But Professor Koomey's enthusiasm was reserved for a series of examples of how clever design can save power. The BigBelly trash compactor is solar powered and crushes waste to 20 percent of its original size. But the real innovation is that it sends a message when it is full allowing the trash collector to minimize collections. "Fewer truck trips means you are moving bits, not atoms," Koomey said.
He discussed wireless sensor motes that can be used to monitor city parking spaces powered by the scavenging energy from radio and television signals. The data is then used to drive street signs that direct drivers. Getting drivers parked quicker means less traffic and less gas consumption.
However, miniaturization and energy efficiency benefits are not automatic, Koomey cautioned. The good news is that, at the current rate of progress, we have until 2041 before we reach the Feynman limit of transistor-type action at the level of a single atom. However, long before that we will have to base integrated circuit operation and production on different principles, he said. The professor interrupted himself to make the observation that a research team drawn from Purdue University and the University of New South Wales has created a reliable single-atom device that uses electron-state switching to denote 1 and 0. The drawback today is that it requires liquid helium temperatures for operation.
The question remains, Koomey said: "Can we do better than historical trends? We could do worse especially if we do not address leakage current issues."
"Performance and efficiency are inextricably linked. We are still far from the theoretical limits. The future belongs to low-power systems," he concluded.
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Cell phones show a variety in talk time energy efficiency that is improving slowly, according to Professor Koomey.