Passive stagnation control for solar collectors

Abstract

A method for controlling stagnation in a solar collector, comprises: providing an solar energy absorbing substrate and a first layer; providing a second layer disposed between the first layer and the solar energy absorbing substrate; coupling an actuator to the solar energy absorbing substrate; and expanding the actuator when the solar collector is exposed to a stagnation temperature to form a gap between the first layer and the second layer.

Description

Background technique [0001] Solar collectors can be efficient and cost-effective for domestic and commercial hot water heating and space heating. Polymeric solar collectors typically consist of a clear polymer cover sheet (e.g. polycarbonate multiwall sheet), a black polymer absorber with extruded water channels (e.g. polysulfone or polyphenylene ether blend multiwall sheet) , insulating liner, and water manifold and frame pieces. Since the absorber is insulated from the front and rear sides, a significantly higher temperature than the ambient can be obtained. Solar collectors are usually designed to produce hot water between 70 degrees Celsius (°C) and 80°C. [0002] The collector is exposed to the sun for a period of time without water or other heat transfer fluid flowing through the absorber, thereby overheating the solar collector. These states are called "stall states". During these stagnant states, absorber temperatures in excess of 130°C or even 140°C are possible. ...

AI Technical Summary

Problems solved by technology

During stagnation, the heat deflection temperature of plastic components may be exceeded, resulting in irreversible bending, thermal expansion beyond design limits, and / or other thermally induced effects that can lead to unit failure

Using only polymers that can withstand such temperatures adds significantly to the cost of the collector

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