I use this activity in my introductory large-lecture physical geology course to introduce the topic of fossil fuels: their origin, extraction, and use, as well as the environmental consequences.

No specific skills or concepts (other than an understanding of how to make concept sketches) are needed in advance, as this is mostly an activity to engage students in the topic of energy and probe their prior knowledge.

The activity is situated at the start of an interactive lecture on fossil energy; it requires no more than 15 minutes and is well-suited to classes of any size.

• A general synthesis of the major components and configuration of the electrical power grid.
• Basic understanding of the current local or national energy mix for power generation (the relative contributions of fossil-fueled, nuclear-fueled, hydroelectric, and other sources).

• Accurately modeling some subset of the grid and energy mix.
• Organizing the components of the grid and mix systematically.

• Designing, creating, and explaining a concept sketch.

Students engage in this brief activity at the start of a module on fossil energy and power generation with no advance notice. They are first asked to form pairs or groups of three (in a large lecture hall, students usually work with adjacent classmates) and to take out a blank sheet of paper. The instructor asks the students to consider the lowly 110-V wall socket: it provides electrical power for their appliances-- but do they know, and can they show, where that power comes from? Without elaboration, they are asked to trace its source as far back as they can envision. If necessary, the instructor can give the basic procedure for concept sketching (after Johnson & Reynolds 2005): list what they know, depict their ideas in an organized sketch, and annotate all of the components with descriptive phrases or short sentences. The class is informed that the sketches will be collected for participation credit. Artistic quality is not required or expected, but students are encouraged to make their sketches as detailed as they can, perhaps for additional credit. Each group may designate one student to sketch, but all members must contribute their ideas.

After about 10 minutes or a noticeable decrease in conversation volume, and if time and logistics permit, the instructor may ask some or all of the groups to present their sketches to the class for review and discussion. (To facilitate this, groups may instead be given transparencies and markers and use an overhead projector.) Each student is reminded to put her or his name on the sketch before it is submitted.

After the activity is complete, the instructor may present his or her own version of this concept sketch (illustrating the present-day local or national energy mix; an example is attached here), or simply proceed into a lecture presentation or discussion on the topic of energy. Students may also be directed to research the electrical power grid or the national energy mix as a homework assignment.

As the Power Source activity essentially constitutes a pre-test, I grade the students' concept sketches for effort rather than accuracy. The sketches are most useful in that they offer an indication of the students' prior conceptions of the energy mix and the energy grid, and enable me to tailor my lessons to address particular misconceptions that present themselves.

(For example: Less than 1 km from our campus there is a natural-gas-fired generating station operated by our local utility, and directly in front of it is a solar-energy research center operated by the same utility. Here, several acres' worth of solar collectors and photovoltaic arrays are being tested and are clearly visible, although no solar power is commercially produced. However, more than half of the students who have done this activity over several years depicted solar energy rather than fossil energy as the primary proximate source of their electrical power.)

I have not yet done this myself, but it could be instructive to reassign this concept-sketching activity to individuals or groups as a post-test.

Energy Information Administration. (2009). Official energy statistics from the U.S. Government. Retrieved 01 May 2009 from http://www.eia.doe.gov/.

Johnson, J. K., & Reynolds, S. J. (2005). Concept sketches—using student- and instructor-generated, annotated sketches for learning, teaching, and assessment in geology courses. Journal of Geoscience Education, 53, 85-95.