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Energy Storage Technology And Grid Development
- May 10, 2018 -

Energy transfer technology is an indispensable prerequisite for human society to move toward a low-carbon economy, and it is also a necessary condition for promoting energy-based energy. Which energy storage technologies are the most promising? What is the future direction of development? What are the latest developments in the development and application of energy storage technologies between China and the United States? How do policies and regulations support the development of energy storage technology? How does the energy storage facility cooperate with the grid? How to give the energy storage facility its market position and ensure that the investment operator has a proper return?

With these questions in mind, in the afternoon of October 27th, Beijing International Energy Experts Club successfully held an international seminar titled "Energy Storage Technology and Power Grid Development" in Beijing. Mr. Shi Dingyi, Vice Chairman of the Honorary Council of the Beijing International Energy Experts Club, and Dr. Liang Zhipeng, Deputy Director of the New Energy Division of the National Energy Administration delivered speeches. Dr. Xinhua Chen, President of Beijing International Energy Experts Club hosted the seminar.

The former Chairman of the US Energy Regulatory Commission, Mr. Jon Wellinghoff, detailed the development of energy storage technology in the United States and explained how the United States used regulatory regulations to support energy storage technologies at federal and state levels and looked ahead at energy storage technologies in microgrids. Apply trends. Dr. Yang Zhengguo, president and CEO of UniEnergy Technologies, Seattle, United States, introduced the development and application of energy storage technology in the United States. Professor Qiang Qiang from Tsinghua University introduced the development and application of energy storage technology in China. Director of the National Center for Climate Change and International Cooperation, Secretary General of the China Renewable Energy Industry Association Li Junfeng, Chief Engineer of the State Grid Corporation of China Zhang Qiping, Chairman of the China Borong Group Liu Yanhui, Chairman of the Zhongguancun Energy Storage Industry Technology Alliance Yu Zhenhua and others successively spoke. More than 30 experts from National Bureau of Energy, National Grid, National Climate Change Center, National Energy Development Institute of National Development and Reform Commission, China Renewable Energy Industry Association, Zhongguancun Energy Storage Industry Technology Alliance and other relevant government departments, industry associations, enterprises and academia attended the conference. Meeting.

The topic of Mr. Jon Wellinghoff's speech was “The role of energy storage in the development of power grids”. The main points are summarized below.

1. There are many kinds of energy storage technologies in the world and can provide a variety of services. These technologies include Supercapacitors, Supersonic Magnetic Energy Storage (SMES), Lead-Acid, Li-Ion, Na-Sulfur (NaS), and Redox Flow. Flywheels, compressed air energy storage (CAES), pumped hydro, etc. These different technologies can provide diversified power supply (from kW level to GW level) and power supply duration (from second to hour level), can be used in UPS systems (uninterruptible power supply systems), peak load shifting and distribution networks, and large Capacity power management systems are applied at three levels. In the provision of large-capacity energy services, energy storage technology can significantly increase the power supply capacity of the power grid and allow power operators to profit from the peak-to-peak electricity price difference. In addition, energy storage technology can also provide many auxiliary service functions for transmission infrastructure, distribution infrastructure, and user energy management, such as: supplementing the wind and light systems with rotating backup capabilities, black start, and coordination supervision.

2. Energy storage technology can play a role in all aspects of the power system. The first is to cooperate with traditional power generation technologies at the power generation end to increase the net energy ratio of clean energy. At the power generation end, the large-capacity energy storage system can be used as an auxiliary service facility for the power plant to stabilize and stabilize the unstable power sources such as solar energy and wind power. The second is that in the transmission and distribution process, energy storage technology can be used in the substation to play a role in peak load shifting. The application of this link in the United States is becoming increasingly important. Energy storage technology can be used as a technology upgrade for substations in distribution networks, postponing the upgrading of the grid and reducing costs. Thirdly, in the consumer sector, there are energy storage technologies in front of the “meter” and “after the meter.” As far as "before the electricity meter" is concerned, grid companies are actively investing in energy storage facilities on the east, west, and west coasts of the United States, especially the East Coast. Because these areas are vulnerable to hurricanes, energy storage facilities can make the grid more resilient and more stable against hurricanes. After "after the meter," energy storage facilities provide services to users, such as Tesla's charging wall. In some parts of the United States, recharging electric vehicles at certain times of the day helps the grid to peak, but it also pays off. In addition to California, Illinois, New York, New Jersey, Texas, and other states have also established good incentive policies to encourage consumers to set up energy storage or self-generating facilities behind electricity meters.

