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-   -   Fuel is Fuel.... An alternative view to economy (https://ecomodder.com/forum/showthread.php/fuel-fuel-alternative-view-economy-37815.html)

owly 09-05-2019 04:25 PM

Fuel is Fuel.... An alternative view to economy
 
....... I look at fuel efficiency a bit more broadly than just gas mileage............. About 80% of the energy in a gallon of gasoline goes out as waste heat...... and we cannot improve much on that. However in my part of the world we heat our houses burning propane or natural gas..... That's fuel too!!! If I could capture my waste heat.... some % of it, and use it for home heating, I can greatly improve my fuel efficiency, but it cannot be measured by a simplistic figure like "gas mileage". If 20% of the energy in my fuel goes to propelling my car, and I can utilize even 10% of that energy to heat my house, I've achieved a 50% increase in fuel economy. If I can utilize coolant heat and exhaust heat, and lets say store it in molten salt in a tank, and actually utilize 20% of the energy in the fuel for heating, and 20% for propulsion, I've DOUBLED my fuel economy.

This would only be of value during the heating season........ but it might be possible to get my 18 mpg pickup up to an effective 36 mpg.......... better than my car.

We need to look at our overall energy consumption not just gas mileage...... In an ideal world, one would have a thermal solution in an insulated tank, and when you filled your car with gas, you would pump out the solution and replace it with cold solution, and get credited for the thermal value based on seasonal demand, and it would be used in homes and buildings..........

H.W.

oil pan 4 09-05-2019 04:36 PM

I bought a Nissan leaf.
If happen to charge it with mostly natural gas then the power likely came from a natural gas combined cycle plant which can easily be 50% efficient.
If it's from a coal plant, less than 38%.
For wind power I'm just going to say it's about 100% efficient.

In Europe they seem to have figured out how to use waste heat for home heating, but in the US no one really seems interested.

freebeard 09-05-2019 05:07 PM

Quote:

If I can utilize coolant heat and exhaust heat, and lets say store it in molten salt in a tank...
You'd need to choose the salts correctly. https://duckduckgo.com/?q=eutectic+salt

A little research should tell you how big a trailer you'd need to move the salt from the vehicle to the house.

Frank Lee 09-05-2019 05:31 PM

Put an overhead door in the living room, drive on in. :thumbup:

That's not a new idea of mine, but for an entirely different reason. I used to have tenants and even though the driveway was RIGHT FREEKING THERE, they always parked on the grass to save that THREE STEPS. So I thought they might like an overhead door into the house, the lazy ****s. :rolleyes:

mort 09-05-2019 05:46 PM

Quote:

Originally Posted by Frank Lee (Post 606149)
Put an overhead door in the living room, drive on in.

Florida couple heeds Dorian warnings and moves their cars
Quote:

Since it is so small, he was able to park his car in the kitchen.
-mort

oil pan 4 09-05-2019 06:02 PM

Good reason to have french doors.

roosterk0031 09-05-2019 06:11 PM

Problem is going to be weight, takes a lot of mass to hold fairly few BTU. Water holds 1 btu per lb per degree F temperature change. To hold 1 gallon worth of LP BTU's (91,500 btu/gallon) assuming a 140(70-210) degree temperature difference in the water/antifreeze you'd need 657 lbs of water (79 gallons). My furnace is 80,000 btu so that would be 68 minutes or run time. I think my last LP fill was $1.25 a gallon but has been over $3 in the past.

So I'd need 2 (40) gallon hot water heaters sized tanks, an heat exchanger in the exhaust (wrap exhaust pipe with copper tube and insulate), an expansion tank and a circulating pump.

Then a way to put the heat into house (already have some radiant hot water floor heat in part of my house so that part would be easy for me. Park in the garage, hook up 2 hoses and turn on the 12v circ pump.

I don't know the specific heat of brine or how that would change things.

redpoint5 09-05-2019 07:06 PM

Just need to concentrate the heat into smaller and smaller space... sounds like the beginnings of a fusion reactor.

freebeard 09-05-2019 09:00 PM

So I used the link I provided and found this:
Quote:

Eutectic salts also use latent heat associated w/ freezing and melting, but one lb. of solid eutectic salt absorbs only 50 Btu to become liquid.
https://www.cedengineering.com/userf...%20Storage.pdf

It's about cooling instead of heat, but phase change is phase change.

owly 09-05-2019 11:13 PM

Quote:

Originally Posted by roosterk0031 (Post 606155)
Problem is going to be weight, takes a lot of mass to hold fairly few BTU. Water holds 1 btu per lb per degree F temperature change. To hold 1 gallon worth of LP BTU's (91,500 btu/gallon) assuming a 140(70-210) degree temperature difference in the water/antifreeze you'd need 657 lbs of water (79 gallons). My furnace is 80,000 btu so that would be 68 minutes or run time. I think my last LP fill was $1.25 a gallon but has been over $3 in the past.

So I'd need 2 (40) gallon hot water heaters sized tanks, an heat exchanger in the exhaust (wrap exhaust pipe with copper tube and insulate), an expansion tank and a circulating pump.

Then a way to put the heat into house (already have some radiant hot water floor heat in part of my house so that part would be easy for me. Park in the garage, hook up 2 hoses and turn on the 12v circ pump.

I don\'t know the specific heat of brine or how that would change things.

Somebody below linked to a site that presumably explains phase change.... We are NOT talking about brine here, but phase change of a salt from solid to liquid. The principle is the same as melting ice. It takes approximately 80 times as much energy to change ice to liquid water, as it does to raise the same amount of water one degree C. Molten salts or eutectic salts if you will, are engineered to have the phase change of the salt from solid to liquid at the temperature you need it.... this would presumably be around 180F, or a bit lower. The latent heat of fusion of these salts probably is not as high as water, but even at 1/2 that, you would need only a fraction as much as you would need water.
The only reason for having an actual brine, is for mobility in the solid state, and faster distribution of the energy through the mass of salts.

H.W.


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