Climate change is making extreme events - such as the recent massive flooding in large parts of southern Germany in June 2024 - increasingly likely. The question of how cities and municipalities can make the supply and safety of the population more resilient to such crises is focussing on so-called microgrids. Decentralised systems for the generation, storage and distribution of energy, for example with networked photovoltaic systems and combined heat and power plants, are intended to make large-scale power outages across the entire urban area less likely and ensure the functioning of critical infrastructures of general interest.

Transatlantic cooperation for a more resilient environment

A group of German and US researchers led by Dr Sadeeb Simon Ottenburger, Head of Department at the Institute for Thermal Energy Technology and Security (ITES) at the Karlsruhe Institute of Technology (KIT), has developed a model for a spatial planning concept for microgrids. Her study is intended to provide urban planners with a template for a planning process that integrates various aspects - including socio-economic factors and issues of social participation in the planning process. In addition to ITES, the Institute for Technology Assessment and Systems Analysis (ITAS) at KIT and, in the USA, the Energy Production and Infrastructure Center (EPIC) at the University of North Carolina and the National Renewable Energy Laboratory (NREL) in Colorado were also involved.

"Energy Gerrymandering": Who has access to the energy supply?

"A special feature of our approach is that we are not looking at technical parameters or cost issues in isolation, but rather at the question of what role the layout of microgrids plays in terms of fair distribution of supply," explains Ottenburger. "Imagine the city as a jigsaw puzzle. How the puzzle pieces are cut can vary. The boundaries of energy grids are the result of conscious decisions and have an impact on the population. In the event of a crisis, it makes a difference how healthcare, security and food supply services are distributed within individual microgrids, but also across the entire urban area." The study uses the term "degrees of freedom" to emphasise the importance of planning freedom. The authors used the term "energy gerrymandering", based on the political gerrymandering known from the USA when drawing electoral districts in favour of certain groups, to point out the potentially negative consequences of divisions that do not take social justice issues into account. The definition of microgrid districts can therefore lead to an unfair distribution of resources and benefits. Strong and wealthy groups could be favoured, while socially weaker and vulnerable groups could be disadvantaged. "Resilience also includes defining how access is organised for different groups of the population," says Ottenburger.

Metrics for assessing well-being

The study focuses on the connection between the different vulnerability of social groups and equitable access to energy and supply. To this end, the researchers used existing vulnerability indices to develop metrics that describe the well-being of the population as a measure and illustrate how energy outages affect socially and economically vulnerable groups in particular: The sick, families with children, the elderly and low-income earners.

Data from case study after hurricane

A comprehensive case study following power outages during Hurricane Florence in New Hanover County, North Carolina, in September 2018 provided the data basis for this. This was provided by the project partners in the USA. The data made it possible to analyse the critical infrastructure, its vulnerability in conjunction with the geographical distribution of socially disadvantaged households and their access to basic services. The project team used this to develop a universal design that makes it possible to comprehensively assess urban resilience for each city and generate proposals for the design of microgrids that take technical and social issues into account.

Several microgrids per city

One of the authors' specific recommendations is that a city should have not just one, but several microgrids to ensure the equitable distribution and accessibility of critical services such as health and safety structures. With regard to the boundaries of the supply networks, city administrations should actively involve institutions in the areas of health care and security and representatives of different social groups as well as educational institutions and social services in the planning and decision-making processes in order to take the needs of all social groups into account fairly.

New sustainable models

"The search for optimised microgrid layouts is highly complex and requires new algorithms to develop viable models from the available data," says Ottenburger. "It is crucial that resilient solutions are not necessarily a question of more investment, but above all of sophisticated planning. We should make sure that all groups have a voice and can participate in these processes."

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