In Taiwan, almost every family in the metropolitan areas uses an air conditioner. Apparently, since the phenomenon of global warming is even more obvious in the recent years, the power consumption of air conditioners has greatly increased, which causes environmental pollution. ‘The Eco-Cooler Grey Dhaka unveils world’s first zero-electricity air cooler made from plastic bottles’ is a video about a company that repurposes bottles to make an environmentally friendly device. After watching this video, our team formulated an improved version of the device. We used PP plastic corrugated board and reused bottles to make an improved natural cooling device, and this device is designed to be installed in windows. The PP plastic corrugated board is transparent, and this won’t affect the lighting quality. Also, the durability of PP plastic corrugated board is greater than other materials. Our cooler applies the thermodynamic principle of the Joule-Thomson effect and the process of throttling to make use of the difference between bottle’s neck and body to reduce the temperature of air the is forced through. This is the same principle that explains how air blow from your mouth is warm if your mouth is wide open but much cooler if you press you lips together and force the air through a smaller space. Through this experiment, we hope to apply this “eco cooler” to our surroundings to help people to cool their homes while conserving energy.