Who has really bad fuel efficiency, air conditioning or open windows?🚗💨

After GW, it was time to start using the air conditioner of the car.

For those of you who thought, "I'm gonna run with the windows open to save money ☀️

Actually, the "fuel economy is bad side" of the air conditioner and the window opening,

There was a structure that changed depending on the speed.

The correct answer changes at around 80 km / h 💡

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🔖 lower speed, the greater the burden on the air conditioner

How much does air conditioning affect fuel efficiency in summer?

Fuel efficiency deteriorates by about 14% in urban driving at 25 ℃ outside air.

When set to 24 ° C at 35 ° C outside air, it worsens by about 20-25% (measured by 2.5L minivan).

So far, it's a number that seems like "Summer is like that,"

Looking at academic research, one can see a deeper structure 📚

According to a US economic study (Mogro & Huertas 2020 / 2021):

In 5 months of actual driving monitoring,

At low speeds below 10 km / h,

Use of air conditioners increased fuel consumption by up to 59%.

▼ Measured Values of Academic Data

Low speed (less than 10km / h): + 17.6L / 100km

・ 50km / h or less average: + 8.2L / 100km

· High speed range: + 1.3 L / 100 km (almost negligible)

In other words, the fuel efficiency effect of the air conditioner is strongly dependent on speed,

It is most effective in low-speed situations such as traffic jams and urban areas.

The structure had little effect on highway cruising.

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🔖 window opening is disadvantageous as the speed increases

Then "Let's run with the window open to save money" is good 🤔

Now let's take a look at the actual measurement data for opening the window.

Fuel efficiency deterioration rate of 2.0L minivan measured

・ 40 km / h: 7.8% worse

・ 60 km / h: 13% worse

・ 100 km / h: 20% worse

The reason why there is such a difference in speed is,

Because there is a physical law that air resistance increases in proportion to the square of speed.

When the speed doubles, the resistance increases four times 💨

When running with all windows open, the air resistance value (Cd value) of the car body

It has also been measured to worsen by about 29% (Ali et al. 2014).

I feel "eco" when the wind passes through the car,

The actual physical phenomenon is "the force that hinders the car from moving forward increases."

The higher the speed, the greater the level at which this effect can not be ignored.

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🔖 70 ~ 90km / h, air conditioner and window opening are reversed

This is the heart of this post ✨

In the study of wind tunnel experiment + fluid analysis (Zhang et al. 2012),

* * At speeds below 90 km / h, open windows are more fuel efficient than air conditioners * *

It has been demonstrated.

Reverses at speeds of over 90 km / h.

Even in another actual car test (ORNL Corolla),

Opening the window at a speed of 80 km / h or more > Deterioration of the air conditioner has been confirmed.

Although there is a range depending on the data,

I want you to think that the correct answer changes around 70 to 90 km / h.

✓ City riding / traffic jam center (30-50km / h): Opening the window is advantageous in terms of fuel efficiency

✓ Commuting and suburban center (40-70km / h): Balanced type

✓ High speed and long distance center (over 80 km / h): Air conditioner is advantageous in terms of fuel efficiency

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🔖 ⚠️ However, be careful with the judgment of "turning off AC (air conditioner) for saving"

Here, I would like to introduce one study on safety.

In the study of indoor environments (Lan et al. 2021, cited 86),

Increasing the temperature in the car from 24 ℃,

* * Cognitive performance declines by 10% at 26 ° C and by 6% at 28 ° C. * *

It has been demonstrated in a 4.5-hour cognitive task.

Moreover, even in a state where you subjectively feel "comfortable,"

Objective cognitive performance was structured to decline.

"Let's keep the air conditioner low to save gas."

I understand the feeling in itself,

If you lose your concentration while driving in the middle of summer,

You risk paying more than the price of gas 💭

Even on X, the female transportation driver

"Midsummer interior 40 ℃ super sauna... air conditioner / idling required to protect safe driving"

The voice of the scene was spreading with over 1700 likes.

Heat stroke and cognitive decline are a higher priority than saving.

The FSC is in the same position 🌿

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🔖 the way you run?

[A: City ride / traffic jam center (30-50km / h)]

At low speeds, the fuel efficiency of the air conditioner is greatly affected.

However, if you forcibly turn it off under the high temperature of summer,

Cognitive performance declines and the risk of accidents increases.

Recommended to increase the set temperature (26-28 ℃) + eco mode 🌿

Not the idea of forcibly turning off the AC,

I want you to think with the idea of "weakening wisely."

[B: Commuter, suburban center (40-70km / h)]

Even if you run with the window open in the cool time of the morning and evening,

The fuel efficiency impact is not so great.

At high temperatures during the day, AC use becomes realistic.

The idea of switching by time zone and temperature,

Easy to balance fuel economy and comfort.

[C: High-speed, long-distance center (80km / h or more)]

Air resistance of the window is dominant in this zone.

Using an air conditioner is the correct answer in terms of fuel efficiency and comfort.

"Saving money by opening windows at high speed" is a structure that tends to have the opposite effect.

📌 Life After Parking Hack

The temperature inside a car parked under the blazing sun rises up to 60 ° C.

If AC is used at MAX as it is, fuel consumption in the initial 5 minutes is large.

For the first 1-2 minutes,

If you open all the windows to let the heat escape and then switch to AC,

AC full power operation time can be shortened and fuel consumption is friendly ❄️

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There is not one right answer 🌸

People of town riding main and people of high speed main,

The best choice changes.

The important thing is not to turn off the air conditioner anyway,

Check the speed range of your way of running once,

Choose between fuel efficiency and safety 💭

I want you to check three things before the next drive 📌

① If the city ride main, be aware of the burden of AC

② For high-speed main, close the window and rely on AC

③ On a hot day, look at safety together

With these three, how to use the air conditioner,

It will be the correct answer you chose ✨

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