Helping photothermal cost reduction and efficiency, and seeking a green future for the industry -- "Opportunities and Challenges for the Large-scale Development of Photothermal Power Generation" theme report.

Time:2024-01-02

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As we all know, my country's photothermal power generation has exhausted the painstaking efforts of many photothermal people from 0-1 to 1-100. It has gone through the construction and operation of the national photothermal demonstration. After several years of climbing over the hurdle, in March 2023, the State Energy The board issued the "Notice on Matters Concerning Promoting the Large-scale Development of Photothermal Power Generation" to clarify that during the "14th Five-Year Plan" period, the national photothermal power generation will increase the scale3 million kWLeft and right. So far, the total installed capacity of photothermal is only 0.588GW, so2023~2025In three years, the installed capacity will reach14.5GWLeft and right. Photothermal power generation has ushered in the opportunity of large-scale development, but also brings new challenges.

 

 

 

 

 

Huang Wenbo, Chairman of Shouhang High-tech, as the executive vice chairman of the National Solar Thermal Industry Technology Innovation Strategic Alliance, was invited to attend the 2023 China Solar Thermal Power Generation Conference. In the conference, he discussed the theme of "Opportunities and Challenges for the Large-scale Development of Photothermal Power Generation". From a macro to a micro perspective, analyze the entire life cycle of the sun island, energy storage island, and power generation islandtechnological innovation,Efficient replication,Cost reduction and efficiency enhancementand other challenges. Part of the report reads as follows:

 

I,The Significance of Large-scale Development of Photothermal Power Generation

1. Peak regulation, energy storage dual function

Not only clean energy, but also has the dual function of peak power and energy storage.

2. Support and regulation of new energy

Can be achieved with new energy regulation, support new energy

3. Peak shaving capacity and moment of inertia

It can provide better long-period peak shaving capability and moment of inertia for power systems

4. Basic power supply

Potential as peak shaving and basic power supply in some areas

5. Alternative to traditional energy

It is an effective means for new energy to replace traditional energy safely and reliably.

Effective support of the energy system

It is an effective support to speed up the planning and construction of a new energy system.

 

Opportunities for the large-scale development of photothermal power generation in 2.

The large-scale development of photothermal power generation can digest and upgrade traditional industries (special glass, steel, cement, molten salt, thermoelectric power generation equipment, etc.), and can also drive new materials (heat absorber materials, heat absorber coatings, thermal protection materials, heliostat back plate materials, heliostat support materials, etc.), precision equipment (molten salt pump, high-precision heliostat reducer, supercritical carbon dioxide steam turbine, carbon dioxide heat pump), intelligent control (concentration system, heat absorption system, heat storage system, heat pump system, heat exchange system control) and other emerging industries Development; large-scale development of photothermal power generation will become a new growth point of my country's new energy industry.

 

 

Challenges of 3. Photothermal Power Generation Scale Development

1. Technological innovation

From the macro to micro perspective, the whole life cycle of solar island, energy storage island and power generation island is analyzed, and the challenges of technological innovation, efficient replication, cost reduction and efficiency increase are analyzed.

 

 

(1)Quality Photothermal Site

"The time is not as good as the place, and the place is not as good as the people." Photothermal power generation not only needs the policy opportunity for large-scale development, but also needs the geographical and climatic environment with high-quality lighting conditions, as well as technical personnel and operation and maintenance teams with mature practical experience.

From this DNI cloud map, it can be seen that in China, Tibet's light and heat resources are better than Qinghai's, Qinghai's light and heat resources are better than Gansu's, even with a difference of 10%-20%. For the same construction scale of photothermal power generation, if DNI is 10%-20% higher, it can not only greatly increase the power generation, but also improve the long-term stable operation of the unit, better play the function of photothermal power generation peak regulation, reduce the shutdown frequency of the photothermal unit, thus reducing the failure rate of the unit, and further improving the return on investment of the photothermal power station. Practice has proved that the national photothermal demonstration project has been built, and the solar island of the same scale and quality is built in an area with better photothermal resources, and its power generation has increased significantly compared with the same period last year. It can be seen that planning the layout in advance, reserving and giving priority to the development of high-quality photothermal sites is one of the three important conditions for photothermal power generation to reduce costs and increase efficiency.

