Electric Cars for Balancing Variable Power on Gotland
Abstract: The share of renewable power grows in the generation mix, wielding promises of substituting traditional CO2-intensive power production. In combination with the trend towards electrification of transport, opportunities are emerging to use electric vehicles for balancing the variability of the renewable power sources. This master thesis explores the potential for such balancing techniques, often referred to as smart charging (SC) or vehicle-to-grid (V2G), on the Swedish island of Gotland. For this purpose, a self-developed model is used, built to reflect the transport and power system on the island. The systems are simulated on minute scale during a year on Gotland. It is also examined, by means of a literature study, whether economic incentives and associated modes of participation encountered in scientific research are aligned with the driving forces and concerns of potential participants. The limited transmission capabilities between Gotland and the mainland together with the large generation of wind power on the island has resulted in the local energy company disallowing further installations of variable power. Therefore, examining these technologies in this context is of particular interest and the findings made here paint the picture of what is possible outside Gotland as well. The SC and V2G systems are evaluated in three future cases with 100 percent electrification of passenger cars, altering the level of power generation between the levels of today and increased production scenarios covering 50 and 100 percent of the additional load from the electric cars, on an annual basis. It is found that suggested systems can increase the usage of locally produced power significantly for all cases and that the potential contribution grows, as variable power production is increased. Introducing a SC or V2G system and simultaneously increasing renewable power generation to cover the increased energy need from the electric car fleet, could lead to a reduction of energy import and export to and from the island. In the SC and V2G system yearly export values found from the simulations made are reduced from 4.4 GWh per year to 2.8 and 0.8 respectively and import is decreased from 612.1 GWh per year to 608.4 and 610.2 when production is increased, and the systems are implemented. The increased energy need for electric passenger cars would be equivalent to that which is provided by roughly 17 wind turbines rated at 3 MW. The amount of wind turbines are a sizeable investment but well in-line with regional and national ambitions. The availability of the electric car fleet as a power sink is high and during the vast majority of the year the chargeable capacity is well comparable to the current transmission capacity to the mainland of 130 MW. Under current levels of power generation, the electric car fleet can be charged at rates of 189 and 191 MWh/h or more in the SC and V2G system respectively during 95 percent of the year. If the power generation is increased to cover the energy need of electric cars, the corresponding numbers are 138 and 183 MWh/h. Furthermore, there seem to be a considerable interest in participation in SC and V2G systems. Most of the current economic incentives and modes of participation encountered in research, could likely be implemented in ways aligned with the concerns and driving forces of future electric car owners. The most commonly found concern being that of mobility restrictions resulting from participation is likely less problematic on Gotland due to the limited geographical extension of the island. Finally, it should be considered that while economic earnings are important, they only provide one of many viable paths for reaching out. Allowing for flexible modes of participation, communicating environmental benefits achieved and carefully minding data privacy issues are examples of important aspects to consider when launching SC and V2G systems.
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