3. At the federal level, regulatory policies have made timely adjustments to support the use of energy storage facilities. When Mr. Jon Wellinghoff was chairman, the U.S. Energy Regulatory Commission enacted Rule 755, which stipulated that ISO should pay remuneration for those service providers who provide FM services. In terms of service metering, it is not only necessary to calculate the total amount of electricity received, but also to calculate remuneration based on the reaction speed and FM accuracy. This provision mainly considers that the demand response of energy storage technology is much faster than conventional power generation technology. The Regulation No. 719 of the Energy Regulatory Commission requires independent power system operators (ISOs) and regional transmission organizations (RTOs) to accept supplementary services from the demand side. This enables commercial and industrial users to use energy storage facilities as demand-side response tools. may. Regulation 745 of the Energy Regulatory Commission requires power companies and retailers to pay large customers for the use of stored energy to replace the cost of grid peaking.

4. At the state level, the United States also has some regulatory policy incentives for the use of energy storage facilities. The California Power System Operator (CAISO) has developed a policy for purchasing flexible power sources, encouraging the assembly and use of flexible power sources with energy storage capabilities to ensure the clean and efficient use of large amounts of clean energy (California passed legislation requiring the installation of clean energy at 2030 Year must reach 50%.). The California Public Utilities Commission (CPUC) has established the Energy Storage Regulations (AB2514), requiring that three public utility companies in California (PG&E, SCE, SGD&E) must purchase at least 1.325 GW of energy storage equipment by 2020. This regulation also sets up framework rules for evaluating energy storage services, cost-effectiveness, and formulating possible grid energy storage indicators. This regulation directly helped California launch a large number of energy storage projects, and many new energy storage technologies were reflected in these projects. The “Self-Generation Incentive Incentive Plan Regulations” formulated by CPUC gives a subsidy of $2,000/kW for energy storage, which is reduced by 10% each year.

5. The rapid growth of the energy storage industry in the United States has seen rapid growth in non-grid-based industrial and residential applications and residential-side energy storage applications. The east and west coasts of the United States are the fastest growing regions for energy storage and the most innovative in the United States. The higher electricity prices in the region make energy storage applications more economical. At present, the installation of battery storage facilities in the United States is increasing at a rate of 30 to 40% per year, which is close to the growth rate of photovoltaics five years ago. At present, the total energy storage capacity of the national battery in the US Department of Energy statistics has exceeded 300MW, and it is expected to increase to nearly 1GW by 2019. At present, the vast majority of battery energy storage is used in power transmission and distribution links, but in the future, the growth rate of industrial, commercial, and especially residential energy storage will be higher than the power grid energy storage.

6. The cost of U.S. wind and photovoltaic power generation has declined rapidly and it has become more competitive. At present, the cost of electricity for photovoltaic power generation in the United States is less than 4 cents/kWh (the lowest bid price is 3.8 cents, including subsidies in the form of tax return), and wind power costs are almost equal to 2 cents/. degree. These prices include a 30% investment tax exemption allowance, but even if this subsidy is deducted, the U.S. photovoltaic and wind power generation costs are already lower than coal, gas, hydro, and nuclear power.

7. Energy storage can solve the unsteady nature of PV output and solve the “duck curve” problem. In California, due to the rapid development of photovoltaics and the characteristics of peaks and valleys, conventional power plants generate less and less power at the peak of photovoltaic output (such as at noon of the day), and at night they have to fully assume the problem of “duck shape” (Figure 1). The development of energy storage technology can fill the duck belly, cut the head of the duck, make the conventional power plant smooth out, and greatly increase the economic efficiency of the entire system. Therefore, CPUC requires the three major public power companies to establish at least 1,325 MW of energy storage facilities by 2020.


