# Forums

Join The Community

Possible heating and cooling solution?

Lately I have read about two ways to store electricity to use later for heating and cooling and it got me thinking about how it could be applied to EVs. One can store electricity in the form of ice to later use for cooling. One can store electricity as heat in ceramic bricks to later use for heating. These two methods have been around for years and are relatively cheap, so instead of using the battery to store electricity to use for heating and cooling one could buy a hot weather or cold weather package depending on where one lives.

So a person in Florida could buy a package that at night uses off peak electricity to create ice in the frunk that would be used for cooling the car instead of wasting electricity stored in the battery. A person in Canada could have an electric thermal storage heater that heats up at night with off peak electricity that could be used to heat the cabin and battery. Both could be built so the heavy parts could be removed from the car during temperate weather.

Now I realize the Tesla air conditioner is probably more efficient than these devices, but this is really more about maximizing stored kWh than efficiency. The cost, weight, and volume of the battery vs the cost, weight, volume of this storage per kWh is really the deciding factor on whether this type of system makes sense. So, and these are just wild guesses, the option might cost \$1000 and provide an extra 10 kWh to use for heating or cooling which is \$100/kWh. In places like Florida or Texas the standard heater is sufficient and there is no need for stored heat and vice versa. Also, this is not that big a deal for the 85 kWh Model S, but the 3rd generation Tesla will need every kWh to get 200 miles of range.

Instead of making wild guesses, do the math.

Nobody with these weird ideas ever wants to do the math.

Hurry up and start you brick I've business! I'm sure lots if people here will sign up for such convenience!

You can make enough money to buy a garage full of half baked / half frozen Teslas!

Sigh.

I've just imagined an etablished man in a suit shoveling a load of heated rocks, or ice cubes into cabin of his premium electric sedan before heading to board meeting of his company...

You are right the Volt doesn't drive around with heated metal!?! Turning water into ice is super difficult!?! Nobody would ever put ice anywhere near a Tesla!!! Using ice for cooling is soooo "weird"...it has only been done since the beginning of air conditioning. Using thermal heat storage is so "weird", it is only done all over Europe.

The math is easy, it is cheaper than the battery but less efficient than a heat pump. You see electricity turns to heat near 100% efficient and it is easy to store at that efficiency. It takes 4-5 kWh to turn 100 pounds of water into ice. Ice and heat can be stored and all cars drive around with motors that are heated to 400 degrees. People drive all the time with ice in their car and some even drive in icy conditions.

Sigh.

An ICE at 400 degrees, even Fahrenheit would be toast. Even 400 Kelvin is too much, engines would be boiling like crazy at 127*C...

Thermal heat storage you are referencing is probably something you can use for heating or cooling a building, it involves lots of "medium" to store actual heat.

Let me do some math: We are freezing a 1L bottle of water to say -20*C. Temperature inside car: 20*C It takes about 440 kJ to heat up (including melting) that bottle to interior temperature. That's 0,12(2) kWh worth of energy. Let's say we are having a hot sunny day and we require 5kW of cooling to maintain interior temp. So we need to melt and heat to 20 degrees Celsius 41 litres of water per hour.

Does it still sound reasonable to you?

Let me reframe this, I read that an electric bus in Canada used a diesel heater to heat the cabin of the bus, the Volt uses the ICE for heat, so the problem is that EVs have shorter range in cold weather. One expensive solution would be to build a bigger battery...that is obvious. But heat storage and ice storage for cooling and heating have been around for decades. Why not couple these electricity storage methods to make the heat pump more efficient? Electric thermal storage heaters in Europe have sizes that store several kWh to heat one room, and they are cheap. Obviously safety is a big roadblock for storing heat, but a Volt rolls around with an ICE so it might not be insurmountable.

The issue is how to extend range in northern winters and southern summers and a bigger battery is an obvious and expensive solution. Another solution is more superchargers. But there might be a cheaper way to essentially add 10 kWh of range.

Gene Frenkle, you are forgetting that you have to carry the water and bricks. The extra mass will degrade range. Dont forget pumps, heat exchangers, tieing this into the existing heating and cooling plant....

