Molten salt is the first choice for solar thermal power generation energy storage materials

Schematic diagram of solar thermal power generation system

When traveling to Qinghai, many people will recommend that you bring sunscreen because the sun is so strong there.

Indeed, Qinghai Province has rich solar energy resources, with an annual total solar radiation of more than 2000kWh/m2 ^and an annual sunshine hours of more than 3200 hours, which means that the sun shines for an average of about 9 hours a day. Qinghai Province also has conditions such as grid access, cooling water sources, and a large amount of desertified land, so it is very suitable for the construction of large-scale solar thermal power stations.

As the core technology of solar thermal power generation, the selection and preparation of heat storage materials are particularly important. Molten salt is the first choice for energy storage materials for solar thermal power generation. Molten salt is actually the molten liquid of salt. It has many unique performance advantages such as large heat capacity, low viscosity, low vapor pressure, and wide temperature range.

Commonly used nitrates and molten nitrates

Purification and high-temperature melting are the only ways to make solar energy storage materials from salt lakes

Qinghai Province has a large number of salt lakes, large reserves, large scale, and extremely rich salt mine resources. It is one of the important production bases of salt chemical industry in my country. Among them, sodium chloride, magnesium chloride, potassium salt, lithium ore, and mirabilite are all ranked first in the country, and it has the development space and advantages of solar thermal power generation.

Salt lakes are rich in inorganic salt resources. How can we make full use of these resources to make molten salt energy storage materials? Generally speaking, the salt obtained directly from the salt lake can only be used as raw materials. It needs to be purified or converted into molten salt through other steps before it can be used as a photothermal energy storage material. Just like Sun Wukong had to practice his fiery eyes in the alchemy furnace of Taishang Laojun, the "salt babies" in the salt lake also need to go through high temperature and other trials before they can become solar energy storage materials that can hold energy.

Molten salt state at different temperatures:

1. It is white solid particles before heating; 2. It gradually becomes molten during heating;

3. Gradually solidify after releasing heat when cooled; 4. The state when completely solidified.

However, traditional nitrate energy storage materials have either high melting points or low decomposition temperatures, and a narrow operating temperature range. In addition, their low thermal conductivity limits the efficiency of energy storage materials in utilizing solar energy to a certain extent.

Wang Min's team, a researcher at the Salt Lake Resources Chemistry Laboratory of the Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, used salt lake resources as raw materials to prepare a new type of molten salt, which not only broadened the applicable temperature range of nitrate molten salt, but also improved the thermal conductivity, further promoting the development of solar thermal power generation.

After nearly years of technical research and development, the team has established a set of relevant platforms suitable for molten salt preparation, purification, analysis and detection, physical property testing, etc., and has carried out a series of international and domestic cutting-edge technology and basic theoretical research work for molten salt work, providing large amounts of accurate and reliable data for major scientific and technological research projects undertaken by the country, the Chinese Academy of Sciences, and Qinghai Province.

The following are the related machines. We not only have high-temperature atmosphere muffle furnaces, but also automatic sample making machines, synchronous thermal analyzers, metallographic microscopes, etc. This is a complete and rigorous system.

Some related instruments

Molten nitrate salts will play a more important role in solar thermal power generation

Wang Min, a researcher at the Salt Lake Resources Chemistry Laboratory of the Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, pointed out that solar thermal power generation technology using molten salt heat transfer and storage can provide continuous, stable and adjustable high-quality electricity, overcoming the defects of wind and photovoltaic power stations that cannot use batteries on a large scale, resulting in poor transmission quality and a large impact on the power grid. It can not only be used as a peak-shaving power station for the power grid, but also as a main power station to bear the basic load. It is internationally recognized as one of the most promising power generation methods in renewable energy generation and may become the main energy source in the future.

"Of course," Wang Min said, "molten salt still has the disadvantages of high cost, low efficiency and low reliability, which limits its application in solar thermal power generation. Based on the development of sodium, potassium and magnesium resources in salt lakes and the utilization of solar energy on the Qinghai-Tibet Plateau, we focus on the performance research and improvement of molten nitrate heat transfer and heat storage media, from binary to ternary, and then to the introduction of additives, which provides a theoretical basis and scientific basis for the wider application of molten nitrate in solar thermal power generation."

"I believe that with the in-depth research and improvement of the performance of molten nitrates, the overcoming of shortcomings and the continuous development of its application prospects, molten nitrate will play a more important role in solar thermal power generation." Wang Min is full of expectations for the application prospects of molten nitrates.