Tag Archives: Heat

EVs and the “heat island” effect?

This report is making its rounds on the internet lately. It basically says that since EVs don’t run as hot as ICE vehicles they don’t contribute to the urban heat island effect (which is that cities tend to be a few degrees warmer than the surrounding countryside).

The interesting thing is that, if you read the report, you can see very detailed figures, references, etc. basically they did their homework. Note that there is no evidence though, the report just does a lot of math to come to the conclusion that EVs would reduce the heat island effect. Thus its basically a hypothesis waiting to be tested. Given that I’ve seen more than a few comments on the articles relating to the report where people state “I just can’t believe that cars driving around can contribute that much heat to raise an entire cities temperature” (this actually sounds very familiar to another argument about greater atmospheric conditions). The reasoning goes: “My car does so little how can it possibly do that much damage?” What if you were to add up all the cars? Your car, your neighbor’s car, that one from the goofy guy down the street? The barber’s car? The butcher’s car? All of them… Then you end up with a very large number (like the 9.85 × 1014 J daily value in the report–or 11 gigawatts). Now it makes more sense! That is a lot of heat.

I’ve often wondered about that from a different perspective. Think of your morning routine: You get up, wash, shave, etc. How about all that hot water going down the drain? What about everyone’s hot water? Is the sewage system running a lot warmer due to everyone’s daily routines? (just asking)

On top of the heat generated by vehicles, now that it is hotter people will run their air conditioning more. This will also add heat. Thus if you can reduce the outside temp a bit you’ll also reduce A/C use.

How would someone go about testing this in a controlled fashion? What kind of scale would be required to verify the effect? e.g. would a small scale test work: put a small ICE inside a large room and let it run for a while and compare that to an electric motor running for the same length of time? Which room is warmer? Would you want to do the test at an even larger scale? Setup a “fake city” and run that city for a few weeks with ICE vehicles monitoring the temperatures and then follow that up with a few weeks of EV? (In that case it would be really hard to match the weather conditions.)

Interesting stuff, and also reasons why this stuff is so difficult: Its very hard to make controls with identical conditions in order to come to hard conclusions.

 

What to do about heat?

When you look under the hood of the FFE you notice that it has a rather large radiator (most likely its the same part in the ICE Focus–they look very similar). A large radiator like that is designed to dissipate a lot of heat something which the FFE doesn’t generate much of whilst driving around. The whole arrangement shows an interesting design decision on the part of Ford…

When you look at the front of the FFE you see the fake grill and a small opening for air below it, permitting a lot less airflow while driving than the conventionally powered Focus. In this pic you can clearly see the difference:
Red Focus Blue Focus
The front of the ICE Focus is open whereas the FFE just has that gap at the bottom. The reason for this is obvious on the ICE Focus: The gas engine generates a lot of waste heat that must be removed to prevent an overheat situation–even in cold weather there is still plenty of waste heat to go around.

For the FFE on the other hand: Very little heat is generated while driving and thus the front can be a solid nose (with a little decoration); even rounded a bit in an attempt to improve aerodynamics (look at most EVs they all will have very little pass-through). What about that large radiator though? This comes into play during charging and on hot days. The FFE has a battery temperature management system. When charging the battery generates a lot of heat. Heat that also must be dissipated to prevent damage to the battery. This is the reason for the large radiator: To help with this heat removal. In addition, when charging, the car is stationary so there is no forced air coming in from the front; airflow must be generated by the radiator fan (most likely also the same part number as on the ICE Focus). Indeed, during charging I quite frequently hear the radiator fan running at full speed (especially near the end of the charge cycle).

The other use for the radiator is similar: removing heat but this is during a hot day. When the outside temperature gets a bit hot out the car will “complain” that its hot out and should be plugged in. This is to use the fan, and if needed the chiller, to remove heat from the battery if it gets too warm (something it won’t do if parked and not plugged in).

Note that the car also complains when parked and its cold out to be plugged in so that it can keep the battery warm.

I bet you were expecting different subject matter when reading the title of the post?