The Register has a great story on a new Stirling Engine driven fan heatsink for northbridge chipsets developed by MSI Computer. As you might know, Stirling engines are an old technology that use the energy inherent in the expansion of air as it warms up, to create mechanical motion. The most common examples use the heat from a cup of coffee to drive a wheel, for example. MSI's Air Power Cooler takes the Stirling Engine concept and uses it to drive a low RPM fan which exhausts air through the fins of a heatpipe heatsink. The beauty of the design is that is requires no electricity to operate. Heat energy is converted into useful mechanical motion to drive the fan impeller. Standard heatpipes and aluminum fins dissipate the heat from the chipset into the surrounding environment.
While this is certainly a novel application of the Stirling technology, there are a few caveat's MSI will have to overcome if reliability is to be assured.
FULL STORY @ REGHARDWARE (http://www.reghardware.co.uk/2008/02/29/msi_stirling_cooling/)