Geothermal Energy Sources Research Articles

Development of a geothermal-flash organic Rankine cycle-based combined system with solar heat upgrade

In this paper, a new concept of clean energy harvesting from solar energy source is explored in which a fluctuating nature of solar energy source is enhanced with a geothermal energy source. Due to solar radiation's diffuse and fluctuating character, an expensive thermal storage system is required in a solar-only system. On the other hand, due to the relatively low-temperature level of geothermal brine, the flash Rankine power plant has low energy efficiency. The method used in the present study is system integration in which solar thermal energy enhances brine temperature and superheats steam for improved power generation efficiency. Synergistically, the geothermal power cycle eliminates the need for a solar thermal energy storage system, and thus, it reduces capital costs. A geothermal flash Rankine cycle is considered, which is cascaded with an organic Rankine cycle and heat recovery unit for cogeneration. Three types of organic Rankine cycles are investigated with various working fluids for regular, retrograde and transcritical configurations. The transcritical configuration, operating with Perfluorocarbon (C3F8), is found the best working fluid. The maximum exergy destruction in the organic Rankine cycle takes place in the turbine with 48%, whereas at the source side heat exchanger, this is 30%. After flashing, the vapour quality influences power generation efficiency, which shows a maximum vapour quality of around 10% for the case studied. Nevertheless, the maximization of cogenerated exergy rate happens at higher flashing vapour quality than the maximization of exergy efficiency for overall cogeneration application. The exergy efficiency for cogeneration is better during nighttime, for instance, 68% versus noontime 40%, because with solar energy input, there is large exergy destruction at solar collectors. However, during the peak solar radiation at noontime, the cogenerated exergy is more than double that of nighttime, showing an enhanced power generation. This concludes that the proposed integration is effective and creates a higher revenue stream potential than the two technologies working independently.

Are Engineered Geothermal Energy Systems a Viable Solution for Arctic Off-Grid Communities? A Techno-Economic Study

Deep geothermal energy sources harvested by circulating fluids in engineered geothermal energy systems can be a solution for diesel-based northern Canadian communities. However, poor knowledge of relevant geology and thermo-hydro-mechanical data introduces significant uncertainty in numerical simulations. Here, a first-order assessment was undertaken following a “what-if” approach to help design an engineered geothermal energy system for each of the uncertain scenarios. Each possibility meets the thermal energy needs of the community, keeping the water losses, the reservoir flow impedance and the thermal drawdown within predefined targets. Additionally, the levelized cost of energy was evaluated using the Monte Carlo method to deal with the uncertainty of the inputs and assess their influence on the output response. Hydraulically stimulated geothermal reservoirs of potential commercial interest were simulated in this work. In fact, the probability of providing heating energy at a lower cost than the business-as-usual scenario with oil furnaces ranges between 8 and 92%. Although the results of this work are speculative and subject to uncertainty, geothermal energy seems a potentially viable alternative solution to help in the energy transition of remote northern communities.

Assessing the physical potential capacity of direct air capture with integrated supply of low‐carbon energy sources

AbstractDirect Air Capture (DAC) is a negative emission technology that can remove up to 10–20 Gt of CO2 per year. However, to achieve this potential, DAC systems must be coupled to suitable locally available energy sources and sited near geological storage. This study explores the potential of low‐carbon energy sources to supply power and heat to the DAC process in a dedicated, self‐sufficient system tailored for each energy source. Solar, geothermal, woody biomass, wind, and nuclear energy sources are assessed for their global energy supply potential and possible land use requirements. While the options differ in area requirement and regional efficacy, we estimate that all the regionally specific technologies considered can supply energy to achieve significant removal of carbon dioxide from the atmosphere globally. The amount of energy physically available from solar, offshore wind, and woody biomass converts to a removal potential of 160–971, 45–150, and 2–5 Gt CO2/year, respectively. Thus, negative emission targets can be reached by utilizing a moderate fraction of the overall potential of several different low‐carbon energy sources for DAC while the magnitude of the potential changes significantly according to the source of energy. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

Optimal design of a hybrid thermal- and membrane-based desalination unit based on renewable geothermal energy

