## 1 Introduction
Average European statistics, average hourly energy consumption, and production profiles for an average day during an average year were used to calculate system component sizes, including safety margins [36]. Rough estimations, such as several days without sun or wind power, were used to define the required back-up and balancing power and energy storage sizes [36]. Hourly modeling will capture the biggest variations for larger systems and is, therefore, more adequate to dimension flexibility requirements [73]. Modeling on an hourly basis and tailoring to geographical energy demand and climatic conditions will give a better insight into hourly, diurnal, and seasonal energy production and consumption mismatch, in other words, the energy storage requirements, and the system design and its related cost. The question is: can solar and wind electricity, together with fuel cell electric vehicles and hydrogen as an energy carrier, provide year-round 100% renewable, reliable, and affordable energy for power, heat, and transportation for smart urban/city areas in two different European climates? To address this question, this study performed a techno-economic scenario analysis and design for a 100% renewable, reliable, and cost-effective energy system. The energy systems provide year-round power, heat, and transportation for smart urban areas. The total system cost and energy performance are compared for two different technology development scenarios and two European climate zones for five years (2012-2016). Analyzing the system over five years will give insight into the inter-annual variability of the cost and energy performance. To our knowledge, no such comprehensive study has been performed up to now. Many studies and pilot projects investigate stand-alone and national grid-connected renewable energy systems using hydrogen as energy storage and stationary fuel cells for the reconversion of the stored hydrogen [74; 75; 76; 77; 78]. Some studies use the produced hydrogen for transportation [79; 80; 81; 82; 83; 84] or solely use the fuel cell in the vehicle as an electric generator [85; 86; 87; 88; 89] without considering hydrogen production. Integration of FCEVs through V2G into a local electricity network for operating in island mode, emergency power, or balancing local renewables has been done mostly on a smaller or a very large scale [90; 91; 92; 93; 94]. Some studies include a cost analysis [95; 96; 97], do not compare with a future scenario with improved cost and efficiency (scenario and trend analysis) [98], are dependent on the grid electricity, do not compare different climate zones nor include inter-annual variability [99], or do not include seasonal hydrogen storage [98]. The authors of [100] focus on a small-scale system in a specific region without considering hydrogen transportation, although includes a future cost scenario. The authors of [101] look into urban areas and road transportation in different regions in different Japanese climate zones, but the described system is not 100% renewable and does not include economics or consider V2G electricity services with FCEVs. A study [102] performs a future techno-economic 100% renewable energy analysis, including multi-annual variability for multiple large national and trans-national regions. Various energy sectors are coupled, where hydrogen is used as energy storage and road transportation fuel along with several other energy carriers and storage techniques. However, here too, but also here V2G electricity services with FCEVs are not considered.