 

 

(2)Layout

Efficient layout of large-scale mirror field-multi-tower two-machine scheme

In addition to selecting the site of high-quality photothermal resources, in the context of the large-scale development of photothermal power generation, the layout of multiple towers and two machines can improve the utilization rate of photothermal resources, improve the stability of unit operation, improve the flexibility of peak adjustment, and improve investment income. At present, in some multi-tower photothermal power station schemes, the heat absorption tower and the steam turbine unit are in one-to-one correspondence, as shown in the figure, which is only a simple copy of a single tower and a single machine, and then collected and dispatched when the power is sent out.

 

 

A multi-tower two-machine scheme of tower crane decoupling, through the common heat storage tank and evaporation system, the heat absorption tower and the steam turbine unit are decoupled, there is no one-to-one correspondence. When a unit has a problem, the heat absorber can still work normally, or when a heat absorber has a problem, all units can operate normally. This arrangement scheme can increase the reliability and flexibility of the system, improve the equipment availability rate, and increase the power generation of the power station. In order to prevent problems with the evaporator, the evaporator adopts a layout scheme in which multiple columns are connected in parallel and any column can operate independently. From the technical and economic considerationsMulti-tower two machineThe program is more reasonable.

 

 

 

In the early stage of the first flight, Dunhuang was divided into three phases for planning and layout. The first phase was 10MW, which was used as a training unit, the second phase was 100MW, which was used as a technical actual combat unit, and the third phase was 300MW, which was a three-tower and two-machine unit, which was used to promote technology and reduce costs.

 

The three-tower two-machine scheme adopts the decoupling method of mirror field and heat absorption tower, energy storage island and power generation island. Among them, the mirror field is not limited to serving a heat absorption tower, and can call each other.

 

Energy storage island is not limited to the service of a heat absorption tower, two sets of power generation system using the master control, can call each other any three steam a package. Three steam and one package can call any heat storage tank. During the maintenance of any heat absorption tower, the heliostat around it can serve other heat absorption towers, thus not affecting the mirror field to play its light gathering function.

 

During the overhaul of any steam turbine, one steam turbine shall be reserved for normal power generation. In particular, the two machines adopt parent control. When the power grid is at a low peak of power consumption, one unit can be stopped and the other unit can be operated at 10% of the load, which is equivalent to 5% of the total installed load, thus ensuring that the system is in a hot state. When the power grid is at a low peak, the other unit can be started quickly. Quickly achieve two units 100% high load operation, so as to achieve long-term broadband rapid peak. Truly achieve flexible, efficient and stable peak function.

 

Dunhuang Phase III Planning Map

 

 

High efficiency energy storage island

New high temperature molten salt energy storage technology of compressed carbon dioxide heat pump

The large-scale construction of photothermal power generation has the function of energy storage, which can store excess photovoltaic or wind heating low-temperature molten salt. At present, molten salt energy storage and consumption of excess electricity, most of the electric heater for heating, the electricity to electricity conversion efficiency is relatively low. Using a new type of high-temperature molten salt energy storage technology based on compressed carbon dioxide heat pump, the supercritical carbon dioxide heat pump is driven to pressurize carbon dioxide to generate high temperature to heat low-temperature molten salt into high-temperature molten salt by using low-valley electricity and electricity from abandoned wind and light, thus realizing the function of both peak adjustment and efficient energy storage, making the cost of energy storage lower.

