The power of the sun

There’s no question that our planet is changing dramatically. Solar energy is well on track toward a bright future.

Few minutes to read
By Rick Gould
Tagged as 
Energy
Climate change
Published on

Do a simple search online for renewable energy, and most results point to wind power and photovoltaic (PV) electricity. Dig a little deeper, and the results typically generate hydroelectric power, biomass energy, tidal power and geothermal energy, almost always related to the generation of electricity. Most people are unaware that electricity accounts for only about 20 % of the world’s energy demand. Another 30 % is used for mobility, but by far the largest share of our energy consumption is heat: hot water, heating and industrial heat account for more than 50 % of the world’s energy demand.

Close view of kettle heating on a solar stove set up on dusty, stony ground. (Ganden Monastery, Tibet)

This is where solar-thermal heating kicks in. This form of energy generation is so simple and efficient that some of the first types of solar collectors were former central-heating radiators painted black. The technology has evolved considerably since then whilst its market has grown, notably for space heating and hot water. According to the International Energy Agency (IEA), in its latest report Solar Heat Worldwide 2020, the most recent global data shows that during 2019, solar-thermal systems produced 479 gigawatts of energy – generating the same output as 43 million tonnes of oil, and preventing emissions of 38 million tonnes of climate-warming carbon dioxide.

Heating, whether for domestic use, commercial buildings or industry, accounts for 50 % of energy use and, according to the IEA, right now renewables provide 11 % of the global heat supply. However, this also means that solar heating has a tremendous potential to make a huge contribution to tackling climate change.

Solar panels for hot water heating stand on the flat rooftop of a house by the sea.

A booming industry

The early market for solar-thermal energy provided hot water for households and was based on flat-plate collectors produced locally. “Now, evacuated tube collectors have gained a larger part of the market,” explains Ken Guthrie, Director of Sustainable Energy Transformation Pty Ltd, a specialist consultancy in solar energy. Guthrie has twice served as chairman of the IEA’s Solar Heating & Cooling Programme and played a leading role in developing ISO standards for solar-thermal heating within ISO’s technical committee ISO/TC 180, Solar energy.

“There is now an increasing market for larger systems to provide heat for industrial processes and for district heating networks,” says Guthrie who started working on solar energy in the late 1970s when it was almost exclusively used for providing hot water for domestic properties. “Over the past two decades in particular, solar PV for electricity has gained market share and solar for heat has grown at a slower rate,” he explains.

A report called Guide on Standardisation and Quality Assurance for Solar Thermal echoes Guthrie’s observations. Published jointly by the European Solar Thermal Industry Federation, the United Nations Environment Programme and the Global Environment Fund, it notes that whilst solar-thermal heating is a mature technology, it has lagged behind other forms of renewable energy. Yet that is now changing, with ISO standards playing a significant part in this growth.

ISO standards are important to assist with market confidence.

Energy for the world

So what will ISO standards do for solar energy? “ISO standards are important to assist with market confidence by providing means for independent evaluation of heating performance, and the durability and reliability of products,” explains Guthrie. Solar thermal is the most area-efficient technology for generating carbon-dioxide-free heat from renewable sources. It is inherently a sustainable energy source to meet the world’s energy demand.

“On the other hand, the lack of standards can lead to poor-performing products,” warns Stefan Abrecht, a design, development and consulting engineer who has worked with solar-thermal systems for decades. He has also contributed to ISO standards and partnered with Solar Heat Europe to support this important industry. “This makes it clear that we need standards to provide guidelines on how to assess durability and performance. They can also provide a basis for third-party certification and acknowledgment of the technology, to stabilize product quality and foster innovation by setting out rules,” he explains.

State-of-the-art quality

Abrecht’s experience is that the ISO standards for solar-thermal heat have been developed in a way which encourages technological development, unifies the basic requirements for all countries, and therefore enables worldwide trading without technological and quality barriers.

Solar Heat Europe’s President, Costas Travasaros, perfectly summarizes the role of ISO standards in enabling the uptake of solar-thermal heating. “We strive to improve quality assurance in European countries and other parts of the world, as this benefits consumers, giving them better options and increased confidence. It also benefits manufacturers, giving them clear guidelines on product requirements defining the state of the art,” he explains.

“And we must not forget that the confidence of consumers and policy makers is crucial to have a growing and stable market for solar-thermal products. This goes beyond borders, representing a global challenge and, as standards are necessary instruments to ensure quality assurance, ISO standards play an essential role in this process at global level,” concludes Travasaros.

Aerial view of the Ivanpah solar electric generating system with its central tower, surrounded by hundreds of solar panels.

The Ivanpah Solar Electric Generating System in the Mojave Desert is one of the largest solar-thermal power-tower systems in the world.

A bankable resource

So what types of standards are there? “There are ISO standards for measuring solar radiation and calibration of such measurement equipment. More relevant for the industry are the durability and performance of components and materials of collectors (ISO 22975 series) as well as the performance of collectors (ISO 9806) and systems (ISO 9459 series),” describes Abrecht. “Standards were and are necessary to make this technology available for the whole market, which cannot afford poor or difficult-to-handle products,” he asserts.

Guthrie echoes these observations. “For large export markets, International Standards that cover the durability and reliability of products help the market operate smoothly and make it easier to identify good products in an independent way. Also, for the new markets with larger collector areas, a means to evaluate expected performance in advance of installation, and measure performance when operating, is becoming more important to produce ‘bankable’ projects.”

Small-town American home with blue slatted wall cladding and solar panels on the roof.

“Subsidies are also important for standards development and product quality,” says Dr Andreas Bohren of the SPF Institute for Solar Technology at the Eastern Switzerland University of Applied Sciences (OST) in Rapperswil, Switzerland. “Authorities will not give subsidies to users of solar-thermal systems unless they are tested and approved,” he explains. The subsidies themselves have been essential in catalysing the new markets for renewable-energy products, until production rates have increased and prices have fallen.

Bohren leads the ISO/TC 180 working group that is developing and improving ISO 9806 for testing solar systems and is Chair of the Solar Keymark Network scheme for testing and certifying solar-thermal systems. Applying ISO 9806, he says, ensures that solar-thermal products perform well when they are installed on buildings and for many years afterwards.

So what will the market look like in 20 years’ time? With a solar future, supported by ISO standards, energy will be more affordable, accessible and prevalent than ever before. This could be good news for the climate, too. Now that’s something bright to write about...

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