Functionality and Performance Tests for Coatings on Glass for Solar Application

Date: 13 August 2020
Copyright:
  • Elisabeth Klimm, Karl-Anders Weiß, Christiane Siess | Fraunhofer-Institut für Solare Energiesysteme (ISE), Heidenhofstr. 2, 79110 Freiburg, Germany
  • Corresponding author: Elisabeth Klimm, elisabeth.klimm@ise.fraunhofer.de
  • First presented at GPD 2019

Date: 7 August 2020

Solar glass is used as glazing for solar devices like photovoltaic modules and solarthermal collectors. In many dry regions dust accumulation lead to extreme efficiency losses due to soiling, up to -80% in 6 month.

This paper was first presented at GPD 2019 by Elisabeth Klimm, Karl-Anders Weiß and Christiane Siess from Fraunhofer-Institut für Solare Energiesysteme (ISE).

For reproducible qualification of glass types and coatings in-house developed soiling test devices are applied to soil samples homogenously with any kind of natural or standardized dust. The results have been analysed with an in-house built transportable soiling sensor measuring the loss of transmittance.

 

Artificial Dry Soiling

A dry soiling method with the soiling chamber, explained in previous publications [Klimm 2015] has been applied so distribute standardized (artificial) dust as well as natural dust types homogeneously to glass coatings.

 

Artificial Soiling with Moisturizing

The second approach uses the dry soiling with the artificial test dust SAE 726j with previous surfaces moisturizing for better dust adherence. Moistening was ensured by an ultrasonic nebulizer leaving the samples with a humidity layer of 1.5 µm to 40 µm, depending on the wetting behaviour of the surfaces. Immediately after wetting, a homogenous dust layer of 5 g/m² was applied to the samples (up to 75 x 75 cm²). Solar transmittance is measured with FT-IR spectrometer, Fig. 1. Afterwards soiled samples are mounted and monitored outdoors.

 

Soiling Sensor Station outdoors

The above mentioned soiled samples with functional coatings and reference samples have been exposed to outdoors to investigate the “self-cleaning” properties. The samples were mounted at the roof in Freiburg, Germany until at least one rain event with > 5 mm or precipitation. Using a PV mini-module provides a very suitable approach to quantify the soiling effect. The ratio of the output electrical energy and the incident solar energy VE allows the comparison of daily values.

 

Results and Conclusion

For all samples, the dust layer caused up to 57 % performance loss. Rain was able, in most cases, to fully restore the initial performance. The measured transmittance loss, due to soiling, show a correlation to the wetting properties of the surfaces. The unaged sample coatings with hydrophobic surface seem to work best. The samples with low contact angles of ~15° also perform well.

The non-coated glass, as expected, showed still a lower transmission after exposure. The evaluation of the energy ration VE shows that due to the soiling the value drops from ~ 10% to values between 7 and 8%. Thus light rain even deteriorate the problem, accumulating dirt. The presented approach describes a meaningful, fast and easy to apply method to determine information about the soiling behaviour of glass surfaces which are exposed to soiling loads with different dust types.

Fig. 1. Solar transmittance (AM1.5) of 8 different glass samples in initial and clean condition, after artificial soiling and after exposure with natural cleaning
Fig. 1. Solar transmittance (AM1.5) of 8 different glass samples in initial and clean condition, after artificial soiling and after exposure with natural cleaning
Fig. 2. Soiled glass sample on soiling-sensor after light (left) and strong (right) rain event
Fig. 2. Soiled glass sample on soiling-sensor after light (left) and strong (right) rain event

 

600450 Functionality and Performance Tests for Coatings on Glass for Solar Application glassonweb.com

Others also read

The latest Glastory blog is dealing with the newest trends coming to the bus glass market - how the cut-outs, digital and screen printing, larger surfaces and thinner glass to reduce weight and fuel consumption is challenging the glass processing.
An Initial Study Towards Optimized Structural Assessment of Glass Components
Constructions at exceptional locations are often challenging but worth one’s while. Extreme boundary conditions and sophisticated demands of the client have to be considered.
The latest Glastory post is dealing with the trends in automotive display glass processing.
In the European Union, Member States are allowed to set minimum performance requirements to construction products available on their market.
In this blog post, we look at trends in the sunroof and windshield business today and how glass processors can prepare for them.
A clean, safe and sustainable source of energy, solar continues to power the world at a faster pace than ever before.
Unitised Façade System Designed with a Highly Transparent Façade of Low G-value Combined with Blast Requirements
For years and years research, development and discussions have been made on the safety of glass structures.
Building code requirements for wind-borne debris protection have been in existence since the mid- 1990s, and as a result, many glazing systems have been tested and certified to these performance requirements.
For nearly 50 years, glass has been used as structural elements in glass fin applications. These applications include interior and exterior projects, supporting facades, canopies, storefronts, curtain walls and skylights.
Anisotropy is the term used in the façade industry to describe the manifestation of patterns and colourful areas in heat-treated glass under certain light and viewing conditions.

FROM INDUSTRY

ARTICLES RELATED PRODUCTS

Guardian Europe
Unelko Corporation
Unelko Corporation
Diamon-Fusion International, Inc.
Walker Glass Company Ltd.
Diamon-Fusion International, Inc.
Unelko Corporation
Diamon-Fusion International, Inc.
Guardian Europe
Diamon-Fusion International, Inc.
Luoyang North Glass Technology Co., Ltd.,
Diamon-Fusion International, Inc.

Add new comment