Figure 1. Load curve of California in each of March of 2012-2020

8. The application of energy storage technology in microgrids is a new trend. Due to different driving factors, all countries hope to develop the microgrid vigorously. The development of the US microgrid has attracted a lot of investment. The total investment in the development of microgrids from 2015 to 2020 is expected to reach US$3 billion. The main drivers of the microgrid include military installations, and the military base hopes to isolate it from the large grid through microgrids to ensure independent and safe power supply. There are also public facilities, universities, islands, etc. The University of California San Diego campus, which has 32,000 students and teachers in California, forms its own microgrid through energy storage, solar power, and gas-fired power generation. More and more similar communities are developing their own microgrids.

9. Energy storage systems need a suitable market structure to bring value to the grid. The application of energy storage technology in various links has produced unique characteristic value chains, and it needs an appropriate market structure so that the service value it provides to the power grid and users can be recognized and real commercial value can be realized.

10. The global energy storage technology is in the initial stage of transition from scientific experiments to commercialization, and policy support is very important. The purpose of policy support should be to embody the value of energy storage in the energy system, that is, the value embodied in energy storage at all stages of the transition from fossil energy to renewable energy.

Dr. Yang Zhenguo introduced the "US grid energy storage technology research and development and application" situation, the main points are as follows.

1. The essence of energy storage technology is to add a time variable to energy. Traditionally, electricity is ready-to-use, with no time factor. Energy storage technology adds a time variable to electrical energy, increases the value of the entire grid system, and helps to access clean energy.

2. There are five key requirements for the application of energy storage technology on electric networks:

 safety. Grid energy storage systems store huge amounts of energy, which can generate huge amounts of heat during energy release. Therefore, thermal design of energy storage systems is critical. There have been a number of battery fire incidents in the United States. Solid lead-acid batteries and lithium-polymer batteries have also experienced major accidents. The U.S. Department of Energy also set up a special project to study the safety of batteries.

performance. Performance includes power, energy, efficiency, reaction time, flexibility, and versatility. According to the application of energy storage system in different links of the power grid, the power requirements range from tens of kilowatts to hundreds of megawatts. The discharge time requirements range from a few seconds to minutes, tens of minutes, hours, even days . An important indicator is that the shorter the reaction time, the better. Generally, the system requirements must be reached within one second. Some applications such as voltage support even require less than 0.1 seconds. Such reaction times are not provided by conventional pumped storage and compressed air systems. Functional flexibility can increase the practical value of energy storage systems.

 Durability, ie system life. The life cycle of traditional energy and new energy power plants is more than 20 years, and the matching energy storage system also needs the same long life. It is generally required that the power grid energy storage system has a life of more than 10 years and can withstand more than 4,000 tests of deep charge and discharge.

Economical. We must not only pay attention to the cost of the battery, but also the system cost of the power transformation system and the auxiliary system; not only the cost of the battery system, but also the installation and construction cost (it is normal to increase the battery cost by 30 to 100%); it is not only the cost of capital. There are also operational maintenance costs - so compare the cost of electricity at different cycle life cycles. At the same time not only depends on the cost, but also depends on the benefits, some expensive battery life is longer, more cost-effective.

reliability. The battery system does not require much maintenance and maintenance.

3. The U.S. current grid energy storage is dominated by pumped energy storage. The future direction is mainly for flexible energy storage systems such as batteries. The total installed capacity of power generation in the United States is about 1200 GW, which is about 2%, that is, 20-30 GW of energy storage capacity. At present, 95% of U.S. power grid energy storage is pumped storage, with a total of more than 20 GW, which was basically built before 1980. Pumped storage systems have the lowest cost, but their future development is very limited due to large environmental impacts, long construction periods, huge investment, and limited geographical location. The main development direction of U.S. power grid energy storage in the future is to use more flexible, versatile, and flexible energy storage systems. The battery energy storage technology is preferred due to its high efficiency, versatility, bidirectional response to charge and discharge, fast response and cleanliness.

