As the world shifts it’s emphasis from fossil fuel to clean power, researchers are desperately searching for the perfect clean energy technology. Wind, solar, wave, tidal, biofuel and biomass are all experiencing renewed interest and new research funding.
One alternative clean energy technology that bears looking at is not really new at all. Compressed air has been used for powering transportation and industrial equipment in cities like Chicago and Paris. Compressed air was even used to chill refrigerators and freezers.
The problem with using compressed air in this way is the method used to compress it in the first place. Modern compressors are gas, diesel or electric powered and enevitably leave small particles of oil and dust in the air itself. Air compressed in this way needs to be filtered for most applications. They all use a lot of energy to obtain the compressed air.
There is another way to compress air that takes no other source of power than gravity. It is a well understood and used system used many years ago, that for some reason has not been recently considered. The process is called a Trompe.
The Trompe takes falling water and funnels it through a group of very small pipes before letting it fall down a larger pipe for a distance of 100 meters or more. The very small pipes have the effect of adding tiny air bubbles to the water streams. As the water falls through the 100 meters the bubbles are compressed. Compression of air always increases the temperature as defined in Boyles law of perfect gases. However in this case the air bubbles are surrounded by water which transfer the heat away from the air and removes foreign materials.
Compressed air made in this way is called Isothermatically Compressed air and it is very valuable in this form. The bubbles are compressed according to the depth of the pipe. For every 32 ft the pipe is deep, the pressure on the bubble increases by 14.7 psi, which means a 100 meter drop will result is air being compressed to 150 psi.
Letting the bubbles surface into an underground chamber collects the air and allows the water to recirculated up a well where the process starts again. A small pipe at the top of the underground chamber allows the air to reach the surface where is can be stored in cylinders or used to do work.
Compressed air made in this way can be used as portable energy for cars and trucks. There are several car makers developing this vehicles. It can also be used to generate electricity in the home simply by using the air to turn a generator.
This is a technology that bears another look by researchers and engineers as we work to remove fossil fuels from our economy.
About Gordon Smith Gordon's expertise in the area of industrial energy efficiency and alternative energy. He is an experienced electrical engineer with a Masters degree in Alternative Energy technology. He is the co-founder of several renewable energy media sites including Solar Thermal Magazine.