Croatia aims to achieve 10% of its energy production from the renewable energy sources in the total energy consumption in the transport sector. One of the ways to achieve this goal is by the use of electric vehicles. This work comparatively analyses the financial and social aspects of vehicle-to-grid charging in standard and fast charging mode, their impact on the renewable electricity production and the total electricity consumption regulated through variable electricity prices. Data were taken for the wider urban area of the Dubrovnik region. The assumption is that the Dubrovnik region will be self-sufficient by the year 2050 with 100% renewable electricity production and that all conventional vehicles will be replaced by electric vehicles. This work aims to show that the fast charging based on 10 min time steps offers more opportunities for flexibility and utilization of renewable generation in the energy system than the standard charging based on hourly time step. The results of this work showed the opposite, where in most of the scenarios standard charging provided better results. Replacement of the existing two tariff model in electricity prices with variable electricity prices contributes to the stability of the energy system, providing better regulation of charging and higher opportunities for renewable electricity utilization in standard and fast charging and reduction of charging costs. According to the financial aspects, fast charging is shown to be more expensive, but for the social aspects, it provides electric vehicles with more opportunities for better competition in the market.

Heat and cooling stands out with the great potential in decarbonisation since they have a large share in the final energy consumption. Power-to-heat technologies may contribute to the heat sector decarbonisation as well as the integration of renewables if they are sufficiently flexible. They are also shown to have a good effect on the system costs. This work will analyse the potential of seawater heat pump system for the utilization of high share of electricity production from the renewables. The Old City of Dubrovnik is selected as a case study because of its specific situation. A large number of the outdoor units are not well approved by UNESCO since the Old City is under the protection of the UNESCO World Heritage Centre. The results of the study showed that the combination of wind and solar electricity production can cover 67% of load for stand-alone seawater heat pump system based on hourly time step. Utilization of renewable electricity generation, for this case, resulted in 433.71 tCO2/y emission reduction. System based on 10 minutes time step gave poorer results by 6%. System with the additional energy storage gained best results in the case of combined wind and solar electricity generation, as well. It resulted in storage capacity reduction by 78% ac-cording to the case of solar electricity generation and by 60% according to the wind electricity generation. Battery energy storage resulted in 40 times lower volume and 13 times higher investment costs and levelised cost of heat in comparison to the thermal energy storage.