Intel has named its solar-powered CPU, which it showed off a few days ago Codenamed Claremont Intel managed this by using a technique to apply voltage to a silicon chip called Near Threshold Voltage. This is based on the idea that processors have plenty of voltage to ensure that the transistors within switch with no trouble. However if you cut the applied voltage to be just above the required level.
Official Post: Fudzilla
Official Post: Bit-Tech