DESIGN, CONSTRUCTION AND EVALUATION OF HUMAN COMFORTABILITY SYSTEM USING ENVIRONMENTAL STRESS INDEX (ESI) METHOD

Abstract

This research is aim at constructing a portable electronic system that can digitally determine and display the environmental stress index (ESI) on a graphical user interface (GUI) with informative warning signals. Its design was based on sensing relative humidity, air temperature through a digital humidity-temperature (DHT11) sensor and solar radiation using a Pyranometer. The measured air temperature, relative humidity and solar radiation of an environment are then fed into an ATMEGA16 AVR microcontroller programmed to compute the environmental stress index (ESI). It is also designed to log all its measured parameters and environmental stress index (ESI) into a computerised data base. Warning signals also feature on this device such as a red indicator to signify a dangerous condition, green for risky condition and turns off for comfortable condition. The microcontroller was also programmed to calibrate the Pyranometer connected to it over a range of 0 to 2000ɥV/W/m2 calibrations constant. A provision was also made for taking readings at desired interval using the Real time clock (RTC) integrated circuit (I.C). An RS232 UART serial converter was added to make the device linkable to any personal computer. When tested, the device was able to instantaneously determine ESI and log data on continuous basis at desired interval of time. Key findings from measurements taking by the device shows that an office completely shut without air-conditioners switched on in Federal university of technology (FUTA) campus was dangerous for humans, likewise direct exposure to solar radiation during dry season. The cost of constructing this device is relatively cheap when compared to a purchasing one from abroad despite offering excellent quality, fast response and good accuracy. Digital determination of comfort and stress index is a task of many importance’s whose overall aim is life saving from hazardous effect of thermal stress such as the heat waves that killed over 1000people recently in Pakistan.