The electrification of means of transport, known as electro mobility (or e-mobility), has been consolidated worldwide as an important tool to reduce greenhouse gas emissions and combat global warming.
According to the International Energy Agency (IEA), in 2018, the number of electric vehicles exceeded the mark of 5 million units. According to automobile industry forecasts, their prices are expected to become equivalent to that of combustion vehicles by 2025, which may lead electric vehicles to represent 30% of the world fleet by 2030.
This advancement in electro mobility should further boost the growth in demand for electricity, which has already been increasing in recent years. This may pose a challenge for electrical systems in the near future.
This growth in demand can be met by the expanding distributed energy generation, such as solar or wind energy, which is also advancing worldwide. However, the distributed generation using sources of solar and wind energy has an intermittent nature, that is, it depends heavily on environmental conditions (solar radiation and wind, respectively), which should require some control by the operators of the electrical grid.
For example, in an electrical system in which a large part of the energy is solar origin, the net load of the electrical grid (that is, the difference between the energy demanded from the grid by the loads and the energy generated for the grid by the solar panels) will be considerably lower in the period of greater solar ray incidence, generating a possible excess of energy. On the other hand, at the end of the day, when there is little solar incidence, the net load will have a big increase, due to the reduction in solar generation, which can generate a peak load.
This phenomenon of variation in the grid load was identified by the California Independent System Operator and named “duck-curve” due to the shape of the system’s load curve, as illustrated in the image below. This variation in the grid load poses challenges for the operation of the electrical system, which must act on the system (increasing or reducing electricity generation from other sources) to guarantee the balance of the energy generated and consumed.
Source: California ISO
It is worth noting, however, that this action to control the electrical system varies, depending on the type of energy source. For example, it is not possible to simply turn off some types of energy sources (such as nuclear), even if its energy is not needed at any given time. The resumption of the charge, after a shutdown or reduction of generation, also has its own characteristics for different types of energy sources.
Thus, an alternative to solve this problem would be to store energy from solar panels (or wind generators) during periods of higher production, so that the energy can be used later, when energy generation is down. Mechanisms exist to carry out this energy storage, such as battery banks, but this would entail additional investments in infrastructure.
In this context, a new concept known as Vehicle-to-Grid (V2G) may allow the use of this growing fleet of electric vehicles to store energy from the electric grid. This could help operators of electrical systems to manage the increase in intermittent energy sources (such as solar and wind), while also guaranteeing flexibility and stability to the grid.
How V2G Technology Works
The basic idea of V2G is to use the battery bank of an electric vehicle (EV) as a storage unit for the grid. In this scenario, a smart charging system could prioritize the recharging of batteries during periods of excess power generation (for example, in periods when there is a lot of energy generation from solar sources) and, later, use part of the stored charge to supply the grid in periods of excess demand.
EVs are connected to the grid through a Charge Station (or CS) that has one (or more) Electric Vehicle Supply Equipment (or EVSE). The control of recharges is done by a central system, the Charging Station Management System (or CSMS).
The communication between these elements is done through protocols such as ISO15118, which allows EVs to communicate with the Charging Station, and OCPP (Open Charge Point Protocol), which allows the CSMS to communicate with the Charging Stations. For more information, see our article Electric mobility and standardization of recharge systems.
In a V2G solution, the energy flow between the vehicle and the Charging Station must go both ways, so that the vehicle’s batteries can receive or supply power. For that, it is necessary that all the elements involved in this process (CSMS, EVSE, EV), as well as the communication protocols, offer support for this energy flow control. Manufacturers of electric vehicles and Charging Stations have already started adding support for V2G to their equipment. The latest versions of the communication protocols (such as OCPP and ISO15118) also already support V2G.
A V2G solution requires an intelligent control system, which performs the recharge and discharge operations of the EV in a way that is appropriate both to the needs of the grid and to the requirements of the drivers. These systems can use technologies such as machine learning to profile users, predict energy demand on the grid and to recommend charging strategies that meet these characteristics.
Projects related to V2G
In the end of 2019, Dominion Energy, an energy utility company in the southern United States, announced a program to bring electricity to the fleet of 1,050 school buses serving the Virginia region. The initiative will have direct benefits for society, such as improving air quality (by reducing carbon emissions) and reducing operating and maintenance costs with school transport.
Dominion Energy also aims to use the batteries of the bus fleet to store energy and inject it into the grid during periods of high demand, when buses are not used for transportation. The project can be considered a major pilot for V2G technology and it will help the company increase the use of solar and wind energy sources in its network, without compromising its stability.
In Brazil, due to regulation limitations in the sector, it is not yet possible to apply V2G technology to practical cases, but it is expected that the regulation will be adapted in the coming years to make the technology and new business models that are derived from this concept feasible.
E-mobility plays an important role in reducing greenhouse gas emissions and in directly combating global warming. In addition, the battery banks of these vehicles will enable energy storage, helping to boost the use of renewable energy from intermittent sources such as solar and wind power.
V2G technology will play an important role in this context, enabling the use of energy stored in electric vehicles to supply the grid. Equipment manufacturers, protocol standardization bodies and software system developers have been working to enable the creation of solutions using this technology.
In the coming years, we will see new pilot projects (like Dominion’s) exploring and verifying the technology. R&D initiatives must also advance not only to mature the technology, but also to identify and point to regulatory changes necessary to make V2G viable.
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