User:Sandra.bitelli/PHYS100: Energy Consumption Comparison of Washing your Car

Problem Statement edit

We will be attempting to solve the problem of whether it is more energy efficient to wash your car at home or go to a car wash, and how much more efficient it is. We will also briefly discuss which is more harmful to the environment.

Case Description edit

Clark has a 2010 Nissan 350Z that he washes once a week, religiously. He usually goes to the local Shell, 5 km away, to wash his car at the commercial car wash. But, with his new interest in environmental studies and his limited budget, he wonders if it would be more cost effective and environmentally friendly to wash his car by hand. He decides to calculate the amount of energy used by a commercial car wash versus washing the car at home. He then researches on which process uses less water to make his final decision on which method is less harmful to the environment.

Project Goals edit

Determine:

The amount of energy needed to drive to the car wash versus staying home
The amount of energy needed to power a car wash versus energy needed by our bodies to physically wash the car
The amount of water used and the effect on the environment in both situations
Overall which is a better choice based on what was learned

Research Information edit

For an hour of washing the car, the average 75kg person will expend 337kCal of energy
Wattage used for a water pump is 3000W
1Hp = 0.7456KwH
An average electric car wash has a 355-430Jp motor running it depending on the amount of air dryers.
The mass of the Nissan 350Z is 1516 kg

Model edit

Models of both our car and our electrical car wash.

By Hand:

The person will use about 337kCals and the energy of the hose 3000W, washing the car by hand for one hour.

An example of the garden hose used to wash the car by hand
An example of the sponge used to wash the car by hand

By Electric Car Wash:

The person will drive to the electric car wash and drive it through a 10 minute cycle.
The electric car wash will use 178 944kJ to power itself
It will also take 89 100kJ to drive there.

An example of the electrical car wash from the inside
This is the car that will be used in both situations

Assumptions edit

Assumptions for washing the car at home:

Chemicals used will be the same as the chemicals used at the car wash
An average person will expend constant (consistent) energy throughout the car washing process
It will take him an hour to wash his own car
He is 75kg

Assumptions for going to a car wash:

Chemicals used will be the same as the chemicals used while washing the car at home
He is driving 50km/hr to the car wash and it is 5 km away
He does not encounter any traffic on route to the car wash
Driving conditions are ideal; there are no hills on route to the car wash
There is negligible friction and air resistance while driving; negligible thermal energy
The car wash has an average 400Hp motor running the system (easy amount to use for calculations between the given values of 355 and 430Hp)
The car wash takes 10 minutes to complete the cycle

Calculations edit

Energy consumption for person washing a car:

         337.3kCal x 4.184 = 1411kJ

Energy consumption for the hose:

         3 000J/s
         3 600s/hr
         3 000 x 3 600 = 10 800 000J
         10 800 000J ÷ 1 000 = 10 800kJ

Total Energy used for washing the car at home:

         1 411kJ + 10 800kJ = 12 211kJ

Energy consumption of a car wash for one hour:

         1Hp = 0.7456KwH
         0.7456KwH x 400Hp = 298.2KwH
         298.24KwH = 1 073 664kJ
         For the 10 minute cycle: 1 073 644kJ ÷ 6 = 178 944kJ

Time it takes to drive to the car wash:

         t = 5km ÷ 50km/hr = 0.1hr
         0.1hr x 60mins = 6 mins

Energy consumption for driving to the car wash:

         Kinetic E = (1/2)*m*v^2
         E = (1/2)*(1516 kg)*(50^2)
         E = 195 000 J = 195 kJ

Total energy for using the car wash:

         178 944 kJ + 195 kJ = 179 139 kJ

Interpretation of Results edit

We had assumed that the total energy consumption would be much higher for using a car wash versus washing your own car due to the following:

the fact that energy would be used driving to and from the car wash station
the car wash uses machinery which uses more energy than a normal person