Kelly Black is a faculty member in the Dept. of Mathematics and Com-puter Science at Clarkson University. He received his undergraduate degree in Mathematics and Computer Science from Rose-Hulman Institute of Tech-nology and his Master’s and a Ph.D. from the Applied Mathematics program at Brown University. He has wide-ranging research interests, including laser simulations, ecology, and spectral methods for the approximation of partial differential equations.
Mobile to Mobil: The Primary Energy Costs for Cellular and Landline Telephones
Nevin Brackett-Rozinsky Katelynn Wilton
Jason Altieri
Clarkson University Potsdam, NY
Advisor: Joseph Skufca
Summary
We determine that cellphones are the optimal communication choice from an energy perspective, using a comprehensive analysis based on mul-tiple factors. We split phones into three categories: cellular, cordless land-line, and corded landline. We average the energy used in manufacture and transportation over the life of each phone. To account for the inefficiency of production, we calculate in terms of primary energy, which is the amount of fuel supplied to a power plant per unit of energy produced for consump-tion. We use real-world data for population, number of mainlines, and cellphone subscriptions.
During the transition, as cellphones overtake landlines, part of the pop-ulation owns both types of phone. As a result, the total energy used by telephones increases. We fit a competing-species model to past statistics;
it forecasts that the net energy cost of the cellphone revolution (1995–2025) in the U.S. will be 84 TWh. At the start of this period, there were 0.1 cell-phones per capita; at the end there will be 0.1 landlines per capita. Energy savings will begin in 2022. After this transition, savings will be 30 GWh/d.
The competing-species model is a proven technique; we apply it to tele-phone lines and celltele-phones per capita, and also use it in conjunction with population projections to develop a closed-form solution.
The UMAP Journal 30 (3) (2009) 313–332. c!Copyright 2009 by COMAP, Inc. All rights reserved.
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The most energy-efficient way to provide phone service in a country with no existing infrastructure is to construct a cellular network. By amortizing the fixed setup costs over the lifetime of the phone system, the energy used during construction is negligible. For a country similar to the U.S., the annual savings would be 12 TWh. Over the next 50 years, the energy savings would equal 0.5 billion barrels of oil.
Cellphone chargers waste energy, but the total energy wasted would be almost five times as great if everyone instead used a cordless phone.
Continuing advances in charger technology are reducing charger waste. If all cellphone chargers in the future meet a 5-star Energy Star rating, they will be 10 times as efficient as now.
Our model is supported by historical data and numerous publicly avail-able statistics. One factor not accounted for is the maintenance and operat-ing power required for cell towers and physical telephone lines.
Introduction
Over the past 15 years, cellphone subscriptions in the U.S. have increased dramatically. At the same time, growing concerns over oil supplies have increased public consciousness of energy efficiency. We compare the energy use of cellphones to that of traditional landlines. Major factors include:
• power used while charging,
• power used while idle,
• time charging each day,
• time idle each day,
• energy to manufacture and transport the phone,
• lifespan of the phone, and
• total number of phones.
These values, many of which depend on the type of telephone, allow for a comprehensive analysis of the energy consequences of the cellphone revo-lution. Our model quantifies the effects of cellular and landline telephones on power consumption.
Assumptions
• Cellphones and landline phones compete for the same market.
• Residential, commercial, nonprofit, and government telephones are in-cluded in the total number of phones.
• The total number of phones is averaged by household.
• Every cellphone comes with a charger and lithium-ion battery [1].
• A cellphone’s battery will not be replaced but discarded with the phone.
• Overcharging or undercharging a lithium-ion battery does not affect its life or performance [6].
• Nickel-hydride batteries are used in cordless phones [7].
• The total energy used in manufacturing a landline phone is half that of manufacturing a cellphone.
• A person may own more than one telephone.
• In a household with cellphones, each of its m members has their own cellphone.
• Every person within the population is part of a household.
• A charger is any item used to recharge batteries, including those within electronic devices such as laptop computers, cellphones, and cordless phones. Appliances such as televisions, refrigerators, and microwaves are not included, since they are not rechargeable devices.
• The fixed energy required to construct telephone infrastructure, when averaged over the duration of the phone system, is negligible.