Wellhead anti-frost technology using deep mine geothermal energy

The auxiliary shaft is an important location for coal mine heating in the winter, where the main purpose of heating is to prevent icing of the shaft. Wellhead heating requires characteristics of openness, no-noise and big heat loads. The original coal-fired boiler heating mode causes significant waste of energy and environmental pollution due to the low efficiency of the heat exchange. Therefore, to solve these prob- lems, we will use deep mine geothermal energy to heat the wellhead by making full use of its negative pressure field and design a low-temperature water and fan-free heating system. Through numerical cal- culations we will simulate temperature fields, pressure fields and velocity fields under different air sup- ply temperatures, as well as different air supply outlet locations and varying number of radiators in the wellhead room of a new auxiliary shaft to find the proper layout and number of radiators that meet well- head anti-frost requirements from our simulation results, in order to provide guidelines for a practical engineering design. Tests on the Zhangshuanglou auxiliary shaft wellhead shows good, look promising and appear to resolve successfully the problem of high energy consumption and high pollution of well- head heating by a coal-fired boiler.

Multi-criteria decision-making method for evaluation of investment in enhanced geothermal systems projects

Deep geothermal energy presents large untapped renewable energy potential could significantly contribute to global energy needs. However, developing geothermal projects involves uncertainties regarding adequate geothermal brine extraction and huge costs related to preparation phases and consequently drilling and stimulation activities. Therefore, evaluating utilization alternatives of such projects is a complex decision-making problem effectively addressed using multi-criteria decision-making (MCDM) methods. This study introduces the MCDM method utilizing analytic hierarchy process (AHP) and weighted decision matrix (WDM) to assess different utilization alternatives (electricity generation, direct heat use and cogeneration). The AHP method determines the weight of each criterion and sub-criterion, while the WDM calculates the final project grade. Five criteria groups - technological, geological, economic, societal and environmental – comprising twenty-eight influencing factors were selected and used for the assessment of investment in Enhanced Geothermal Systems (EGS) projects. The AHP-WDM method was used by 38 experts from six categories: industry, educational institution, research and technology organization (RTO), small- and medium-sized enterprises (SME), local community and other. These diverse expert inputs aimed to capture varying perspectives and knowledge influence investment decisions in geothermal energy. The results were analysed accordingly. The results underscore the importance of incorporating different viewpoints to develop robust, credible, and effective investment strategies for EGS projects. Therefore, this method will contribute to more efficient EGS project development, enabling thus a greater penetration of the EGS into the market. Additionally, the proposed AHP-WDM method was implemented for a case study examining two locations. Locations were assessed and compared on scenario-based evaluation. The results confirmed the method's adequacy for assessing various end uses and comparing project feasibility across different locations.

Cooling Systems for Borehole Tools

Since 2012 the work on a cooling system for borehole probes is going on at the IAI. It is supposed to allow the usage of standard electronics, as a first approach in borehole environments at 5 km depth, with 200℃ and 600 bar. Within ZWERG, the cooling system serves as base to realize different measurement operations without time limitations. Therefore it contains an insulation to reduce outer heat input, an active cooling system to cool down components which are sensitive to heat inside, like electronics, as well as a cooled room where the electronic can be installed. The first approach based on the example borehole in Soultz-sous-f6ret, France （5 km, 200℃） shall initiate further project in this field, with the perspective to conduct measurement operations in even hotter boreholes. Alternative methods of heat management in borehole probes investigated and developed at IAI, are high temperature electronics and PCM-systems.

CO_(2)Plume Geothermal(CPG)Systems for Combined Heat and Power Production:an Evaluation of Various Plant Configurations

CO_(2) Plume Geothermal(CPG)systems are a promising concept for utilising petrothermal resources in the context of a future carbon capture utilisation and sequestration economy.Petrothermal geothermal energy has a tremendous worldwide potential for decarbonising both the power and heating sectors.This paper investigates three potential CPG configurations for combined heating and power generation(CHP).The present work examines scenarios with reservoir depths of 4 km and 5 km,as well as required district heating system(DHS)supply temperatures of 70℃ and 90℃.The results reveal that a two-staged serial CHP concept eventuates in the highest achievable net power output.For a thermosiphon system,the relative net power reduction by the CHP option compared with a sole power generation system is significantly lower than for a pumped system.The net power reduction for pumped systems lies between 62.6%and 22.9%.For a thermosiphon system with a depth of 5 km and a required DHS supply temperature of 70℃,the achievable net power by the most beneficial CHP option is even 9.2%higher than for sole power generation systems.The second law efficiency for the sole power generation concepts are in a range between 33.0%and 43.0%.The second law efficiency can increase up to 63.0%in the case of a CHP application.Thus,the combined heat and power generation can significantly increase the overall second law efficiency of a CPG system.The evaluation of the achievable revenues demonstrates that a CHP application might improve the economic performance of both thermosiphon and pumped CPG systems.However,the minimum heat revenue required for compensating the power reduction increases with higher electricity revenues.In summary,the results of this work provide valuable insights for the potential development of CPG systems for CHP applications and their economic feasibility.