Wanted: Complete Radiant Heat Solution for EVs

OCT 21 2013 BY MARK HOVIS 39

MIT heater prototype uses minimal battery

MIT heater prototype uses minimal battery

So, it is getting close to that time again to turn the heaters on in our EVs.

Some BEVs like the Nissan LEAF are offering heat pumps as an improved method of heating the cabin, as well as proper radiant heated seats and steering wheels.

EREVs like the Chevy Volt have enabled the ability to run their ICE at any time in order to heat the cabin while providing thermal capabilities to the batteries with this inefficient bi-product (heat) of running the ICE.

We are also eagerly watching our esteemed engineers at MIT as they work on scaling their ingenious discovery to fit in an EV.

Meanwhile, I am still in search of a complete radiant heat solution. Pardon me if I find it a bit ironical that in our EV community, we become anxious with why the global market does not comprehend faster the advantages of the EV, and at the same time we hold on to our old forced air approach to keeping ourselves warm.

In colder climates, it is quite acceptable to heat a home through radiant methods and at least until the MIT engineers provide such a product, the best methods are found in keeping our extremities warm.

heat matHeated seats are accepted quite well, and heated steering (or gloves) are generally accepted at least in the EV community. So, why are we so slow to accept warming our head and our feet? I suppose some people’s hair grooming does not allow them to wear the proper head gear but it certainly is an easy solution to the problem.

But for me, it is warming the feet which is the final and simple stage to keeping the body warm and maximizing energy efficiency. Not double socks or electric socks, it is an electric mat that I seek. What is simpler than a heated mat?   Now, certain dead end ads exist,  but I have yet to find a reputable product that works on a timer with maybe two heat settings.   Not a single OEM offers this simple integration  even as an option. This could be a one, two, or four mat option for the OEM. But even more frustrating is that no aftermarket products exist. OK, maybe the mat is over simplifying the issue but I can’t believe engineers have exhausted efficiencies just yet.

We are quite prepared to let the ICE go and for many good reasons, but we just can’t seem to let go of their method of heating. For the ICE, forced air is a given. For the EV, at least for the present, I hope this winter produces some improved options.                                                                 

Categories: General


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39 Comments on "Wanted: Complete Radiant Heat Solution for EVs"

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scott moore

How about using some of that thermal energy left in the battery (leaf)? solve two problems at once…

Mark H

I thump my chest in EV superiority in every category but heat. We have some paradigms to overcome. Talk about needing some purpose built solutions. Right now I would be happy for someone to tell me they have a radiant mat or other solution for the flooring. It is just glaring at us waiting to be solved.


Are you saying that thermal energy in the battery is a problem in the cold? I don’t think it is. I know the S manages the temp of the pack as an integral part of the cabin climate control (if one has the energy the other needs, they can share). I don’t think the LEAF has that kind of elegance, but I don’t think that in the cold even the S has any battery heat to spare–at winter temps what heat is generated in the cells once they are pumping doesn’t do anything other than maintain battery performance.


What I would really like to see is an improved method of windshield defrost. Running heat just to get defrost is wasteful, especially when you can heat people easily through seats.

I remember some European cars used to have mesh in the windshield, but that disappeared due to overall costs. Shame, because they could clear the windshield very quickly.


I agree. While the cabin heater may be seen as a wasteful use of energy, there is no other solution currently available to prevent ice from forming on the windshield and side windows while driving. We need targeted solutions for the windshield and side windows.

Bill Howland

This problem was solved decades ago. The Lincoln Continental had a fast defrost option which was gold wires in the windshield (gold is so ductile that if you stretch it enough it becomes transparent). I’m uncertain as to the unpopularity due to the expense of the gold itself, or the cost of the 120 volt separate alternator.


How about some thermal storage in the seat and mats. Pre-warm and watch them stay warm for 2 hours, no battery drain at all.

Mark H

I like it! Still, I am looking for a no fuss solution. It might even expand to arm rest or place for your hands in the rear seating area. The heat pump isn’t bad but I am just convinced there is a radiant solution here. Maybe this group of innovators will solve it!

Yves Laurin

I am presently studying on passive house heating (also studying the effect of thermal mass) at university and really like your idea. In addition, they can also put more insiluation.


I don’t know about you but I wear shoes when I drive. Radiant floor mats have a lot of overcome through the soles of my snow boots.

Mark H

You might be right on the energy Brian, but don’t you have to overcome the same with forced air? Radiant heat in a home is more expensive to install but generally more efficient. It does work better with materials that transfer heat easier which is your point.


