Low Enthalpy Geothermal Research Articles

3D FE modeling of a real-world energy piled foundation

3D FE modeling of a real-world energy piled foundation

Bibliometric Analysis and Review of Low and Medium Enthalpy Geothermal Energy: Environmental, Economic, and Strategic Insights

Bibliometric Analysis and Review of Low and Medium Enthalpy Geothermal Energy: Environmental, Economic, and Strategic Insights

Contribution of Low Enthalpy Geothermal Energy in the Retrofit of a Single-Family House: A Comparison between Two Technologies

In recent years, the European Union has developed a sustainable, competitive, safe, and “decarbonised” energy approach. To achieve this objective, especially in highly urbanized contexts, there is a need to drastically improve the energy behavior of buildings and related energy systems. For this purpose, the aim of this paper is to analyse two very promising technologies that exploit the geothermal energy of the ground: the Earth-to-Air Heat eXchanger (EAHX) and the Ground Source Heat Pump (GSHP). These two systems are used as an energy retrofit strategy for the air conditioning system in an existing single-family house, located in Naples (south Italy). The building and the related systems are dynamically simulated using the DesignBuilder software. The results show energy savings of these two systems (compared to a traditional solution with an air-to-water heat pump) between 13% and 28%, with a total yearly primary energy consumption of about 80 kWh/m2 for the case with EAHX and around 67 kWh/m2 for the case with GSHP.

Improving Regulation and the Role of Natural Risk Knowledge to Promote Sustainable Low Enthalpy Geothermal Energy Utilization

The use of geothermal energy resources to support anthropogenic activities have a long-lasting tradition, renewed in recent decades with the increasing use of low enthalpy geothermal energy (LEG) with combined systems of heat pumps and geothermal exchange, exploiting the enormous thermal capacity and very low temperature variability of subsoil, including rocks and water. The further potential global increase of LEG use could be enormous, although LEG is already the main geothermal energy sources in Europe, contributing significantly to reach 2030 UN sustainable development goals (SDGs) on renewable energy resources, as a further leg to support all necessary efforts for these scopes. This research pursues LEG spreading improving knowledge on limitations of guidelines, technical regulations and/or laws, briefly rules, especially in terms of potential risks or limitations due to environmental constrains or natural phenomena. A global documentary research, including scientific articles, books, technical reports from qualified institutions, technical standards, guidelines, regulations, and laws, was realized with three different groups of keywords. A total of 161 documents were selected after some steps, including quality check. Identical English and Italian keyword sets were used to span from an international global scale to the complex local scale which characterizes the Italian experience. A complex sheet was filled in for each document, supporting data discussion, planned with a geographical criterion, from global to local. The system of rules resulted worldwide inhomogeneous and complex, with high differences from countries, nations or regions, also at local scale. The low quality or the absence of simple and careful “rules” emerged an important obstacle to LEG diffusion that can guarantee sustainability and the absence of natural risks. Main virtuous systems of rules were recognized as very useful to promote LEG spreading but these are still uncommon. The discussion of optimal experiences and the overview of potential natural risks due to LEG complete the paper.

Geothermal Salt Factory (GSF) Design in Parangwedang Geothermal, Bantul, Special Region of Yogyakarta

Indonesia has the largest geothermal energy potential in the world with potential value ±28 GWe, but the potential of geothermal low enthalpy is still not utilized properly. On the other hand, improvement in the salt industry needs to be done because the salt industry in Indonesia has not been able to meet domestic salt demand. Domestic salt supply deficit is caused by the salt industry in Indonesia just relies on salt traditional farmers who are very dependent on the sunlight and the absence of a modern and sustainable salt-making industry. Therefore, the authors made a salt factory design using low enthalpy geothermal by utilizing Parangwedang geothermal as a heat source energy. Parangwedang geothermal is located in the Special Region of Yogyakarta with existence manifestation as a hot spring. Based on previous research, the potential of Parangwedang geothermal was 10 MWe. The reservoir rock may have a temperature range 115 °C and the hot spring fluid temperature 43 °C. The hot spring distance from the seashore is 403 meters with elevation reach 8 meters. The method used in this study is literature study and data collection in the field. Literature data is obtained from various sources and then compiled and grouped for the design of the salt factory that utilizes low enthalpy geothermal energy. This factory system will involve two pumps, one of which will drain the hot water from the Parangwedang hot spring and the other will drain the water from the ocean to the salt production pan. A boiling tank and condenser are used to boil the sea. Hot water from the boiling tank is used for drying the salt brine and brine is dried in the salt pan. In the result, the authors calculated factory production capacity, the GSF production capacity is ±14 tons salt each year.

