In the course of the global transition to renewable energy, the expansion of decentralised energy systems constitutes a major trend. With an increasing number of distributed energy resources connected to the electricity grids, many consumers also turn into producers (so-called prosumers). This development represents a challenge for policymakers, grid operators and electric utilities alike.
Several countries like Germany have gained substantial experience with deploying and integrating distributed energy resources such as photovoltaic and wind power. The technical, organisational and regulatory experience accumulated by frontrunners should also prove relevant for countries that are about to start this transformation of their energy systems. This project investigated the practical experiences with integrating distributed energy systems into the electricity grids, based on representative interviews with large-scale distribution grid operators in Germany.
The article „The German experience with integrating photovoltaic systems into the low-voltage grids" investigates the technical challenges posed by the integration of decentralized energy systems into the distribution grid. Our findings show that grid expansion measures are primarily undertaken to ensure compliance with the permissible limits for voltage and current. Grid optimization measures represent the most economical initial step and include, for instance, changes in grid structure and wide-area control. Once their potential is maximized, classic grid expansion measures such as laying parallel cables are implemented. In individual cases, the low-voltage grid is reinforced by so-called intelligent operating equipment such as voltage regulators or voltage-regulated local distribution transformers. Moreover, improved grid planning measures lead to a better use of the available low-voltage grid capacity.
The article „The German incentive regulation and its practical impact on the grid integration of renewable energy systems" contains a comprehensive review of the current incentive regulation scheme and its 2016 amendment. In addition, the interplay between the German incentive regulation and renewable capacity integration is analysed based on the interviews with distribution system operators. The results show that all necessary grid integration measures could so far be implemented. Nonetheless, creating proper incentives for intelligent operating equipment to partly substitute conventional grid expansion remains a challenge. At the same time, the discussions on further improvements to the incentive regulation scheme reveal a distribution conflict between grid operators and grid users.