The UK government introduced legislation in June 2021 to phase out the sale of halogen light bulbs. It is expected that light emitting diode (LED) lighting will become the dominant lighting source by 2030.

i.A 45-watt halogen lamp produces 700 lumens of light. It is now possible to buy a LED lamp, equivalent in light output, but which only consumes 7 watts of electricity. The UK governments 'Energy Price Guarantee' scheme, published in October 2022, quotes a maximum electricity price of 34 p per kWh. Using this value, calculate the hourly electricity cost for the halogen lamp and the LED lamp.

ii.A halogen lamp costs 2.50 and lasts for 2500 hours. The LED lamp costs 5.00 but lasts for 15 000 hours. Calculate the total costs of each type of lamp (including replacement lamps) over 15 000 hours, and also the financial saving in using the LED lamp.

c.

i.The efficacy of an early 20th century gas light was 0.90 lumens per watt (of town gas). What would have been the rate of energy consumption in watts of a 700 lumen lamp?

ii.Using the data in Figure 12.8 of the Energy Systems and Sustainability textbook, calculate the approximate hourly running cost of such a gas lamp in 1920, expressed in 2019 pence per hour.

iii.According to UK government statistics, the consumer price index increased by 13.5% between 2019 and 2022. Use this fact, and your result in part (b)(i) above, to express the fuel cost of your modern LED lamp in 2019 pence per hour.

iv.Calculate how many times more expensive the fuel costs of a 1920 700 lumen gas lamp were compared to the electricity costs of an equivalent modern LED light.