Today we interview Jin Jianxiang, president of Cosin Solar Technology Co., Ltd.

Cosin Solar Technology Co., Ltd. is one of the pioneer enterprises in China to engage in the promotion of research and industrialization of CSP technology. Specializing in the application of CSP, CSP+ hybrid solution and molten salt thermal energy storage technology, we are able to provide our customers with advanced, mature, and cost-competitive CSP and molten salt energy storage products and solutions.

Who is Cosin Solar and what are your areas of interest?

Cosin Solar Technology Co., Ltd. is often known as “Cosin Solar” and was formerly named as “Supcon Solar”. We were founded in 2010 and are headquartered in Hangzhou, China. It is one of the pioneer enterprises in China to engage in the promotion of research and industrialization of CSP technology. Specializing in the application of CSP, CSP+ hybrid solution and molten salt thermal energy storage technology, we are able to provide our customers with advanced, mature, and cost-competitive CSP and molten salt energy storage products and solutions.

As a tower CSP technology company with years of R&D and engineering practice, so far, we have yielded 308 patents (including 218 invention patents) and 181 authorized patents (including 133 invention patents), covering areas from solar energy concentrating and collecting, heat storage & exchange to power generation. Meanwhile, We have led or participated in the preparation of 4 international standards (IEC 62862-4-1, IEC 62862-4-2, IEC 62862-3-5, IEC 62862-3-6) and 8 national standards, relating to heliostat field control system, heliostats and receiver which are core components of Tower CSP project.

Cosin Solar has extensive experience in construction and operation of large-scale commercial tower CSP plants. In 2013, we independently developed and constructed Supcon Solar Delingha 10MW Tower CSP Project, which has been running stably for more than 10 years. In 2016, we independently developed and constructed the Supcon Solar 50MW Tower CSP Project of which the performance has repeatedly broken industry records after the grid connection on December 30, 2018. In the same year, we participated in the construction of POWERCHINA Gonghe 50MW Tower CSP Project as the technology supplier and equipment supplier of solar field, which was connected to the grid in September 2019. So far, we have won a total of 600MW CSP projects widely distributed in Qinghai, Gansu, Xinjiang, Jilin and other provinces which are under execution now.

What is the operation status of Supcon Solar Delingha 50MW solar thermal power plant?

Supcon Solar Delingha 50MW Molten Salt Tower CSP Project (hereinafter referred to as “Delingha Project”) is one of China’s first batches of pilot CSP projects. It has 7-hour molten salt energy storage and is designed to generate 146 GWh of electricity per year. The project was successfully connected to the grid on December 30, 2018, reached full-load operation on April 17, 2019, and was handed over to commercial operation at the end of July 2019.

After the plant was put into operation, its performance steadily improved and repeatedly broke records in non-stop operation hours, daily, monthly, and annual performance. In the first full year of operation after the handover, the cumulative actual power generation reached 122 GWh. In the subsequent operation, our plant operation team continuously accumulated experience and optimized operation strategies to cope with all kinds of complex working conditions and weather changes. In 2022, the cumulative actual power generation reached 146.4 GWh, i.e., 100.26% of the designed annual power generation(146 GWh), setting a world record among all Tower CSP plants.

It’s also the only CSP plant in China of which the performance has been evaluated and certified by an international third party. Fichtner, a German independent engineering consulting company, evaluated and verified this plant. Based on their findings, they concluded that our production from October 2019 to March 2020 hit 97.06%, the plant engineering has reached state-of-the-art level among the peer technology providers worldwide, and all main equipment are in good operational status.

Regarding the key elements for a power station in order to achieve the production capacity, what experience can Cosin Solar share in terms of CSP design and operation?

CSP plant performance is subject to many factors, such as compatibility of systems, equipment performance and reliability, O&M of the solar field, TESS, SGS and STG systems. We have done a lot of work in order to achieve the best operation for Delingha Project.

Firstly, it’s critical to have good integration of solar field, TESS, SGS and STG systems. The key is to match the parameters of all systems and ensure all interfaces are well designed per the characteristics and operation modes of CSP. With our self-developed tower molten salt CSP plant engineering software and operation experience from Supcon Solar Delingha 10MW Tower CSP Plant (our pilot project), we made the most optimized engineering for all the systems which significantly increased the overall efficiency of the whole system.

