too bad there is no Diesel with enough power-density to power modern commercial aircraft...
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Old 10-10-2019, 09:35 PM   #58 (permalink)
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A very old link describes how some British engineers designed a sort of turbo generator that generates electricity from the turbo being spun by hot exhaust gases. They claimed up to 6kw of power available, although that number seems a bit stretched. Seems like a neat concept, but I see no instance of this having made it to production. The link to the original article in the site is dead.

https://www.greencarcongress.com/200..._exhaust_.html

Honda is either using, or will be using, a Rankine cycle system in their hybrids that follows a similar method by using exhaust gases to evaporate water and generate electricity through steam.

If we consider that the average ICE engine is 30% efficient, or perhaps 40% efficient if it's a lean burn Honda or Atkinson cycle car, then for every 5 hp the car generates, 7-12 hp is being wasted (5.2 - 8.9 kw).

Even if such a system is only 15% efficient, that's still around a kilowatt of power being generated. And that's at 5hp; at highway speed more power could be generated.

This electrical power could then be stored and used for a variety of purposes, from a constant electrical boost to an engine to storing the electricity in batteries for home use. This would allow a more practical use of the wasted energy than trying to use the direct heat from the exhaust - which contains many toxic chemicals and therefore shouldn't be used to heat a house or other building.

One also has to consider the cost of implementing such a system - are we talking about efficiency, or economy? There is a difference between the two. Economy has to take into consideration implementation cost.
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Old 10-10-2019, 11:28 PM   #59 (permalink)
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There will be something about that here:https://duckduckgo.com/?q=bmw+exhaust+heat+recovery.

A quick scan of the result suggests BMW achieve 2% better fuel mileage.

Quote:
BMW provides an update on waste heat recovery projects ...
https://www.greencarcongress.com/201...-20110830.html
Insulation of the engine compartment, gearbox oil heating with exhaust heat exchangers installed with gasoline engines, or the heating function of the exhaust heat exchanger for diesel engines are features that are well-suited for vehicles that are predominately driven over short distances, BMW says.
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Old 10-11-2019, 02:03 PM   #60 (permalink)
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Quote:
Originally Posted by Ecky View Post
This is a very pertinent point. An EV may be 80-90% efficient from outlet to road miles, but there's also the efficiency of power plants to account for, and transmission of that power.

Honda and Toyota both have engines which can make 40% of energy in gasoline usable.

How does one compare the fuel "efficiency" of a solar panel or hydro?

Cost per mile is one way of looking at things, but over what period do you calculate it? A projected lifespan of the vehicle? Do you calculate only cost you have to pay, or should overall cost of production and disposal (and even pollution) be accounted for?
Ecky, you quoted the 40% ICE efficiency, but isn't that just the PEAK efficiency when you're riding the island on the BSFC plot? For most drivers, most of their driving is far off this peak. So the average ICE efficiency is down <20%.
People on this forum are aware of that and drive for efficiency but the vast majority of people do not. So if an electric motor is at 90% for all driving conditions, then doesn't that make more sense for majority of people?

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