Shulou(Shulou.com)11/24 Report--

As a kind of secondary energy, electric power has only one obvious disadvantage-it is difficult to store, which is the reason for the emergence of peak-valley electricity price. It is difficult for power stations to adjust their output power according to people's electricity habits, and reducing electricity prices at night to encourage the use of electricity can ensure the stability of the power grid. Coupled with the instability of photovoltaic and wind power generation, today's power grid has an increasing demand for energy storage.

People try to store electricity in various ways, such as the Hebei Fengning pumped storage power station built last year. It has two reservoirs, the upper reservoir has a capacity of 58 million cubic meters and the lower reservoir has a capacity of 60.7 million cubic meters, with a drop of 425m. It can pump water from the lower reservoir to the upper reservoir when the power consumption is low, and discharge water from the upper reservoir to the lower reservoir to generate electricity at the peak of power consumption. It can be said that a pumped storage power station is literally a "battery"-a large pool for storing electric energy. However, this technology has very strict requirements on the terrain, and pumped storage power stations cannot be built in many places. Now, a new network of electric energy storage is emerging around us.

Batteries around now, there are more and more electric cars on the road, which are becoming more and more popular because of the advantages of no refueling, simple maintenance and policy subsidies. Compared with traditional fuel vehicles, the biggest advantage (or the biggest difference) of electric vehicles is that they use batteries to store energy. It seems that overnight, people have a good place to store electricity. According to the 2020 data, the per capita electricity consumption in China is about 73 kilowatt hours per month, while the battery capacity of pure electric vehicles is generally more than 50 kilowatt hours, which can fully meet the energy storage needs of ordinary families.

In fact, as early as 1997, someone envisioned the possibility of using cars to power the grid. At that time, Dr. Willett Kempton of the University of Delaware and Steve Letendre, an economist at Green MountainCollege College, imagined the prospect of integrating electric vehicle batteries into the grid itself in Transport Research D: transport and Environment (transportation research part d:transport and environment).

At that time, electric vehicles were not as popular as they are today, and most of them were distributed in public utilities such as buses and taxis. They simulated the situation at that time and analyzed the benefits of using electric vehicles as part of the energy storage of the grid. It turns out that the total cost of the traditional charging mode to accomplish the same task is $2370, which can be reduced to $955 if the electric vehicle is used as part of the energy storage on the grid. The two authors of the study, along with Timothy Lipman of the University of California, Berkeley and Alec Brooks of AC Propulsion, laid the groundwork for vehicle-to-grid (V2G) vehicle-to-grid technology, which supplies power from vehicles to the grid.

Pilot cities and now, in the Dutch city of Utrecht, someone is bringing this technology to life.

Utrecht is located about 30 kilometers south of the Dutch capital Amsterdam, with a population of about 350000. The main mode of transportation is bicycles. The wave of car electrification has not been missed here, and now the streets of Utrecht are full of charging piles, of which about 800 are different from ordinary charging piles, which can be charged in both directions. The key to the realization of two-way charging is a special inverter, which can convert the direct current used by the electric vehicle into alternating current acceptable to the power grid, and can also charge the electric vehicle like the general electric vehicle charger. The inverter is about the size of a bread basket and can be installed in a charging pile or modified on an electric vehicle.

The technology has matured, but there is an important question to consider if you want to promote it-what benefits can it bring to car owners? This technology facilitates energy storage on the grid, but at the cost of frequent charging and discharging of electric vehicles, which accelerates the aging of power batteries. If it does not bring enough benefits to car owners, there is no reason for them to risk the health of tram batteries to accept this technology.

