Читать книгу Smart Charging Solutions for Hybrid and Electric Vehicles - Группа авторов - Страница 21

The global energy system is characterized by the interconnected electricity grid which comprises of generation, transmission, and distribution systems, as well as the utilization of renewable energy sources. The price of electricity varies for regions around the world. Each country tries to ensure energy security by planning generations within the boundary. In most cases, renewables come to the rescue because recent advancements in local energy storage systems have not increased energy security. EVs are also considered as mobile/local energy storage due to the capacity of batteries used to power the drivetrain. Hence, an increase in the number of EVs in a country has achievable implications to impact the global energy system.

The direction of the flow of power plays a significant role in determining the impact of smart charging. In the case of charging, two types of viz., unidirectional and bidirectional, are described in the literature. In the case of unidirectional, there is a controlled power flow from the utility grid to the EVs to charge, while in bidirectional the power flow is exchanged between EVs and the utility grid [3, 5, 23, 24, 28-31]. When the grid is in peak load hours, controlled power flow from EVs to the utility grid meets the surplus demand and while during off-peak hours, the EVs charge using surplus power in the grid. Note that the charging process is spread out over the day and mostly controlled using algorithms. Of the two, the bidirectional flow of power is found to be better in reducing the impact of uncoordinated charging. A study by the International Renewable Energy Agency (IRENA) states that, in the short term, bidirectional smart charging is able to reduce more curtailment when compared to unidirectional smart charging [32].

Further, CO₂ emissions are also reduced more in the bidirectional case, compared to the unidirectional. The long-term analysis by IRENA is done considering renewables’ integration, which includes solar and wind-based isolated systems. For the long-term, a reduction in CO₂ is noticeable in bidirectional viz. when power renewables augment power production as compared to unidirectional. Hence, smart charging promotes the integration of renewables [27, 32].

The impact of smart charging is not limited to supporting the integration renewables, it also helps reduce stress on various equipment in the utility grid’s infrastructure. The impact is widely discussed in the subsequent subsections.