Through virtual power plants, the integration of distributed energy such as renewable energy, energy storage equipment, and backup power has become a new science in energy management. As the proportion of renewable energy gradually increases, to solve the problem of intermittent power supply, flow batteries that can store electricity for a long time have attracted much attention.
The Development Status of the Global Power Industry:
Global electricity production will increase by 63% from 2009 to 2030, and most of the energy growth will depend on renewable energy generation. Electric energy has become the secondary energy. However, the concept of early planning and design of the power system was to divide it vertically into generation, transmission, and distribution, each with its function and interconnectedness. This design method is mainly based on the construction of large-scale centralized power plants, high-voltage towers, and transmission lines. The primary energy such as oil and natural gas is converted into electric energy through the generator, and the voltage is increased through the power transformer. The electric energy is transmitted through the high-voltage transmission line, and then the voltage is reduced, and the distribution system is responsible for transmitting the electric energy to the user. The transmission process will consume a lot of energy. Taking the input of 100 units of energy as an example, the power generation energy loss of the power plant is about 70%, and the energy is continuously lost during the transmission and distribution process. Only 9.5 units of energy can be obtained, is the efficiency low and the impact on the environment is great.
The traditional large-scale centralized power plant planning must pay attention to high efficiency and energy saving nowadays. On the other hand, using distributed energy resources can supply load demand nearby, improve energy efficiency and reduce pollution. The problem of global warming has become more and more serious in recent years, and the main factor aggravating global warming is the doubling of carbon dioxide content in the atmosphere. Forcing all countries in the world to face up to the extreme climate caused by global warming and the natural and man-made disasters caused by it. Relevant international organizations and advanced countries have devoted themselves to developing various feasible improvement plans and countermeasures, which are listed as priorities for the country's future development, to reduce or eliminate the disasters caused by extreme climates.
What is a Decentralized Energy System?
The decentralized energy system is relative to the traditional centralized energy supply system. The traditional centralized energy supply system adopts large-capacity equipment and centralized production. All kinds of energy are delivered to many users in a large range. While the decentralized energy system is directly facing users, producing, and supplying energy locally according to the needs of users, with multiple functions, and can meet multiple goals. Small and medium-sized energy conversion and utilization systems.
What are the Characteristics of a Decentralized Energy System?
- As a local energy supply center, it directly faces the needs of local users and is arranged near the users, which can simplify the transmission link of the system to provide users' energy, thereby reducing the energy loss and transmission cost in the energy transmission process, while increasing the user's energy.
- Because it does not adopt the model of large-scale and long-distance output energy, but mainly targets the energy needs of local users. The scale of the system will be restricted by the needs of users. Compared with the current traditional centralized energy supply system, both are medium and small capacities.
- With the development of the economy and technology, especially the active promotion and application of renewable energy, the energy demand of users have begun to diversify; at the same time, with the development and maturity of different energy technologies, the available technologies are also increasing. As an open energy system, the decentralized energy system begins to show a multi-functional trend, which not only contains multiple energy inputs but also can meet the various energy needs of users at the same time.
- People's concepts are constantly changing, and new requirements (high efficiency, reliability, economy, environmental protection, sustainable development, etc.) Are constantly being put forward to the energy system. The new type of decentralized energy system can be optimized by selecting appropriate technologies and optimizing the system. Better meet these requirements simultaneously and achieve multiple functional goals.
What are the Advantages and Disadvantages of a Decentralized Energy System?
- Advantages of Decentralized Energy Systems:
The advantage of a decentralized energy system is its use in combined cooling, heating, and power. Co-generation conforms to the cascade utilization criterion of the total energy system and will obtain a good energy utilization rate and has a great development prospect. Although large-scale (thermal) power plants can transmit electricity over long distances, they need to build power grids, substations, and distribution stations and have transmission losses, while heat, especially cold, cannot be efficiently transmitted over long distances like electricity. Therefore, unless it is specially designed and arranged in advance, it is difficult to achieve the purpose of conveying cold and heat energy. Because the site selection of large power plants has its requirements, it is difficult to have a large enough number of suitable cold and heat energy users nearby, and it is impossible to carry out effective co-generation. The distributed energy system is just the opposite. It can be set up nearby as needed and can cooperate with users as well as possible. There is no problem with the long-distance transmission of cold and heat energy, and the problem of power transmission loss in large power grids does not exist. Therefore, although the pure power device of the decentralized energy system itself has low efficiency and high price, it can give full play to the advantages of its co-generation and reflect its advantages.
