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Discussion Starter #1
To over come some of issue with energy losses do to running the heat pump, could it be feasible to have a hot or cold storage. I've heard of building that will cool water overnight while electricity is cheap and the temperature outside is lower and then use it for cooling in the day time. A similar thing could be done with the Volt. That way you're not burning up precious battery stored energy, to convert mechanical energy, only to then conduct heat transfer from cold to hot. I think storing heat energy might be more efficient.
 

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That's actually an interesting idea. I know of delivery vehicles that do the same thing, so that they don't burn gas on generators to keep things cool in transit. Since it is an added mass, regenerative braking would prevent too much loss of energy in accelerating / decelerating that mass, so it is a possibility.
 

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To over come some of issue with energy losses do to running the heat pump, could it be feasible to have a hot or cold storage. I've heard of building that will cool water overnight while electricity is cheap and the temperature outside is lower and then use it for cooling in the day time. A similar thing could be done with the Volt. That way you're not burning up precious battery stored energy, to convert mechanical energy, only to then conduct heat transfer from cold to hot. I think storing heat energy might be more efficient.
Where would that hot storage come from when the vehicle sits overnight at -30 F?
 

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Where would that hot storage come from when the vehicle sits overnight at -30 F?
That's a great question. I would assume that the vehicle would be plugged-in overnight, to recharge batteries as well as power a heat / cold reservoir. This reservoir would be "topped-off" with heat and insulated, until you pull the plug the next morning and drive to work.

You are correct, that any heat / cold reservoir would lose it's storage over time, when not plugged in, but as long as it is plugged in, you have a "topped-off" reservoir for your commute.
 

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not too practical

Many ideas that work in buildings or large vehicles are not practical for a small sedan. Like giant flywheels, or huge battery packs, or phase change material to store thermal energy.

Not that it can't be done, but the return on investment is not going to make it very worthwhile to do it. The size of the thermal mass needed to make it worthwhile is going to add weight and take up valuable storage space.

However, it would be nice if you could pre-cool/pre-heat the vehicle while it's plugged in, that would make the drive to work more pleasant. The drive home after being in the sun all day might be more problematic.
 

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There are salt like crystals which store energy or give it up much like ice does except at higher temperatures. Kind of like blue ice but warm.
 

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Discussion Starter #7
just a thought anyway

js1k - yes you are correct that the economy of scale doesn't apply here, however, I think there will be some benefit. I have yet to crunch any numbers. I'll probably use antifreeze (water/prop-glycol) as the storage medium, but I'm sure the goo in ice packs would work as well.

as for the -30 statement, it'll be a wash. Your going to heat up your car anyway. you'll get the benefit of what ever heat is stored in the reservoir. Think of it as another, cheaper battery.
 

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thermal storage

The most efficient cooling storage per pound and cubic foot would be ice. It works out a lot better than the eutectic salts. It will store 80 BTU's per pound. 8 pounds = 1 gallon. Assuming the Volt needs 3,000 BTU/hr of cooling (1/4 ton). ), you can see that 20 pounds of ice (2.5 gallons) would give you about a 1,600 BTU's, or a half-hour of cooling. That may be OK for the typical 40-mile range to get you most of the way there. Most heat pumps should be able to generate glycol temperatures sufficient to make ice.

Ice is now really catching on in the HVAC industry as a way to shift cooling loads. I

Heating storage might be tougher. Heat pumps can only make about 120 degree F water. Cooling that water to 80 degrees would give 40 BTU's per pound. That's not a lot of heat. A higher temperature change-of-phase storage medium would be more efficient per pound.

Most cars' AC units are rated at 1/2 ton or more, but I bet the Volt engineers are looking at ways to cut down cooling/heating loads as much as everything else.
 

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Lion-EV does conversions. They maintain the the OEM heater core. They insulate and re-route the hoses to the old radiator overflow tank which is disconnected from the radiator. Thus creating a closed loop from a tank to the heater core. They insert a small pump and two small electric submersion heaters, fill the system with anti-freeze and presto...a very good heater. (So they claim)

A small low current version of this could be used to augment the heating side of the heat pump, because as hvacman points out, heat pumps cool much better than they heat. Actually, I don't believe a heat pump alone will provide sufficient heat for colder climates.

I suppose with some electric valves, a heat exchanger in the heater core and a bit of computing power we could also connect the AC, and the ICE and Battery cooling systems. Hmmm a hybrid HVAC system?

Not completely different in concept to a three stage residential air to air heat pump that has electric back up for heat; or gas, or radiant...

Properly managed I bet a single heat pump could provide all of the heating and cooling for both the passenger compartment and the drive systems. But it would require at least one heat exchanger, maybe two...?
 

