Energy Efficiency
Finding a way to efficiently harness the power of ocean waves might provide the renewable energy of the future.Copyright NASA http://blogs.nasa.gov/cm/wiki/?id=2714
Students measure energy outputs and inputs to determine the efficiency of conversions and simple systems. One associated activity includes LEGO® motors and accomplishing work. The other investigates energy for heating water. Students learn about by-products of energy conversions and how to improve upon efficiency. Conduct either or both activities. The calculations in the water heating experiment are more complicated than in the LEGO motor activity, making the heating activity more suitable for older students, and only the LEGO motor activity suitable for younger students.
Engineers always work to improve the energy efficiency of processes. This can sometimes be accomplished by recovering energy that is lost through inefficient energy conversions. For example, a typical cogeneration facility burns fuel to heat steam that turns electricity-generating turbines. The steam, partially cooled in the first step, is then used to heat homes and businesses. Cogeneration effectively combines two processes of electricity and heat production. Electric generation is about 30-40% efficient, while adding thermal production in a cogeneration facility can result in overall efficiencies of 80-90%.
After this lesson, students should be able to:
- Explain where energy is "lost" in conversions and why, based on the second law of thermodynamics.
- Compute the efficiency of an energy conversion given input and output.
- Identify system by-products and explain how they can be used effectively to increase overall system efficiency.
- Design a simple energy conversion system and test its efficiency.
- Use data they have collected to calculate the efficiency of a system.