How Does the Energy Density of a Lead-Acid Battery Compare to Gasoline?

[aaronb]

Homework Statement

A fully charged 15.0 kg lead-acid battery can deliver power 1450 W for 1.0 hr. (For comparison, the "heat of combustion" of gasoline is about 44 MJ/kg.)

Battery _____ MJ/kg

Homework Equations

Unit conversion problem
1W = 1 J/s

The Attempt at a Solution

(1450 J/s / 15kg) = 96.7/10^6 = 9.6 *10^-5

 

[Pengwuino]

You should notice immediately if you kept your units that your final answer does not have the units of MJ/kg as I see your answer requires. Remember, Watts (or Power) is a unit of energy per time. You're missing one part of the calculation.

 

[nlightner]

MJ/kg

The potential energy in fuels, such as gasoline, is typically measured in terms of its heat of combustion, which is the amount of energy released per unit mass of the fuel when it is burned. In the given scenario, a fully charged lead-acid battery has a potential energy of 9.6*10^-5 MJ/kg, which is significantly lower than the heat of combustion of gasoline (44 MJ/kg). This highlights the need for alternative and more efficient sources of energy, as fuels like gasoline have a limited potential energy and also contribute to air pollution and climate change. As scientists, it is important to continue researching and developing new technologies that can harness and utilize energy from renewable sources with higher potential energy, such as solar, wind, and hydro power.