Optimising the thermal use of groundwater for a decentralized heating and cooling supply in the city of Munich, Germany

Abstract

<p>Shallow geothermal energy can contribute to a regenerative supply of urban heating and cooling loads and hence, reduce primary energy consumption and greenhouse gas emissions. In the city of Munich, which hosts a very productive shallow aquifer, conditions are outstanding for the thermal use of groundwater. Therefore, already more than 2800 shallow geothermal systems are installed and due to better economic incentives, numbers are rising. Thus, the future development of this already intensely used urban aquifer holds challenges to avoid conflicting uses, but also opportunities to build synergies and balance the energy budget.</p><p>However, fostering a sustainable development is only possible with knowledge about the dynamic hydraulic and thermal behaviour of the groundwater and its anthropogenic and natural influences. Currently, this information is missing on a city scale as a decision basis for the responsible growth of thermal groundwater use. As a consequence, water authorities have to become increasingly restrictive when granting licenses to cope with preventive drinking water protection. Therefore, tools for the thermal management of aquifers are needed to enable resilient decision making.</p><p>The project GEO.KW (2019-2021), funded by the German Ministry for Economic Affairs and Energy, took up this challenge and develops a flexible management and optimisation tool for the thermal use of groundwater. As pilot area for an implementation, Munich offers a dynamic and well-monitored hydrogeology. The tool’s core element is the coupling between a thermal-hydraulic groundwater model and a linear optimisation model for distributed energy systems. This interdisciplinary approach, allows us to include the heat storage potential of the aquifer and study the coverable heating and cooling demand depending on the thermal resource at high temporal and spatial resolution. The optimisation integrates all regulatory restrictions of water resource management, like temperature or extraction limits, and comparatively analyses conventional heating and cooling systems alongside with thermal groundwater use. As cost factor in the optimisation, greenhouse gas emissions and economic cost is evaluated.</p><p>The development focuses on using highly parallelised open-source codes and efficient code coupling. The numerical groundwater simulation is performed with <em>PFLOTRAN</em>, a code specifically built for scalability on supercomputers. It is coupled to the linear optimiser <em>urbs </em>through the minimally invasive coupling library <em>preCICE </em>and the simulations are performed on the <em>SuperMUC-NG</em> in Garching, Germany. Since the parallelisation of optimisation problems is not straightforward, a decomposition procedure is introduced to assure performance with high resolution models.</p><p>The optimisation tool and associated methods will also be applicable to other urban areas. Thus, it will offer the decision support for an optimised growth of thermal groundwater use to assure its contribution to emission-free and decarbonised heating and cooling of cities.</p>

preCICE v2: A sustainable and user-friendly coupling library

“…To lower the entry barrier, we provide a virtual machine (VM) image with all components needed to run the preCICE tutorials. We create 11 and distribute 12 this image as a Vagrant 13 Box, which is currently available for VirtualBox, but could easily be packaged for other providers as well. We chose Vagrant instead of a provider-specific system, as Vagrant allows us to highly automate the box generation, integrates with the host system automatically (SSH access, shared folders), provides infrastructure to distribute the box, and works with various host platforms and virtualization providers.…”

“…Over the past ten years, preCICE has developed into a far more general tool for partitioned simulations, which can handle different types of coupling (weak/strong, explicit/implicit, surface/volume) and any type of equations. Examples range from fluid-structure-acoustics interactions 6 , over blood flow simulation in the human body 7 , free-flow porous media coupling 8 , conjugate heat transfer 9 , muscle-tendon system simulations 10 , flow-particle coupling 11 , to coupling between subsurface flow and planning tools for geothermal energy infrastructure 12 . The coupling is not restricted to a pair of solvers, but has been extended to enable multi-component coupling of arbitrarily many solvers 13 .…”

preCICE v2: A sustainable and user-friendly coupling library

“…Applications and Software A non-exhaustive list of application fields includes mechanical and civil engineering (astronautics 59 , manufacturing processes 66 , 69 , aerodynamics 23 , 64 . 107 – 111 , urban wind modeling 106 , aeroacoustics 6 , 112 , explosions 113 , 114 ), marine engineering 22 , bio engineering (heart valves 115 , aortic blood flow 7 , fish locomotion 116 , muscle-tendon systems 10 ), nuclear fission and fusion reactors 9 , 117 , 118 , and geophysics 8 , 12 , 119 . Many users do not only use the official adapters (cf.…”

“…Over the past ten years, preCICE has developed into a far more general tool for partitioned simulations, which can handle different types of coupling (weak/strong, explicit/implicit, surface/volume) and any type of equations. Examples range from fluid-structure-acoustics interactions 6 , over blood flow simulation in the human body 7 , free-flow porous media coupling 8 , conjugate heat transfer 9 , muscle-tendon system simulations 10 , flow-particle coupling 11 , to coupling between subsurface flow and planning tools for geothermal energy infrastructure 12 . The coupling is not restricted to a pair of solvers, but has been extended to enable multi-component coupling of arbitrarily many solvers 13 .…”