Secondly, building a well-performed solar field is always the key to plant performance. While solar field performance is highly dependent on heliostat control accuracy, we achieved accuracy from two aspects. On the one hand, we ensure mechanical precision of heliostat during structure engineering and manufacturing process while keeping a regular calibration of the solar field through our machine vision-based automatic calibration methodology. Our calibration proves to be 25 times more efficient than the traditional whiteboard calibration. It greatly reduces the time for calibration during commissioning and maintains the highest level of heliostat accuracy during its lifetime. On the other hand, upon our 30+ years of experience and know-how in control systems, we developed a quite advanced heliostat field control system that can be used to control a large cluster of heliostats. By coupling with the receiver control system, we can achieve safe and stable operation of solar field to enhance the utilization of solar resources.

Thirdly, we ensure all core equipment is reliable, including heliostat, molten salt receiver, molten salt storage tank, molten salt pump, molten salt valves and steam turbine generator set. We have designed and developed equipment like heliostat and receiver that can operate stably under extremely harsh conditions on plateau areas. We overcame technical challenges such as electric control at the high-altitude area, low temperature high driver efficiency, low air pressure sealing, etc. In 2019, our heliostat was graded as “Excellent” by German Aerospace Center (DLR) and CSP Services, which is the highest level as per their rating. We also work with all the best international and domestic leading suppliers and engineering companies to guarantee reliable key equipment from all aspects, like material selection, flexible structure design and operation process of the receiver, structure design and welding quality control of storage tank, wear resistance design at high temperature of the molten salt pump, joint design of molten salt pump with pipeline and platform, and the sealing of molten salt valves. All above-mentioned equipment/engineering solutions have been long tested and verified in our Supcon Solar Delingha 10MW Tower CSP Plant, Delingha Project and PowerChina Gonghe 50MW Molten Salt Tower CSP Plant.

Fourthly, optimized operation is very important to maximize the generation capacity of the plant. The core here is to ensure the safe and stable operation of the receiver and improve the utilization of solar resources on cloudy days. According to statistics, the Delingha project site suffers more than 200 days of cloudy weather in a year, which greatly impacts the operation of the plant. What we do is to use our highly accurate solar field controls system to dispatch solar energy to keep an even distribution of solar flux on the receiver to avoid shutdown or evacuation of salt. Meanwhile, being aware of the importance of selecting the right operation strategy given to different cloud shadowing periods, we developed our cloud forecast system to track clouds and predict DNI in 30mins, which gives the best operation strategies to the operators to increase utilization of the plant, through coupling with solar field control system.

Fifthly, we keep working on reducing equipment operation failure caused by human errors through the maximum level of automatic operation under different scenarios. We developed our equipment expert diagnosis system and operation analysis system to give early failure warnings on key plant equipment to facilitate operators to continuously improve the operation strategies and greatly reduce the troubleshooting time of the plant.

Finally, we have developed automatic cleaning vehicles to tackle the frequent occurrence of sandstorms on our project site. The vehicles, featuring automatic navigation and water/dry cleaning functions, greatly improve the cleaning efficiency of the heliostat field and ensure power generation efficiency while reducing the operation cost. Being the first of its kind worldwide, our automatic cleaning vehicle won the SolarPACES 2020 Technology Innovation Award.

Why does Cosin Solar firmly stand with tower CSP technology?

Among the large-scale CSP projects in China, Tower CSP accounts for approximately 63%, Parabolic Trough about 25.5%, and Linear Fresnel 11.4%. Most regions with high DNI in China are located in the middle to high latitudes areas, with low solar altitude angle during winter. For Parabolic Trough CSP that uses single-axis tracking reflector, the Cosine Efficiency in winter is only about 30% of that in summer. Since Tower CSP uses dual-axis tracking heliostat, the Cosine Efficiency will not decrease significantly in winter like Parabolic Trough. Furthermore, benefiting from less rainfall during the winter season, production of Tower CSP projects often exceeds its generation in summer. Due to the general dry period of hydropower in winter, the peak shaving resources of the power grid are seriously insufficient, Tower CSP can maintain a high number of available operation hours in winter, which can provide greater guarantee for power supply.

