- #1
jacstar
- 2
- 0
Need help - my brain is mush and the longer I look at it the more I don't understand it...can someone please tell me if this calculation is correct:
A car is run for 400 hours per year, with a total mileage of 10,000 a year.
The car uses diesel and consumes 2,000 litres a year.
A litre of diesel costs £1.10 and holds 38.7MJ of primary energy.
If the engine is 20% efficient overall, how much energy would need to be stored in 95% efficient batteries to give a range of 300 miles on full battery charge?
n/a
Background Calcs:
Convert MJ to J: 38700000J
Total Joules (J x 2000 litres): 77400000000J
Convert 400 hours to seconds: 1440000s
Energy 77400000000 J
Time 1440000 seconds
= Power 53750 Watts
53.75 kW
1 watt = 0.001341022 horsepower
Convert W to hp: 72.07993734 hp
Answer (attempt!):
Primary energy (1 year): 400h*53.75kw=21.5MWh
Energy to 95% efficient batteries: 21.5 x 100/20 x 100/95 = 113.2MWh
Therefore 300 miles: 300/10000*113.2=3.4MWh
I appreciate your help!
Thanks guys
+ :zzz: +
= me
Homework Statement
A car is run for 400 hours per year, with a total mileage of 10,000 a year.
The car uses diesel and consumes 2,000 litres a year.
A litre of diesel costs £1.10 and holds 38.7MJ of primary energy.
If the engine is 20% efficient overall, how much energy would need to be stored in 95% efficient batteries to give a range of 300 miles on full battery charge?
Homework Equations
n/a
The Attempt at a Solution
Background Calcs:
Convert MJ to J: 38700000J
Total Joules (J x 2000 litres): 77400000000J
Convert 400 hours to seconds: 1440000s
Energy 77400000000 J
Time 1440000 seconds
= Power 53750 Watts
53.75 kW
1 watt = 0.001341022 horsepower
Convert W to hp: 72.07993734 hp
Answer (attempt!):
Primary energy (1 year): 400h*53.75kw=21.5MWh
Energy to 95% efficient batteries: 21.5 x 100/20 x 100/95 = 113.2MWh
Therefore 300 miles: 300/10000*113.2=3.4MWh
I appreciate your help!
Thanks guys
![Cry :cry: :cry:](/styles/physicsforums/xenforo/smilies/cry.png)