The “negawatt”: Striving toward energy efficiency nirvana

by Debra Vogler, Senior Technical Editor, Solid State Technology

May 20, 2008 – Paul Westbrook, TI’s sustainable development manager and energy efficiency guru, presented data to ConFab attendees to illustrate the power of zero — as in “negawatts,” described as a measure of efficiency as in a unit of energy saved in watts. Saving energy, Westbrook stressed, is far most cost-effective than producing it. “Efficiency should be considered an energy source — a very cost-effective one,” he said.

As an example, Westbrook discussed Google’s installation of 1.6MW of solar photovoltaic panels on its corporate headquarters, noting various sources suggest Google will get a payback in ~7.5 years. He calculated $5/watt for the installation cost as a “best case,” though “much of that cost was covered by state/local/federal incentives, so Google probably paid ~$3M of the estimated $8M+ total,” he said. Using $0.10/kWh for the power cost (and noting that the peak power in California probably runs closer to $0.20/kWh), he deemed that online references to $400K/year in savings “would be accurate at that energy rate.”

Westbrook estimates the ROI for the Google project, though, is only <15%. "All energy production has some downside," e.g., getting the raw materials, production, transport, etc., "so getting rid of that need is the most cost-effective."

To illustrate his point, he noted that worldwide, TI’s fabs in 2007 were able to save, through the implementation of energy efficiency projects (at a cost of $1.2M), 14,717 MWh/yr, for a savings of $1,471K/yr at $0.10/kWh — that translates into an ROI of >100% (see Figure). “These savings were the equivalent of having installed 27 acres of solar panels,” said Westbrook — but without the downside of actually installing solar panels!

Figure. Efficiency examples: Google and TI.

Part of the search for energy efficiency in fabs involves the processing tools themselves. A SEMATECH/ISMI energy working group, including TI, Samsung, Intel, and AMD, has listed ways in which tool suppliers could step up to the plate and improve energy efficiency. Among the key points are: minimizing exhaust, using efficient, variable speed vacuum pumps with idle signal response, thermoelectric chillers or plant PC water for cooling, using mini-environments with better flow per unit of energy (cfm/kW); and resource use minimization with reclamation. Westbrook pointed to SEMI’s S23 document on tool energy use for additional improvement targets. — D.V.


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