a) What is energy labelling of appliances? Why is it an important mean for saving electrity? (4 marks)

 

b) The energy saving potential for lighting could be 11% of the total energy use. Describe briefly how to achieve energy saving in lighting without replacing the lamps. (3 marks)

 

c) The energy efficiency of a 220V 75W compact fluorescent lamp is 18% and operates 2600 hours a year. Determine the total energy loss and the cost to operate it for one year if the cost of electricity is 120 cents/kWh. (4 marks)

 

d) The energy efficiency of a LED lamp is 36%. If it could replace the 75W fluorescent lamp, estimate the power of the lamp and determine the cost to operate it for one year. Compared with the fluorescent lamp, what is total saving in one year? (6 marks)

 

e) If the cost of replacing the fluorescent lamp is $234, determine the payback period ,and the return on investment. (4 marks)

 

f) Apart from energy efficiency, list four advantages of LED lighting? (4 marks)

a) Energy labelling in the appliances are guides on how energy-efficient appliances are, such as and mostly found in an air conditioner, refrigerator, washing machine, dishwashers and lamps. This energy guide will surely make a difference in your electricity cost and more significantly, in protecting the environment, too.

Most of the countries sourced its electricity production from fossil fuels, low-carbon sources, renewables and nuclear energy. Among these, non-renewable resources are still top sources until now. Thus, saving energy directly connects to saving the environment, not only preventing sooner exhaustion of fossil fuel sources but above all reducing the amount of toxic fumes released by the power plants.

To conclude, most countries have standards of minimum energy guide efficiency per appliance to ensure compliance to energy saving.

b) The best way to save energy without replacing lower energy saving potential lamps is to change the way how you use it. Energy conservation can be as simple as turning off the lights when you do not need them. Also, Demand Side Management is good practice to aid energy conservation by efficiently managing energy consumption with the aim of cutting the costs incurred for the supply of energy.

c) Based on the power efficiency:

efficiency = (power out / power in)

thus,

power out = efficiency x power in

= (0.18) x (75 W) = 13.5 W

and

power loss = Power in - Power out = 75 - 13.5 W = 61.5 W

while operating for 2600 hours per year the total energy loss is determined as:

total energy loss = power loss x operating hours

= (61.5 W) x (2600 h)

= 159,900 Wh or 575,640,000 Joules ( since 1 Wh = 3600 Joules)

And the total electricity cost is determined as:

electricity cost = power in x operating hours x energy rate

= (75 W) x (2600 h) x ( 1/1000) x (1.2 $/kWh)

= $ 234 in a year

d) Assuming that we will be needing the same power output of 13.5 W lightning thus the equivalent LED light we need with 36% efficiency is:

Power in = Power out / efficiency

= (13.5 W) / (0.36)

= 37.5 W as the estimated power of the LED Lamp

the operational cost for 2600 hours will be:

electricity cost = power in x operating hours x energy rate

= (37.5 W) x (2600 h) x ( 1/1000) x (1.2 $/kWh)

= $ 117 in a year

comparing the energy cost for fluorescent lamp and LED lamp, we save as much $117 . since saving is equal to $ 234 - 117 = 117

Thus, the energy cost is cut into half.

e) If the LED lamp cost is $234. and the annual saving is $117. The payback period will be

payback period = lamp cost / saving

= $ 234 / $ 117 years

= 2 years

f) Advantages of LED lamps are:

1) Longer life span than conventional lamps

2) Higher brightness and intensity

3) lower heat emission

4) Durable and reliable form of lighting