• A renewable-based hybrid desalination system consisting of HDH and RO is evaluated. • Two different operating modes of the introduced system are investigated. • Exergoeconomics is used to identify the optimal working condition of the system. • Maximum exergy efficiency of the plant is 28.86% for the second operating mode. • The first operating mode can provide freshwater at a maximum rate of 22070 m 3 /day. In this article, exergoeconomic analysis of a hybrid desalination system driven by renewable geothermal energy source is investigated. Freshwater and electrical power are the products of this system. Humidification – dehumidification (HDH) unit works in parallel with reverse osmosis (RO) unit to produce freshwater and Kalina cycle is the power generator unit. Thermoelectric generator (TEG) is responsible for providing the energy required by RO unit. As both HDH and TEG can operate with low-grade energy, two different modes are suggested for the proposed system. In the first mode, the geothermal low grade energy stream is passed to TEG unit, while in the second, it goes through the HDH unit. The effect of different parameters on four main objective functions is examined in parametric study. Moreover, with the aid of selection maps, the objectives of modes can be compared in different operating conditions. The maximum attainable exergy efficiency is calculated to be 28.86% for mode 2. Single objective optimization studies revealed that the first mode produces the largest amount of freshwater at a rate of 22,072 (m 3 /day), while the minimum achievable freshwater cost and total product cost rate can be obtained in the second mode, which is calculated to be 21.94 (¢/m3) and 37.19 ($/GJ). Besides, Sankey diagrams for exergy flow and mass flow of saline water are presented to unravel the impact of each sub-system on exergy and salinity.

Prospects for the development of geothermal energy supply

The paper addresses methodological and technological issues of building environmentally friendly and efficient energy supply based on geothermal energy sources. Geothermal potential in the world, accentuating that in Russia (areas of the Baikal natural territory) and Mongolia, is analyzed considering the possibility of its implementation in the thermal power industry. Geothermal areas of Central Mongolia are characterized by increased heat flows and occurrences of thermal waters. The most promising thermal spring occurrences are the Shivert, Shargalzhuut, Tsenkher, Otgontenger, and Khuzhirt, to name some of them. Currently, the thermal energy potential of the Khangai arched uplift in Central Mongolia is employed to heat industrial, agricultural, and civil facilities. There are also plans to consider the possibility of large-scale employment of thermal waters of the region for electricity generation. An example of using geothermal waters for electricity generation is given, and the possibility of establishing a heating system in the city of Tsetserleg based on a geothermal heat pump unit with a wind power plant is assessed.

Estimation of radioelements concentration in Sokoto Basin for geothermal energy studies using airborne radiometric data

High resolution aero-radiometric data of Sokoto basin Northwestern, Nigeria were used in this research work. The location of the basin is between latitude 11o30I to 13o30IE and longitude 4o30I to 6o30IN. Sixteen (16) sheets of high resolution of airborne radiometric data were used to obtain the concentration of Potassium (K), Uranium (U) and Thorium (Th) respectively in the area of interest. The data were gridded and analyzed using Geosoft software. The result of the analysis revealed that potassium concentration is between -0.577935% to 7.34347% with an average of 3.3827%. The Thorium concentration values ranged from -3.81541ppm to 91.9404ppm with an average of 44.0624ppm. The Uranium concentration revealed values from -4.44524ppm to 46.1767ppm with an average of 20.86572ppm. The ratio of potassium and equivalent thorium (K/eTh) indicated values between -8.69847%/ppm to 39.567%/ppm and ratio of equivalent uranium and equivalent thorium (eU/eTh) revealed values between -412.181ppm to 99.4613ppm. The ternary diagram of the radiometric data showed that the south and southeastern regions of the study area have high radioactive mineral concentration above the average normal value of radioactive minerals in a natural environment and radioactive minerals are good source of geothermal energy. The results obtained has shown that the basin has geothermal potential which can cause non productivity of hydrocarbon in the area of interest and the research area can be recommended for geothermal energy resource to compliment the electric power supply in the nation.

