Project Examples

PV System for a house on Tohono O’odham Reservation

Course: 22.527 Solar Systems Engineering
Semester: Spring 2009
Instructor: John Duffy
Partner:Tohono O’odham reservation

We are working with a tribal college on the Tohono O’odham reservation near Tucson, AZ. The tribal college (TOCC, http://www.tocc.cc.az.us/about_ton.htm ) is constructing modular bathrooms for the elderly and for families in remote regions of the reservation. Many of the 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 would do the solar engineering and TOCC the construction. Initial sizing of the PV system have been made by Vivian Crespo and design of a variable-slope support structure by a capstone design group Spring 2008. What is needed is a detailed system design with all the components for a load with an evaporative cooler.

The specific objectives/tasks included:

  • Measure the Isc and Voc of at least two 180 W PV modules along with the module temperature and incident solar irradiation on a sunny day outside with the module normal to the sun. There is a DVM with a thermocouple attachment along with a pyranometer in the lab. Do they meet the specifications of the module for Pmp? (Thanks to Evergreen for donating the modules; they may not meet the specifications since they are gifts, so we need to check them out.
  • Check the sizing of the PV and battery system to supply 3200 Wh per day in July (worst case) for a family of 9 people with an LOLP of 5%.
  • Choose the components of the PV system: battery charge controller, compact fluorescent lights, radio, thermostat/humidistat for the evaporative cooler, circuit breakers, wire sizing, etc. Ensure the system is in compliance with the National Electrical Code, and specify wire gages so that the energy loss in the wires does not exceed 2%.
  • Sketch the detailed electrical diagrams so that the TOCC students can take the diagrams and produce detailed plans for the construction of the system.