Flywheel UPS market has unlimited potential - new power supply system (1)

With the increasing awareness of energy conservation and emission reduction in the world, improving energy efficiency and utilizing renewable energy have become the key strategies and policy orientations of many countries and the major trends in the development of the power industry. The technology and products of traditional UPS power supply systems have made great progress after more than 40 years of development, but they still have problems in terms of safety, reliability, and high energy consumption. There are some shortcomings and defects. Therefore, how to improve the power conversion efficiency and find a low-cost and high-efficiency power supply system has become the focus of attention in the industry, and the traditional UPS power supply system needs to accelerate to the more efficient "green energy-saving UPS power supply system" evolution.

According to foreign media reports, the flywheel UPS as a means of energy storage, providing a highly reliable and stable power supply, can provide a few seconds to several minutes of power, this time enough to ensure the user to switch power. Its advantages and market potential compared with traditional UPS using battery have attracted people's close attention. What do the industry experts think about it?

To this end, the journalist invited four industry-leading power supply experts and generator experts to elaborate and analyze the development and application prospects of flywheel energy storage UPS (hereinafter referred to as flywheel UPS) technology.

(Zhong Jinghua, Senior Engineer, currently Deputy Chief Engineer of China Electronics Engineering Design Institute, Chief Electrical Engineer of Shiyuan Science and Technology Engineering Co., Ltd., currently serves as Vice Chairman of the Computer Room Technology Committee of the China Information Technology Promotion Alliance, and expert of the national engineering construction standard design weak current. Committee members, members of the National Building Electrical Installation Standardization Technical Committee, etc.)

Reporter: Mr. Zhong, what are the problems facing the data center? What are the requirements for large-scale data center requirements for power supply systems? What are the characteristics of flywheel UPS in terms of reliability?

Zhong Jinghua: The biggest problem in data centers is the huge power consumption, ranging from a few thousand kilowatts to as many as tens of thousands of kilowatts. Large data centers consume hundreds of millions of kWh each year. All data centers are powered by UPS systems. According to the requirements of IT equipment manufacturers, IT equipment needs to be powered by UPS. Because UPS guarantees the quality of power supply, it can eliminate all kinds of high-frequency clutter, voltage surges, sags, momentary power failures, etc. in the city power, and harm the information equipment to ensure the safe operation of the information network at all times. The large number of applications of UPS and load leads to high power consumption in the data center.

The power supply system is first to provide sufficient capacity, the data center is normal with tens of thousands of kWh of electricity per hour, the larger the data center is, the greater the power consumption; secondly, the reliability is very high, and the first point of the data center is high reliability. Then we can talk about energy saving. To achieve high reliability, the first is to rely on the power grid itself, the second is to provide uninterrupted power by UPS and diesel generators.

From a reliability perspective, people's concerns are in the duration of the flywheel. For large data centers, the flywheel UPS can provide a guaranteed time of 15 seconds. This process can ensure the normal start-up of the diesel generator and keep the data center power supply uninterrupted. I believe that more flywheel UPSs will be applied to modular data centers or containerized data centers in the future. Data centers in foreign countries also use flywheel UPS for power supply, and they still need some specific experience and data in the country.


(Zhang Naiguo, editor in chief, Associate Professor, School of Information Science and Technology, Tsinghua University. Consultant of AC Power Professional Committee of China Power Supply Association. His main research interests are power electronics and UPS technology. Over 60 articles have been published in professional journals and technical journals. He has written more than 20 books and obtained more than 10 scientific research achievements.)

Reporter: Mr. Zhang, as an expert in the power electronics industry, please talk about the technology and application prospect of the magnetic suspension flywheel UPS.

Zhang Naiguo: Currently, the static UPS power supply system composed of semiconductor devices is widely used in the computer room or data center of communications, finance, electric power, transportation, education, and government departments in China. In order to prevent damage caused by a commercial power failure or sudden interruption, batteries are generally used as a backup power source. The specific method is: When the utility power is interrupted, the stored DC power of the battery is converted into AC power through the inverter, and the power is supplied to the load, so that the load is continuously operated.

As early as the 1960s, there was application of flywheel energy storage technology, but for various reasons there has been no breakthrough. Until the 1990s, due to the development of circuit topology technology, the extensive application of carbon fiber materials, and the increasing importance of battery pollution worldwide, this type of energy storage method has rekindled people's R&D enthusiasm and achieved rapid development. In recent years, due to the following three breakthroughs, new energy has been brought to the flywheel energy storage: First, the appearance of high-strength carbon fiber and glass fiber has increased the rotational speed of the flywheel and greatly increased the kinetic energy reserves per unit mass; It is a new development in power electronics technology that provides a solid technical foundation for the energy exchange between flywheel motors and systems. Third, the development of electromagnetic suspension and superconducting magnetic levitation technology, coupled with vacuum technology, has greatly reduced the loss of mechanical friction and wind force. Flywheel UPS shows a broader application perspective and quickly moves from the laboratory to the community. At present, the flywheel UPS is gradually being recognized by people in the industry.