Design and Development of a Solar-Powered Smart Heater

Renewable energy sources are those that replenish naturally without depletion. Example of such sources are bioenergy, hydropower, geothermal, wind and solar energy sources. The alarming rate of global energy demand and consumption necessitates an immediate solution for energy conservation and maximum efficiency of new technological gadgets now being built. As a gadget, a solar water heater transforms dc electricity into heat energy, which is then transferred to the water in which it is immersed. The size of the heater is determined by its design, capacity, and intended purpose; it might be for household or industrial use. As an alternative to conventional electric water heaters, this effort focuses on the design and development of a solar-powered smart water heater. In tests using a variety of settings, the solar-powered smart heater that was constructed performed admirably. The components used include a PIC16F876A microcontroller, a 12 V/300 W monocrystalline PV, a 12 V/ 40 A charge controller, and 12 V / 150 W dc submersible heating element among others The temperature control capacity of the fabrication makes it useful in water management system applications such as in aquaculture fingerling hatchery, hot water dispenser and shower among others. The system showed excellent performance in water temperature control using a 150 watts dc heater. Keywords:Solar, heater, photo-voltaic, temperature-controlled, direct current, alternating current .

The Relationship Between CO2 Emissions and Economic Growth in Turkey

The relationship between environmental pollution and economic growth has recently been the focus of discussion between policy makers and scientists around the world. The relationship between environmental pollution and economic growth has recently been the focus of discussion between policy makers and scientists around the world. In order to meet human needs, energy is needed in the activities to be carried out and the demand for this energy has increased exponentially over the years. Today, energy is produced from two sources: fossil fuels and renewable resources. Turkey renewable energy resources, particularly hydropower, wind energy, solar energy and are a country with significant potential for geothermal energy sources. Compared to fossil fuels, the carbon emissions from renewable energy sources are low. CO2 emissions from the use of fossil fuels vary depending on the type of fossil fuel used. In this study, the energy sector between Turkey's 1990-2016year, agricultural activities and carbon emissions per person from industrial processes and the per capita change in the manufacturing sector with the relationship between GDP energy imports, health care costs have been analysed.

Borehole Thermal Analysis for a Closed Loop Vertical U-Tube DX Ground Heat Exchanger

The borehole geometry configuration and its sizing represent great challenges to the thermal equipment designer in the field of geothermal energy source. The present work represents a piece in that direction to avoid elaborate mathematical and computation schemes constraints for the preliminary design of the U-tube ground heat exchanger operates under a steady-state condition. A correlation was built for the prediction of the borehole thermal resistance. The U-tube diameter, leg spacing, borehole diameter, and the offset configuration with respect to the center of the borehole were introduced in the present correlation. An equivalent tube formula and borehole configuration were postulated to possess the same grout volume as the original loop. A variety of geometrical configurations were tested at different U-tube and borehole sizes. The predicted total thermal resistance of the borehole was implemented into the thermal design of the (DX) ground condenser to sizing the borehole U-tube heat exchanger. A hypothetical cooling unit of (1) ton of refrigeration that circulates R410A refrigerant was chosen for the verification of the present model outcomes. The predicted thermal resistance revealed an excellent agreement with other previously published work in this category.

Machine Learning Tools for Fossil and Geothermal Energy Production and Carbon Geo-sequestration—a Step Towards Energy Digitization and Geoscientific Digitalization

Eighty percent of current world energy consumption is satisfied by subsurface resources. In future, billions of watts of electrical power will be generated from geothermal energy sources. Subsurface earth can store the energy produced from renewable sources, such as wind and solar, and could provide safe storage of contaminants and hazardous nuclear waste. Engineering of subsurface earth is critical for fossil energy production, geothermal energy production, and carbon geo-sequestration. However, the subsurface is opaque, inaccessible, and heterogenous with nano-scale to kilo-scale processes that limits our understanding (characterization) and constrains the efficient engineering of the complex subsurface earth resources. There has been rapid increase in sensor deployment, data acquisition, data storage, and data processing for purposes of better engineering and characterizing the subsurface earth. This has promoted large-scale deployment of data-driven methods, machine learning, and data analytics workflows. Subsurface data ranges from nano-scale to kilometer-scale passive as well as active measurements. Subsurface data is acquired in the form of physical fluid/solid samples, images, 3D scans, time-series data, waveforms, and depth-based multi-modal signals, to name a few. Subsurface data sense various physical phenomena, e.g., transport, chemical, mechanical, electrical, and thermal properties. Integration of such varied data sources being acquired at varying scales, rates, resolutions, and volumes mandates robust machine learning methods to better characterize and engineer the subsurface earth. Machine learning has shown to improve the efficiency, efficacy, and productivity of subsurface engineering and characterization efforts required to produce fossil/geothermal energy and to sequester carbon dioxide.

