Contributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder

 conduction, convection, cooling, efficie ncy, energy, heat, heat transfer, heating, housing, materials, m odel, radiation, renewable, renewable energy, solar, solar energy, sun, thermal conductivity, thermal energy, water, water heater, water heating

 Identify locations in the solar water heater at which each type of heat transfer is being utilized.  Explain why solar energy is a good alternative to the combustion of natural gas.  Explain how the engineering concepts in this design project can be applied to solve real-world problems.

 Each group needs the following items to make a heated water storage tank:  Water Jug  5” x 5” x 5” Cardboard Box  Metal Coffee Tin  Shredded Paper for Insulation  2 feet clear plastic tubing.

 In homes today, most of the methods used to heat water, to warm or cool your living room, or to cook food, involve the burning of fossil fuels (typically natural gas or oil), which not only costs money and is limited in its supply, but contributes to the emission of greenhouse gasses into our atmosphere. So how do we fix this problem, or at least make an improvement?

 If you want to create an environmentally-friendly house, it is a smart idea to create a device that can extract solar energy from the sun and convert it into thermal energy to heat water for use throughout your house. Since up to 25% of a typical home's energy bill goes to heating water.

 How solar water heating systems work: Solar water heaters function through the combination of two parts — a storage tank and a collector.

 Stores hot water for immediate use.

 Uses radiation to heat water.

 The storage tank is a well-insulated container that stores the circulating water. The water travels to the solar collector, which is usually located on a rooftop. The collector consists of either a long coiled copper pipe through which water flows (Example A) or a series of parallel pipes across which water flows (perpendicularly) (Example B).

 Radiation energy from the sun is absorbed within the collector, and travels through the pipe via conduction. After the water has passed through the collector and absorbed heat, it returns to the storage tank and increases the temperature of the remaining water via convection.

 The copper pipe and bottom of the collector are painted black to improve their ability to absorb thermal energy. Black reflects the least amount of radiation (about 3%) of any color, and therefore absorbs almost all the radiation energy to which it is exposed.

 Looking at this table of conductivity values for certain metals, what is the reason for choosing copper tubing for a heating device?  What is the purpose of insulating a water tank?  What is the point of painting the copper tubing black in a heating device?

 Design on paper your storage tank and collector  When design is approved begin to build the storage tank.

 Use the appropriate size box to house the metal container.  Cut or drill a hole that matches the diameter of the ½-inch plastic tubing near the bottom of the water container.  Fit the container into the box and cut a hole in the box, also the same diameter as the plastic tubing, at the point at which the water container hole lines up.

 Creating a collector with a long coiled copper pipe through which water flows (Example A) works in a cardboard box collector. Creating a collector with a series of parallel pipes across which water flows perpendicularly (Example B) requires a waterproof container such as a disposable baking sheet pan with a fitted clear cover.

 Use the disposable baking sheet to make a solar collector.  Line the inside walls of the box with aluminum foil, shiny side out if you chose to just use the cardboard box or you can place the disposable baking sheet inside the cardboard box.

 For one design approach, bend the copper tubing into a continuous S- shape.  Use spray paint to paint the copper tubing black.

 Cut two holes in the box that align with the points at which the copper tubing comes out.  Insert the copper tubing into the box and secure it with glue.  Cover the box with its plastic sheet cover, and seal the edges.

 For another design approach, cut three or four 8-inch pieces of straightened copper tubing and glue them to the bottom of a disposable baking pan. Paint the entire bottom black.  In this approach, water flows over the tubes so the collector must be water tight.

 Cut holes in both of the shorter sides of the baking pan. Make the hole diameters the same size as the copper tubing.  Insert two pieces of short, straight copper tubing (½-inch to 1-inch length, or 2.5 to 5 cm) extending out of each hole in the pan.  Cover and secure the box with its transparent cover.

 Attach the plastic tubing to the end of the copper tubing. Seal the connection with waterproof glue.  BE SURE to plan how the heat will transfer efficiently from the collector to the tank.

 Take materials outside.  Follow the experimental test procedure steps described in the worksheet.  As a class we will perform calculations together.