A microgrid, such as that deployed in Smartcity Malaga, can be defined as a small low voltage grid capable of integrating generation sources, energy storage and manageable
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can therefore be understood as a set of microgrids, to a greater or lesser extent, all interconnected and managed intelligently, to achieve a more effective, efficient and robust electricity system.
Moreover, the current virtual generator systems under development are based on the management of electric loads and microgenerators, which can function as autonomous small generators, supplying energy to the grid, thus optimising its functionality when a distributed generation system is configured. These small generation systems may be made up of wind micro-generators, photovoltaic applications, energy storage systems and, of course, electric vehicles that, depending on the grid’s demand, can charge or discharge their batteries, becoming contributors to the electricity system instead of consumers. This indicates a true technological turning point.
In fact, an electric vehicle can itself be considered a microgrid, as it can function autonomously or connected to the electricity grid, has consumption coming from its engine, potential electrical generation from its regenerative system of braking and restraint, an energy storage system in its batteries and/or super-capacitors, diverse loads (control systems, brakes, active safety systems, fans, air conditioning, pumps, hydraulic systems, etc.) and, in addition, all of these systems and devices are managed by different control strategies that depend on both the type of conditions and whether the vehicle is connected to the electricity grid.
The vehicles are able to not only charge their batteries when they are connected to the electricity grid, but also to send electricity to the network making use of “vehicle to grid” or V2G technology. A particular case of the aforementioned V2G technology is the energy the vehicle provides for use directly in the home, supplying low-level consumption. In this case, the correct name is “vehicle to home” or V2H.
V2G electric vehicles are a chance to improve the efficiency of the whole electricity system as recharging or discharging their batteries can be done when the user and the grid management systems desire to do so, which cannot happen with most electrical consumption. This ability to manage the demand presents significant advantages as it offers the electricity system the possibility of improving global efficiency, flattening the demand curve, increasing the demand cover ratio,
improving the safety in the supply of energy, and facilitating the integration of the energy from renewable resources.
Equivalent to the above regarding energy storage, recharging the batteries of these vehicles during the reduced demand period (during the night), flattens the demand curve as the large differences that occur between the periods of greatest and least electricity demand are reduced. In addition, in the event of different time tariffs, the price of the electricity is lower during the night (when there is less demand). Conversely, the partial discharge of the energy contained in electric vehicles in the period of greater energy demand from the grid reduces the power generation requirement of the plants, which enhances the efficiency of the electricity system.
Fig. 36. Integration of electric vehicles with storage capacity and energy discharge
(Source: http://www.itrco.jp/)
Grid
V 2H H E M S
Electric cars with V2G technology can play a very significant role in integrating renewable energy into the electricity system. For example, wind production, generated mainly during the night, has a great variability. In addition, as it is not possible to store it, when the wind energy supply is greater than the demand, it is possible that not all the wind energy produced can be entered into the system. Therefore, recharging the electric vehicles during the night will help make use of this energy. Moreover, this renewable energy stored in the vehicles may be returned to the grid during the periods of highest electricity demand.
Connecting V2G electric vehicles to the grid also means that we have energy resources that, in certain conditions, can provide an electric supply to ensure the demand coverage ratio and even the security of the supply in certain situations.
Fig. 37. Flattening of the demand curve by electric vehicles and V2G recharge points
(Source: Red Eléctrica de España)
The installation of smart meters will enable these options to be developed, which will be essential for the operation of the electricity system in the future.
In parallel to the V2G electric vehicles, it is necessary to develop the corresponding V2G recharge points able to not only provide energy to the batteries to charge them, but also inject energy coming from the vehicles into the grid. These recharge points have to be managed by the system operator, under a specific system of set points that enable them to run efficiently and to be integrated into the electric grid.
Within the scope of the Smartcity Malaga project, infrastructure for recharging electric vehicles with V2G capacity was deployed, made up of a recharge point installed on a public road, designed specifically with the requirements of this technology, which provides support for a conventional electric vehicle that has been modified to include the aforementioned V2G capacity. The recharge infrastructure and the vehicle, have been fully integrated into the microgrid and its management and data capture systems of this project, thus becoming an element that plays an active part in Smartcity Malaga and facilitates the development of a complete protocol of trials and tests on the use of these recharge points and vehicles, which has enabled us to obtain relevant results on the real use of this technology, its possibilities and the next steps to take, and recommendations to follow for its progressive implementation within the whole electricity system.