Hydrogen farm concept: A Perspective for Turkey

Hydrogen farm concept: A Perspective for Turkey

Stochastic Techno-economic Analysis of CO2-circulated Geothermal Energy Production in a Closed Reservoir System

Many wells become abandoned with the depletion of oil and gas reservoirs, and low-enthalpy geothermal energy could be extracted from these abandoned wells. CO2 has been proposed and studied as the working fluid for mining such geothermal energy sources, owing to its favorable thermodynamic properties. The objective of this study is to develop an uncertainty-based simulation-optimization approach to analyze the techno-economic feasibility of CO2-circulated geothermal production in a closed reservoir system. In doing so, we address the particular geothermal reservoir conditions found in North Oman`s foreland basin where several large oil/gas fields are located. The geothermal reservoir conditions in this area can be characterized by inclined and thin layers, partially to fully fault-blocked, and relatively homogeneous and low permeable formations. Such conditions have not been investigated in the context of CO2-circulated geothermal production. Another key novelty of this work is to analyze a triplet horizontal well placement designed particularly for such thinly-bedded fully-closed reservoirs. The main building blocks of the proposed methodology are the application of a non-isothermal, multi-phase, multi-component numerical reservoir simulator, a neural network-based metamodel, Monte Carlo simulations, and genetic algorithm. The findings suggest the proposed well pattern is technically feasible and economically viable to harvest low-enthalpy geothermal energy from the type of depleted reservoirs found in North Oman region.

Heat transfer analysis on the tool of heat exchanger of plate type

North Sulawesi has a geothermal energy source which is renewable energy and can be used as a geothermal power plant or Geothermal power company(PLTP). The Geothermal Power Company(PLTP) is located in Lahendong and is a power plant that is friendly to the surrounding environment because it uses geothermal energy as its resource. In Lahendong Geothermal Power Company(PLTP) unit 2, there are important components used to convert steam into electricity, one of which is a heat exchanger. The research aims to find out the heat transfer coefficient and the effectiveness of the heat exchanger during commissioning with real time, based on operational data and installation data on heat exchangers in the Geothermal Power Company(PLTP) Lahendong Unit 2. From this study the results obtained were the highest heat exchange coefficient at commissioning was 107.47 kW / m2. K and the lowest at real time II was 66.93 kW / m2. K. Furthermore, the effectiveness of the highest heat exchanger occurred at commissioning of 51.96% and the lowest at real time II was 37.19%. From the results obtained, the heat exchanger has decreased both in the heat exchange coefficient and the effectiveness of the heat exchanger. The Increase of the effectiveness of the tool of heat exchanger will affect the increase in the heat transfer coefficient on the tool of heat exchanger.

Applying Harmonised Geothermal Life Cycle Assessment Guidelines to the Rittershoffen Geothermal Heat Plant

Heat production from a geothermal energy source is gaining increasing attention due to its potential contribution to the decarbonization of the European energy sector. Obtaining representative results of the environmental performances of geothermal systems and comparing them with other renewables is of utmost importance in order to ensure an effective energy transition as targeted by Europe. This work presents the outputs of a Life Cycle Assessment (LCA) performed on the Rittershoffen geothermal heat plant applying guidelines that were developed within the H2020 GEOENVI project. The production of 1 kWhth from the Rittershoffen heat plant was compared to the heat produced from natural gas in Europe. Geothermal heat production performed better than the average heat production in climate change and resource use, fossil categories. The LCA identified the electricity consumption during the operation and maintenance phase as a hot spot for several impact categories. A prospective scenario analysis was therefore performed to assess the evolution of the environmental performances of the Rittershoffen heat plant associated with the future French electricity mixes. The increase of renewable energy shares in the future French electricity mix caused the impact on specific categories (e.g., land use and mineral and metals resource depletion) to grow over the years. However, an overall reduction of the environmental impacts of the Rittershoffen heat plant was observed.

