Importance of Electric Vehicle charging
The anxiety of driving range has been the greatest barrier of wide EV adoption. Thus the convenient access of charging facilities and fast charging technology are essential for success of EVs. Residential are unlikely to purchase EVs until there are sufficient charging facilities on the road. On the other hand, commercial investor will build charging facilities only when there are enough charging demand, i.e., EVs on the road. In this case, both consumers and investors are waiting for the movement of each other. Studies indicate that a positive feedback exists during the initial adoption stage when EV sales and EV charging services exceed a certain threshold; the market share of both EVs and EV charging services will likely grow at a substantially higher rate henceforth.This result justifies that the government needs to spend efforts to establish charging facility network at the launch time of EVs.
The United States, by 2016, has built about 12,700 charging stations with about 31,800 charging outlets, thanks to the direct and indirect investments of federal and local governments. For example, the Department of Energy (DoE) provided $230 million dollars from 2013 to establish 13,000 charging stations. There are also private initiatives in establishing networks of charging facilities. For example, PG&E announced in 2015 a plan to install 25,000 charging stations. Kroger, the largest grocery store owner of the U.S. has installed over 300 charging stations in key markets over the country. Walmart and Kohl’s also expanded their charging stations.
Sufficient development of EV charging not only helps the successful launch of electric vehicles, but also is believed as a promising solution to the pollution and an essential component of the future smart grid.
The growth in energy demand and greenhouse gas emissions is mainly due to car ownership and economic development. In 2014, 26% of the total greenhouse gas emissions in the USA came from the transportation, which have increased by 17% since 1990. The majority of greenhouse gas emission from transportation are CO2 emissions, which is due to the combustion of fossil energy in vehicles. The prevailing conjecture is that the electrified transportation with “clean” power generators such as wind turbines or solar panels is an efficient way to reduce this emission. The well managed charging of EV can be helpful to improve the shape of the overall demand, allow the power utilities to operate more efficiently, and maximally make use of the renewable energy. For example, the peak output of wind generators usually happens in the evening when the load is low. Without EVs, the output of wind generators is limited to maintain the stability of the system. However, large scale adoption of EVs makes it possible to fully use the wind energy to charge EVs during the night without any emission. In, it has been shown that, EV charging during the off-peak period will contribute to the adoption of renewable energy and largely reduce the emission of CO2 .
Besides the environmental benefits, the adoption of EVs can also provide potential services back to the power grid. Vehicle to grid (V2G) services typically include spinning reserves, frequency regulation and peak power supply.
Spinning reserves and frequency regulations are referred as ancillary services, which account for up to 10% of electricity cost, or about $12 billion per year in the U.S.
Spinning reserves refer to additional generating capacity that can quickly response to the requirements of the independent system operator (ISO), typically within 10 minutes. When there is an unplanned event, such as loss of generation, the spinning reserve providers are required to supply power back to the grid. Spinning reserves are paid for by the amount of time the service providers are available. Traditionally, it requires generators to be “spinning” at low or partial speed so that they can act upon the request. For the charging services, however, this only requires having EVs plugged in to the system.
When the spinning reserve is required, the EV charging station stops charging EVs or discharges the battery to power the system or simply . The requirements of spinning reserves are called occasionally, limited by the contract to 20 calls per year and 1 hour per call at maximum, which requires small amount of energy and makes it suitable for EV charging to participate in. Frequency regulation accounts for over 80% of the cost of ancillary services.
ISOs monitor the load, generation balance, and the frequency deviation of the grid and send out signals to service providers to follow. For example, when the power load is less than the generation and the frequency of the grid increases, ISOs will ask the charging stations, who participate in the regulation market, to consume more power. When the generation is less than the demand, ISO will ask the participants to consume less. The calls for regulation happen more frequently than those to spinning reserve (400 time a day) and require much faster response (less than one minute). The payment is measured based on how fast the response is and how well the demand of the charging station tracks the regulation signal sent by ISO. The frequency regulation market is also suitable for EV charging to participant in. The action of EV charging station is agile due to the fast response of batteries.
The peak power market is established to deal with times of high power consumption, e.g., hot summer afternoons. Since the peak power time during one year lasts about a few hundred hours, it is economic to use some generators with small capacity cost, even with higher marginal cost, such as gas turbines. For EV charging stations, charging EVs during off peak hours and selling energy back to the grid during the peak hour may increase profit.
Given the possibility of the V2G service of EVs, social planners have more motivation to help the successful launch of EVs. Simply by allowing the EV charging stations to participate in the ancillary service and peak power markets, the social planner will help the grid to be cleaner, more reliable, and more efficient. Meanwhile, the option to participate in the power market may attract more investment in charging facilities. The charging cost would be lower not only due to the competition between charging stations, but also due to the extra income from the V2G services. The EV consumers enjoy the cheaper operation cost of EVs and other consumers have cleaner energy. Everyone wins.