Storage requirements and system costs in the power supply for energy-self-sufficient regions and districts (Möller 2020)

Energy self-sufficiency is a central issue in the transformation process towards a supply of 100% renewable energies, both at the regional and district level. In the regional context, the main aim is to achieve full self-sufficiency on the balance sheet, while at the district level, real partial energy self-sufficiency is sought. The expansion of storage facilities is not necessary for the balancing concepts at the regional level. At the district level, on the other hand, semi-self-sufficient concepts with electricity storage systems are widespread. Based on the regional efforts for self-sufficiency, the real implementation possibilities at the district level and the need for storage in the overall system, the influence of the size of the partially self-sufficient systems at the regional and district level on the storage requirements and the resulting system costs is investigated.

This answers the question of the extent to which energy regions and energy-efficient districts can sensibly implement their self-sufficient supply goals while taking storage systems into account. To answer these questions, energy system analyses based on linear optimization were carried out for a range of system sizes from a regional and district perspective and evaluated from a technical-economic point of view. The basis for the investigations is the master plan model region “Osnabrück-Steinfurt”. At the district level, fictitious and real amalgamations of household, commercial and agricultural buildings with different photovoltaic expansion scenarios were mapped. In addition, in addition to the systemic optimum, the resulting storage requirements resulting from economic profitability were investigated. At the regional level, the results show that the size of the semi-self-sufficient system has a strong influence on storage requirements and system costs. Under certain conditions, the coverage of regions at district level can be mapped in the range of 80 to 90 % in real terms self-sufficiently. At the municipal level, a self-sufficient view of the electricity supply does not make sense due to the strong heterogeneity of the municipalities in generation and consumption. The investigations at the district level show clear synergies in the networking of individual households and the use of a common district storage system.

Compared to the regional level, the implementation of storage systems at the district level to achieve comparable degrees of self-sufficiency leads to significantly higher specific storage capacities and system costs. From the actor’s point of view, however, their investment is worthwhile and leads to similarly high degrees of self-sufficiency as at the regional level.

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