Saving Battery Life on a
Laptop Computer
Adam Brandt
Kelly Layland
The Problem
• Laptops generate a lot of heat, especially
when used on your lap
• A pillow is often used to insulate your legs
Objectives
• Determine if resting on a pillow causes a
laptop to use more energy.
• Find out what is the best way to use a
laptop computer.
2
Heat Transfer Problem
• What is the heat flux
when the laptop is
rested on different
materials?
• How does the heat
flux affect the
temperature of the
laptop and the energy T1 T2
used by the laptop q" k
L
3
Methods
• Ran laptops on
different surfaces until
steady state
temperature reached
• Measured
temperature at same
spot on laptop for
each experimental
run
• Tested 2 laptops and
compared data
4
Results and Analysis
• Used thermal conductivity to calculate
heat flux from laptop
Results from laptop 1
Surface t1 (C) t2 (C) t3 (C) Thickness (m) q'' (W/m^2)
Table 39.1
Cardboard 41 30.9 0.00635 334.0157
Pillow 53.7 25.3 0.0889 19.1676
Pillow & Cardboard 47.7 45 24 89.29134
Results from laptop 2
Surface t1 (C) t2 (C) t3 (C) Thickness (m) q'' (W/m^2)
Table 40
Cardboard 42.1 35 0.003 497
Pillow 45 26 0.08 14.25
Pillow & Cardboard 44.7 42.8 25.6 133
• Lowest temperatures occurred on a table
• Highest temperatures and lowest heat 5
flux occurred on a pillow
Conclusions
• Using your laptop on a pillow is the worst option
– significantly lowers the heat flux and increases the
temperature of the laptop which could possibly cause
damage to the laptop
– causes the fan to run continuously which uses more
energy
• Placing a conductive material on top of the pillow
lowers the temperature and increases the heat
flux through the material, but not a lot
• Using a laptop on a table, not on your lap, is the
most energy efficient
6