Tohono O’odham Reservation: Solar Hot Water Collector Improvements
Course: 22.521 - Solar Fundamentals
Semester: Fall 2008
Instructor: John Duffy
Partner:Tohono O’odham reservation and the TOCC
Improvements to key features of the TOCC thermosyphon solar hot water collector design. The tribal college on the Tohono O’odham reservation in Arizona (TOCC, http://www.tocc.cc.az.us/about_ton.htm ) is constructing modular bathrooms for the elderly. Many families on the reservation have no electricity or running water, and the folks use outhouses. It is estimated that there are 10,000 families on reservations in AZ that do not have electricity from the grid (Alternative Energy Retailer, Oct. 2007, p. 14). The students at the college are learning plumbing, carpentry, and electrician skills. We have formed a partnership in which UML is doing the solar engineering and TOCC the building and testing. An initial design of a thermosyphon solar hot water system was developed by four ME seniors (capstone report available). Additional work has been done by Vivian Crespo as part of her MS thesis in progress. However, a visit to TOCC a couple of weeks ago revealed that there are some aspects of the design that need additional development. (a) Select tubes, absorber plate, and a process of bonding them so that the system can be built locally at TOCC and that a microenterprise can be developed to build the solar hot water system. See photo available of test piece. (b) The Ut of the collector needs to be carefully estimated. (c) The stagnation temperature needs to be estimated theoretically and experimentally by placing a test box similar in thermal characteristics to the collector out in the sun. We have a small prototype collector up in the solar lab that you can use as well as thermocouples and pyranometers. (d) The temperatures of water in the storage tank need to be estimated on the basis of hourly weather data. (e) A pressure relief valve needs to be selected in case of boiling water.