Improved mechanical design and thermal testing of MIT Solarclave

Abstract

Solarclave is a solar-powered autoclave designed for use in rural health clinics in developing countries. The autoclave must sufficiently sterilize medical instruments to ensure that they can safely be used in providing patient care. The medical instruments are sterilized in a pressure cooker that is heated by concentrated sunlight from a parabolic reflective surface. Previous iterations and testing of the Solarclave proved that sunlight and a pressure cooker could sufficiently sterilize equipment. However, usability problems and cost constraints require that the design be further improved before dissemination can occur. Critical design decisions that this work makes include updating the reflective structure, the pressure cooker, and the pressure cooker insulation. The combination of choices must meet user needs and provide sufficient sterilization at a minimum cost. A reflective structure was selected based on its low cost and listed ability to meet existing power consumption needs. A mathematical model was created to estimate the actual usable power output of the selected reflective structure based on its dimensions and reflectivity, as well as expected intensity of solar radiation. Furthermore, a thermal circuit model was developed to predict the temperature over time inside the pressure cooker as a function of input power, pressure cooker dimensions, and insulation material choice. The mathematical model was evaluated by measuring the temperature outside the pressure cooker over time, recording all relevant parameters, and comparing the results to those predicted by the model. The results indicated that the theoretical input power estimate was too high, but that the thermal circuit was an appropriate approach to modeling the heat loss of the system. The usability of the system showed major improvements in terms of ease-of-use, but needs further design in terms of its aesthetics.