4. The comparison of various battery energy storage technologies shows that the advantages of the flow battery are outstanding.

Lithium Ion Battery. The concept of lithium-ion batteries was introduced in the 1970s. After nearly two decades of material research and development and improvement, the first commercial lithium-ion battery appeared in 1991, and after years of substantial capital investment and development, the technology of lithium-ion batteries has matured. The biggest advantage of lithium batteries is their high energy density and efficiency, so they have been widely used. To this day, the world has built a more mature industrial system around lithium batteries. The disadvantages of lithium batteries are: 1) Low safety and frequent accidents, such as the lithium battery accident of the Boeing 787 and the large-scale fire accident of lithium polymer batteries in Arizona. The flammability of the electrolyte makes the danger always exist; 2) The capacity decreases as the number of charging cycles increases, and the battery needs to be changed frequently; 3) The discharge time is basically short, and the long-term discharge has a great challenge to the lithium battery.

 Sodium battery. Sodium batteries According to the positive case, one is a sodium-sulfur battery and the other is a sodium-metal chloride battery. The operating temperature of these two kinds of batteries needs to be in the range of 300-350 degrees Celsius. The energy density is comparable to lithium batteries. If it can be used continuously for a long time, good battery efficiency can be achieved. Battery life (charge and discharge 20~80%) can reach 4000~5000 times. At present, this type of battery technology is relatively mature. Tokyo Electric Power, NGK, GE and other large companies have made great investments. However, safety cannot yet be fully guaranteed. In 2011, a 2 megawatt sodium-sulfur battery system in Japan caused a fire, which greatly affected the promotion of technology.

Flow Battery (RFB). The energy of the flow battery is stored in the electrolyte instead of the solid electrode. The battery module converts the chemical energy stored in the electrolyte into electrical energy through an oxidation-reduction reaction. The current more mature is a vanadium flow battery. The advantage of the flow battery is that: 1) The theoretical life is infinite and can be recycled. Because its working characteristic is that the electrode does not participate in the specific reaction, the cycle life is not limited, nor is it affected by the degree of discharge and charge; 2) The power and energy can be designed according to the needs to be flexibly designed, for example, a 100 megawatt power is determined. , But it takes 4 hours or 8 hours for the power supply to change; 3) The battery has a simple structure that facilitates modular assembly and can also be made large; 4) The safety is good. Because the electrolyte is water-based, it is an extinguishing agent. In addition, because the specific heat capacity of water is large, even if it is full of instantaneous release, the temperature of the entire system will only rise by 15 to 16 degrees. 5) The cost of leveling is lower than that of lithium batteries and is suitable for large-scale energy storage projects. The disadvantage is that the energy density is relatively low. At present, it is not suitable for installation on mobile devices, and engineering needs to be further improved. The largest project for the application of flow batteries on the power grid is the 5MW/10MWh project of Rongke Energy Storage Co., Ltd. under the China Borong Group. It has been operating stably since its completion in 2012.

5. The future development of energy storage battery technology will also bring hundreds of flowers together, and the flow battery will receive more attention. Humans have not yet invented a battery to meet all energy storage needs. In the future, the market for energy storage applications in power grids is very large, and there will not be an ideal technology to cover all needs. In the future, energy storage technologies must be used in a variety of ways to apply different technologies in different fields. The multi-functional and flexible technology will produce better benefits and value and occupy a larger market share. Currently in the United States, a battery with a shorter discharge time is basically a lithium battery. The sodium-sulfur battery that everyone sees has been discharged for a long time, but due to safety issues, the flow battery has gradually been taken seriously. Current research trends in energy storage batteries have largely shifted to flow batteries. One trend is to use safer water-based electrolytes, and the other is to use cheaper materials such as zinc, iron, silicon, and the like.

