Design Con 2015

Big numbers, big confusion

-May 07, 2013

It seems that big numbers carry with them big confusion. Big numbers from the age of the universe to the national debt can lead to interesting conversations at the lunch table. The magnitude of such numbers draws our attention, and the engineer in us leads us to make some use of these numbers. For example, the recently updated estimated age of the universe is 13.82 billion years, an increase of about a million years.1 It is interesting that the reported value doesn’t even have 1 million as a significant digit in the reported age. The real point of the change is that the universe is expanding slower than originally thought.

 

In my last post, I talked about the power drain on my cell phone when comparing 3G to 4G networks. In April of this year, Centre for Energy-Efficient Telecommunications (CEET) published a report titled, “The Power of Wireless Cloud.”2 This is an excellent report and quite easy reading. The report makes several interesting points and predictions. For example, the wireless cloud consumes about 9.2 TWh in 2012, and is expected to grow by 460% to 43 TWh by 2015. Another point is that only about 9% of the wireless cloud energy is consumed by data centers. With all the focus on data center energy efficiency, I would have thought that data centers are a far bigger energy hog.

 

An earlier report by Dr. Jonathan Koomey states that data centers consume between 1.1 to 1.5 percent of global electricity.3 This is a very large number. The World Bank estimates that the global production of electricity is about 21.49e12 kWh or 21,490 TWh.4 Even 1.1 percent is about 236 TWh. This is considerably more than estimated by CEET. So where is the confusion?

 

Alcatel-Lucent reported on the power and energy of worldwide base stations and their connected systems.5 This analysis shows that the big energy appetite comes from wireless base stations. Figure 1 shows that the estimated energy consumed annually by wireless base stations is about 60 TWh, while the server and related services consumed is about 14 TWh. This ratio is not quite what was reported by CEET. The Alcatel-Lucent report also addressed the power amplifier’s (PA) power efficiency, showing a range of efficiencies from 6 to 40%, depending on the output power.  

 

Terawatt hours are certainly large amounts of energy. A Terawatt is roughly equal to a megaton of TNT. In some ways it is hard to imagine that the world produces so much electricity.

 

So what does it all mean? It may be that the current energy consumption estimates should not be the main focus. It may be that the growth is the issue. There are tremendous expectations for cloud growth and that most connectivity will be wireless. From smart phones to the “Internet of Things,” it seems that wireless will be a big part of the solution. Growth will demand either increasing our energy output or improving our energy efficiency to help hold the demand at today’s level. It may be that we can meet the cloud traffic demand while decreasing the energy demand.

 

There is some effort to improve PA efficiency from envelop tracking to digital PAs. However, the solutions are not coming fast enough. The growth of the wireless cloud is outpacing the innovations needed to reduce energy demands.

 

It seems that it is not so much about the magnitude of any number, but about the magnitude of growth in the numbers. This is true for nearly all those giant numbers, like our growth in demands for wireless data and the energy to make it happen. Growth in any large number should draw our attention. From the expected growth of the national debt to the number of exabytes in Internet traffic, it is the growth that demands our attention. I would like to hear your thoughts about these predictions and the innovations needed to meet the growth. The power electronic industry has a big role to play. Everything from improving conversion efficiency to helping the system use the power more efficiently.

     
 

Figure 1. From smart phones to the cloud and the energy need.5

 

For more information about this and other power topics, visit TI’s Power House blog: www.ti.com/powerhouse-ca.

 

References

 

1.      Paul Preuss, “Planck Mission Updates the Age of the Universe and What it Contains,” Berkeley Lab, March 31, 2013

2. ”The Power of Wireless Cloud,” Centre For Energy-Efficient Telecommunications, April 2013

3. Jonathan G. Koomey, “Growth In Data Center Electricity Use 2005 to 2010,” August 2011

4. “Electricity Production (kWh),” World Bank Data

5. Alberto Conte, “Power Consumption of Base Stations,” Alcatel-Lucent Bell Labs France, Ghent, February 14, 2012

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