Based on our findings, Tower CSP technology, compared to Parabolic Trough, is more efficient and cost-effective. Tower CSP can heat molten salt up to 565℃ to produce superheated steam at higher parameters. We all know that the higher the steam parameters, the higher the efficiency of the turbine power generation. Additionally, since the temperature range of the molten salt energy storage system for Parabolic Trough is only 290°C to 390℃ and for tower system is 290°C to 565°C, the thermal storage systems of Parabolic Trough CSP is about 2.7 times more expensive than the Tower CSP in order to store the same amount of energy.

China is building a number of large new energy hybrid projects equipped with solar thermal energy storage. What are the configurations and roles of Cosin Solar in these projects?

Currently, China provinces like Qinghai, Gansu, Xinjiang, and Jilin, are executing ambitious new energy hybrid base plans with molten salt CSP technology involved. As per statistics, the total installed capacity of CSP is expected to reach approximately 3.36 GW after all these projects start operations by 2023 or 2024.

Among these new energy hybrid base projects, most of the CSP projects are 100MW with 8-12 hours energy storage. The CSP plants will play the role of peak-shaving, running at a load as low as 15% during the peak hours of PV to reduce the regulation pressure of the grid, and operating at full capacity during the morning and evening peaks. The annual utilization hours of these CSP plants are mainly between 1,500 and 2,500 hours. Furthermore, to reduce the curtailment from PV/Wind, most CSP plants are equipped with 20-100MW molten salt electric heaters, further enhancing their peak-shaving capabilities.

Up to now, Cosin Solar has obtained several CSP project orders as part of new energy large bases, and the total installed capacity hits 600MW. The Jinta ZhongGuang Solar «CSP + PV» Pilot Project, which we developed with 100MW CSP and 600MW PV, is in the construction process. The project started construction in March 2022 and is progressing well, with the concrete tower successfully reaching the top last year.

Meanwhile, we got the EPC contract for CTGR Qinghai Qingyu DC 100MW CSP Project by working with PowerChina Northwest and Energy China ZTPC as a consortium. We won the bid for the procurement of solar field equipment for CGN New Energy Jilin Daan jixi lugu DC 490MW integrated energy project and will provide advanced solar field equipment and related services for the part of 100MW CSP project within this integrated project. We successfully won EPC contract for the 100MW CSP project of the Xinjiang Turpan CSP + PV hybrid project and the EPC contract has been signed. Most recently, we won another bid for the procurement of solar field equipment for the CGN New Energy Delingha 2GW solar thermal storage hybrid project (Phase I 1GW) and will provide solar field equipment and related services for the 200MW CSP project out of it.

What other technological innovations has Cosin Solar made in the field of CSP?

To further improve efficiency and reduce cost of CSP, we have been carrying out R&D of the new generation of high-temperature Tower CSP technology. We are currently developing new high-temperature molten salts, high-temperature particle thermal storage technology, medium to long-term energy storage technology, and high-efficiency electric heating equipment, some of which have been tested and validated, and soon we will begin manufacturing.

Another important area of our business is the electrical heater sector. We saw problems such as short lifespan, low single-unit power, and high low-voltage distribution costs in the mainstream electric heater products, so we developed our own high-voltage and high-power molten salt electric heater product which can be directly connected to the system with a rated voltage of 6.3kV. Compared with conventional 380V or 690V low-voltage molten salt electric heaters, this eliminates the need for low-voltage distribution equipment and design, greatly saving distribution cost of the electric heater system, and avoiding system efficiency decrease due to low-voltage transformers and line loss. More importantly, with a single unit capacity of 30MW, it can directly heat molten salt up to a temperature of 565℃.

In addition, based on our 10+ years of R&D experience in intelligent heliostat and solar field control systems, we have designed and developed a series of PV trackers which could significantly increase the PV power plants generation with intelligent tracking algorithms.