A Green Light for CFLs?
In this problem-based learning case, three housemates in an environmentally-themed college house debate the pros and cons of compact fluorescent lamps (CFLs) over incandescent lamps. The students raise issues of the cost difference between the lamps (both in the short and long term), energy use and greenhouse gas production in the manufacture and use of the lamps, and the mercury content in CFLs and the risks that poses to people and the environment. Students are asked to identify the information needed to evaluate the choice between the two lamp types, and then use a published life-cycle analysis to find and evaluate that information. To conclude, they make a decision and argue for it using quantitative evidence and reasoning. The case was developed for an intermediate-level course designed to help environmental studies students understand the role of scientific information and scientific thinking in resolving complex environmental problems.
- Define the terms watt, lumen, incandescent, and fluorescent.
- Explain how light is generated in incandescent and compact fluorescent lamps.
- Explain how the different methods of light generation lead to the relative efficiencies of the two different light sources in lumens per watt.
- Describe the basic principles and process of a life cycle analysis.
- Calculate the payoff time for the switch to a compact fluorescent lamp (i.e., the time required before the cost savings from operations equals the additional cost of the lamp itself).
- Compare incandescent and compact fluorescent lamps based on their contribution of greenhouse gases into the environment.
- Compare incandescent and compact fluorescent lamps based on their contribution of mercury into the environment.
- Use quantitative data to draw conclusions and support a position.
- Appreciate the importance of a life cycle analysis in evaluating the impact of a product or practice on the environment.
- Recognize that other factors (e.g., aesthetic preferences or other constraints) may limit the extent to which a favorable option is adopted, even when the benefits are clear.
KeywordsLife-cycle analysis; life-cycle assessment; LCA; compact fluorescent lamp; CFL; incandescent lamp; greenhouse gases; energy; mercury; quantitative skills
Topical AreasScientific argumentation
Educational LevelHigh school, Undergraduate lower division
Type / MethodsAnalysis (Issues), Dilemma/Decision, Problem-Based Learning
Subject HeadingsEnvironmental Science | Science (General) | Interdisciplinary Sciences |