In the domestic market, the introduction of flywheel UPS in the past two years has completely changed the way that lead-acid batteries are used to store energy in UPS power supply systems, and creatively uses vacuum-suspension flywheel energy storage technology to replace batteries. Simply put, when the utility power is normal, the mains supply power to the load, and the motor drives the 200-kilogram flywheel to rotate in vacuum; once the utility power is interrupted, the flywheel uses its inertial energy to drive the generator (with the above motor It is a motor to generate electricity. This time can completely start the diesel generator and achieve stable operation, thus achieving uninterrupted power supply.

It can be seen that this solution is to replace a large number of batteries with a flywheel, and the flywheel equipment does not require high ambient temperature, thereby saving a lot of air conditioning and refrigeration equipment and power consumption. The storage battery here is generally a lead-acid battery. As we all know, lead and sulfuric acid are the raw materials that pollute the environment. Now our government calls on battery manufacturers to recycle used batteries, but many batteries are difficult to transport in remote and high mountain areas and have to be discarded. In various places, it has caused serious pollution to the local environment.

Calculating from the above two aspects without batteries and large savings in air-conditioning equipment can save a lot of operating costs and CO2 emissions. It is a good product for green environmental protection and should be vigorously promoted.


(Wang Hongzao, Senior Engineer, Petroleum Exploration and Development Research Institute. He has long been engaged in electrical automation professional work and motor production and research work. He has worked on UPS technical work for more than 20 years and has published many articles. Now is the editorial board of this publication.)

Reporter: Mr. Wang, as an UPS industry expert, please talk about the problems faced by traditional UPS and the main working principle of magnetic levitation flywheel UPS.

Wang Hongzao: The application of UPS has been for decades, and the technological development of UPS is also great. But no matter how the UPS changes, generally do not leave the battery. Therefore, people think that a UPS without a battery cannot be called a UPS. In fact, this view is one-sided.

The current use of a large number of batteries in a UPS power supply system also brings some problems: the batteries cause pollution to the environment during the production process of manufacturing and regeneration. The battery is the weakest link in the UPS power supply system, and its failure rate is the highest. More than 70% of UPS system failures are caused by the battery. If it is light, it cannot be discharged, and when the battery is on fire, it will cause heavy losses. The cost of the battery system is high. There are two main points: First, the battery life is short, and the replacement cycle is short. Second, the battery is more demanding on the ambient temperature, resulting in high air-conditioning power consumption. In addition, the storage battery needs to occupy a large space.

Flywheel UPS is to get rid of the use of batteries, is a new type of UPS came into being. It uses a flywheel to store energy. When no utility power is available, the energy stored in the flywheel is released, converted into electrical energy, and the inverter is powered so that the inverter can continue to supply power for a period of time. This replaces the battery.

The core component of a flywheel UPS is a flywheel device. A flywheel can be understood as a motor/generator device. When there is commercial power, it is powered by the inverter to the electromagnetic coil, making it an electric motor, and the suspended flywheel rotates in vacuum at a high speed, reaching 7700 rpm. In the absence of utility power, it releases energy from a high-speed rotating flywheel and becomes a generator that powers the inverter. Thus the entire UPS continues to operate to supply power to the load to meet the requirements of an uninterruptible power supply.

At present, people have some doubts about the flywheel UPS. The flywheel powers the inverter, and the inverter continues to supply power. How long can it last? According to the full load calculation, it can supply 15s. Is this short enough for 15s? This depends on the power supply system. The power supply of a general UPS power supply system has at least two lines, and the backup one line may be another line power supply, or it may be a diesel generator set. If it is another way of power, automatic conversion with ATS, the conversion time is about 1s, the spare time of the flywheel is enough. If the standby is a diesel generator set, the input from the diesel generator start to the inverter tracking genlock does not exceed 12s, so the standby time of 15s is also sufficient. You don't have to worry too much.

The performance of magnetic suspension flywheel energy storage UPS is also more advanced. Its output voltage stability, overload capacity, input current harmonic content, input power factor and other indicators are also advanced, in addition, its efficiency and footprint and other indicators are also very good, can be called green power.