6. The industrialization of energy storage technology faces challenges. Many energy storage technologies are still in the laboratory stage, attracting a lot of venture capital, and also have some prototype products, but they are still far from engineering and industrialization. High performance and low cost are still a contradiction. In the energy storage system, not only the importance of the battery, but also the electrical conversion system, auxiliary system, management system, and energy efficiency management are all important. The United States now invests the most in energy efficiency management systems with low investment and quick results.

7. Business model innovation and policy support are critical to energy storage technology and market development. The maturation of the three conditions will make the energy storage market mature and be applied in large scale in the power system. First, the technology will be mature and the cost will be reduced. Second, the strong support of policies and regulations. The third is the combination of technology, investment and finance. Create innovative business models.

Academician Lu Qiang introduced the development and application of China's energy storage technology. The main points are summarized below.

1. China should build energy storage projects on a large scale. The total installed capacity of wind power in China now exceeds 100 GW, but 70 to 80% of wind energy is not well utilized. In particular, wind energy in the latter half of the night is completely abandoned. Even if 50% of energy is recovered, it is equivalent to rebuilding three to four Three Gorges power stations. . Although pumped storage is the first choice for large-scale energy storage technology, pumped storage is strictly limited by geographical conditions, and there are problems such as leakage and evaporation of the reservoir. Therefore, we cannot rely on pumped storage to solve the problem of large amounts of wind and light.

2. Waste battery pollution is the main risk for the development of large-scale battery energy storage. Now China's extensive use of lithium iron phosphate battery life is too short, shallow shallow light charge for eight years, deep charge deep release up to four years, waste batteries cause a lot of pollution to the environment. In addition, the operating temperature of the lithium battery is strictly required (the temperature does not exceed 27 degrees Celsius (+ or minus 2 degrees Celsius) in order to effectively use), which further increases the cost of the battery.

3. China can deploy large-scale self-developed non-combustion compressed air energy storage technologies. The advantages of this technology are: 1) The system configuration is flexible, the system efficiency can reach more than 70%; 2) The investment cost is low, almost equal to the pumped storage; 3) It is suitable for large-scale energy storage and decentralized energy storage, not generating electricity. The time can be used for peak adjustment; 4) The carbon emission is zero; 5) It can provide natural heat, electricity, and cold triple supply, not only can provide uninterrupted hot water, but also can provide 2~3 degrees Celsius cooling environment for fresh fruits and Food can be used in many places in the northeast and in China; 6) It can provide natural support and pressure regulation when the voltage is low.

The “non-combusting compressed air energy storage” related technology developed by Tsinghua University and supported by the State Grid Corporation of China has been accepted by Chinese and US patents for inventions. A 500kW demonstration project has been completed in Wuhu, Anhui Province, and has been operating for 18 consecutive months. The project's electricity-to-electricity conversion efficiency is 33%, plus the system efficiency of cold and heat utilization can reach 72%. At present, the State Grid and Tsinghua team are planning a 20MW demonstration project and improving the technology, increasing the "electricity conversion" efficiency from 33% to 55%, and the system efficiency (heat + electricity + cooling) to 80%.

Experts from the conference conducted further discussions on issues such as China's power grid and energy storage construction. The main points are summarized below.

1. Energy storage technology is the key technology of the third industrial revolution and the cornerstone of the energy system's transition from fossil energy to renewable energy. From a global perspective, energy is transforming and the grid is gradually moving from large-scale long-distance transportation to smaller-scale community-based microgrids. The structure of the entire power grid is from high to large and far to medium-small, intelligent and regionally optimized. Feature change. In this transformation process, energy storage plays an extremely crucial role. China started from the “Tenth Five-Year Plan” and has put energy storage technology as an important direction in the mid- and long-term plans. It is now time to consider formulating special plans for the development of energy storage technologies.

2. The most needed breakthrough for energy storage technology is automotive battery technology. The requirements for vehicle power batteries and grid energy storage batteries are not the same. At present, the most urgent breakthrough in battery energy storage technology is electric vehicle battery technology. The breakthrough in automotive battery technology represents a real marketization of energy storage batteries. At present, China's power system has not reached the stage of large-scale energy storage. As a whole, the power system further regulates the absorption of wind power and solar energy and has great potential to be tapped. In the application of energy storage in power systems, microgrids are more useful. Demonstration projects should be encouraged and technical reserves should be improved. Large-scale energy storage on the power generation side is still dominated by pumped-storage power in China, and there are also adjustments for thermal power units.

