Thermograms

1. Thermograms

2. Look at the thermogram of the row of houses. Which house is insulated best? How do you know this?

3. Can you think of three areas in a house where you commonly install insulation?

4. Look at the table of U-values below. Which house is the best insulated?

5. How a solar panel works

6. How a solar panel works

7. Solar panels on a roof

8. Different ways of reducing your energy consumption

9. Different ways of reducing your energy consumption

10. Solar panels and payback time: Overview

11. Look at this solar panel. How is the water heated?

12. Energy transfer: Infrared radiation from the sun is absorbed by water, increasing its temperature.

13. Payback time = cost savings per year This is the equation for calculating payback time. To decide whether a method of insulation is worth doing you need to calculate the payback time.

14. 50 mm loft insulation • 270 mm loft insulation • Payback time = = cost £100 £20 per year savings per year £250 cost Payback time = = savings per year £100 per year Look at the two payback equations above for insulating a loft. Calculate the answers and decide which method is most cost effective.

15. Can you think of the three areas of a house which are commonly insulated? 1 windows – double glazing 2 walls – cavity wall insulation 3 roof – loft insulation

16. Specific heat capacity of various materials

17. The specific heat capacity of a material is the amount of energy needed to raise the temperature of 1 kg of the material by 1°C. Its units are J/kg°C.

18. The amount of thermal energy an object stores is related to its mass and temperature. It is also related to the material the object is made of…

19. Some specific heat capacities are given in the table below.

20. Using the specific heat capacity we can calculate the energy needed to raise the temperature of a material by a particular amount.

21. Calculate the energy transfer needed to bring 1.5 kg of water to the boil from a room temperature of 18°C • Energy needed • = mass  specific heat capacity  temperature change • = 1.5 kg  4200 J/kg°C  (100 – 18)°C • = 1.5  4200  82 J • = 516 600 J = 516.6 kJ

22. Calculate the energy required to raise the temperature of 12 kg of aluminium from 15°C to 35°C • Energy needed • = mass  specific heat capacity  temperature change • = 12 kg  880 J/kg°C  (35 – 15)°C • = 12  880  20 J • = 211 200 J = 211.2 kJ

23. 114 kJ of energy is required to raise the temperature of copper by 20°C. Calculate the mass of the copper. • Energy needed • = mass  specific heat capacity  temperature change • 114 kJ = mass  380 J/kg°C  20°C • 114 000 J = mass  7600 J/kg • Mass = • Mass = 15 kg

24. 10.8 kJ of energy is required to raise the temperature of 1 kg of cooking oil by 9°C. Show how you would calculate the specific heat capacity of cooking oil. • Energy needed • = mass  specific heat capacity  temperature change • 10.8 kJ = 1 kg  specific heat capacity  9°C • 10.8 kJ = 9 kg °C  specific heat capacity • 10 800 J = 9 kg °C  specific heat capacity • Specific heat capacity = • = 1200 J/kg°C

25. Energy transfers

26. Remember energy cannot be created or destroyed. It can only be transferred from one form to another.

27. Here is a list of some of the different forms of energy: • electrical • kinetic • light • elastic potential • gravitational potential • heat • wind • sound

28. Look at this wind-up torch. Can you explain the energy transfer needed to make it work? • kinetic  electrical  light + heat

29. What about this wind turbine? Can you explain the energy transfers that are taking place? • kinetic  electrical + heat + sound

30. What energy transfer is taking place in this kettle? • Electrical  heat + sound

31. Imagine a ball at the top of a hill. What form of energy does the ball have? • Gravitational potential What form of energy is the potential energy transferred to when the ball rolls down the hill? Kinetic

32. Useful energy and energy efficiency: overview

33. Look at this Sankey diagram for a light bulb.

34. What do we mean by wasted energy? What form does the wasted energy from the light bulb take?

35. What do we mean by useful energy? What form is useful energy in?

36. What is the total energy transferred? Can this ever be more or less than the total energy supplied?

37. efficiency = useful energy transferred total energy supplied Work out the efficiency of the light bulb by using the equation above.

38. Efficiency rating labels

39. Most electrical appliances carry the EU Energy Label.

40. The energy efficiency of the appliance is rated from A to G. Here is an EU Energy Label for an energy efficient light bulb.

41. The EU Energy Label for the light bulb also specifies its brightness in terms of lumens and its average life length in hours.

42. For appliances that are particularly efficient, like this refrigerator, ratings of A+ and A++ are permitted.

43. The EU Energy Label specifies the energy consumption, noise and volume of the refrigerator.

44. Here is an EU Energy Label for a washing machine. The flower you can see is called the European Ecolabel. This means that the washing machine will have a low environmental impact.

45. What other information does the EU Energy Label tell us about this washing machine?

46. Have a look at the EU Energy Label for another washing machine.

47. This washing machine only has a B energy rating. Why do you think this is? What differences are there between the A-rated and B-rated washing machines?

48. Electricity meters

49. Energy used is measured in kilowatt-hours (kWh) and is calculated by the following formula: • energy transferred (kWh) = power (kW)  time (hours)

50. A television uses 400 W and is switched on for 2 hours. Calculate the energy transferred. • Energy transferred = power  time • = (400  1000) kW  2 hours • = 0.8 kWh