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This document was prepared by Technical Committee ISO/TC 180, Solar energy, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 312, Thermal solar systems and components, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This third edition cancels and replaces the second edition (ISO 9806:2017), which has been technically revised.

The main changes are as follows:

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

According to the International Energy Agency (IEA), heat is the largest end-use of energy, accounting for nearly 50 % of global final energy consumption. This is significantly more than the shares of electricity and transport, which are approximately 20 % and 30 %, respectively. More than 50 % of the total heat consumption is used in industrial processes, with the rest consumed in buildings for space and water heating, and other applications. Furthermore, heat generation is responsible for over 40 % of global energy-related carbon dioxide emissions. This significant contribution to CO2 emissions is primarily due to the continued reliance on fossil fuels for heat production, with renewable sources meeting less than a quarter of global heat demand.

Solar thermal technologies directly use the sun's energy to produce heat for various applications. Solar thermal technologies are, therefore, key technologies for reducing global carbon dioxide emissions. The core element of any solar thermal system is the solar thermal collector. There are several different types of solar thermal technologies and solar thermal collectors, with typical characteristics and applications such as the following.

Solar thermal applications are also used to power many other technologies, such as solar thermal desalination, solar thermal electricity generation, ground source regeneration or as a source for heat pumps, to name only a few. Solar thermal technologies can be used wherever heat is used, either as a replacement or as a supporting technology to reduce the use of other energy sources.

Various solar thermal collector technologies can be used for the applications listed above. The most common products are given in the list below.

Some solar thermal collectors combine the generation of heat with the direct generation of electricity, usually by using photovoltaic elements as absorbers.

The heat transfer fluid in solar thermal collectors is usually plain water, water-based antifreeze or air. For some specific applications, other media such as high-temperature oils or evaporating liquids are used.

Collectors tested according to this document represent a wide range of applications, e.g. glazed flat plate collectors and evacuated tube collectors for domestic hot water and space heating, collectors for heating swimming pools or other low-temperature systems or tracking concentrating collectors for thermal power generation and process heat applications. This document applies to liquids, air, and heat transfer fluid collectors. Similarly, collectors using external power sources for regular operation and/or safety purposes (overheating protection, environmental hazards, etc.) and co-generating devices generating thermal and electrical power are also considered.

This document defines procedures for testing fluid heating solar collectors for thermal performance, reliability, durability and safety under well-defined and repeatable conditions. It contains outdoor test methods using solar irradiance and natural or simulated wind. as well as indoor procedures using simulated irradiance and simulated wind. Outdoor tests can be performed either as steady-state or as quasi-dynamic measurements.

This document intentionally does not specify any product requirements, as these depend on the intended use and place of installation. Specific local standards, building codes, certification schemes, tax rebates and incentive schemes define applicable requirements as appropriate. This document is intended to provide a solid basis for these schemes with harmonised and reliable product testing.

Climate change is expected to accelerate the degradation of all exposed products, such as also solar thermal collectors, potentially undermining their performance, reliability and safety. Requirements should be re-evaluated and adapted from time to time to future operating conditions to lower degradation rates and the chances of failure using the methods set out in the ISO 14090. This process also ascertains solar thermal collectors' durability, functionality, and safety amidst changing climate patterns and reinforces the commitment to advancing sustainable and adaptable technologies to environmental and climatic shifts.

By providing the tools to assess the materials used in the production of solar thermal collectors and their potential for energy savings and greenhouse gas reductions, this document is aligned with the principles of the ISO 14000 series on environmental management, with the ISO 50000 series on energy management systems and with the ISO 59000 series on circular economy.

The annual yield and the efficiency of converting incoming solar radiation into useful heat can reach more than 80 %, depending on the temperature required and the technology chosen. In fact, the annual energy yield per area is higher with solar thermal collectors than with any other technology. The yield per area is around three times higher than photovoltaic power generation and 50 to 100 times higher than photosynthesis for biomass production. Given the range of products and applications, it is impossible to quantify this technology's greenhouse gas reduction or climate change mitigation potential in general terms. The greenhouse gas reduction potential of a solar thermal collector depends on the environmental conditions and the application in which it is used. It is recommended to make this quantification using the global warming potential (GWP) for each greenhouse gas (GHG) as per Table 7.15 of the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) by aggregating the reduction potential in CO2 equivalent emissions.[1] Quantification should be made for the whole heating system’s lifecycle in analysis, from raw material extraction to end-of-life disposal. It should account for direct (scope 1) and indirect (scope 2 – from electricity, heat, or steam use; scope 3 – all other indirect GHG emissions in the value chain) GHG emissions. Special care should be taken regarding GHG emissions if supplementary external power sources are used, which can lead to indirect GHG emissions that should be considered. Special care should also be taken regarding other GHGs, such as freon-charged solar heating systems, as these systems are associated with the potential release, intentional or unintentional, of fluorinated gases (F-gases). Quantification should first define the baseline GHG emissions associated with a specific system's most commonly used technology (e.g., conventional water heater – natural gas or electric). Comparing the projected GHG emissions of the system when using solar thermal collectors using the methods defined in Annex B with the baseline GHG emissions will give the potential GHG reduction.

Solar thermal collectors are typically made of separable and clean materials such as glass, copper and aluminium, which have a high potential for recycling and reuse. Considering the potential energy yield and the greenhouse gas emissions associated with producing solar thermal collectors, typical carbon and energy payback times are 6 months to 2 years. To further reduce the environmental impact of solar thermal collectors, no material, form of construction, fixture, appurtenance, or items of equipment is employed that can introduce toxic substances, impurities, bacteria, or toxic chemicals into potable water and air circulation systems in quantities sufficient to cause disease or harmful physiological effects. Following circular economy and green procurement principles, all goods and services used in solar thermal collectors, instrumentation, test installation, and facilities should seek to incorporate as much as possible reused and recycled content, make efficient use of energy and materials, promote waste reduction, and the use of renewable energy to minimise overall environmental impact. Adopting a comprehensive eco-design strategy that encapsulates the entire product lifecycle, from material sourcing to end-of-life management, is recommended for the design and production of solar thermal collectors. this approach should include the application of life cycle assessment (LCA) methodologies to systematically evaluate and aim to minimise the environmental impacts associated with all lifecycle stages of solar thermal collectors. Such impacts include but are not limited to greenhouse gas emissions, resource depletion, and energy consumption. Materials and components selected for the construction and testing of solar thermal collectors should be scrutinised for their environmental certifications and performance characteristics. This scrutiny ensures that these materials contribute positively to the collectors' sustainability profile, thus aligning with the broader objectives of climate change mitigation. It is advisable to prioritise materials that offer a balanced compromise between minimising environmental impacts and maintaining or enhancing solar thermal collectors’ performance efficiency, durability, and reparability. This selection process should particularly consider materials with lower embodied carbon, higher recyclability potential, and those that adhere to recognised environmental standards and certifications.

Achieving the Sustainable Development Goals (SDGs) established by the United Nations in 2015 has become a high priority for society. This document is aligned with the following United Nations Sustainable Development Goals 1, 3, 6, 7, 8, 9, 11, 12, 15 and 17 by promoting and supporting the following.