Utilization the Heat Pipe Heat Exchanger Techniques at Low Enthalpy Geothermal Energy to Coffee Drying Process

Coffee is one of Indonesia’s main commodity which competes in international market. However, Indonesia’s coffee production still faces some problems. One of the main problems is for the drying process. Moisture contents of coffee need to be reduced to 12%. All this time, most coffee producers use conventional method by using heat source from sunlight. However, uncertain weathers become one of the factors which slows down the drying process. Therefore, the purpose of this research is to find and utilize an alternative energy to solve the drying process problem. One of energy sources which is possible to be used for those criteria is geothermal energy especially with low enthalpy that usually is used for daily activities such as bathing, cooking, and warming houses. In this research, Heat Pipe Heat Exchanger (HPHE) which consists of 42 straight heat pipes with staggered configuration is used for utilizing geothermal energy. The heat pipe has a length of 700 mm OD 10 mm with filling ratio of 50% and added by 181 pcs of aluminum with dimension size of 76 x 345 x 0.105 mm as a fin. Geothermal fluid is simulated by water that heated by 9000 watt heater. Temperature of hot water with range of 50, 60, and 70?C and air speed of 0.2, 0.4, 0.6 m/s are variations for the experiment. The result shows that the highest effectiveness of HPHE is 78.8% with the temperature of 70?C and 0.2 m/s air speed while the lowest effectiveness is 68.8% with the temperature of 50?C and 0.6 m/s air speed. Other than that, the drying process with the temperature of 70?C and 0.6 m/s air speed is the fastest while the slowest is at 50?C and air speed of 0.2 m/s. This result proves that increasing the temperature and air speed lead to the less time needed for the drying process.

Study on Geospatial Distribution of the Efficiency and Sustainability of Different Energy-Driven Heat Pumps Included in Low Enthalpy Geothermal Systems in Europe

This research work aims at a multinational study in Europe of the emissions and energy costs generated by the operation of low enthalpy geothermal systems, with heat pumps fed by different energy sources. From an economic point of view, natural gas and biogas prices are, usually, lower than electricity ones. So it may be advantageous to use these energy sources to feed the heat pumps instead of electricity. From the environmental point of view, it is intended to highlight the fact that under certain conditions of electricity production (electricity mix), more CO2 emissions are produced by electricity consumption than using other a priori less “clean” energy sources such as natural gas. To establish the countries where each of the different heat pumps may be more cost-efficient and environmentally friendly, data from multi-source geospatial databases have been collected and analyzed. The results show that in the majority of cases, the electric heat pump is the most recommendable solution. However, there are some geographic locations (such as Poland and Estonia), where the gas engine heat pump may be a better alternative.

Low Enthalpy Geothermal Systems in Structural Controlled Areas: A Sustainability Analysis of Geothermal Resource for Heating Plant (The Mondragone Case in Southern Appennines, Italy)

In this study, the sustainability of low-temperature geothermal field exploitation in a carbonate reservoir near Mondragone (CE), Southern Italy, is analyzed. The Mondragone geothermal field has been extensively studied through the research project VIGOR (Valutazione del potenzIale Geotermico delle RegiOni della convergenza). From seismic, geo-electric, hydro-chemical and groundwater data, obtained through the experimental campaigns carried out, physiochemical features of the aquifers and characteristics of the reservoir have been determined. Within this project, a well-doublet open-loop district heating plant has been designed to feed two public schools in Mondragone town. The sustainability of this geothermal application is analyzed in this study. A new exploration well (about 300 m deep) is considered to obtain further stratigraphic and structural information about the reservoir. Using the derived hydrogeological model of the area, a numerical analysis of geothermal exploitation was carried out to assess the thermal perturbation of the reservoir and the sustainability of its exploitation. The effect of extraction and reinjection of fluids on the reservoir was evaluated for 60 years of the plant activity. The results are fundamental to develop a sustainable geothermal heat plant and represent a real case study for the exploitation of similar carbonate reservoir geothermal resources.

Numerical analysis of downhole heat exchanger designed for geothermal energy production

A traditional way of geothermal energy production implies hot brine extraction from the reservoir to a surface facility. This method is economically profitable only for high enthalpy reservoirs associated with shallow depths and high temperatures. The low enthalpy geothermal (LEG) projects are out of consideration due to the high cost of produced electric power related to expensive drilling, cost of the binary cycle system, and long term installation cost. This paper presents a new zero mass extraction method utilizing downhole heat exchanger (DHE) with no geo-fluid production to the surface. The well design stays as a single horizontal well with coupled production and injection sections. The brine pump is located between the sections providing hot brine circulation through the DHE. The coupled fluid flow and heat transfer mathematical model was developed and simulated using nodal analysis method. The LEG reservoir prototype located in South Louisiana was used to study several cases of the DHE lengths, inclination angles, reservoir permeabilities, and flow rates optimization. According to the analysis, the power unit is able to provide 160 kW of net electric power with CO2 working fluid circulating inside a single lateral well. Increasing the reservoir temperature and the number of laterals, the available power production rises up to 600 kW with an attractive electricity cost of $21.84/MWh at 7000 m well depth. This methods opens a new prospective for the depleted petroleum wells converting them to the electricity production units.