 

 

High temperature carbon dioxide molten salt energy storage system

The carbon dioxide heat pump high-temperature molten salt energy storage system is divided into a supercritical carbon dioxide heat pump heating molten salt process and a molten salt supercritical carbon dioxide discharge process. This is the first high-tech company to invest more than 5 billion yuan in succession for ten years. In addition to the technological innovation of the sun island, it is also committed to the continuous research and scientific research investment in the technological innovation of the energy storage island and the power generation island. Strive to make efforts for the large-scale development of photothermal power generation, improving quality, reducing costs and increasing efficiency through the technical research and innovation of solar island, energy storage island and power generation island, and playing more roles in the new power system with increasing new energy. A compressed carbon dioxide energy storage system based on the current molten salt temperature, in which the pure electricity-heat-electricity conversion efficiency is 65.8%. In the next 3 to 10 years, the temperature of molten salt will be further improved. Using 800 ℃ high temperature molten salt combined with supercritical carbon dioxide power generation system, its electricity-electricity conversion efficiency is as high as 76.6%, which is very promising.

 

The combination of carbon dioxide heat pump high temperature molten salt energy storage system and photothermal power generation system has natural advantages, its dual system combination, molten salt-compressed carbon dioxide energy storage electricity-electricity conversion efficiency is higher, far more than the current compressed air energy storage.

 

Comparison of carbon dioxide molten salt energy storage scheme for the first voyage with other energy storage

The table lists the comparison between the first voyage carbon dioxide molten salt energy storage scheme and other energy storage, from the power range, floor area, electricity conversion efficiency, cold, heat and electricity cogeneration, multi-energy complementarity and future efficiency improvement space and other aspects of comparison, carbon dioxide molten salt energy storage scheme has very large advantages.

 

 

2. Cost reduction and efficiency enhancement

Application of New Materials and New Technologies

The challenge of localization of new materials and new equipment: The first phase of Dunhuang Photothermal Power Station is not only used as a training machine for operators, but also as a testing machine for operation strategies. At the same time, it also provides domestic equipment testing and actual combat opportunities for upstream and downstream colleagues in the industry, contributing to the localization rate. By improving the localization rate, not only reduce the cost, but also shorten the after-sales service time, can reduce the power station unexpected downtime. For example, when the weather is fine, if the 100MW of Dunhuang is shut down unexpectedly, it will reduce the income by more than 200 million yuan a day. It can be seen that the localization rate and service efficiency are very important.

 

 

Localization of heat absorbing equipment materials and coatings

As the heat absorption system is faced with frequent start-stop and load rate changes, changes in wind speed, cloud cover and other aspects also require the heat absorber to have high adaptability and anti-fatigue performance. According to the requirements of the working conditions of the heat absorber, Shouhang Hi-Tech cooperated with Baosteel to develop the domestic nickel-based alloy material SHBG-2. Through the unremitting efforts of the research and development team, it has overcome the process difficulties such as difficult deformation of the SHBG-2, and has been successfully used for 5 years and 7 years in the two photothermal power stations built by the first voyage. It has also conducted research on heat absorber coatings in conjunction with Lanzhou Institute of Chemistry, Chinese Academy of Sciences. The research and use of these new materials is of great significance to the cost reduction and efficiency increase of the solar thermal power station.

 

 

 

Localization of heliostat back plate

After a lot of research and experiments, the first flight has gone through the development process of heliostat without back plate to with back plate. Practice has proved that the heliostat and back plate, its structural strength is greatly improved, not only the stability of the heliostat surface is greatly improved, but also the ability to withstand wind pressure is stronger, and the ability to withstand the high pressure and rapid cleaning of the cleaning vehicle is stronger. The backboard selected for the first flight requires not only large plasticity, high strength and stability, but also special anti-corrosion ability. Its surface anti-corrosion layer adopts active anti-corrosion materials. When the surface layer is scratched due to construction or dust and other reasons, this Active material will move and protect the wound, realize the wound self-healing function, and have stronger anti-corrosion ability. In the early days, there was no qualified supplier for this material in China, so the first flight Dunhuang Phase II used imported backboard materials. Through continuous technical exchanges and repeated experiments with domestic and domestic suppliers in recent years, domestic suppliers that meet the technical requirements have been basically cultivated to reduce the material procurement cycle and production cost of the sub-mirror without reducing the anti-corrosion ability of the heliostat strength.

