Light Bulbs

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The use of lighting in the household is a continuos environmental issue, one of which is energy efficiency. One of three main greenhouse gases, carbon dioxide (CO2), is emitted whenever lighting is switched on. This report is going to look at four types of light bulbs available on the market today and compared each in the form of efficiency, lifespan and costs.

Incandescent light bulbs are only about 10% efficient, with 90% of the energy lost through heat. Although incandescent light bulbs are inexpensive to buy, due to their inefficiency of power usage, long term consumers will pay more for their electrical bills than with newer energy efficient light bulbs. Incandescent light bulbs have a shorter life span than energy efficient light bulbs, as the filament that is heated up inside the bulb eventually burns out. The atoms of the filament evaporate from its surface, so that it continuously becomes thinner until it breaks. Therefore incandescent bulbs need to be more readily replaced.

Halogen light bulb can last 2-3 times longer than an incandescent light bulb. The bulb is filled with a chemically active gas that increases the life span of the filament. Halogen light bulbs are 10-20% more efficient than an incandescent light bulb. They are also relatively inexpensive, however also lose a significant amount of their energy usage due to heat loss.

Compact Fluorescent Lamps (CFL) contain a gas that produces invisible ultraviolet light when the gas is excited by electricity. The UV light hits the white coating inside the fluorescent bulb and the coating changes it into light. As CFLs don’t use heat to create light, they are far more efficient than halogen or incandescent bulbs. CFLs use 75% less energy and last 10x longer than incandescent bulbs, as a filament is not a limitation. The Environmental Defense estimates that by replacing five 60-watt bulbs with CFLs (which can last over 6000 hours) that over the life of the CFL the consumer would have saved $160.78 in energy, and more importantly 1026 pounds of CO2 from entering the atmosphere. CFLs use approximately 25% of the wattage of an incandescent to produce the same amount of light. The disadvantage to CFLs is the bulbs contain mercury. If the bulbs are broken or disposed of improperly, potentially mercury could end up in the environment. CFL are approximately double the cost of an incandescent bulb, however still relatively inexpensive.

Light Emitting Diodes (LED) are tiny light bulbs that fit easily into an electrical circuit and are illuminated by the movement of electrons though semi-conducting material producing only light- not heat. LEDs (life span of approximately 60 000 hours) last 5 times longer than CFLs and 50 times longer than incandescent bulbs. LEDs last for years therefore energy is saved in maintenance and replacement costs. LEDs are extremely efficient, using only a fraction of the wattage of incandescent bulbs. The disadvantage of LEDs is the cost is quite expensive. Replacement of a single 25-watt incandescent globe can cost $40. Another disadvantage to LEDs is the light produced is classified as a ‘focused light’. The light produced does not radiate in a 360 degree motion as the incandescent bulbs light does, but its more directed and beneficial for activities such as reading.

On board the Gato Verde, a 42-ft bio-diesel/electric engine catamaran, are 23 halogen light bulbs. Gradually LEDs are replacing the halogen bulbs. Data was collected and calculated on the difference in kilowatt hour (kWh) usage between the halogen bulb and the LED.

Halogen (kWh) LED (kWh) Salon 0.6 0.018 Mast 0.12 0.0036 Heads 0.024 0.00072 Berths 0.24 0.0072 Total 0.984 0.02952 Table 1. Comparison of kWh usage of halogen bulbs and LED around various sections of the Gato Verde

Then assuming the consumer will pay 10 cents per kWh, comparison between the running cost of the halogen bulbs and the LEDs onboard the Gato Verde were made per day, per week, per month, per year and per 11 years, see Table 2.

Halogen ($) LED ($) Savings ($) Per Day 2.36 0.071 2.29 Per Week 16.53 0.5 16.03 Per Month 66.12 1.98 64.14 Per Year 793.5 23.8 769.7 Per 11 years 8728.5 261.8 8466.7 Table 2. Comparison of halogen and LED bulbs over different time frames and hence the savings

The life span of the LED bulbs were 100 000 hour, which is equivalent to 11.4 years. A life span of a halogen bulb is 1000 hours, which is approximately 6 weeks. So initially to replace the halogen bulbs with the LEDs it would cost between $345-$690. However as is demonstrated in Table 2 the savings in energy costs over a period of 11 years (life span of LED) is $8466.7, which greatly exceeds the cost of replacing the LED bulbs. With the added cost of replacing the halogen light bulbs 95 times within that 11-year period, at approximately $4 each, the consumer would add an additional cost of $380.

Halogen ($) LED ($) Savings ($) Energy cost per 11 years 8728.5 261.8 8466.7 Maintenance cost of bulbs over 11 years 380 690 -310 Total costs over 11 years 9108.5 951.8 8156.7 Table 3. Comparison of halogen and LED bulbs in energy and maintenance, and hence total savings over an 11 year period

As Table 3. Demonstrates that although the initial cost of the LED is relatively expensive, overall the savings are going to be great. For the Gate Verde , assuming the lighting is run approximately everyday the same amount of time as calculated in this report, the consumer can potentially save $8156.7 over an 11 year period.

More importantly LED bulbs cut carbon dioxide (CO2) emissions greatly compared to incandescent globes. For example replacing a 75-watt incandescent globe with a 7-watt LED, the reduction in CO2 emission would be 6 920 pounds over the life span of the LED.

A report by the International Energy Agency claims that the world can reduce its energy use by almost 10%- more energy than that produced by hydro or nuclear stations- and reduce CO2 emissions by 232 million tons by switching to energy efficient lighting.

References Sited 16th October 2007 Sited 16th October 2007 Sited 16th October 2007 Sited 16th October 2007 Sited 16th October 2007 Sited 17th October 2007