The thing is, in a home, you aren’t wearing shoes with thick soles. In fact, radiant heating doesn’t work well at all if you are wearing slippers.

I don’t want to seem like too much of a pessimist. Like others, I am happy that you are thinking outside of the box. Nissan is still stuck thinking like an ICEV maker. This kind of innovation will most likely come from Tesla.

Bill Howland

Not sure about Tesla, Brian, as you yourself often say, they’re actually pretty conventional. Other people are dealing with multimotor in-wheel drives and unsprung weight, and that kind of thing.

I’ve mentioned above that 40 years ago, Lincoln had the perfect solution for defrost.

Incidentally, I’ve been reading the v2g stuff on plug in cars. Its obvious Herron and Matovoli know nothing about the utility business.


Brian, just in case you were actually serious with your previous comment: the boiler in my garage pushes over 40 kWth (130 kBTU/h) through about 150 m2 (1600sq.ft) of flooring.

I trust you’ll have a hard time believing what comes next, but I promise it’s true: somehow, the air, the walls etc all get comfortably warm — EVEN if I have the audacity of covering a tiny fraction of that floor with slippers instead of my bare feet.

Crazy I know…


I apologize, my post was very poorly worded. Obviously radiant heating works to warm houses. Plenty of people have it as their sole source of heat, even in upstate NY.

What I was trying to say is that radiant heat can be more efficient at warming the human body (compared to forced air) because the heat transfers through the soles of your feet. In fact, you can feel just as warm at a much lower temperature. But if you wear slippers around the house, you are actually negating some of that benefit.

In a car, I am not convinced that a radiant floor mat would be more efficient than blowing hot air over your feet.

Mark H

Hey Brian, I did not respond because I understood you the first time. As I responded to you earlier, you may be right on the energy transfer of simply flopping a DC mat down. I am just not convinced that there is not a better way and like io, I plan on entertaining myself this winter trying some things. It took GM a year to provide the “Hold” mode and Nissan a year to provide a heat pump and heated seats. I just can’t believe that we are done with perfecting the solution here.

I was already thinking they should have some kind of radiant heat lining the knee pane.l to leg area.

Mark H

Now you’re talking. Localized heat…


Make a tiny exhaust vent, install a tiny pellet burner. Haha only extremely serious.


Look, combustion is bad for everything because of wasted heat, right? Heat is always normally seen as wasted energy, right? Whenever you meet up with heat in designing any device, it’s wasted energy. EXCEPT in a heater. What I’m getting at is: put a combustion heater somewhere it can blow heat into the cabin and vent exhaust gases outside. YES, it’s combustion of a fossil or only-semi-renewable fuel. But NO there is no wasted energy. A heater in a small closed, insulated space right next to you is always, by definition, 100% efficient.


I don’t know Mark, I think the heated floor mat might us too much juice but I don’t know for sure. Good to think outside the box though. I ride motorcycles in the winter and I use Gerbings heated Vest. I know you guys have heard that but thought I’d throw it in anyway.


Mark H

Maybe a permanent inductance shoe insole! There is just gotta be something different than forced air.


an inductive charging system for your feet.
Just like the EV1

Mark H

I ran into the marketing director, John Dabels, for the EV1 by chance on a recent solar project. Hope to have a good retro article from his point of view in the near future.

Ocean Railroader

What I wounder about EV’s are the AC’s on them in that you leave a car in a parking lot most likely it will be pre heated by the time you get into it. I really hope these things don’t have weak AC’s.


Is the electric A/C in your house weak?

No, they aren’t weak. They only have a small space to cool as well. Apparently the Volt’s A/C is good for homesick Inuits.


Pre-heating while still plugged in should be used often but that doesn’t help when you are parked where there is no power.

A small propane heater could do the job. It seems like such a waste to use valuable battery energy for heat.

What about an infrared lamp?

Mark H

Thats thinking out of the box. I could see some possibilities.


They work great if you are tent or RV camping too.
Flick it on in the bathroom for 4 minutes and it’s like heaven.


Actually the Nissan Leaf heat pump is the right way to go, the only thing that is still left to do is use a better heat pump.
A thermoacoustic heat pump that is. It moves heat trough a stack by a powerfull standing sound wave. No refrigeration gas is required. Best of all it can even double as a range extender by turning heat into electricity. So, you get an airo unit and a rex in a single package.

