Catalogue of operational criteria and constraints Catalogue of operational criteria and constraints for shallow geothermal systems in the Alpine environment Deliverable D.3.2.1 – Catalogue of operational criteria and constraints for shallow geothermal systems in the Alpine environment 15/05/2016 – 15/06/2017: Based on the analysis of the case studies, operational criteria and technical / environmental constraints for shallow geothermal plants will be summarized in a catalogue, which will serve as reference for the activities of WPT4 and WPT5. This document was written in the course of the ERDF funded project GRETA (2016 – 2018). It is the second deliverable of the Work Package 3 (WP3 or WPT2) “Operational criteria for the utilization of Near-Surface Geothermal Energy in the Alpine environment”. The Geological Survey of Austria (GBA), as responsible partner in this WP, elaborated this catalogue with the contribution from the involved project partners1. The preliminary studies for this deliverable (Del. 3.2.1) were carried out within the Activity 3.2 “operational criteria and constraints for shallow geothermal systems in the Alpine environment” from 15.05.2016 – 15.06.2017. The outputs of this study will be taken into account by WP4 (WPT3) (operative constraints and thresholds for the assessment and mapping of Near-Surface Geothermal potential) and WPT4 (elaboration of technical concepts on existing and possible future uses of NSGE for its integration into the energy plans of pilot areas). 1/108 GRETA is co-financed by the European Regional Development Fund through the Interreg Alpine Space programme. Send us an email at [email protected] and see more about GRETA at www.alpine-space.eu/projects/greta. Catalogue of operational criteria and constraints TABLE OF CONTENTS 1 Introduction ..................................................................................................................................... 4 1.1 Terms and definitions referring to NSGE ................................................................................ 4 2 Description of technical and environmental constraints ................................................................ 6 2.1 Environmental constraints ...................................................................................................... 7 2.2 Technical constraints ............................................................................................................... 8 3 Description of operational criteria for shallow geothermal systems ............................................ 12 3.1 Given natural conditions (natural operational criteria) ........................................................ 13 3.1.1 Ground temperature ..................................................................................................... 13 3.1.2 Effective thermal conductivity ...................................................................................... 24 3.1.3 Effective heat storage capacity ..................................................................................... 30 3.1.4 Aquifer temperature ..................................................................................................... 30 3.1.5 Transmissivity ................................................................................................................ 31 3.2 Demand side (design operational criteria) ............................................................................ 33 3.2.1 Peak power .................................................................................................................... 36 3.2.2 Thermal demand ........................................................................................................... 39 3.2.3 Conclusions .................................................................................................................... 42 3.3 Economic considerations/factors .......................................................................................... 44 3.3.1 Investment costs ........................................................................................................... 44 3.3.2 Operating costs .............................................................................................................. 48 3.3.3 Financing ....................................................................................................................... 50 3.3.4 Conclusions .................................................................................................................... 50 4 Influence of the single operational criterion to the NSGE system ................................................ 52 4.1 Borehole heat exchanger (BHE) fields ................................................................................... 52 4.1.1 Mathematical model ..................................................................................................... 52 4.1.2 Modelling of BHE fields (reference cases) ..................................................................... 56 4.1.3 Influence of parameters on SPF: Ranges, results and discussion ................................. 62 4.1.4 Conclusions .................................................................................................................... 64 4.2 Open-loop .............................................................................................................................. 66 4.2.1 Factors affecting the energy efficiency of open-loop geothermal systems ........... 66 4.2.2 Numerical simulation of GWHPs ................................................................................ 70 2/108 GRETA is co-financed by the European Regional Development Fund through the Interreg Alpine Space programme. See more about GRETA at www.alpine-space.eu/projects/greta. Catalogue of operational criteria and constraints 5 Innovative Systems ........................................................................................................................ 79 5.1 Thermal Tunnel Activation .................................................................................................... 79 5.1.1 Open Systems / Drainage Water Utilisation .................................................................. 80 5.1.2 Closed Systems: traditionally constructed Tunnels ....................................................... 81 5.1.3 Tunnels constructed with tubbings ............................................................................... 81 5.1.4 Design Guidelines .......................................................................................................... 84 5.1.5 Economics ...................................................................................................................... 85 5.2 Geothermal Reservoirs coupled with traffic infrastructure .................................................. 86 5.2.1 Traffic Surfaces coupled with geothermal Sources via Heat Pumps ............................. 89 5.2.2 Design Guidelines .......................................................................................................... 90 5.2.3 Economics ...................................................................................................................... 92 5.3 Geothermal Train Switch Heating ......................................................................................... 93 5.4 Heat Pipe Borehole Heat Exchangers .................................................................................... 94 6 Annex ............................................................................................................................................. 95 3/108 GRETA is co-financed by the European Regional Development Fund through the Interreg Alpine Space programme. See more about GRETA at www.alpine-space.eu/projects/greta. Catalogue of operational criteria and constraints 1 Introduction Within WP3, the aim is to define and analyse criteria relevant for the NSGE use in the Alpine space. The output of this assessment shall be the base for considerations and calculations especially for the potential mapping methods. In order to identify and quantify operational criteria, information is collected by literature research, the monitoring of best practice examples, field measurements in the case study areas and numerical simulations. To achieve this deliverable, the first step was to identify technical and environmental constraints (see chapter 2) as well as operational criteria in general (see chapter 3). In order to be able to answer the question about how big the influence of these operational criteria are to the NSGE system in a whole, numerical simulations were carried out considering the same load curves for BHE and GWHPs and varying the operational criteria (see chapter 4). This leads to the identification of relevant operational criteria and shows the influence of these to the system. 1.1 Terms and definitions referring to NSGE Resource: the term refers to the source – i.e. thermal energy stored underground, from which benefit can be produced. Potential: these terms define the amount of a known natural resource that may potentially be used in the future, regardless of technical feasibility – i.e. the amount of thermal energy stored underground. This definition refers to the “heat in place” definition by USGS. Technical potential: this term refers to the exploitable thermal energy stored underground, defined according to the “Recoverable Heat in Place” definition by USGS. Techno-economical potential: this