The Model S doesnt use much power for AC. Heating is a power drain... try storing the car in a heated garage.

Not sure how the Volt rolling around with an ICE in the front is relevant. It carries an ICE but the heating in that car is TERRIBLE when in electric mode.

Ice hasn't been used for portable cooling since the 'icebox' was replaced by the electric refrigerator in the 1930s. And using heat sinks for heating is only done in fixed base setups- NOT in a MOBILE platform.

Well, you go ahead and start an electric car company with ice blocks and heat bricks... if it is better, you should be able to show it.

More mass, lots of water, frunk full of bricks... surely you can see how this is not only impractical, and ridiculous, but UNSAFE?

Maybe he ran headlong into a brick wall while sloshed, and was inspired?

The Volt has an ICE in its frunk, is that impractical? An electric bus in Canada has a diesel heater to heat the cabin, is that impractical? Is having a cooler with ice in a car impractical? Using natural gas to heat a garage so your EV is warm, is that impractical?

The economics with the heater most likely work, safety is the only roadblock...but that is obvious. Is it safe to drive in a car with an ICE in the front? EVs have an issue that people on this forum want to solve by building bigger batteries while Tesla is trying to build cars with smaller batteries.

Also stored heat could be used to power an absorption chiller, so if ice is too heavy and too much volume the 10 kWh of stored heat could be used for cooling. Once again effiency is not the concern, adding cheap kWh is the goal.

Gene, all buses used in colder climate, even diesel ones have diesel heaters, ICE produces not enough heat to provide reasonable temperature inside poorly insulated 12m long metal tube that opens up to 3 pairs of doors for 10 seconds every minute or two.

A combustion (or catalytic) heater is likely the best way of providing heat. It eliminates energy conversions and it's efficency is in 80%-90% range (some heat is lost with exhaust). It can also burn cleaner than ICE because it's easier to control it's combustion chamber. But if our goal is making a "zero emmisions" vehicle then this heater would ruin it...

I would say an electric bus with a diesel heater is a hybrid. I searched for surface temperature of diesel/kerosene space heaters and I found that they get up to 500 degrees Fahrenheit, so buses apparently are currently rolling around with something that is very hot, so the heat of a thermal storage device could be at least 500 degrees and still be as safe as the kerosene heater. So now all that is needed is an electric thermal storage device that is as safe in a crash as a heater.

Electric thermal storage heaters can compete with heating oil on price if there is an off peak electricity rate, that is why they are used all over Europe and beginning to be used more in the US. The kWh cost has to be substantially cheaper than batteries in an electric car because the kWh can't be used to power the wheels, but an electric bus appears to need a way to store electricity as heat in order to not be a hybrid.

Umm, yes @Gene, diesel fuel gets really hot when when it burns. In an engine, it is much hotter than 500 degrees F- the compression stroke heats the cylinder contents adiabatically to 1022F- that's before the combustion cycle. Flash point of diesel at ambient pressure is 210C or 410 F so that is the minimum temperature at which it could be burned in a heater.

You do know that the ICE in the front of the volt is an engine not a block of ice I hope. And, yes, EV enthusiasts are going to tell you that carrying around an ICE motor JUST FOR CABIN HEAT is ridiculously impractical; and that carrying around diesel fuel and burner JUST FOR CABIN HEAT is impractical.

Wasnt aware anyone was discussing battery powered electric buses. All the ones I have ever seen are trackless trolleys- overhead wires- and they, of course are electrically heated. Stringing wire for a bus or trolley is OK due to fixed route.

DTsea, thanks for the reply. BYD make an electric bus with huge batteries and buses and trams that use both batteries and overhead wires will also become more common

What I am trying to figure out is if there is a way to store electricity for heat or cooling in a cheaper medium than a battery. Outside of an automobile ice and ceramic bricks have been used for decades to store electricity to use later for heating and cooling and will be used more in the US to store electricity from wind and solar. The two mediums are cheap and in Europe the electric ceramic brick heaters are cheaper than oil IF one uses off peak electricity. Ice is cheaper if one uses off peak to freeze water.

