How can we make a robot more energy efficient?

Look at the Sankey diagrams on your tables, and work out the scale – one square = ? JoulesThen:1) What are the output energy

amounts?2) What is the energy

efficiency of the ipod?

iPodInput energy = ?

What is Power?

• What does the word mean?• When can it be used?• Group discussions – 2 minutes

• Power is defined as the rate of transfer of energy. It is given by:

Power = Energy / Time

The normal unit used to measure power in is therefore joules/sec or J/s (Or a WATT – W)

Example One

• A shaver has a power of 10W, and is used for 30 seconds.

• How much energy does it use?– Power = 10W– Time = 30s– Energy = ?

• Energy = 10 x 30• Energy = 300J

Show-me boards

• Power = 10W, Time = 3s, Energy = ? • Power = 30W, Time = 20s, Energy = ? • Power = 3kW, Time = 5s, Energy = ? • Power = 3kW, Time = 1 min, Energy = ?

Rearranged equations

• Power = Energy / Time• Time = Energy / Power

• Energy = 500J, Time = 25s, Power = ?• Power = 200W, Energy = 1kJ, Time = ?

Upgrading a robot

• Your task is to improve a robot to make it as energy efficient as possible

• You need to think about how to calculate the energy efficiency of different parts of the robot

Stuck Board1. Work out how much energy that part will use in

the required time (Energy = Power x Time)2. Work out the energy efficiency of each part

(Energy efficiency = useful output energy / total input energy)

3. Are the upgrades always more energy efficient?

What have you learned today?

• At least one point on the post-it note

These are the answers, what are the questions?

1. 10J2. 50W3. 1 minute

Power Calculations

Device Energy Transferred Time Taken Power  

Torch 60J 60s

Light bulb 1440kJ 4 hours

Cooker 30 minutes 10000W 10kW

Engine 10MJ 1000000W 1MW

Rocket 3000MJ 30s

Power Station 144000000MJ 10000000000W 10000MW

         

         

  kilo watt (kW) = 1000 W      

 mega watt (MW) = 1000000

W      

Answers

Device Energy Transferred Time Taken Power  

Torch 60J 60s 1W 1W

Light bulb 1440kJ 4 hours 100W 100W

Cooker 18MJ 30 minutes 10000W 10kW

Engine 10MJ 10s 1000000W 1MW

Rocket 3000MJ 30s 100000000W 100MW

Power Station 144000000MJ 4 hours 10000000000W 10000MW

         

         

  kilo watt (kW) = 1000 W      

 mega watt (MW) = 1000000

W