Magnetic levitation flywheel energy storage UPS can be operated in parallel, which is especially suitable for large-capacity system operation. There are many application cases in large-scale IT systems, industrial automation systems, and manufacturing industries. There will be a broad future for development in these areas. It is reported that at present, Google, Microsoft, Yahoo and other internationally renowned companies have adopted magnetic suspension flywheel energy storage UPS systems. It incorporates the latest magnetic levitation technology, power electronics technology, new material technology, and vacuum technology to further reduce operating energy losses. As a new type of electric energy storage method, its advantages and market potential compared with traditional batteries have attracted people's attention.

In today's UPS power supply system, the two-way power supply plus diesel generator power supply system and two-way UPS dual bus power supply system are commonly used. The use of flywheel UPS is more reliable and it will have wider applications.

(Zhang Zhenyi, Senior Engineer, Institute of Aerospace Science and Technology Group, 710. He has long been engaged in the research and technical work of diesel generator sets. He has a profound theoretical foundation and rich practical experience. He is currently a member of the AC Power Supply Professional Committee of the China Institute of Power Sources, editorial board of the publication. )

Reporter: Ms. Zhang, please further analyze the application fields, working methods and market prospects of flywheel UPS.

Zhang Zhenyi: Synchronous generators and motors (also translated as synchronous compensators in the translation of flywheel UPS technology) share a special rotor, which not only has the magnetoelectric function of the generator rotor and the motor rotor, but also has The function of the flywheel rotating at high speed. It can be called: rotor - flywheel. The integration of such a synchronous generator and a motor is a basic construction of a flywheel type UPS. The flywheel is of high quality, its shape and material make it have good magnetoelectric conversion performance. The faster it rotates, the greater the kinetic energy and inertia it gains and, therefore, the energy conversion core of a dynamic UPS.

When there is commercial power, the electrical energy is directly supplied to the load through the auxiliary circuit in the dynamic UPS and all the way to the synchronous generator/motor. The alternating magnetic field generated by the excitation winding of the motor drives the rotor—the flywheel rotates at high speed. In order to obtain the maximum kinetic energy, the rotation speed is usually 5,000 to 8,000 revolutions per minute. When the utility power is suddenly interrupted, the rotor-flywheel rotates in inertially based on the existing kinetic energy. Its magnetic field causes the armature windings of the synchronous generator to output electrical energy, and the uninterruptible power supply is provided by the use of electrical equipment through the auxiliary circuit.

However, after all, the kinetic energy of the rotor-flywheel reserve is limited. If the flywheel UPS alone is used for uninterrupted power supply, its standard kinetic energy buffering time (equivalent to the back-up support time of the static UPS) has a great relationship with the amount of load it carries. When the general load is 100%, the back-up time is 15s; at 75% load, the backup time is 20s; at 50% load, the backup time is 30s; at 25% load, the backup time is 56s. This is because the delay (backup) time is too short compared to an ordinary static UPS that uses a battery as an energy storage device.

Flywheel UPS relies on mechanical devices for energy storage and energy conversion, so its capacity cannot be made too small in terms of cost and market competitiveness. The common output power is around 200~1600kVA. This limits the scope of application of the flywheel UPS.

The advantages of flywheel UPS are particularly prominent in industries with large loads such as power, chemical, energy, and large data centers. It completely abandons large-capacity, large-capacity battery packs. It can not only save the area of ​​the engine room but also reduce the maintenance workload. It is also conducive to environmental protection and energy conservation. Although the flywheel UPS can only support 15s at 100% load. However, this time can already meet the requirements of modern diesel generators from starting to output voltage stability.

As for the market prospects of Flywheel UPS, I think that Flywheel UPS has a complete set of completeness, and adopts the industry's advanced mechatronics technology and intelligent control system. Compared with the market price of 500kVA flywheel UPS stand alone and time delay 15min 500kVA ordinary static UPS standalone; there is not much difference between the two. In the long run, the reliability, availability, and environmental benefits of flywheel UPS are the best choices. Therefore, in the high-power UPS market, the prospect of flywheel UPS is very clear.

Flywheel UPS is not new, it can even be the originator of static UPS. However, it has been re-expressed with a new look after it was combined with modern technology, providing fresh elements for the construction of high-end high-power uninterrupted power systems.

Reporter's Notes At present, all industrial powers in the world are vigorously carrying out research on energy storage flywheel technology, which has been applied and tested in a small amount. Although the current understanding and acceptance of Flywheel UPS technology and products requires a certain amount of time and process, we believe that by satisfying the needs of users and the promotion of various successful cases and the increasing awareness of Flywheel UPS, in the near future, magnetic suspension Flywheel energy storage UPS technology and products will be accepted and applied by users in various industries.