Tesla is trying build cars with smaller batteries but still get 200 miles, so if there is another way to store kWh on board that will definitely get used in air conditioning then those kWh increase range. Obviously if the battery is 85 kWh with a robust supercharger network then one should always have stored electricity for heat, so this discussion is really about the 3rd Gen and 2nd Gen Leaf. I think everybody got hung up on the storage mediums I mentioned when those were just examples of storage mediums currently in use. So the issue is, is there a cheap solution to store heat on board outside the battery so the next generation of EVs can get their rated distance even in the northern winter? Those people might just have to opt for the bigger battery which is an obvious solution.

Gene: "What I am trying to figure out is if there is a way to store electricity for heat or cooling in a cheaper medium than a battery"

Not in a long term reliable way. Batteries that hold electricity that runs heaters and coolers is the BEST way to do this in an automobile.

Other ways are too heavy, or too unreliable.

If a technology is found that is more reliable, lighter, or energy efficient, Tesla will do it, and so will other automakers.

Holidayday--are you taking a holiday from thinking?? Didn't Tesla just make a modification to the battery pack shield?? So nobody needs to think about improving things because other people are thinking about it!?! That is a great way of thinking...or really NOT thinking. EVs are an emerging technology, we can now harness the power of the internet to improve technologies more quickly.

For example, I thought of a good way to deal with level 2 chargers getting filled up. Malls and restaurants can offer 15-30 minutes of free level 2 charging by having 4 plugs for 1 level 2 charger. If a person is plugged in for 2 hours at a mall the charger would level 2 charge on a first come first serve basis for 30 minutes per plug, no need to unplug or worry about others unplugging. This would allow the mall to buy less level 2 chargers while serving more EVs.

Gene: "So nobody needs to think about improving things because other people are thinking about it!?"

Sure, they can think all they want.

But actual implementation takes money. REAL MONEY that is used for improvements. When deciding where to put improvements, real world solutions will get the money. Not thoughts.

"we can now harness the power of the internet to improve technologies more quickly"

Once it moves from internet talk to proven technology, Tesla will not do it. Now, if TESLA is the one creating the technology and improving it, then that will make them use it faster. But saying "why don't we just use a fusion generator range extender for unlimited range?" is just that. . .talk.

Your reference to fusion means you don't have a clue what you are talking about. Electric thermal storage is a proven cheap way to store electricity in a relatively small package to be used for heat. The usefulness of this storage would be limited in autos because it can't be used to power the wheels, but that does not mean it can't be useful if the price is right...and apparently electric buses in northern climates might need more than a battery for heat. The economics and reliability of the heat storage system makes economic sense, the obvious impediment is safety and the costs associated with safety. I have an economics background, not a STEM background, so I was interested in a discussion with knowledgeable people from other backgrounds like Named User.

Using mass to carry or absorb thermal energy is efficient only at extremes. As temps approach ambient, it's literally "dead weight" which must be hauled around. So is all the insulation it necessarily needs to control its temperature.

And 15-30 minutes of free L2 isn't worth enough to motivate good behaviour. The stalls would fill with shoppers cars, and they wouldn't bother coming back early to move them. Same as now.

My solution to L2 charging does not require any behavior by the person charging--that is why it is a solution. 4 or more plugs per L2 charger, but only one of those plugs is getting L2 charging at a time. The cords could be short if the charger was built in the middle of 4 spots. After the 30 minutes the car get level 1 charging. A pay L2 charger could be off to the side for people that need more range. People only stay at mall or restaurants for a set period time like 1-3 hours.

This seems very like the solar idea. The technology itself is good and useful in the right implementation. Putting it in a vehicle is not the right implementation. The amount of heat or cold it can store is related to the mass of the material, which is extra mass that the car needs to move around, consuming extra energy. If you have two different mediums, the one you are not using is just dead weight you are lugging around. If the temperature is medium, where you don't need heating or cooling, then they're both dead weight. Also, for whatever amount of weight you are talking about using that is substituting for battery weight, it can only be used for one purpose--climate control. That stored temperature energy cannot be accessed to move the car, so that's less flexibility of its use.

I'm saying the idea is great for buildings, where a lot of mass doesn't matter, but if you try to use that in a vehicle, it's such a drain on efficiency that I think it kills its own possible usefulness.

