The charging problem of smart energy interaction with vehicle networks

First, ultra-fast charging problems

At the moment, charging is not as fast as refueling. During the eleventh long holiday, many users complained that electric vehicles had become "electric daddies". In fact, the high-power power battery can be charged as fast as refueling, but its specific energy is low and cannot meet the requirements of long endurance. Now there are more and more long-lasting electric vehicles, equipped with energy-based power batteries that emphasize high specific energy, and it is not easy to charge super fast.

For example, 350 kilowatts of ultra-fast charging, 5 minutes of charging close to 30 kWh of electricity, there are many problems to be solved: the charging rate is too large, the battery can not stand; the charging current is too large, the car can not stand; the charging power is too large, the power grid can not stand. To this end, the battery itself must have a fast charging capacity, that is, a relatively high peak charging rate. The voltage of the on-board electrical system should be increased to 800 volts in order to reduce the total charging current when charging at superpower. It is best to use energy storage batteries to discharge to achieve a high power of 350 kilowatts to reduce the load on the grid, so as to facilitate ultra-fast charging.

The most difficult thing in this is the power battery itself to play the potential of fast charging. The charging process is most prone to safety accidents, mainly because of the internal short circuit caused by lithium dendrite caused by fast charging. To this end, in addition to the need to develop lithium-free fast charging technology, but also to choose ultra-fast charging range and amplitude, the study shows that the more appropriate is to charge 1/3 of the power in less than half of the power, 5 minutes, rather than full, full will encounter safety, life, heat and many other problems, more than worth the loss.

Ultra-fast charging should be mainly used in highway emergency power replenishment. For example, a car that has an endurance of 500 or 600 kilometers now has 1/3 of the power charged in 5 minutes and is 200 kilometers, which is more scientific and reasonable. In addition, consider the full climate, heating in winter and dissipating heat in summer. Therefore, it must also be equipped with rapid heating and rapid cooling. Rapid heating can now be achieved with a maximum heating of 7 to nearly 8 degrees Celsius per minute. In the summer, the forced cooling power should also be increased. The Tsinghua team has developed ultrafast technology that meets the above requirements, and in cooperation with Shell, several ultrafast charging demonstration stations have been built at gas stations for test assessment. The super fast charging standard developed by the China Electricity Federation has begun to solicit public comments.

Super fast charging based on energy storage battery discharge, where does its energy storage battery come from? First, the charging station with direct energy storage, but the cost is high. The second is to combine with the power exchange. Because the battery swap itself has a lot of battery backup, it can be used as an energy storage battery. The trend of rapid power replacement of commercial vehicles has been very obvious, the Ministry of Industry and Information Technology has been in the country to carry out power replacement pilots, in general, the current high attendance rate, heavy loads, short-distance transportation of trucks to change electricity is the hottest, such as mining areas, construction sites, steel plants, ports, etc., this is the first to be carried out, the future gradually expanded to cities and highways.

The combination of fast charging and fast power exchange, fast charging of trucks and fast charging of cars, and fast charging of backup batteries for cars will be a solution for sharing complementary advantages and resources. Moreover, the use of this fast charging and fast changing station is very close to the habits and frequency and location of the original fuel vehicle refueling. Large energy companies are very suitable for building fast charging and fast change coupling stations at gas stations. At the same time, the battery replacement is leased, and the energy company opens a battery bank. For large energy companies, this is also a very good direction for transformation. Today's charging companies will face new competitive pressures.

Second, slow charging interacts with the car network

According to statistics, 75% of the current household electric vehicle charging capacity is obtained through slow charging. With the rapid increase in the number of electric vehicles, slow charging will put a lot of pressure on the power load. Beijing now has 400,000 electric vehicles, and the frequency of use is much higher than that of fuel vehicles, and at least 20% of the daily bus flow is electric vehicles, and it will soon reach 30% and 40%. Charge when you go home from work, the power system can't stand it, and this problem has appeared in Shenzhen and other places. Therefore, the era of disordered charging is coming to an end, after which it will enter the orderly charging stage, there is a background to manage charging, and the charging will be adjusted to the trough range of power load through the electricity price mechanism. Now Shenzhen has begun to do demonstrations.

The information network that manages charging will intelligently dispatch the charging energy of the power grid, and the prototype of the energy Internet will appear, which is a big thing. Orderly charging or one-way energy flow, control when to charge. Further development is a two-way street, electric vehicle batteries will both charge and discharge. For example, electric vehicles are connected to buildings or houses to form an energy system, and electric vehicles can power buildings as energy storage devices. With the transformation to renewable energy, wind power photovoltaic power generation fluctuates greatly, when there is more electricity, first store and store a part, and then release when there is no electricity, the role of energy storage will be very large, the price difference between electricity will become larger and larger, and the value of electric vehicles as energy storage devices will be played out.

If the battery capacity of electric vehicles exceeds 2 billion kWh in 2025, there will be 300 million electric vehicles in 2040, and the average electricity of a vehicle is 65 kWh, which is almost 20 billion kWh of electricity, which is the total electricity consumed by the whole society in the mainland today. This huge energy storage system will generate huge carbon emission reduction potential, and the initial calculation can be as high as 1 billion to 2 billion tons, which is a very large amount, and it also needs to be confirmed by carbon emission calculation experts.

In short, the potential of electric vehicle energy storage is great, and it will be a huge blue ocean market. Now, all levels of government are reducing carbon emissions towards the dual carbon target. One of the most important ways is based on the intelligent energy of electric vehicles, including photovoltaics, power batteries, charging and discharging devices, household appliances connected into a network, a community, a unit, a community can form a microgrid, an administrative district has many microgrids connected to become a regional grid. Finally, the smart energy of the entire city is formed, which becomes an important part of the green smart city.

How can this ideal result be achieved if electric vehicles are decentralized, mobile, randomly used, and charging devices are not everywhere? First of all, slow charging facilities should be widely popularized. The future plan for slow charging is to have at least one charging pile per vehicle, preferably two, one for work and one for home. In the end, the ideal state is that the car is connected to the power grid when it stops, so as to form the realization of the interactive functions of energy storage and power grid.

The battery energy storage with electric vehicles as the core and the intelligent energy system integrating light, storage and charging will soon be gradually launched across the country. It is estimated that it will be mainly orderly charging before 2025, and from 2025 to 2030, it will develop interaction with buildings and microgrids. After 2030, there will be interaction with the distribution network. From the perspective of system classification, the bottom layer is the charging and discharging hardware facilities, the middle layer is a large number of electric vehicle energy storage and microgrid aggregators, and the upper layer is the dispatch management platform for government intervention, with district-level, city-level, provincial-level and national-level state grid general dispatching.

The power system with renewable energy as the main body will be characterized by distributed and market-oriented. The basic policy of the national electric power reform is to open up the two ends, control the middle, that is, only manage the power grid, open up the user end and the power generation end, and build a unified national electricity market. Electric vehicle charging and discharging will also be a market, charging, discharging is the same as the purchase and sale of stocks, low electricity prices will be charged, high electricity prices will be sold. Achieving automatic regulation and balance of renewable energy sources such as volatile wind power and photovoltaics through economic incentives is a beautiful vision of the future green smart city.

This article comes from the charging pile horizon