Maximization of Energy Collection Efficiency of a Solar-Powered Passive Thermosiphonic Hot Water Heater

Indianapolis, IN

The efficiency of solar energy collection of a solar-powered thermosiphonic hot water heater operating passively through buoyancy-driven flow without external power or active pumps is experimentally maximized through iterative variations of various parameters on a scale model. An experimental apparatus consists of a water tank eight inches in diameter and four feet long positioned horizontally above a solar collector consisting of two horizontal copper manifolds connected by vertical risers, with tank and solar collector connected so as to form a loop and vented to ensure an atmospheric operating pressure. Four parameters are iteratively varied in a controlled environment in an effort to maximize the efficiency of energy collection: height difference between tank and solar collector, solar collector angle, hydraulic resistance in the loop, and rate of heat addition to the solar collector. Solar collection efficiency is determined by measuring the temperature of fluid flow at the inlet and outlet of the solar collector using thermistors and measuring the volumetric flowrate through the solar collector using an open-bore flowmeter employing an RTD-based temperature difference method. Data is captured using a custom LabVIEW data acquisition program and analyzed using a MATLAB program code.