Saving Battery Life on a Laptop Computer

Adam BrandtKelly Layland

2

The Problem

• Laptops generate a lot of heat, especially Laptops generate a lot of heat, especially when used on your lapwhen used on your lap

• A pillow is often used to insulate your legsA pillow is often used to insulate your legs

• Determine if resting on a pillow causes a Determine if resting on a pillow causes a laptop to use more energy.laptop to use more energy.

• Find out what is the best way to use a Find out what is the best way to use a laptop computer.laptop computer.

Objectives

3

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 used by the laptop

LTTkq 21"

4

Methods• Ran laptops on Ran laptops on

different surfaces until different surfaces until steady state steady state temperature reachedtemperature reached

• Measured Measured temperature at same temperature at same spot on laptop for spot on laptop for each experimental each experimental runrun

• Tested 2 laptops and Tested 2 laptops and compared datacompared data

5

Results and Analysis • Used thermal conductivity to calculate heat

flux from laptop

• Lowest temperatures occurred on a table• Highest temperatures and lowest heat flux

occurred on a pillow

 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 1

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

Results from laptop 2

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Conclusions• Using your laptop on a pillow is the worst optionUsing your laptop on a pillow is the worst option

– significantly lowers the heat flux and increases the significantly lowers the heat flux and increases the temperature of the laptop which could possibly cause temperature of the laptop which could possibly cause damage to the laptop damage to the laptop

– causes the fan to run continuously which uses more causes the fan to run continuously which uses more energyenergy

• Placing a conductive material on top of the pillow Placing a conductive material on top of the pillow lowers the temperature and increases the heat lowers the temperature and increases the heat flux through the material, but not a lotflux through the material, but not a lot

• Using a laptop on a table, not on your lap, is the Using a laptop on a table, not on your lap, is the most energy efficient most energy efficient