In the Philippines, which is a tropical country, an air-conditioning unit is considered more of a luxury than a necessity. Unfortunately, owning or using one results in astronomical electricity bills, the Philippines having one of the highest power rates in Asia.
The solution is to make your own air conditioner.
According to an article from Geek, the Eco-Cooler requires no electricity and can be made using commonly discarded items, mainly plastic bottles and a piece of board. The bottles have their bottoms cut out and inserted side-by-side into one side of the board which pretty much completes the entire assembly.
This eco-tech was originally conceived in Bangladesh where temperatures can soar up to 45 degrees during summer. The principle of the device leans on air pressure changes as it passes from a large opening and out a smaller one. The cut-out portions of the bottles faced outwards to allow air to be funneled in and produce a cooler breeze from the mouths of the plastic bottles.
Despite its apparent simplicity, it has been reported to lower temperatures inside a room down at least 5-degrees Celsius. Alfred Bayle