The many possibilities of solar energy – SPE

June 27, 2024 International Electrotechnical Commission (IEC)

Hydrogen (H2) is considered a promising source of clean energy if it can be produced carbon-free from start to finish. To be able to do this at a reasonable price remains an enormous challenge. Yet governments around the world appear increasingly keen to focus on it, often as part of a mixed economy of green energy options.

However, as it stands, more than 90% of the world’s H2 is produced from fossil fuels through processes such as steam methane reforming, partial oxidation of methane and coal gasification. This alone produces emissions of approximately 830 million tons of CO2 per year, which accounts for more than 2% of global annual CO2 emissions.

That is certainly not a sustainable way forward. An alternative is to replace methane and coal with a carbon-free source such as water (H2O). Electricity is used to split water into hydrogen and oxygen through a process called electrolysis and, in theory, produce H2 without generating any greenhouse gas emissions. The catch is that this depends on whether the electricity source is also carbon-free and in many parts of the world the infrastructure is simply not yet suitable or economically viable for this route. In addition, the various types of electrolyzers required for the process use metals such as nickel and platinum group metals (PGMs), which come with high costs, environmental impacts and supply chain concerns.

Solar-powered thermochemical hydrogen could be an option

Attention is focused on an emerging technology that offers a completely zero-emission solution. This is solar thermochemical hydrogen (STCH), which relies on heat, rather than water, generated from solar energy to power H2 production.

In this method, the power to drive STCH hydrogen production comes from concentrating solar energy (CSP). Arrays of hundreds of mirrors collect and reflect sunlight to a central receiving point. The heat from the receiver is then absorbed by an STCH system, which directs the water to split water and generate hydrogen. Temperatures above 1,400 C can be used to boil water to produce steam to drive a turbine, which in turn can generate electricity. However, there is a catch. Until now, STCH designs have had limited efficiency: only about 7% of incoming sunlight is used to make hydrogen, making such systems low efficiency and high cost.

In October 2023, a team at MIT claimed a breakthrough. Their concept for a system of reactors could utilize up to 40% of the sun’s heat. According to the MIT researchers, this increase in efficiency could reduce the overall cost of the system, making STCH a potentially scalable and affordable option to help decarbonize industries such as transportation.

“This could dramatically change our energy future – enabling 24/7 hydrogen production,” said Christopher Muhich, assistant professor of chemical engineering at Arizona State University. “The ability to make hydrogen is the key to the production of liquid fuels from sunlight.” The next phase is to build a prototype that will be tested in concentrated solar energy facilities.

Where IEC standards come in

Several IEC technical committees prepare international standards for solar energy systems and installations, including concentrating solar energy. IEC standards pave the way for their widespread adoption by ensuring they meet the right safety and efficiency requirements.

IEC TC 117 is working on international standards for solar thermal power plant systems for the conversion of solar thermal energy into electrical energy. One of the standards, published in 2022, IEC 62862-3-1 specifies the requirements for the design of parabolic trough solar power plants. Future standards are expected to address issues of connectivity and interoperability with the power grid and environmental aspects. IEC TC 82 sets standards for solar PV energy devices, covering all elements of the entire photovoltaic energy system TC 105 which publishes papers related to fuel cell technologies.

A different approach to improvement of thermochemical technology comes from a team of engineers at ETH Zurich, funded by the Swiss Federal Office of Energy. They took on the challenge of maximizing heat transfer from a CSP system to the interior of a reactor.

At the heart of the production process is a solar reactor that is exposed to concentrated sunlight from a CSP array and reaches temperatures of up to 1,500 C. Within this reactor, a thermochemical cycle takes place to split water and CO2 previously captured from the air. . The product is synthesis gas or syngas: a mixture of hydrogen and carbon monoxide, which can be further processed into liquid hydrocarbon fuels such as kerosene (jet fuel) to power aircraft.

Two ETH spin-off companies (Climeworks and Synhelion) are further developing and commercializing the technologies. “This technology has the potential to increase the energy efficiency of the solar reactor and thus significantly improve the economic viability of sustainable aviation fuels,” said Aldo Steinfeldprofessor of renewable energy carriers at ETH Zurich.

Hydrogen-producing solar panels

Researchers at KULeuven in Belgium have developed roof panels that capture both solar energy and water from the air. Hydrogen panels resemble conventional PV modules, but instead of an electricity cable they are connected via gas pipes. The researchers claim that one panel produces 250 liters of H2 per day, with an efficiency of 15%, and are now preparing to bring the technology to the mass market through a spin-off company.

Project researcher Jan Rongé explains“The hydrogen panels do not store hydrogen themselves and operate at very low pressure. This has several safety and cost benefits. The hydrogen is collected centrally in the hydrogen panel factory and compressed if necessary.” The product is expected to be commercially available in 2026 and prices will fall in line with those of PV modules today.

The International Electrotechnical Commission (IEC) is a global non-profit membership organization that unites 174 countries and coordinates the work of 30,000 experts worldwide. International IEC standards and conformity assessment are the basis of international trade in electrical and electronic goods. They facilitate access to electricity and verify the safety, performance and interoperability of electrical and electronic devices and systems, including, for example, consumer equipment such as mobile phones or refrigerators, office and medical equipment, information technology, electricity generation and much more.