Solar Water: Heat it Up!
Students explore energy efficiency, focusing on renewable energy, by designing and building flat-plate solar water heaters. They apply their understanding of the three forms of heat transfer (conduction, convection and radiation), as well as how they relate to energy efficiency. They calculate the efficiency of the solar water heaters during initial and final tests and compare the efficiencies to those of models currently sold on the market (requiring some additional investigation by students). After comparing efficiencies, students explain how they would further improve their devices. Students learn about the trade-offs between efficiency and cost by calculating the total cost of their devices and evaluating cost per percent efficiency and per degree change of the water.
A school in Peru with a tin roof and three solar water heaters in series.Copyright 2011 Montoya Lab
With a growing need to reduce our nation's dependency on fossil fuels, improved energy efficiency is the key to the successful design of renewable energy options, but at what cost? Engineers spend a great deal of time and effort in improving efficiency of their designs, and the trade-off between cost and efficiency is an important concept to understand in the engineering world. To engineers, efficiency often means maximizing the amount of work done or energy produced from a given design while also minimizing the resources used. In the developing world, minimizing the use of resources and keeping costs low are two important factors that must be considered when deciding on the suitability of a given technology and its ability to improve a community's quality of life. Engineers use the engineering design process to help strike this balance between cost and efficiency.
After this activity, students should be able to:
- Identify heat transfer properties of different materials.
- Explain the concept of efficiency and how it relates to energy.
- Calculate the efficiency of a solar water heater given heat input and output of a system.
- Compare the efficiency of built solar water heaters to those achieved by commercial models and explain why they might differ.
- Explain the engineering design process.