The decentralized energy system can also allow the user to have a greater ability to adjust, control, and ensure that the various secondary energy of the user can be fully supplied. Which is very suitable for developing areas and commercial and residential areas, villages, pastoral areas, and Mountainous areas provide electricity, heating, and cooling, which greatly reduces the pressure on environmental protection. In a word, the decentralized energy system can meet the needs of special occasions, provide the possibility for the comprehensive cascade utilization of energy, open a new direction for the utilization of renewable energy, and can improve energy utilization, improve safety, and solve environmental pollution made outstanding contributions.
- Disadvantages of Decentralized Energy Systems:
The disadvantage of the decentralized energy system is that, because it is a decentralized energy supply, the single-unit power is small. Compared with the single-unit power of the largest power plant, which is more than 1 million kilowatts, the single-plant power is nearly 10 million kilowatts. The power generation efficiency is not as good as the latter. This is because the existing power equipment is the larger the unit, the higher the efficiency. The efficiency of a 400,000-kilowatt gas turbine-based combined loop device is twice that of a 40-kW regenerative gas turbine. The price of unit power of large units is much lower than that of small units, the difference is nearly several times. The large units are concentrated together, and there are specialized senior technicians for operation and maintenance, the safety and working life should be guaranteed. Therefore, to compare the pure power generation cost and the initial investment per kilowatt, the investment in the decentralized energy system must be much higher than the current large power system. In addition, the technical requirements of the decentralized energy system for the local users are higher than that of simply using the large power grid for power supply, and corresponding technical personnel and a suitable cultural environment are required.
Decentralized Energy Application Trends:
Distributed energy applications are the main direction, including renewable energy and low-polluting non-renewable energy distributed generation systems and energy storage devices. Such as biomass power generation, ocean current power generation, hydropower generation, solar power, wind power generation, fuel cells, micro-turbine generators, etc. Both are used as the source of electric energy and cooperate with the structure of coexistence of traditional power networks and micro-grid. To provide cleaner electric energy and improve the energy efficiency of the power system, to slow down the global warming phenomenon.
In the past, the centralized power distribution system responded to the demand by building more and larger large-scale centralized power plants. Therefore, an increasingly large power transmission and distribution network was required, and more and more power were passed over a longer and longer period. Distance and increasingly complex transmission and distribution systems are distributed to consumers who consume more and more power, which will lead to intermediate transmission and distribution losses, with a loss rate of about 9%.
However, the concept of decentralized energy is just the opposite. The way it responds to demand is to improve energy efficiency on the one hand so that the end demand is directly reduced. On the one hand, distributed power generation is used to supply power, and on the consumer side, such as On-Site power generation methods, including rooftop solar cells, thermoelectric symbiosis, etc., directly offset the demand. The community uses its microgrid, energy storage devices, and smart grid software to respond to demand, allocate electricity demand within the microgrid, and only draw electricity from the grid when it is insufficient. In this way, most of the balance of supply and demand does not need to go through the transmission and distribution network, so it will not burden the transmission and distribution network, and it can save a lot of costs for the expansion and maintenance of the transmission and distribution network, and avoid the loss of the transmission and distribution process.
In addition to large power plants, it includes solar energy, wind power, energy storage equipment, backup generators, UPS systems, and electric vehicles scattered in enterprises, factories, and homes. With the ever-increasing challenges of supplying electricity, there will be a need for greater flexibility in the use of these power resources in the future. The concept of a virtual power plant came into being, which is to aggregate decentralized small and medium-sized resources into a reliable source of power supply, just like a controllable power plant. Taiwan's microgrid and advanced meter reading standard formulation and construction, microgrid exhibition area (solar photovoltaic, biomass energy, wind power), revision of laws and regulations related to electricity liberalization, green industrial parks, etc. To assist in the establishment of high-quality, high-efficiency projects, and an environmentally friendly power network system to achieve the vision of improving energy security, improving temperature emissions, and creating an energy industry.
User-Agents Play a Key Role:
When the traditional centralized power system dominated by large-scale units moves to a decentralized power system, it was originally a consumer of electricity and turned into a producer and seller of electricity supply. Because of the participation of various types of users, virtual power plants have greater dispatch flexibility, can provide peak load power in a short period, and can also provide auxiliary services for power companies.
