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Pedal-powered Air Purifier

03/2019 ~ 07/2019

In South Korea, air pollution has been a serious problem since I was young.

(BBC news article about air pollution in South Korea, 2019,

According to the KORUS-AQ, a research conducted by NIER and NASA, the average density of PM2.5 (28ug/cm^3) in Korea was above the recommended level from WHO (25ug/cm^3). 

People wear masks and install electronic air purifiers to protect themselves from dust.

However, these are not satisfying solutions because they basically do not remove outside pollutants.
Masks only protect respiratory systems, and electronic air purifiers require too much electricity to purify the entire nation.

Young-suk, Jiwon, and I put a lot of effort into designing a new air purifier to filter the dust covering the whole country.

This device has two constraints.
First, this device cannot use electricity as an energy source since it will consume a vast amount of energy. Therefore, we decided to harvest energy from the pressure generated during walking.
Second, this device must consist of a small repetitive unit because it has to cover the entire nation.

In conclusion, we developed a block-shaped air purifier that can be installed on the sidewalk.
The final design of the device is shown below.

The left one is a compression unit that compresses the air by the pedal power of humans, and the right one is a filter unit that filters the dust. Each unit was connected by check valves, which make a unidirectional airflow. 

Several compression units were connected in series, and two filter units were connected at both ends of the series of compression units. When a person presses any compression unit, strong airflow is generated.  

Below is the demonstration video of our device.

According to the calculation, the average volume of filtered air per step is 0.6L. Considering the walking speed of people, it is more efficient than a commercial electronic air purifier. However, its required compressibility increases drastically as the number of compression unit increase.