Quality and Certification

Why is quality of importance for Solar Water Heating Systems (SWHS)?

Broken glass tubes must be replaced

For SWHS it is important to care for a minimum quality, because:

How can quality be defined?

The quality of a SWHS can be defined in very different ways, since a lot of parameters can be taken into account to describe the quality. For example, the quality of a solar collector can be described by its efficiency of converting sunlight into heat, by its level of heat losses through the collector case, by its tightness against rain, by its resistance against hail, and/or by its durability against the pressure of the heat transfer fluid.

This means, there is not one “right” definition of quality. The definition of quality is always an agreement of the market actors, which depends on the specific conditions of the market. For example, if it never hails, the resistance against hail is not a relevant quality criteria.

The relevant quality parameters and the methods, how these parameters can be measured, are described in the standards. Following standards for SWHS and collectors are available:

Global standards of the International Standardisation Organisation

ISO 9806:2013 on Solar Thermal Collectors

Indian Standards

  • IS 12933:2003 on Solar Flat Plate Collectors
  • IS 12976:1990 on Solar Water Heating Systems
  • IS 16543:2016 on Evacuated Glass Tube Collectors (ETC)
  • IS 16544:2016 on ETC SWHS systems

Following these standards, the components and systems are manufactured and tested. Upon qualifying the requirements as laid out in standards products are certified.

Flat plate collector test at Fraunhofer ISE

Customers are mainly interested in the ability of a SWHS to deliver solar heat and in its reliability. Therefore, the quality of a SWHS should be evaluated and certified in relation to these aspects. This means, that not only the quality of a specific component like the collector, but also the quality of the SWHS design as well as the quality of construction and maintenance work is relevant.

However, it is much easier to define and measure the quality of a specific SWHS component produced in a factory, than a SWHS designed and installed at a specific place. This is the reason, why standards exist only for components (collectors, storage tanks) and factory-made systems (e.g. compact thermosiphon SWHS).

Finally it is important to be aware, that it should not be the goal to achieve the highest quality possible, but to define a minimum level of quality, which assures the reliability of the product under typical conditions and therefore identify the best quality-to-cost relation to provide the customer with the best value-for-money.

Who benefits from quality assurance and certification?

The definition of minimum quality requirements helps:

  • the manufacturer to optimise their products according to the required quality,
  • the system integrator, designer and installer to design and install a well-adapted SWHS, since they are able to identify the best products for specific conditions and the expected energy output from the system, and
  • the customer to trust the components and to compare products.

Certification of products and systems by independent test institutes helps:

  • the manufacturer to proof if they fulfil the quality requirements with their products and
  • the distributer, system designer, installer as well as the final customer to recognize if the product fulfils minimum quality requirements.

Why is monitoring needed during operation?

With a certificate on quality, the customer receives information, on how efficient and reliable a collector or a SWHS is, based on measurements of this type of product in the test centre. Monitoring is needed to know, how the SWHS is actually performing during operation at the site, where it is installed.

The quality of components is fixed during their production and the quality of design and installation of a solar system is fixed during the design and installation process. But further factors influence the solar yield during operation. Therefore it is necessary to control the SWHS during operation to be sure that the SWHS is performing well and identify needs of improvements.

Since usually the SWHS yield cannot be observed directly and is depending on several factors, a special monitoring system is necessary. There are different ways to monitor the functionality of SWHS with varying levels of information and accuracy.

Within the SoPro India project, scientific monitoring of two SWHS was done with high accuracy to provide sound and precise figures of the solar yield and performance of the SWHS at different places in the system. However, for normal SWHS simplified monitoring it is sufficient to detect the system operation.

Components of Scientific Monitoring System