May 26, 2009 Keeping electronic components cool is a constant problem for electronics manufacturers – computer manufacturers in particular. While desktop PCs have a few options open to them, such as water-cooling, laptops are more limited in how they can be cooled. As laptops and other electronic devices continue to shrink while the heat they generate increases, the search is on for alternatives to the bulky, noisy fan-based systems widely used. A cooling system developed by Tessera has discovered a way to create a cooling airflow through ionizing air particles.

The Electrohydrodynamic (EHD) ionic wind pump technique involves applying a voltage to an electrode, which produces a high intensity electric field. Air molecules surrounding the electrode tip ionize and as they move from the corona electrode to the collector electrode, they collide with neutral air molecules and their momentum pushes these neutral air molecules across a hot spot, cooling it down.

Such ionic-cooling systems have been demonstrated in research labs before, but Tessera is the first to test the technology inside a working laptop by replacing the standard rotary fans with EHD blowers.

One of the main hurdles for researchers had to overcome was designing a sufficiently compact voltage converter that could change the laptop battery's 12-volt DC into the some 3,000 volts required to operate the cooler. They succeeded by using a power supply from a cold cathode fluorescent lamp to construct a supply that is only three centimeters square.

The tests showed that the ionic-cooling system extracted roughly 30 percent more heat from a laptop than a conventional fan and could potentially consume only half as much power. Aside from these efficiency improvements, the EHD system is solid-state, which means it has no moving parts and therefore no noise, while its decreased size and weight mean it is suited for thinner, lighter portable devices.

But there remains challenges for the EHD technology, such as the reliability of the electrodes. While laptops are built to last at least 30,000 hours, certain electrode materials corrode in significantly less time. The engineers have identified better materials to optimize their lifetime, but at this stage the company is keeping details under wraps due to pending patents. Another problem is dust. The company is trying to make sure the ionic-cooler is as insensitive to dust as a fan. One option to protect the cooler is a pre-filter.

Although these teething problems are likely to mean the EHD technology won’t be ready for the next generation of laptops, the company believes it is still well-placed to commercialize the technology next year. Tessera is also working at optimizing the technology to fit it into small form factors for use not only in laptops, but also game systems, projectors and servers.

Darren Quick

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