Evaluating the effectiveness of the 'eco-cooler' for passive home cooling

Constructed with used plastic bottles, the eco-cooler has been widely adopted in resource-poor communities in Bangladesh and other countries. We tested the eco-cooler under controlled conditions using a scientific wind tunnel in a climatic chamber. In our tests, we used seven eco-cooler designs in 27 climate conditions typical of Bangladesh (temperatures of 40 °C, 35 °C, and 30 °C; humidity levels of 70%, 60%, and 40%; and wind speeds of 4.0 m s^-1, 2.0 m s^-1, and 0.2 m s^-1) in 92 experiments (N = 7686 measurements in 87 short experiments and N = 23,428 measurements in five long experiments). We found no significant temperature reductions with eco-cooler use, except at low wind speeds, where temperature reduced by up to 0.2 °C. In theoretical calculations extending our empirical findings, the greatest temperature drop was 0.85 °C at 4.0 m s^-1 with a 40 °C static air inflow temperature. However, this temperature drop did not extend beyond the nozzles of the bottles in the eco-cooler. The eco-cooler did not work effectively as an indoor air cooler.