Tag Archives: Effect

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.