Do It Better: solar water heater |
Project Description: For our final project, we redid a previous project in an attempt to exceed the prior standards. We chose to take another shot at the solar hot water heater, a smaller project from the Outdoor Classroom unit. By building on the lessons from our last attempts, we created a new and improved solar water heater that is far more efficient.
The first solar water heater (picture at right) had 100mL of water running from one insulated bottle to the other through a copper pipe. The water was then poured from the lower bottle to the one on top, and the process was repeated. The reflective flaps were meant to direct solar rays towards the copper pipe, and the entire heater was covered in plastic wrap to contain the heat. Though effective in theory, the test did not go as well as we hoped. The water gained only 5 degrees C, and leaking connections caused us to loose half of our water. Our total heat gain was 1046.5 J. Our new heater (picture at right) had 1000mL of water spread along the bottom of a tin pan. Copper pipes were used as "hot cubes". Also, the bottom of the pan was covered in black plastic to tint the water black and increase absorption. The reflector was slightly bigger, and we used Mylar tape rather than aluminum foil. The smooth Mylar allows the solar rays to bounce off as predicted, while the crumpled foil likely scattered the rays. All of these changes proved to have a big impact on the heater's success. The 1000mL of water gained 19 degrees C in only 15 minutes, and the resulting heat gain was 79,534 J. |