One-fifth of the energy consumed in the world today is use to cool people and things. As average temperatures rise, more energy will be devoted to air conditioning for overheated humans. Conventional air conditioning operates on principles that date back to 1833, when John Gorrie was appointed chief medical officer of the US Naval Hospital in Apalachicola, Florida.
At that time, the area around the tiny fishing village was a mosquito infested swamp and malaria a common ailment at the hospital. Gorrie wanted a way to cool his feverish patients and invented a wooden box with a crude piston inside. A wood burning steam engine compressed the air inside the box and when it was released it expanded and became somewhat cooler than the surrounding air. The rest, as they say, is history.
Since then, engineers have learned how to mechanically compress gases like hydrofluorocarbons and hydrocarbons. When the pressurized gases expand, they drop in temperature, cooling the surrounding air. The problem is, both are flammable and harmful to the environment when released into the atmosphere. The process is also quite inefficient in terms of how much cooling is obtained from a given amount of energy.
Researchers at the University of Cambridge in the UK and the Universitat Politècnica de Catalunya and the Universitat de Barcelona in Spain have developed an eco-friendly alternative that may represent a quantum leap forward in air conditioning technology. “Refrigerators and air conditioners based on HFCs and HCs are also relatively inefficient,” said Dr. Xavier Moya of the University of Cambridge. “That’s important because refrigeration and air conditioning currently devour a fifth of the energy produced worldwide, and demand for cooling is only going up.”
Moya and his colleagues in Spain have discovered a way to achieve cooling by changing the microscopic structure of plastic crystals. The changes can be achieved by applying a magnetic field, an electric field, or through mechanical force. For decades, this process has been inferior to the compression of gases but the researchers have found that using a plastic crystal known as neopentylglycol leads to results that are as good as conventional methods.
Neopentylglycol or NPG is non-toxic, non-flammable, and made from readily available organic compounds. The word “plastic” in “plastic crystals” refers not to the crystal’s chemical composition but rather to its malleability. Plastic crystals lie at the boundary between solids and liquids. NPG is commonly used to make paints, polyesters, plasticizers, and lubricants. It’s not only widely available, it is also inexpensive.
According to Science Daily, NPG molecules are composed of carbon, hydrogen, and oxygen. They are nearly spherical and have weak chemical bonds between molecules. These loose bonds permit the molecules to rotate relatively freely. Compressing NPG yields unprecedentedly large thermal changes due to molecular reconfiguration. The temperature change achieved is comparable with those typically associated with compressed HFCs and HCs.
Lower cost, eco-friendly, high efficiency coolants could be hugely important to New York City’s plan to lower the carbon emissions from its largest buildings by 40% over the next decade. Many of those buildings rely on outdated, inefficient cooling technology that soaks up lots of electricity.
Building owners are concerned that the cost of meeting the new guidelines will be enormous, but if new technology could lower their utility bills, that would take some of the sting out of the city’s initiative. Professor Moya is now working with Cambridge Enterprise, the commercialization arm of the University of Cambridge, to bring this technology to market. Let’s hope that happens soon.
Have a tip for CleanTechnica, want to advertise, or want to suggest a guest for our CleanTech Talk podcast? Contact us here.