Carbon Nanotube Solar Absorber Coating With Low Thermal Emission

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Solution Overview

Problem

Existing absorber coatings for solar radiation in parabolic trough collectors are complex and costly to manufacture, with high radiation losses due to multiple layers, and their absorption and emission properties are difficult to specify for targeted wavelengths.

Innovation Solution

A coating comprising carbon nanotubes with a protective oxide layer, where the carbon nanotube proportion and layer thickness are optimized to absorb a high percentage of solar radiation while minimizing emission, allowing for customizable absorption and emission properties without the need for vacuum coating techniques.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple barrier and reflective layers are used in absorber coatings, then the absorption and emission properties can be controlled, but the manufacturing complexity and costs increase significantly

Engineering Contradiction:

Improveabsorption and emission properties controlVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the complex multi-layer vacuum coating structure, replacing it with a single cermet layer containing carbon nanotubes. This extraction removes the barrier and reflective layers that caused manufacturing complexity while retaining the essential absorption and emission control functions through the carbon nanotube-cermet composite structure.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent employs composite materials by combining carbon nanotubes with cermet (ceramic-metal) to create a single-layer coating that achieves the optical properties previously requiring multiple layers. The carbon nanotubes dispersed in the cermet matrix provide selective absorption and emission characteristics without needing separate barrier and reflective layers.

Inventive Principle:

Principle #40Composite materials

2Reliability

If multiple layers are used in absorber coatings, then absorption and emission properties can be controlled, but the manufacturing costs increase

Engineering Contradiction:

Improveabsorption and emission properties controlVSAvoidmanufacturing costs

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent adopts a simpler, more cost-effective coating approach using carbon nanotube-cermet composites that can be applied without expensive vacuum coating equipment. This replaces the costly multi-layer structure with a more economical single-layer solution that achieves comparable or superior performance.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If more layers are used in absorber coatings, then absorption and emission properties can be controlled, but the radiation losses increase

Engineering Contradiction:

Improveabsorption and emission properties controlVSAvoidradiation losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent employs composite materials by combining carbon nanotubes with cermet (ceramic-metal) to create a single-layer coating that achieves selective absorption and emission characteristics. The carbon nanotubes dispersed in the cermet matrix provide broadband absorption in the solar spectrum while maintaining controlled thermal emission, eliminating the need for multiple layers that would increase radiation losses through additional interfaces.

Inventive Principle:

Principle #40Composite materials

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 coating significantly reduces heat losses by absorbing a large proportion of solar radiation and emitting less than 25% of thermal radiation, achieving efficient energy absorption and minimizing radiation-induced energy losses, thus enhancing the usability of solar radiation for energy generation.

Implementation Method 1

Carbon nanotubes are contained in the layer. The proportion of carbon nanotubes contained per unit area or volume and/or the layer thickness of the layer is selected such that electromagnetic radiation from the wavelength spectrum of sunlight is absorbed with predeterminable proportions.

Methodology Applied

Scientific EffectAbsorption of electromagnetic radiation: Absorption (EM radiation)

Implementation Method 2

The proportion of electromagnetic radiation from the wavelength spectrum of a black radiator at a temperature greater than 50° C., preferably greater than 200° C. and particularly preferably greater than 350° C., should be emitted significantly less.

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Data Source

PatentEP2970698B1Coating, process for the production thereof and the use thereof

Publication Date: 2017.12.13 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

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AI summary

The invention relates to a coating which has particular absorption properties for electromagnetic radiation from the wavelength spectrum of sunlight, and also a process for producing the coating and the use thereof. The coating is formed with a layer formed on the surface of a substrate or a reflective layer formed on the surface of the substrate. Carbon nanotubes are present in the layer. The proportion of carbon nanotubes present per unit area or volume and/or the layer thickness of the layer are selected so that it absorbs electromagnetic radiation from the wavelength spectrum of sunlight in predeterminable proportions and the proportion of electromagnetic radiation from the wavelength spectrum of a black body radiator emitted at a temperature above 50°C is very small.