 

The mirror field of the first 100MW molten salt tower solar thermal power station project in Dunhuang

 

183 square meters heliostat

 

Localization of actuators and control elements

According to the needs of heliostat configuration, we collected qualified suppliers from all over the world, and found that this kind of large-load, high-precision and high-efficiency actuator is also a heavy-duty robot joint. Its technology and price are monopolized by foreign markets. We later communicated with relevant domestic technical teams to carry out product research and development and production, which promoted localization and compared with international products, all aspects of performance indicators (load, accuracy, friction, etc.) have reached the trial standard, thus trying to meet the needs of 100MW large mirror field, opening the process of localization for the large-scale supply of 100MW and mirror field.

 

Heavy Duty Robot RV Reducer

 

Reducer production line

 

3. Efficient replication

New requirements are put forward for intelligent manufacturing and large-scale mass production of core equipment (heliostats and heat absorbers).

With the large-scale development of photothermal power generation, tower core equipment such as heliostats, heat absorbers, etc., must be the same as the trough concentrator, and the products will be standardized and standardized. Further enhance the automation rate of the manufacturing process, improve production efficiency and quality, in order to meet the needs of large-scale development.

 

 

Mature and Replicable Operation Rules-Operation Personnel Training Mechanism

DCS real-time screenshot of 7/5

 

This is a screenshot of DCS real-time operation screen with half a day of cloudy days (DNI fluctuates frequently), the unit is operating at more than 62% load, and the molten salt level is still continuously rising and the tank is full:

 

This screen shot is a real-time screen shot on July 5. Through this screen shot, you can see that the day is sunny to cloudy. In the afternoon, there are more clouds, the DNI curve changes greatly, and the teeth are staggered. In this complex and changeable weather conditions, it not only tests the photothermal efficiency and hardware adaptability of Sun Island, but also tests the intelligence and adaptability of the operating system, and even tests the proficiency of the operators. It can be seen from DNI curve, operation curve and molten salt curve that under the condition that DNI fluctuates greatly and frequently and DNI value is also very low due to half-day cloudy, except that DNI is extremely low from 12: 00 noon to 1: 00 noon and the unit load is artificially adjusted downward (50MW), other time periods are still stable at the maximum safe load (62.76MW), and the molten salt level is still rising continuously, at 18:49, the molten salt tank was full of salt and reached the highest level.

 

It can be seen that in complex and changeable weather conditions, the unit not only has excellent hardware quality and flexible control system, but also has mature and rich experience in operating personnel.

 

DCS real-time screenshot of 7/20

 

This is a screenshot of the real-time operation screen with good weather. When only about 50% of heliostats are activated, the load of the unit continues to be 63% and the molten salt level is still full:

 

This screenshot is a real-time screenshot of the 7th/20th. The DNI value on that day was very good,(993), which was one of the best weather this year. Through the smoothed DNI curve, it can be seen that there are few clouds currently.

 

Pink line (number of heliostats tracking): Only half of the heliostats in the field are activated at about 9 am. Until 6 pm, the heliostat input rate averaged about 50%. When only about 50% of the heliostats are activated, the load of the unit is continuously increased from the previous day (green line) to 63MW (the maximum load currently allowed by the unit), and the load is not reduced for 24 hours.

 

Blue line: The salt level of hot salt continues to rise as the sun rises, and it is full one hour in advance around 7 pm.

 

To sum up, under the condition of fine weather, only about 50% of the heliostat is put into the heliostat, the unit load is continuously higher than 63%, and the hot salt level reaches the highest salt level one hour in advance. From only 50% of the solar island can continue to generate 63% of the load, and the molten salt level fills the tank one hour in advance, which shows that the hardware and control system of the solar island are of excellent quality, and the photothermal efficiency far exceeds the design value.

