Ancient Technology
Rendering by Francesco M. Lucini/ courtesy Yael Issacharov A graphical rendering of Issacharov’s tubular terra-cotta tile, the building block of her Nave AC system.
Did you ever wonder how people in the desert stayed comfortable before the discovery of electricity? Inventor Yael Issacharov thought there had to be a better way to cool down a home than blasting an air conditioner and paying a large electric bill. So Issacharov asked this very question. She knew the ancient desert people had to have found a way to stay cool in order to survive.
Issacharov found the Palestinian “jarrah” to be an inspiring idea. The traditional terra-cotta drinking water container is hung in a room to cool both the drinking water and the surrounding room. The clay used to manufacture these containers can be traced back to the Neolithic and Bronze Age. The clay is full of small pores that not only filter the water to make it safe for drinking, but also allow small amounts of the water to evaporate.
The evaporation process causes the temperature of the remaining water and the terra-cotta to cool down. This happens as the state of the water changes from liquid to gas; it must get the energy for the transition from somewhere, and that somewhere is the heat in the water. The water gets progressively cooler, similar to how sweat cools your body on a hot day.
The good news is this method can be used to cool a room without using any power source other than the heat in the water and air. The bad news is that it will not work well in humid climates, like Missouri. If the humidity is high in the air, the water has nowhere to go and requires more energy to evaporate. Some of the most energy efficient cooling systems in the world are based on the same concept. Evaporative cooling is used in several computing centers to cool massive computer systems. NASA’s large, high performance computing clusters utilize evaporative cooling, saving NASA millions of dollars a year on their power bills.
The evaporative coolers in use today pump cold water over a fabric-like filter and use electricity to draw air across the filter, evaporating the water and lowering the temperature of the filter and the air passing through it. The process involves electric fans and water pumps and uses quite a bit of electricity, not to mention the loss of water. The process works very well when you have hot and dry air to power the process, but not so great if the air is humid.
Issacharov is taking the process to the next level with her new idea, utilizing the ancient technology of the “jarrah” and combining it with ancient Egyptian architecture inspired by Hassan Fathy.
Fathy is an architect that is responsible for bringing to life the adobe and mud construction techniques from ancient Egypt. These ancient techniques are extremely energy efficient and help to provide comfort in many climates. The adobe and mud create what is referred to as thermal mass. The more mass an object has, the longer it takes to change the temperature. The adobe structures slowly heat up over the course of the day and slowly cool over the course of the night, maintaining a fairly constant temperature.
Combining the evaporative cooling properties of terra-cotta with the thermal mass of adobe, Issacharov has achieved the unthinkable. She has designed a wall mounted terra-cotta cooling system that will keep a home around a constant 77 degrees in the 120 degree desert temperatures without utilizing a drop of electricity. Her Nave AC system is a very simple design. The basic building block of her design is a terra-cotta tile made of hollow tubes; her intricate design is then filled with water and, given enough tiles, you can get any size space to “Thermal Comfort” 77 degrees Fahrenheit and 30-50 percent humidity.
Issacharov graduated from Holon Institute of Technology and currently lives in Barcelona, Spain. She believes her invention is perfect for desert areas from Texas to Iran, and though the upfront cost is significantly higher than conventional AC units, the additional cost is quickly offset by the lack of power consumption by the unit. Issacharov is seeking funding to fully develop her product, but so far has no takers, so this great idea may die a silent death.
Until next week stay safe and learn something new.
Scott Hamilton is an Expert in Emerging Technologies at ATOS and can be reached with questions and comments via email to sh*******@te**********.org or through his website at https://www.techshepherd.org.