Rocky_H, thanks for the reply. I agree that for it to make sense it must weigh about as much as the battery per kWh and it must fit in the frunk and be removable. Also it must be substantially cheaper than the battery because like you say the energy stored is not as useful as the energy stored in the battery. That said, most drivers infrequently use all 85 kWh of their battery, but they are still driving around with a battery with 85 kWh capacity. This is really about an option for people that live in cold climates or desert climates that don't want to opt for a bigger battery to get the rated range in the winter or summer.

Once again, this is really about the next generation of EVs, Tesla is building smaller batteries while others build bigger batteries trying hit the range/price sweet spot for mass adoption. It sounds like the best solution is getting the cost per kWh of batteries down.

Hmm, well, I hadn't thought about that side of it--that most people are toting around a bunch of "dead weight" of battery capacity that they don't use most days. So if you wanted to substitute some of that weight of range you're not using for heating/cooling efficiency, that might be interesting.

I'm surprised (and disappointed) nobody has mentioned dry ice, LN2 or LHe for cooling.

For cabin heating, forget about clunky hot rocks, how about RHUs that last longer than the car itself?

So many pseudo scientists! So disappointing!

Why stop at a rhu heater? 5 pounds of plutonium will provide 1Kw of charging continually. Keep the car charged without plugging in. (500 miles a week, if you want more you need to plug in!)

Careful in accidents though.
What does plutonium cost anyway!? :)

ir, I was thinking about that in relation to LNG vehicles. Many people are pushing for LNG for long haul trucking and those vehicles carry around a very cold and relatively heavy tank for LNG and it is apparently economical in relation to diesel.

grega, I don't know if you are familiar with Twitter but the users, not creators, of Twitter are the people that really thought up the great ideas that made it so popular. The two storage mediums I mentioned are cheap and widely deployed and people currently drive around with ice in their car and buses roll around with very hot diesel heaters burning.

A conversion is needed; electricity transmits at a sizable fraction of c. Heat, not so much.

Hi Gene. For the record I didn't suggest an RHU, LR did. I just thought plutonium in a car on Earth wasn't a good idea. A 1KW radioisotopic generator on Mars may be very useful, combined with a battery pack, perhaps a future Mars Tesla will be battery powered with an optional plutonium generator for safety, but that's not for this discussion.

Also for the record, I don't think carting ice or heated ceramic bricks will work overall. I'm sure they would help maintain a car temperature, but the weight added is significant. Also the energy used to heat or cool is probably less efficient than using the battery (whether it saves money by allowing a smaller battery or not).

I do know that starting a trip with a car that was parked out of the sun makes a big difference to my first 10-20 minutes. My AC doesn't strain at all. Similarly when I was 10 I remember my grandfather used to hose down my parents car before we left, which made the trip cooler. And if I was plugged in and could start the AC 10 minutes before I left I would always choose that, just so that it used grid power instead of my battery to get the car down to a reasonable temperature.

Adding ice would mean that the car has to be parked out of the sun or even regular heat, and it would need to continually power the freezer to keep the ice cold. If you were plugged in this would just be a waste of electricity, and otherwise would drain the battery. It's more effective to cool the car with 5 minutes of AC than keep it cool for 8 hours. Even if in my garage, it would be like running a Freezer with bad insulation - perhaps just improving the insulation of a Tesla would have a better effect.

This is about electricity storage, and ice and ceramic bricks are just examples of ways to store electricity for future use for heating and cooling...just like one stores electricity in a battery to use to power an EV. Tesla is trying to build smaller batteries because they are very expensive, so for long trips a relatively cheap electric thermal storage device would essentially act as a range extender because those kWh will be used for heating and cooling. The thermal storage device would have to be substantially cheaper than batteries in 3 years which probably means that bigger batteries will win out. That said, electric buses might need some thermal storage device if they don't want to use diesel heaters.

Also, efficiency was not my objective, cheap electricity storage for a range extender was my goal...a bigger battery is an obvious and expensive way to extend range.

Cheap and inefficient. Yeah, I can see Tesla going for that.

Not.