How the invention works. Principle
The physical principle underlying the invention is very simple. Hot air rises above cold air because hot air is less dense and therefore, it is lighter than cold air. In atmosphere masses of warmer air are constantly moving and cooler air goes down. The process can be made more intense if we can prevent mixing warm and cool air. For example, hot air balloon contains hot air inside and that allows the balloon to rise in the atmosphere. A chimney is very similar to balloon, in the sense that it prevents inside air from mixing with the outside air until the air exits the chimney. Just as a hot air balloon, the chimney needs to have difference of temperature between the air inside and outside. In a conventional chimney, like one in a house, the difference in temperatures is maintained by burning some fuel. Notice, that chimney height is a very important factor when determining the speed of smoke/air passing through. The taller the chimney, the faster the smoke rises. In fact, speed increases exponentially with every extra foot of height.
Speaking in terms of thermodynamic, we can say that chimney prevents adiabatic cooling of a rising parcel of air. Normally, when hot air freely rises in atmosphere, it expands as it gets higher and pushes the surrounding air. That causes surrounding air to heat and rising air to cool. That process continues until equilibrium is reached. At that point air stops its ascending. Unlike freely rising parcel of air, the air in the chimney is restricted in its horizontal expansion and thus, it is not free rising. When air rises in the chimney it also expands but only into upper direction. It compresses the layer of air above it, heats it up and loses its own heat. At the same time air below does the same thing. And that’s how it goes all the way until the chimney exit: layers of air are being pushed and push themselves. That results in maintaining the same amount of heat in every layer of air, and that is how the chimney works.
Now, let us consider our atmosphere. As we climb up, the temperature drops 10° C (roughly 20° F) every 1000 meters (roughly 2/3 of a mile). Our atmosphere absorbs heat from the sun, and it absorbs more at the surface than high above. Let us just assume we can build a chimney 5 kilometers (3 miles) high. Let us call it a super-chimney. The air at the base of this super-chimney will be roughly 50°C (100°F) warmer than at its top. Such a difference in air temperatures, enhanced by the height of the super-chimney, will produce an incredible airflow. The air from the earth’s surface will be sucked inside and will travel up at the amazing speed of 300 miles per hour (see Calculations).
There is no miracle to this: just like a normal chimney, the super-chimney operates because of a difference of temperature between the air inside and outside. The super-chimney maintains this difference because it prevents hot air inside from mixing with cold air outside until its very exit at the top. What’s more, the super-chimney will operate as described for as long as our atmosphere is heated unevenly. Notice that this is not a perpetuum mobile, because the super-chimney actually uses Sun energy, which warms the atmosphere.
The next portion of the article assumes that we are capable of building such a five kilometer-tall super-chimney and examines various benefits we can derive from it.
 |