Energy Fundamentals

1. In this problem, we will explore how the amount of work that can be done by a human compares

to the amount of work that can be extracted by burning fossil fuels in an internal combustion

engine. Clearly state any assumptions you make.

a) Estimate the total kWh an average human could realistically produce in a year pedaling a

bicycle with an average output of 0.25 hp. Clearly explain your approximations such as

time for resting.

b) If all 8 billion people in the world cycled for 1 hour per day for a year, could they generate

enough energy to power the US? The current consumption level of primary energy in the

US is 100 quads per year.

c) How much energy (in kWh) is produced by burning a gallon of gasoline? Assume that the

gasoline is made up of a representative hydrocarbon molecule (a branched hexane or

heptane) and compute the heat of combustion for that compound.

d) Assuming a reasonable efficiency for an automotive internal combustion engine (ICE),

how much gasoline would it take to do the same work as a human for one year?

e) For how much time would an average human have to cycle to move a car 250 miles?

Assume the car can drive 25 miles per gallon of gas and use the same ICE efficiency from

part d.