Wind and solar PV have become the lowest-cost alternatives for power generation in many countries and are expected to dominate the renewable power supply in many regions of the world. The temporal volatility in power production from these sources leads to new challenges for a stable and secure power supply system. Possible technologies to improve the integration of wind and solar PV are electrical energy storage and the flexible power provision by bioenergy. A third option is the system-friendly layout of wind and solar PV systems and the optimized mix of wind and solar PV capacities. To assess these different options at hand, a case study was conducted covering various scenarios for a regional power supply based on a high share of wind and solar PV. State-of-the-art concepts for all the stated technologies are modelled and a numerical optimization approach is applied on temporally-resolved time series data to identify the potential role of each option and their respective interactions. Power storage was found to be most relevant in solar dominated systems, due to the diurnal generation pattern, whereas bioenergy is more suitably combined with high wind power shares due to the less regular generation pattern. System-friendly wind and solar power can reduce the need for generation capacity and flexible options by fitting generation and demand patterns better.

In future energy scenarios with a high share of renewable energies within the electricity system, power-to-heat technologies could play a crucial role for achieving the climate goals in the heating sector. District heating systems can integrate volatile wind and photovoltaic energy sources and resolve congestions within the electricity grid, leading to curtailment of renewable electricity generation. This paper presents a design approach for setting up system-beneficial power-to-heat-based district energy systems. Within the scope of the project QUARREE100 an existing district in the provincial town Heide in Northern Germany is examined. A linear investment and unit commitment optimization model is applied. By considering local dynamic emission factors for grid-sourced electricity, which contain information on local wind energy curtailment as well as the emission intensity of the overall electricity generation, a renewable and system-beneficial design can be derived. With this method, the minimal rated power and capacity of energy converter and storage units can be determined to achieve emission reductions with respect to minimum costs. The approach of using different methods for the consideration of the emissions of grid-sourced electricity is analyzed based on different scenarios. By using a dynamic emission factor for grid-sourced electricity, lower emissions with fewer costs can be achieved. It is shown that a dynamic assessment leads to different design decisions and far-reaching deviations in the unit commitment. The results clearly show that a constant emission factor is no longer an option for grid-sourced electricity in urban energy system models.

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