Example of the Final Project Possible Reduction of Greenhouse Gas Emissions by Replacing Incandescent Lights with Compact Fluorescent Lights (CFL)

Outline Introduction What are CFLs and why are they more efficient than incandescent bulbs? How much energy can be saved per year in British Columbia of all incandescent light bulbs are replaced with CFLs? What is the effect on the CO 2 emissions?

Introduction Government web pages and media suggest replacing incandescent light bulbs with compact fluorescent light bulbs to save energy. We want to know how much energy is saved per household and estimate the energy savings in BC if all the home lights were replaced by CFLs. We also estimate the corresponding reduction in CO 2 emissions. In our estimates, we take into account energy used to manufacture incandescent bulbs and CFLs. For the estimate of the BC energy savings, we assume that ½ of all lights could be replaced by CFLs on average.

What is a CFL? Ordinary incandescent light bulbs emit light due to electrical heating of a thin tungsten wire. They convert only a few % to visible light (Lab 8). 90% – 95% of the electrical energy is converted into heat. A CFL is based on light emission from a gas discharge: An electric current is driven through a gas ionizing the gas molecules. The recombination of ions and electrons results in light emission. For the same light output as a 60 W light bulb a CFL needs only 13 W of electrical power. (Source: Wikipedia)

How many light bulbs can we replace in BC? Number of households in BC: ~ (in 2004) –( ssions.pdf) Estimated number of lights: 20 per household. Estimate that due to the light quality issues, fixtures and so on, ½ of the light bulbs will be replaced: 10 per household on average. This includes the fact that some light bulbs were already replaced by CFLs in the past. Total light bulbs that could be replaced = 10 bulbs per household  households = light bulbs

How much energy would be saved annually due to replacing these bulbs? Assume each bulb is switched on an average of 4 hours/day Average power 60 W. Replaced by 13 W CFL = Savings of 47 W per bulb replaced Each home would save 10  47 W  (4 h/d  3600 s/h  365 d/y) ≈ 2.5  10 9 J per household per year. For the whole province: 2.5  10 9 J  households ≈ 4  J per year

What would be the total reduction in CO 2 Emissions? CO 2 emissions in the US are 1.34 pounds (0.608 kg) of CO 2 per kWh averaged over all methods of generating electricity –(1998 – 2000, Source: US Government, DOE). Conversion between kWh and J 1kWh = 1000 J/s  3600 s/h  1h = 3.6  10 6 J Annual reduction in CO 2 emissions is: 4  J per year  (1kWh / 3.6  10 6 J)  kg/kWh = 8  10 8 kg of CO 2 per year in BC

What would be the percentage decrease in energy consumption? Total BC power production ≈ GWhours ≈ 53  10 9 kWh  3.6  10 6 J/kWh ≈ 2  J –( The savings of 4  J by switching to CFLs would decrease our provincial energy consumptions by 2%

Net Energy Savings BC generates most of its power from hydro power and only 10% from fossil fuels. So is there less benefit? Energy market is international and so is pollution: Energy saved here will still impact global carbon emissions. But we need to include energy needed to produce the CFLs and light bulbs. Hard to find numbers: Higher manufacturing cost of CFL is offset by its much longer lifetime –Lifetime ~ h (CFL) vs ~1000 h (incandescent) (Source: Wikipedia) So the raw energy savings we estimated in the previous slides are approximately equal to the net energy savings.

Negative Effects CFLs and other fluorescent lamps have small amount of mercury (~ 20 mg Hg). Since mercury is toxic, CFLs should be recycled. Ordinary fluorescent bulbs can be recycled and almost all of the mercury can be recovered. –(Source: Heat? Quality of light? –

Conclusion Replacing incandescent bulbs with CFL leads to significant savings in energy (and money). BC’s energy consumption would decrease by approximately 2% if all households would replace. Higher production cost of CFLs are offset by much longer lifetime. Concerns about mercury content in CFLs could be addressed by mandatory recycling programs.