The rapid growth of variable renewable energy (VRE), such as wind and solar energy, will increase the unpredictability and fluctuations in energy systems in general, resulting in a need for increased flexibility measures. Simultaneously, global urbanization will strengthen the importance of urban energy systems in the future. Therefore, it is highly important to find solutions to enable large-scale variable renewable energy generation in cities. This dissertation aims to find ways to increase flexibility and to enable higher shares of VRE in urban energy systems. For this purpose, three new computational models were developed in relation to both electricity and thermal energy (heating and cooling) in cities. The first model simulates the spatiotemporal energy consumption in cities, the second focuses on distributed production and cooperation between different energy networks, and the third describes the energy system operation with existing power plants and large-scale VRE schemes. Results from Helsinki, Finland, show that power-to-heat (P2H) conversion with electric resistance or heat pumps can help to increase the wind power production in the city by 4–5 times (up to 60% of electricity demand) compared to the self-use limit of wind power, in which the focus is on the electric system only. Part of the increased wind power production would then be used to cover up to one third of the heat demand. Simultaneously, P2H makes coal very sensitive to price changes, which could lead to the removal of coal from the city's energy portfolio. In another case, in Concepción, Chile, the solar capacity of the city is, in theory, large enough to satisfy all energy demand, but the technical efficiency and the power grid infrastructure limits the PV share in electricity to around 24%. With P2H, this could be increased to at least 34% without overloading the power grid; simultaneously a quarter of the heat demand would be filled. These results demonstrate the importance of system-wide consideration when planning integration of VRE. The thesis shows that, by viewing energy systems as a whole instead of focusing on only one energy form, the flexibility of the system can be remarkably increased, even without massive investments in traditional network infrastructure. Through smart design and multi-energy thinking approaches, variable renewable energy sources can be turned into a main-stream option for energy production in urban areas.
|Publication status||Published - 2017|
|MoE publication type||G5 Doctoral dissertation (article)|
- urban energy systems, energy system modeling, renewable energy, optimization, energy flexibility