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Problem Title: Energy and the Cell Phone

  Year: 2009      
  Student Level: Undergraduate      
  Source: MCM      
  Commentary: Yes (2)      
  Student Papers: Yes (5)      

This question involves the "energy" consequences of the cell phone revolution. Cell phone usage is mushrooming, and many people are using cell phones and giving up their landline telephones. What is the consequence of this in terms of electricity use? Every cell phone comes with a battery and a recharger.

Requirement 1

Consider the current US, a country of about 300 million people. Estimate from available data the number H of households, with m members each, that in the past were serviced by landlines. Now, suppose that all the landlines are replaced by cell phones; that is, each of the m members of the household has a cell phone. Model the consequences of this change for electricity utilization in the current US, both during the transition and during the steady state. The analysis should take into account the need for charging the batteries of the cell phones, as well as the fact that cell phones do not last as long as landline phones (for example, the cell phones get lost and break).

Requirement 2

Consider a second "Pseudo US"-a country of about 300 million people with about the same economic status as the current US. However, this emerging country has neither landlines nor cell phones. What is the optimal way of providing phone service to this country from an energy perspective? Of course, cell phones have many social consequences and uses that landline phones do not allow. A discussion of the broad and hidden consequences of having only landlines, only cell phones, or a mixture of the two is welcomed.

Requirement 3

Cell phones periodically need to be recharged. However, many people always keep their recharger plugged in. Additionally, many people charge their phones every night, whether they need to be recharged or not. Model the energy costs of this wasteful practice for a Pseudo US based upon your answer to Requirement 2. Assume that the Pseudo US supplies electricity from oil. Interpret your results in terms of barrels of oil.

Requirement 4

Estimates vary on the amount of energy that is used by various recharger types (TV, DVR, computer peripherals, and so forth) when left plugged in but not charging the device. Use accurate data to model the energy wasted by the current US in terms of barrels of oil per day.

Requirement 5

Now consider population and economic growth over the next 50 years. How might a typical Pseudo US grow? For each 10 years for the next 50 years, predict the energy needs for providing phone service based upon your analysis in the first three requirements. Again, assume electricity is provided from oil. Interpret your predictions in term of barrels of oil.


Judges' Commentary: The Fusaro Award for the Cellphone Energy Problem

Marie Vanisko
Dept. of Mathematics, Engineering, and Computer Science
Carroll College

Peter Anspach
National Security Agency


Judges' Commentary: The Outstanding Cellphone Energy Papers

Marie Vanisko
Dept. of Mathematics, Engineering, and Computer Science
Carroll College

  Student Papers      

Team 5261: Energy Implications of Cellular Proliferation in the United States

The College of Idaho, ID


Team 5265: Wireless Networks: An Easy Cell

University of Delaware, DE


Team 5522: America's New Calling

Southwestern University, TX


Team 5717: Energy and the Cell Phone

Clarkson University, NY


Team 5898: Modeling Telephony Energy Consumption

Cornell University, NY