Compared with Tai power’s control of large power plants in the past, only one command is required. When many small resources are assembled, how to manage them effectively becomes the key. The aggregator must aggregate user resources, and agents will be new business opportunities in the future. There are many different mechanisms for virtual power plants, and different companies have different operating strategies. At present, there are many successful cases of virtual power plants in the world.
A Virtual Power Plant Must Meet Five Conditions to Take Advantage of it:
- ICT infrastructure: To allow agents to grasp the status of each participant, it is necessary to import ICT applications such as smart meters so that they can grasp the data in real-time.
- Prediction: The agent needs to understand the power system status, make load prediction, let the participants know the electricity consumption trend in the next few days in advance so that the user can be psychologically prepared, improve the user's willingness to participate, and will not suddenly receive a disconnection notice, caught off guard.
- Create a customized solution: According to the characteristics of different participants, customize the power supply status, not the rules applicable to everyone, or even adjust the user's production behavior. Asking to reduce electricity usage during peak hours may be able to discuss changes to production schedules with the factory.
- Understanding of the market: The agent needs to be keen on the market, subdivide into different groups according to user attributes, and participate in different plans in the market. To participate in the electricity market in the future, the agent must obtain the qualification of Qualified Scheduling Entity (QSE), which means that the agent has a basic understanding of the market.
- Decision-making technology: How to arrange the most appropriate method to reduce the cost of participants and obtain relatively high returns in the electricity market. It is necessary to prepare in advance. When an accident occurs during execution, how to activate the emergency mechanism depends on precise scheduling decisions.
Flow Batteries Have Energy Storage Advantages:
In the decentralized energy system, renewable energy and energy storage equipment are not only an important part of it, but they are highly related. With the gradual increase in the proportion of renewable energy, in the face of intermittent characteristics, more long-term energy storage equipment is required to supply green electricity 24 hours a day, and flow batteries with higher safety and longer energy storage time have begun to attract attention.
A flow battery is a battery with liquid flowing in it. It contains two large electrolyte tanks, which contain active substances that can store electricity. The electrolyte is transported to the central element by pipelines, which is a stack. When charging and discharging are required, the liquid is pumped to the stack to generate electron transfer to discharge or store electricity.
Depending on the type of battery, flow batteries can be composed of different metal elements. At present, the most mature is the flow battery system using vanadium ions. Compared with traditional lithium batteries, flow batteries have more advantages. Flow batteries belong to long-distance runners, and their potential is suitable for continuous long-term discharge and storage. Therefore, flow batteries are particularly suitable for long-term energy storage. In the face of intermittent renewable energy, they can safely and stably store green electricity and play an important role in regulation.
- Safety: The first safety consideration is the selection of batteries. The water solution is highly safe, and there is no risk of explosion and spontaneous combustion.
- The design is more flexible: Since the energy is stored in the liquid, the larger the tank, the more energy it can provide. According to different application scenarios, the tank and electrolyte are added, and the stored energy and time can be more and longer.
- Long service life: Deep charge and discharge cycles can exceed 20,000 times, with no problem for at least 20 years, and the average energy storage cost is amortized, which is more cost-effective than lithium batteries for long-term storage.
- Active substances: Active substances are easy to recover in the liquid, and even after the battery is used for a long time, the valuable metals in it will not be consumed.
Active application into the industry:
In the future, it is hoped that it will reach a level of 50% self-sufficiency in electricity. The energy storage system can adjust peak loads, support power consumption at night, and even serve as emergency backup power during power outages. In response to the future trend of trams, we started to build a fully green energy station that uses 100% renewable energy to provide the gas station itself and the electric scooter charging and swapping needs. The energy storage system uses vanadium liquid flow with higher safety. Battery electric power users with a certain contracted capacity or above should set up management measures for renewable energy power generation equipment. It is regulated that users with a contracted capacity of more than 5,000kW must set up renewable energy with 10% of the contracted capacity within 5 years. Flow batteries are suitable for promotion in industrial areas and residential buildings.
In addition to the domestic industrialization progress, there are international battery material companies that have entrusted the Industrial Technology Research Institute to carry out testing work, showing that the technology has been recognized internationally. ITRI is also actively transferring technology to Taiwanese battery and energy storage companies. By supporting Taiwan's potential manufacturers, this technology can achieve 100% MIT for stacks. With the development of decentralized energy and renewable energy, ITRI continues to help Taiwan embrace the new era of energy with its solid technical capabilities.