The indoor climate monitoring using Zigbee wireless network for building thermal comfort application

This paper presents the design and implementation of a wireless sensor network using Zigbee protocol for monitoring the indoor climate of an air-conditioned room. The wireless sensor network included the measuring unit, data transmission unit and data collection unit. The measuring unit consisted of an embedded system module Fio mote-ST (microcontroller), XBee (Zigbee protocol) and HIH6131 (temperature/relative humidity sensors). Gateway and base station were the last two components of the network. The sensor units communicated with the base station and the collection unit via the gateway. Indoor weather was measured then information transmitted to the computer for displaying on the screen in real time whilst at the same time storing the information. The design of the graphical user interface was done using Visual studio, an open source program. The Blockset diagram that came with the hardware was used in the setting up of the Zigbee wireless sensor network. The measured indoor temperature and humidity was displayed in real time. It was found that the Zigbee wireless sensor network for indoor weather monitoring operated effectively and continuously without delay. The temperature sensor provided the measurement value within 2% difference compared to the measurement using Thermocouple type K in the same operating conditions. The occupant comfort calculated by the simple predicted mean vote equation from literature was found during the thermostat temperature setting of between 24°C and 26°C. This temperature setting was slightly low compared to an air-conditioned room in the lower floor as the demonstration test room was located on the top floor of the building with the flat slab roof above, thus higher heat gain could be expected. The advantage of the Zigbee wireless sensor network is that it can operate individually and perform a portable local weather monitoring system.