Mark H

That would definitely be an improvement and fits with what MIT is doing. That is why I did not rule out forced air completely. Never say never to an engineer, but at least for now I am still looking to get away from heating the entire cabin. The cheesy mat is just to force the the thought process toward heating the body not the cabin. Second to the battery, distributing heat is the next largest area for improvement.


Pardon my stupidity, not yet owning an EV… But isn’t there a fair bit of heat coming off of the MOSFETs of the ESC? why not use that as the source for the heat to be transferred? Otherwise isn’t it just wasted?

Bill Howland

Steven, I own 2 EV’s. I believ the heat is recovered in my volt but it is wasted in my Tesla Roadster.


They have these cool devices called internal combustion engines, which are not very expensive, have a plentiful supply of cheap fuel, and which are very good at making heat. Maybe they could add one of those.

Mark H

Right on all accounts except the cheap fuel and that they are killing us part. All kidding aside no one denies the superiority of heat from an ICE. It is a bi-product of a terribly inefficient process. This is why EREVs like the Chevy Volt use their ICE not only for range extension but also heat generation as mentioned in the first sentences of the article. It is brilliant, for now.
For an ICE, heat is a given. Except I have to keep buying gas and oil and anti freeze, and timing belts, and transmissions, and mufflers, and ……
Its main source of energy is not cheap. On average, it cost 4x compared to electricity. If you make your own electricity it is more like 8x. And whether or not you believe it is effecting the planet, there is no getting around the respiratory problems caused by the ICE. Somebody has to pay for those miles. I don’t want to.

Mark, sorry to join the discussion a tad late. As a fellow Leafer, I thought along the exact same lines as you and researched the same topic, stumbling over the same not-actually-sold floormat… I’m equally frustrated with both cold-ish feet and the apparent lack of products that could elegantly remedy this — because, yes, unless I have passengers or I’m close to solid frozen, I stubbornly refuse to fire up the vehicle’s main heater (mine predates the heat pump). Also, while heated shoes or insoles would surely work wonder, I haven’t found a model which I could wear in public and not instantly die of ridicule (or discomfort). Pointers welcome. So anyhow, for this coming season, I’m about to give a try to at least one of the following less-elegant combinations: 1) Some 120/230V heating element (those are much easier to find than 12V): Either an actual mat, unfortunately not quite the right size, e.g: http://www.samsclub.com/sams/electric-foot-warmer-mat/prod1600036.ip http://www.homedepot.com/p/Cozy-Electric-Foot-Warmer-Mat-FW/202930325 Or heat wire, which I can attach to the existing floormat, e.g: http://www.morelectricheating.com/products/PIPE%20HEATING%20AND%20FREEZE%20PROTECTION.aspx 2) A step-up converter Either some shockingly cheap inverter (but then it’s all-or-nothing), e.g: http://www.aliexpress.com/item/150w-power-inverter-car-laptop-power-supply-converter-12v-110v-charger-belt-usb-mouth/1284164401.html Or a more modest but adjustable DC-DC, e.g: http://www.aliexpress.com/item/DC-DC-Boost-Converter-10-32V-Step-up-to-35-60V-Power-Supply-Module-120W/751733536.html http://www.aliexpress.com/item/LM2577-3-34V-3-7-7-4V-to-4-60V-DC-Step-up-Converter-Adjustable-Charge/754722175.html http://www.aliexpress.com/item/LM2577-rosy-high-voltage-DC-DC-booster-module-IN3-5-35v-OUT5-56v-indicator-light-belt/1143147197.html Note that power in… Read more »
Mark H

io, I am exactly there in my research! The four ideas I like the most from the responses was
1) Your idea of building your own which is the course that currently am pursuing. If you have success contact Jay and/or write the follow-up
2) Kdawg’s infrared heater. I can see us adapting that easily.
3) Inductive shoe liner.
4) And of course the OEM could implement any or all but they could also do wonders with radiant in cabin components in and around a persons feet or head as Elroy mentioned.

Battery technology or MIT’s experiment could render it moot in a decade but I don’t think so. I still feel this will always be the superior method unless it is a bi-product of combustion. As you know with your home system, it also does not stir dust through forced air AND it adds to the quiet experience of driving an EV. There is definitely no getting around that one with any type of forced air.


I’d be happy to have some way to heat just the accelerator pedal and a small area to the left of the brake pedal- just enough to keep the toes warm. Surely that wouldn’t draw much juice; Nissan ought to be able to pull that off.