Parabolic Trough Receiver With Hot Mirror for Thermal Loss Reduction
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Solution Overview
Problem
Parabolic trough solar collectors face significant thermal radiation losses at high temperatures due to thermal emission from the receiver unit, limiting their efficiency, and existing methods such as spectrally selective coatings decompose at high temperatures, further reducing efficiency.
Innovation Solution
A receiver unit design featuring a conduit for heat transfer fluid with a tubular glass cover that forms a vacuum and includes a reflective surface and a hot mirror coating to reflect thermal radiation back onto the conduit, reducing thermal radiation loss and maintaining efficiency at higher temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a spectrally selective coating is applied to the receiver unit to minimize thermal emission, then thermal radiation loss is reduced, but the coating decomposes thermally around 500°C, reducing the temperature ceiling and thermal efficiency
Solution Approach 1:
The cover is divided into two distinct portions: a first portion (window) that allows solar radiation transmission and a second portion with a reflective surface for thermal radiation reflection. This segmentation enables each portion to be optimized for its specific function without the limitations of a single coating material.
Solution Approach 2:
A hot mirror coating is applied to the first portion (window) of the cover to act as an intermediary that selectively transmits solar radiation while reflecting thermal radiation. This intermediary layer enables the window to maintain both transmission and reflection properties that would be contradictory in a single material.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design significantly reduces thermal radiation loss and increases the temperature ceiling of the heat transfer fluid, enhancing the overall efficiency of the solar collector system by reflecting thermal radiation and minimizing energy loss through the use of a hot mirror coating and a highly reflective cavity mirror.
Implementation Method 1
A vacuum is formed between the absorber pipe and the glass cover in order to minimize convective losses
Implementation Method 2
a second portion carrying a reflective surface so as to reflect thermal radiation back onto the conduit
Implementation Method 3
a second portion carrying a reflective surface so as to reflect thermal radiation back onto the conduit
Implementation Method 4
The window preferably carries a hot mirror coating for reflecting thermal radiation back onto the conduit
Implementation Method 5
a hot mirror coating for reflecting thermal radiation back onto the conduit
Implementation Method 6
a conduit for conveying a heat transfer fluid, the conduit being designed to absorb thermal radiation
Implementation Method 7
solar radiation is focused onto a linear focal line aimed at a receiver unit. The receiver unit heats up
Data Source
AI summary
This invention concerns a receiver unit (10) for a parabolic trough solar plant. The receiver unit (10) has a conduit (12) for conveying a heat transfer fluid (14) and a cover (16), which is located about the conduit (12) such that a vacuum is formed between the conduit and the cover. The conduit (12) is designed to absorb thermal radiation. The cover (16) has a first portion (26) defining a window (22) through which incoming solar radiation (24) passes into the vacuum and onto the conduit (12) and a second portion (28) carrying a reflective surface (20) so as to reflect thermal radiation back onto the conduit (12). The invention also concerns a method of reducing thermal radiation loss from a parabolic trough receiver.