 

DCS Real-time Screenshot of 7/26-7/29

 

From the DNI curve of No. 26-29, it can be seen that the daily maximum value decreases day by day. From 964, 919, 800 and 760, the pink line is the tracking quantity of heliostats: the input rate of No. 26 and 27 is 50%, the input rate of No. 28 is between 60% and 70%, and the mirror field is fully put into operation on the last day. However, the load of the unit, when DNI drops in the first three days, keeps running in a straight line, the load remains unchanged (the maximum safe load allowed for 63MW units at present), and the hot salt salt level reaches the full tank in the first three days. On the fourth day, when the total amount of DNI was very low, the hot salt basically reached the high salt level, and the load was partially adjusted.

 

Note: Under the condition that the weather of the unit does not change, the unit can still operate at high load continuously. Under different weather conditions, the heliostat input rate changes from 50% to 70%, which can still reach the highest power generation capacity, and the performance of energy storage while generating electricity is excellent. This shows that through the construction and operation and maintenance of the national photothermal demonstration power station organized by our country, the world's largest mirror field composed of large heliostat with back plate is coupled with the heat absorber with the largest energy flow density in the world, the hardware quality of the Sun Island is excellent and its control system is flexible. Its scale and quality have reached the leading level of the international 100MW equivalent unit, and the operators have skilled experience in controlling and operating 100MW units, laying a solid foundation for the large-scale construction and operation and maintenance of 100MW photothermal power generation.

 

Higher requirements for power station operation and maintenance level

The level of operation and maintenance directly affects the power generation. With the development of scale, higher requirements are put forward for mirror field cleaning, mirror field automation operation level, and operation and maintenance personnel training.

 

Automated cleaning

 

Automatic operation

 

How photothermal can provide flexible scheduling challenges for the grid

The flexibility of photothermal power station and power grid scheduling is one of the important challenges in the development of photothermal scale.

In order to better realize the dual functions of high-quality power station and peak regulation and energy storage for the power grid, we, together with the Chinese Academy of Sciences and North China Electric Power University, have conducted topics such as "Optimal Control of High Proportion of New Energy Connected to Power Grid Photothermal Power Generation-Thermal Power Joint Peak Regulation" and "Research on Optimal Configuration of Photothermal Power Generation Supporting Full Renewable Energy DC Delivery" for the National Academy of Gansu Electric Power Sciences, the minimum capacity requirement of photothermal power generation for the operation scenario of the full renewable energy base and supporting synchronous stability, the configuration of installed and optimal heat storage capacity, and the optimization technology of UHV DC multi-scenario transmission plan adapted to the load characteristics of the receiving end, the resource characteristics of the sending end and the adjustment capacity. Prepare for the large-scale development of light and heat, and better achieve peak adjustment and energy storage.

 

 

4. Summary

Driven by the construction and operation and maintenance of the national solar thermal power generation demonstration project, my country's photothermal power generation technology level has been continuously improved, and the industrial supporting capacity has been significantly enhanced. It is promoting the large-scale development of photothermal power generation and giving full play to the increasing proportion of photothermal power generation in new energy. The role of the new power system helps accelerate the planning and construction of a new energy system, ushering in new opportunities and challenges, fully discuss the challenges and practices of policy timing, solar thermal resources, and talent reserves for the entire life cycle of solar islands, energy storage islands, and power generation islands, as well as technological innovation, efficient replication, cost reduction and efficiency. In the early stage of the large-scale development of light and heat, the cost is still relatively high, calling for attention to planning and layout, giving priority to the allocation of high-quality light and heat resources to new light and heat projects, so as to alleviate the current situation of high cost of light and heat; strengthening the combination of "production, teaching, research and application", strengthening the space for improving quality, reducing costs and increasing efficiency; The large-scale development of light and heat, especially the investment in Sun Island, improve efficient replication, improve supply capacity and reduce costs on the basis of high efficiency and high reliability. A good car also needs a good driver, good photothermal power generation hardware and control system, and the training of well-trained operators, so that photothermal power generation can be stable and far-reaching. The construction of operation and maintenance system and the training of operation and maintenance personnel are the fundamental guarantee for the high-speed and large-scale development of light and heat.

 

 

Welcome everyone to have more exchanges, more opportunities for creative cooperation, complement each other's advantages, and jointly meet the opportunities and challenges of the large-scale development of light and heat.