Grid to vehicle and vehicle to grid systems for large-scale penetration of renewable generation

Panel: 6. Transport and mobility

This is a peer-reviewed paper.

Authors:
Pedro Manuel Soares Moura, Institute of Systems and Robotics - University of Coimbra, Portugal
Joaquim Delgado, Institute of Systems and Robotics, Portugal
Anibal de Almeida, Institute of Systems and Robotics, Portugal
António Pires, Institute of Systems and Robotics, Portugal

Abstract

The electric power system is quickly changing due to the growing penetration of intermittent and non-dispatchable renewable energy sources. Simultaneously, the demand should ideally be able to be adapted to the renewable generation availability, directly with demand response or indirectly using energy storage technologies. The transport sector with electric vehicles (EVs) is increasingly an important consumer of electricity, and as fleets increase, EVs can be used as controllable loads, charging in periods of high renewable generation or low prices, using the Grid to Vehicle (G2V) system. With adequate technology, in addition to absorbing power from the grid, EVs can also use some of their storage capacity to inject energy into the grid, in order to ensure the balance between the generation and demand, using the Vehicle to Grid (V2G) system. However, the additional charging cycles due to V2G will accelerate the degradation of batteries and therefore its associated cost must be taken into account.

This paper discusses the technologies and methodologies for the implementation of Grid to Vehicle and Vehicle to Grid systems, as well as their potential benefits for the grid in a scenario with large-scale penetration of renewable generation. To assess such impact a case study for the Portuguese grid is presented, considering three scenarios of penetration of EVs in the Portuguese vehicle fleet (in which EVs constitute 10%, 25% or 50% of the fleet). The obtained data allowed to assess the potential of V2G to transfer the generation surplus between hours of low and high demand. Additionally, the economic benefits from the grid and user point-of-views were assessed considering the degradation of the batteries (evaluated through a model developed in Simulink environment), associated with the use of V2G, and their replacement cost. The results show a high impact on the compensation of renewable generation surplus, as well as economic benefits from the grid point-of-view. Even considering the battery degradation, in some scenarios, there is also a potential economic benefit for the user.