Ground Thermal Diffusivity Calculation by Direct Soil Temperature Measurement. Application to very Low Enthalpy Geothermal Energy Systems.

This paper presents a methodology and instrumentation system for the indirect measurement of the thermal diffusivity of a soil at a given depth from measuring its temperature at that depth. The development has been carried out considering its application to the design and sizing of very low enthalpy geothermal energy (VLEGE) systems, but it can has many other applications, for example in construction, agriculture or biology. The methodology is simple and inexpensive because it can take advantage of the prescriptive geotechnical drilling prior to the construction of a house or building, to take at the same time temperature measurements that will allow get the actual temperature and ground thermal diffusivity to the depth of interest. The methodology and developed system have been tested and used in the design of a VLEGE facility for a chalet with basement at the outskirts of Huelva (a city in the southwest of Spain). Experimental results validate the proposed approach.

Geophysical Methods for Monitoring Temperature Changes in Shallow Low Enthalpy Geothermal Systems

Low enthalpy geothermal systems exploited with ground source heat pumps or groundwater heat pumps present many advantages within the context of sustainable energy use. Designing, monitoring and controlling such systems requires the measurement of spatially distributed temperature fields and the knowledge of the parameters governing groundwater flow (permeability and specific storage) and heat transport (thermal conductivity and volumetric thermal capacity). Such data are often scarce or not available. In recent years, the ability of electrical resistivity tomography (ERT), self-potential method (SP) and distributed temperature sensing (DTS) to monitor spatially and temporally temperature changes in the subsurface has been investigated. We review the recent advances in using these three methods for this type of shallow applications. A special focus is made regarding the petrophysical relationships and on underlying assumptions generally needed for a quantitative interpretation of these geophysical data. We show that those geophysical methods are mature to be used within the context of temperature monitoring and that a combination of them may be the best choice regarding control and validation issues.

Modelling of the Response of the Niutuozhen Low-Enthalpy Geothermal System in Hebei Province, China

The Niutuozhen geothermal system, located in North China, is composed of the Jixian system dolomite reservoir and a Neogene sandstone reservoir. A three-dimensional model with 5437 elements and seven layers based on the geological and geothermal data was built using the AQUA3D package designed for solving flow and heat transport problems. Production history of forty five wells and pressure monitoring data from six wells were used for calibration. The calibrated model was then used to predict the geothermal system response of the geothermal field. The maximum predicted drawdown after 20 years of production without any reinjection ranged from 30 to 120 m in the north and south, respectively. The rate of drawdown was predicted to be kept at a lower level if 50% of the produced water was reinjected into the system. Cones of depression were predicted to gradually enlarge due to an increased production rate without reinjection, but were effectively limited and even diminished with a reinjection ratio of 50%. A maximum temperature decrease of 2.75°C was predicted to occur in production well A34, located near the reinjection well R3, for a production rate of 162 l/s with 50% reinjection. The maximum temperature decrease of 24.81°C was predicted to occur in the southern reinjection well R2. Prediction of temperature response indicated that the reinjection rate, the temperature of the reinjected water and the distance between the reinjection and production wells are the three factors affecting the reservoir temperature change. Reinjection is a indispensible measure for maintaining pressure of the reservoir. However, reservoir cooling induced by reinjection of the cold water should be considered carefully.

Utilization and Research on Medium-Enthalpy and Low-Enthalpy Geothermal Energy in WSHP System

Geothermal energy is a stable energy, stored underground and not influenced by the geographical, seasonal weather and the change of day and night. Medium-enthalpy and low-enthalpy geothermal energy are distributed in many areas of China, having a broad prospect for development. Taking water resources heat pump (WSHP) engineering in Tianqiao District as an example, medium-enthalpy and low-enthalpy geothermal energy is combined with the technology of aquifer thermal energy storage (ATES), providing cold energy in summer and warm energy in winter for the buildings. On the base of analysis of hydrogeological conditions in Tianqiao District, the temperature field of energy storage aquifers is numerically analyzed in the period of heating and cooling. The results show that the energy storage well can meet the requirement of heating and cooling conditions. The system of WSHP greatly utilizes medium-enthalpy and low-enthalpy geothermal energy, making the running costs economical.

Low Enthalpy Geothermal Energy for Greenhouse Heating at Nea Kessani Xanthi, Greece

This article deals with the direct use of a low enthalpy geothermal energy source situated in Northern Greece (Potamia-Nea Kessani) to heat a greenhouse where vegetables (such as tomatoes) could be grown. A description of the geothermal field in Potamia-Nea Kessani is given together with the technical characteristics of the developed greenhouse and the heating installation. A technoeconomic analysis of two different greenhouse-heating approaches is given and the simple payback period is calculated. It was found that in Nothern Greece there are many areas (such as the one described in this article) where low enthalpy geothermal sources could be exploited easily at a very reasonable cost.