A well-aerated house is very convenient to stay in. The temperature of the house is properly regulated reducing any sort of uncomfortability. Intelligent aerated houses are the new norms in real estate business. Modern houses nowadays have an automated system that controls the temperature and air levels in the house. Normal ventilators are not sufficient to assist in ventilation process. However, they are still important in buildings. Ventilators are mostly placed on the walls to let in dense cold air and allow for the exit of hot less dense air. They are positioned highly on the outer walls of the building for effective operation. This is possible because the ventilators operate on the principle of heat transfer by convection. When the room occupants breathe out, they exhale hot air that is less dense compared to the fresh and cold air entering the room through the ventilators. When the cold air enters the house, it moves downwards to occupy the position of less dense hot air that rises to exit the house via the ventilators. This happens because cold air is denser than hot air. Intelligent aerated homes do not rely only on this natural convection process.
An intelligent aerated home
An intelligent system for aerating homes consists of air-conditioners, heaters, microcontrollers and temperature sensors. Air-conditioners are interfaced with microcontrollers, pressure sensors and temperature sensors. The temperature sensors detect increase in temperature of the house and send signal to the microcontroller that responds by turning on the air-conditioner. When the temperature of the house stabilizes, the microcontroller sends the signal to turn off the air-conditioner. The microcontroller has a central processing unit that coordinates and controls all the activities of the air-conditioners. It contains the GSM Modem (Global Sim for Mobile Communication) that connects the entire system to the user’s cellphone. The user’s cellphone has an app that can be used to turn on and off the air-conditioner at will. When the air-conditioner is turned on, it creates a forced convection by stirring the air. This enhances the cooling process. It makes it much faster than the natural convection. The microcontroller can also be set to turn on and off the air-conditioner at a specific time. This is possible through the app as it contains all the necessary features for controlling the system remotely. When it is extremely cold, temperature sensors notifies the microcontroller that turns on the heaters to provide warmth. Heaters are made of several coils that get heated when electric current passes through them providing the needed warmth. Those coils are made of nichrome wire whose resistance is very high. When the current flows through them, they glow red hot. Infrared radiation emitted from the element are reflected into the room by a parabolic reflector.
If a current of 0.25A flows through the coils of a heater when it is connected in a 240 V circuit. The amount of electrical energy that will be converted into heat after 60 seconds can be calculated as follows:
1. P = VI whereby P represents power in Watts, V represents voltage in volts and I represents current in Amperes.
P = 240 × 0.25
2. E = Pt whereby E represents energy in joules and t represents time in seconds.
E = 240 × 0.25 × 60 = 3600 J
When the microcontroller turns on the heater for 60 seconds the amount of electrical energy that will be converted into heat is 3600 joules.
When the mass of air in the house is about 10 kg and the temperature of the surrounding is 100 C, the amount of heat energy that will be required from the heater to change temperature of the room from 100 C to about 300 C can be calculated as follows:
1. Q = mc∆ө whereby Q stands for heat energy, m stands for mass, c stands for specific heat capacity in J Kg 0C-1 and ∆ө stands for change in temperature.
2. Since specific heat capacity of air is 720 J Kg 0 C-1
Q = 10 × 720 × (30 – 20) = 72000 J
The microcontroller is programmed in such a way it is capable of determining the amount of heat energy required to change the temperature of the room to the set value. Then, it switches off the heater.
Advantages of this system are:
1. It is more convenient. The system detects temperature changes on its own and restores normalcy by turning heater on and off when it is appropriate.
2. It saves time by eliminating time wastage on switching on and off air-conditioners manually.
3. It keeps the house properly ventilated. In addition to ventilators, it enhances ventilation process by introducing forced convection mechanism.
Disadvantages of this system are:
1. They are expensive to install. The system requires a lot of money to be installed compared to normal ventilators.
2. The system can be affected by power failures especially when there is no back up power supply.
Normal ventilators are not sufficient for keeping houses ventilated. Therefore, modern houses need to make good use of this system fully.
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