3. The development of energy storage technology is of great significance to the power grid. China currently has pumped storage, with peaks in thermal power, which can solve some problems in grid operation. However, engaging in pumped storage needs to be carried out by mountains, line construction, step-up and step-down, and finally delivered to users through the power grid. This series of projects is very large. If the battery storage capacity in the future is large enough and installed directly in a large city or in a nearby substation, it can replace pumped storage. Therefore, the development of large-scale new energy storage technologies for the power grid is the future direction. At the same time, grid construction is just as important as the construction of energy storage facilities. At present, China's windy and bright local grids are very weak and their loads are very small. Without energy storage facilities, if they can't be consumed, they will have to abandon their electricity. Therefore, as the grid company's primary task is to strengthen the power grid construction. For example, now Hami is building 8 million kilowatts of wind power, which needs to be sent to Zhengzhou via UHV DC. Nowadays, HVDC cannot send renewable energy, because the fluctuation is too large. Therefore, if there is no suitable means of pressure adjustment, the power loss will not be avoid. The current solution is to build a thermal power plant in the local area. After calculation, 8 million kilowatts of wind power is required to be equipped with 7 million kilowatts of thermal power, plus 3 million kilowatts of photovoltaic power, so that the amount of renewable energy energy delivered by DC can account for 30% of the total. . But if there is energy storage technology regulation, UHV power transmission will be much simpler. Therefore, energy storage technology is of great significance to the development of clean energy.

4. The development of China's energy storage industry still needs to overcome many challenges.

First, the market mechanism is not perfect. The Chinese energy storage industry started late and the country has only begun to pay attention in the past five years. North America and Japan had industrial policies for energy storage 20 years ago, and they have all formed their own operating mechanisms. At present, there are some local regulations in the country that provide some development opportunities and market models, but there is still a long way from the healthy development of the whole industry. Energy-storage companies hope that these regulations will rise to the policy level in the future, and they will be truly included in the reform of the power system and become a law. This will increase the reliability of investor participation and minimize investment risks.

Second, the technical outlook is still uncertain. How to turn technology directly into an actual business model will ultimately support the company's true profitability, and there are also risks. At present, it has not completely understood what technology is the most economical and competitive in terms of energy storage, that is, the most promising energy storage technology from a commercial perspective is still uncertain. For example, it has been known for a long time that silicon is the main technical direction of solar power generation, and business models can be proposed. Now that energy storage technology has not yet reached that stage, it is not clear whether the future direction is flow batteries, compressed air or lithium batteries. So do not know how to invest funds and efforts to reduce costs. From the perspective of future development, there may be two main types of technology. First, for long-life applications, it should be a flow battery. Second, for short-lived applications, it should be a lithium battery. However, no matter what kind of technology, only when the stage of scientific experimentation is completed and profits can be achieved, can it be discussed and applied in a wide range.

Third, energy storage equipment also needs to improve reliability. If the battery energy storage can not be used for more than 10 years, it is meaningless for power system regulation. If life problems and safety cannot be solved, it does not make sense to talk about prices. In the operation of wind power and photovoltaics, we do not need 1:1 energy storage equipment, and we can provide 10 to 15% of it. If the weather forecast estimates that the wind power error is 20%, adding 15% of the energy storage can improve power generation efficiency and improve grid stability. Moreover, the grid dispatching agency can make reasonable arrangements for other units. Since wind power and solar energy projects generally have to run for 20 years, energy storage equipment must have a lifespan of at least 10 years.

To effectively respond to these challenges requires the government to increase research and development investment in research institutes, and provide appropriate R&D support for enterprises. On the basis of successful pilots, the government can introduce supporting policies and set industry standards. At present, the Zhongguancun Energy Storage Industry Alliance that has already been established in China can play a role in these aspects.