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improved envelope efficiency

Improved body insulation, a blend of recirculated air and outside air or outside air energy recovery, and better glass treatments will do wonders for improving the vehicle's heating and cooling loads. Before all-electric vehicles, energy efficiency on the automotive heating/cooling side hasn't been much of an issue. After all, 160 HP gas engines generate a surplus of heat, so that was "free" and 1 HP of engine load to cover the AC was pretty insignificant.

Homes and buildings, on the other hand, have been fighting that energy battle for decades and the battle will be getting worse. The new low-e glass coatings used on home windows could cut the heat gain in car glass to 1/3 what they are now. Granted, car glass has a lot rougher life than window glass, so dual-pane may not pencil out. Better body insulation would help. Also, optimized fresh-air ventilation and recovering the heat/cooling from the exhausted air could cut heating/cooling loads in half.

I am intrigued about a high-temperature phase-change heat storage material, though, that could be "melted" during the re-charge cycle. Maybe a wax of some kind with a high specific heat of fusion. People played around with that type of stuff a lot during the solar heating heyday of the late 70's-early 80's.
 

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Low-e

I agree with hvacman, Low-e glass would have a significant effect on the interior cooling load inparticular.
I find it surprising that low-e hasn't been more aggressively pursued by the auto industry...but I think I know why and may have a solution.

For those who don't know, Low-e (low emissivity) glass has a soft coating on the surface that is a spectrally selective reflector. Basically it is a reflector, like a mirror. But unlike a mirror it is a reflector that is specific to only certain frequencies of the light spectrum, usally low frequencies (infrared) and high frequencies (ultraviolet) both of which are higher and lower than the visible light spectrum. The result is a highly reflective glass that appears clear to the human eye.
Since a large part of the heat energy of the sun is contained in the infrared spectrum, it is reflected away from the glass resulting in much cooler interior temperatures. The ultraviolet spectrum contains very little heat energy by comparison but is damaging to our eyes, upolstry, plastics, etc.
By tuning the Low-e glass to slightly encroach into the visible light spectrum we can reflect even more heat and provide a tinted glass appearance that out performs basic tinted glass. Tinted glass which can get hot enough to burn you absorbs heat, low-e glass actually reflects the heat away remains relatively cool to the touch.
The problem is that the low-e coating on the surface of the glass is so soft that it can be rubbed off with your fingers. This is why low-e glass is always used in double pane windows with the low-e surface toward the inside for protection.
Double pane glass is too big and bulky to be used in automobiles, but a low-e coating between the layers of laminated glass (like your windshield) is conceivable. Laminated glass is also a better conductive heat insulator than tempered glass and has good sound transmission characteristics to help minimize road noise.
I think Cardinal Glass was experimenting with Low-e laminated glass a few years ago. Anybody have any info on that?
 

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Heat 'battery' through chemical recombination

One of the very first attempts to store hydrogen for ICE automobilies involved metal hydrides. The hydrides would sponge-up hydrogen and release it for combustion. Since the absorbtion was essentially a chemical phenomenon, there was an endothermic/exothermic effect: mixing the hydrogen with the hydride produced heat, which had to be removed. In order to get the hydrogen out to burn, the hydride had to be heated with waste heat from the engine (which would run on a small amount of pressurized hydrogen until coming up to temperature).

Years later, I found myself wondering if a sealed variation of this could become the equivalent of a 'heat battery:' Heat from the engine would release hydrogen from the hydride, storing it in a separate chamber. Later, perhaps months later, you would allow the hydrogen to go back into the hydride, releasing heat.

My idea was to pre-heat an engine using this chemically-stored heat prior to starting it, to prolong it's life.

There is a huge difference between exploiting endothermic / exothermic chemical reactions, and simply storing latent energy: as long as the endothermically separated chemicals are kept apart, be it months later and sub-freezing temperatures, the energy is stored; released only when the chemicals are allowed to recombine.

If heat energy could be stored this way, waste heat from the range-extender could be kept ready even if it is run rarely.

Obviously, there are problems with the hydrogen/hydride idea, but other chemical couples may be possible.

This is extremely theoretical, and I wouldn't expect this to appear for quite a few years. Just something to think about, for now.
 

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hydrogen/nitrogen/ammonia

You can do the trick with hydrogen and nitrogen.

The reaction to form ammonia from hydrogen and nitrogen is exothermic.

A company in Australia is developing this concept.
You have a tank with hydrogen/nitrogen/ammonia.
In the Concentrated solar collector, the ammonia is split into hydrogen and nitrogen. Those are transported to the tank.

When you need the energy, you convert the hydrogen and nitrogen back to ammonia. This releases heat, used for electricity production.

Lucas
 
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