Assessing the contribution of simultaneous heat and power generation from geothermal plants in off-grid municipalities

Abstract

A growing number of German municipalities are striving for energy autonomy. Geothermal plants are increasingly constructed in municipalities in order to exploit the high hydrothermal potential. This paper analyses the potential contribution of simultaneous geothermal power and heat generation in German municipalities to achieving energy autonomy. A linear regression estimates the achievable hydrothermal temperatures and the required drilling depths. Technical restrictions and cost estimations for geothermal plants are implemented within an existing linear optimisation model for municipal energy systems. Novel modelling approaches, such as optimisation with variable drilling depths, are developed. The new approach is validated with data from existing geothermal plants in Germany, demonstrating a Root Mean Squared Error of about 15%. Eleven scenarios show that achieving energy autonomy is associated with at least 4% additional costs, compared to scenarios without it. The crucial role of geothermal plants in providing base load heat and power to achieve energy autonomy is demonstrated. The importance of simultaneous modelling of electricity and heat generation in geothermal plants is also evident, as district heating plants reduce the costs, especially in municipalities with high hydrothermal potential. Further work should focus on the optimal spatial scale of the system boundaries and the impact of the temporal resolution of the analysis on the costs for achieving energy autonomy. Highlights  Analysis of hydrothermal potential in German municipalities  Optimisation of simultaneous geothermal heat and electricity generation  Drilling depth and hydrothermal temperature are implemented endogenously  Integration of geothermal plants in a holistic energy system optimisation  Geothermal plants reveal a potential for cost reduction in off-grid municipalities

Reviewing energy system modelling of decentralized energy autonomy

“…This means, the smaller a region is chosen, the more details can be included in the analysis. In [8,61,77,105,107,112,144] different spatial scales were compared as case studies, i.e. the number of households or inhabitants was varied.…”

“…In Petrakopoulou et al [103,104], the plants of the energy system are over-dimensioned and complementary technologies are used. In addition, the optimization model in Weinand et al [8] considers extreme days on which demand is particularly high and no wind or solar radiation is present.…”

“…In almost all studies (91, 74%) the time resolution is set to hours. There is only one study with a higher time Overall it seems, however, that the number of time steps decreases with the complexity of a model, presumably in order to avoid computing time problems: the RE³ASON model based on public data uses only 288 [93] or 432 [8] time slices and the multi-objective optimizations of Fuentes-Cortés and Ponce-Ortega [55] or Yazdanpanah Jahromi et al [125] use only 96 and 744 time slices respectively. Another example is the optimization with multitier targets (e. g. scenarios with different demands) according to the World Bank Global Tracking Framework by Fuso Nerini et al [57], which comprises only 18 time steps per year.…”

“…In contrast to a completely energy autonomous solution, imports and exports are possible. In Germany, for example, municipal energy autonomy projects have increased exponentially since 1995 [8]. In 2017, 1,300 municipalities already participated in these projects, corresponding to 12% of all municipalities and 15% of the population in Germany [8].…”

Reviewing Municipal Energy System Planning in a Bibliometric Analysis: Evolution of the Research Field between 1991 and 2019

“…Section 3.3) deal with this subject. Since 2016, there have always been at least six articles on this topic, including the last nine in 2019: [46][47][48][49][50][51][52][53][54]. Furthermore, the top five of the most relevant journals increasingly deal with district heating in studies on MESP: most frequent subject in Energy Policy and Applied Energy and second most frequent subject in Energy as well as Energies (cf.…”