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By offering cheap energy storage, concentrated solar thermal power has huge potential. However, it needs international standards to become a competitive proposition in the market.
Solar thermal energy, also called concentrated solar power (CSP), is a renewable energy that uses the suns heat collected by various types of focusing mirrors. The concentrated sunlight energy heats a high-temperature fluid in a receiver, passes through a heat exchanger, and finally drives a steam or gas turbine to produce electricity.
The market for concentrated solar thermal power, a very promising renewable energy in the 1990s, has not really taken off in recent years and although several plants are being built around the world, particularly in China, prices have not come down enough to make it economically viable. Building and maintaining concentrated solar collector fields in harsh, often desert-like conditions is often more expensive than other forms of renewable energy, such as solar photovoltaics (PV) and wind power.
Storing energy at a low price
“Competition from solar PV has taken market share away from the more complex solar thermal technology, because solar panel prices have fallen sharply over the past 15 years and they are very easy to install. However, solar thermal has one major advantage over PV: cheap energy storage,” explains Eckhard Lüpfert, chairman of IEC TC 117, the International Electrotechnical Commission (IEC) committee that draws up standards for solar thermal power plants.
Typical thermal storage systems consist of insulated storage vessels filled with hot molten salt, with pumps and heat exchangers. According to Lüpfert, the price of thermal storage is much cheaper than that of lithium-ion batteries, which are currently one of the most widely used forms of energy storage. “Battery performance is improving, but thermal energy storage has a major advantage and is still about a hundred times cheaper,” he says.
An article published in Science Direct highlights that “in areas with high solar resources, CSP can play a crucial role, and important advances are being made to increase its competitiveness by improving energy storage systems integrated with CSP.” The paper highlights the potential of CSP thermal energy storage to stabilise the grid by “being able to generate energy during peak demand hours (high price periods, morning and evening), and to store energy efficiently, when electricity demand is low but renewable energy is available in excess (low price periods, midday).” The idea is that CSP will be combined with other renewables, such as solar PV, and provide grid-scale energy storage.
Concentrated solar thermal energy for industrial processes
Another selling point for concentrated solar thermal energy is its use in industries that require a large amount of energy to heat their processes, known as industrial process heat. This includes oil refining, chemical production, steel, cement, and the food and beverage industries.
To make cement, for example, raw materials such as limestone and clay are ground into a fine powder and heated to a temperature of 1,450°C in a cement kiln. The heating process relies on energy from fossil fuels, which are major carbon emitters. Pressure is mounting from all corners to decarbonise. While some research is focusing on materials that require less heating, the concentrated sunlight used to heat transfer fluids in CSP can be used to provide the high temperatures needed.
CSP can also be used to make solar fuels, which are of growing interest.
Absolute need for rules
IEC TC 117 published its first standards in 2017 and has developed key benchmarks for the industry over the past few years, all of which are crucial to stabilise the quality of components and installations and to help reduce the costs of the various CSP technologies, making them more competitive. The standards also ensure the safety and reliability of CSP systems used around the world. “A CSP plant is not just an electrical installation, it is almost a chemical process plant. It works with hazardous materials, such as organic fluids, which are heated to very high temperatures. Ensuring the safety of workers and the plant environment is therefore of vital importance and one of the key points of our standards,” describes Lüpfert.
Looking ahead, another area where standards will be needed relates specifically to the use of CSP for niche applications, such as industrial process heat. According to Lüpfert, “We can take the lessons and achievements from CSP plants and apply them to industrial process heat applications. We need to expand the applications of the TC 117 standards. It is often about extending what we have already achieved in terms of performance and reliability.”
One of the main challenges in the coming years will be attracting the right kind of experts to participate in standardisation work. “We have a lot of scientists and researchers, but we need more people involved on the ground and experts from industry,” says Lüpfert.
But there is also hope. “Since COVID, we have changed the way we work, and meeting online has been a blessing. Thanks to online tools, we have started to attract more qualified people for the work we need, especially from the industrial sector. We also use forums like SolarPACES, a technology collaboration platform that allows us to discuss pressing CSP-related issues, before we had the formal constraints of standardization,” he says.
As the race to achieve net-zero carbon emissions targets accelerates, concentrating solar power technologies can play an important role in ensuring we achieve this, with the help of IEC international standards. |
