Example of the Final Project

1
Example of the Final Project

• Possible Reduction of Greenhouse Gas Emissions by
  Replacing Incandescent Lights with Compact
  Fluorescent Lights (CFL)

2
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 CO2 emissions?

3
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
  CO2 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.

4
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)

5
How many light bulbs can we replace in BC?

• Number of households in BC 1 600 000 (in 2004)
• (http//www.env.gov.bc.ca/air/airquality/pdfs/wood
  _emissions.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 ? 1 600 000 households 16
  000 000 light bulbs

6
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 save10 ? 47 W ? (4 h/d ? 3600
  s/h ? 365 d/y) 2.5?109 J per household per
  year.
• For the whole province2.5?109 J ? 1 600 000
  households 4?1015 J per year

7
What would be the total reduction in CO2
Emissions?

• CO2 emissions in the US are 1.34 pounds (0.608
  kg) of CO2 per kWh averaged over all methods of
  generating electricity
• (1998 2000, Source US Government, DOE).
• Conversion between kWh and J1kWh 1000 J/s ?
  3600 s/h ? 1h 3.6?106 J
• Annual reduction in CO2 emissions is 4?1015 J
  per year ? (1kWh / 3.6?106 J) ? 0.705 kg/kWh
  8?108 kg of CO2 per year in BC

8
What would be the percentage decrease in energy
consumption?

• Total BC power production 53 000 GWhours
  53?109kWh ? 3.6?106 J/kWh 2?1017 J
• (http//www.bchydro.com/rx_files/info/info46749.pd
  f)
• The savings of 4?1015 J by switching to CFLs
  would decrease our provincial energy consumptions
  by 2

9
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 10 000 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.

10
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 www.worldwise.com)
• Heat?
• Quality of light?
• http//www.npr.org/templates/story/story.php?story
  Id7431198

11
Conclusion

• Replacing incandescent bulbs with CFL leads to
  significant savings in energy (and money).
• BCs 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.