Author

Rohit Gulati

Date of Award

5-2017

Document Type

Thesis - Open Access

Degree Name

Master of Science in Mechanical Engineering

Department

Mechanical Engineering

Committee Chair

Sandra K.S. Boetcher, Ph.D.

First Committee Member

Marc Compere, Ph.D.

Second Committee Member

Yan Tang, Ph.D.

Abstract

As the production of clean electricity has gained importance, photovoltaic (PV) panels have become a widely used technology. But, during operation, PV panels heat up due to the solar insolation and suffer a drop in electrical output. The goal of this investigation is to use phase-change materials (PCM) to passively cool PV panels. The PCM is inside an aluminum container attached to the back surface of the PV panel. Four configurations of the container are investigated. The first configuration is a container with bulk PCM occupying its entire interior volume. The depth of this container is varied. The second configuration adds straight aluminum fins to a container of fixed depth. The length, width and spacing of the fins are parametrically varied. The third configuration uses an aluminum honeycomb core acting as a fin inside the container. Two cell sizes of the honeycomb are modelled. The fourth configuration utilizes PCM encapsulated in pellets, which are suspended in a water bed inside the container. Numerical simulations are conducted using ANSYS Mechanical APDL for finite element heat conduction. The solid-to-liquid phase change is modeled using the enthalpy method. A constant heat flux to simulate the highest value of local irradiance averaged over a day is applied to the PCM container modules. For all cases, temperatures as a function of time at different locations of the container are reported. Results show that a deeper container regulates PV temperature for a longer time. In the finned configuration, as the length of the fins is increased and the spacing is decreased, the PV surface is maintained at lower temperatures for longer; fin width only has minimal effect. The honeycomb configuration matches these criteria and has the lowest PV temperature at PCM saturation time. The encapsulated configuration performs much worse due to the substantially reduced PCM volume. A cost function developed to compare the results from different configurations shows that a honeycomb fin with cell size of 0.5” is most effective at maintaining low PV temperature for an extended duration.

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