The answer is peak-valley electricity price. Electric vehicles can sell electricity at high prices when electricity is tight during the day and charge at low prices at night when there is a surplus of electricity, thus earning a price difference. In the past, the cost of the battery was too high to offset the loss of the battery due to the difference in peak-valley price. However, the situation has changed somewhat "naturally". With the rapid popularity of electric vehicles, the production of power batteries is also climbing rapidly, followed by economies of scale that have greatly reduced production costs. Last year, Heta Gandhi and Andrew White of the University of Rochester modeled and studied the economic effects of V2G technology in ACS Sustainable Chemistry and Engineering (ACS Sustainable Chemistry& Engineering). They found that the cost of power batteries for electric vehicles had fallen from $1000 per kilowatt-hour in 2010 to $140per kilowatt-hour in 2020, and the additional economic cost of battery depletion was already low.

V2G technology can also alleviate the installation problem of electric vehicle charging pile itself to some extent. After the power plant generates electricity, it will be transmitted by high-voltage power lines, but it is impossible for ordinary families to connect directly to the high-voltage power grid, and the power also needs to be reduced by medium-voltage transformers and low-voltage transformers, and then connected to thousands of households through the distribution network. The power of electric vehicle charging piles far exceeds the electricity consumption of most households, and if there are too many electric vehicles in a station area (which is powered by a transformer), they are likely to overload the transformer at the same time. The two-way charging pile can relieve this pressure. The municipal government of Utrecht places two-way charging piles in every corner of the city on demand based on population, household, vehicle and power grid configuration data, and this arrangement can increase the total number of charging piles without making significant changes to the municipal power system, so that more people can install their own charging piles.

Robin Berg, a Dutchman, is thinking about bigger plans, starting a company called We Drive Solar in Utrecht in 2016 to start a "car-sharing" business. His fleet uses 225 electric vehicles of various brands, 27 of which can be charged in both directions, and he already plans to retrofit an additional 150 electric vehicles with two-way charging. There are a total of 8 million cars in the Netherlands, and he envisions that if 1.5 million of them have two-way charging, that would be enough to store energy for the entire Dutch grid and ensure that the Dutch energy supply is completely shifted to less stable renewable energy.

The emerging technology is not unique to the Netherlands. Other European countries, the United States, Japan and South Korea are experimenting with V2G technology, and China is no exception. At the regular policy briefing of the State Council on November 3, 2020, Vice Minister of Industry and Information Technology Xin Guobin said that he would encourage places with conditions to explore and carry out V2G application demonstration. On April 29, 2021, the first practical demonstration zone of intelligent fusion terminal of State Grid Co., Ltd. passed the on-site acceptance of the State Grid equipment Department, and was officially completed and put into operation in Meishan area of Ningbo City, Zhejiang Province. Residents can park the new energy vehicle at the charging station to recharge, and submit the parking time and the remaining power needed to pick up the car in advance on App. If the parking time is right, the car can be fully charged not only free of money, but even make money. Compared with foreign countries, the situation at home is more intuitive. According to the State Grid News, a car owner recharged at a charging station and even earned 6.25 yuan when the car was fully charged 10 hours later due to the "low buying and high selling" of peak and valley electricity prices.

V2G technology can also improve the disaster resistance of the power grid. When the power was cut off in some urban areas after the rainstorm in Zhengzhou last year, some owners of new energy vehicles used the function of external discharge to charge their neighbors' mobile phones, and the new energy vehicles were directly transformed into a large account "portable battery". In places where the construction of the power grid is not perfect, or when there are sudden major natural disasters, each new energy vehicle is an emergency power supply, which can ensure the basic power supply.

So, do you like electric cars that can make money instead of money?

Reference link:

Http://www.escn.com.cn/news/show-1213409.html

Http://www.escn.com.cn/news/show-1123582.html

Https://news.sina.cn/2021-07-24/detail-ikqcfnca8783097.d.html

Https://spectrum.ieee.org/vehicle-to-grid

Https://pubs.acs.org/doi/abs/10.1021/acssuschemeng.1c05490

Https://www.sciencedirect.com/science/article/abs/pii/S1361920997000011?via%3Dihub

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by: Wang Yu revision: clefable

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