DRILLING FOR GEOTHERMAL HEAT

An abandoned coalmine is being repurposed as a source of geothermal energy that will heat council-owned buildings in South Tyneside.

Life cycle assessment (LCA) of a novel geothermal-based multigeneration system using LNG cold energy- integration of Kalina cycle, stirling engine, desalination unit and magnetic refrigeration system

A comprehensive and detailed investigation is conducted on a novel multigeneration system developed for Minab city (as a case study) in terms of thermodynamic, economic and environmental aspects. The system utilizes geothermal energy source to simultaneously generate four useful commodities: 36 ton/h pure water, 7774 kW net electricity, 354 ton/h hot water (at 77 °C), and 45 ton/h cold water (at 5 °C). The integrated system consists of four subsystems (Kalina cycle, Stirling engine, magnetic refrigeration system and desalination unit). The process simulation and exergetic evaluation are conducted by Aspen HYSYS V 11 and MATLAB software, respectively. The whole system is 42.95% efficient in terms of exergy and exergy destruction rate is 11382 kW. A sensitivity/3D analysis is also conducted to investigate the mutual interactions among exergy destruction, costs and environmental impact of each component. The exergoeconomic analysis and life cycle assessment conclude that heat exchanger HX-8 should be re-designed to improve the cost-affectivity and decline the negative environmental impact of the designed integrated energy conversion system. A comparison between the proposed multigeneration system and four other geothermal energy based systems consisting of LNG regasification sub-unit shows a significantly higher exergy efficiency and lower cost flow rate of product.

Solar collector field and thermal energy storage for auxiliary component in organic rankine cycle for bottoming unit to utilize exhaust steam from back pressure turbine of Ulumbu geothermal power plant

Flores has a vast geothermal energy sources, one of the fields, Ulumbu, producing electricity from the geothermal power plant (PLTP). PLTP Ulumbu has two back pressure turbines generating 2.5 MW electricity. Besides geothermal power, Flores has potential solar energy sources that are recorded as much as 5 to 6 kWh/m2/day. The exhaust steam from the backpressure turbine adds the binary cycle as the bottoming unit. It is able to generate electricity continously to supply the baseload. Currently, the peak load of electricity usage in Flores is supplied by the diesel power plant (PLTD). This paper studies the addition of solar collectors and thermal energy storage (TES) as auxiliary components in the binary cycle and simulates the system by using the Aspen Plus. The solar energy is stored in TES during the day and then released to the heat exchanger in the evening. This idea reduces the dependency on diesel power plants in the evening. To increase power as much as 500 kW, the collector area needed to supply the system is 1.1 ha using synthetic oil as HTF. The volume of TES to stored the energy by using nitrate salts as HTF is 1,120 m3. As a result, the efficiencies of the non-hybrid system and hybrid systems are 11.38% and 11.31% subsequently.

ANALISA KINERJA DEMISTER SELAMA TAHUN 2019 DI PLTP LAHENDONG

Geothermal is now widely used by several developed countries, there are very many roles of geothermal energy sources, it is necessary to use one of them by utilizing geothermal heat energy itself into electrical energy. In chemical process industry there are a number of processes where a gas and a liquid come into contact with each other and whenever this happens, the gas will introduce a number of liquid particles. This liquid phase carried over to the gas phase can cause a number of problems such as equipment breakdown, process inefficiency etc, and need to be eliminated. Equipment used to remove entrainment is known as a Demister. This study aims to calculate Demister Efficiency throughout 2019 at PLTP Lahendong. Research conducted is to collect data at the Lahendong Geothermal Power Plant Unit-2 and this research uses data processing methods that use applications, namely steam tables and Microsoft Excel. Demister's performance in 2019 for 3 months got 88.90% J results which were influenced by heat loss, pressure and inner diameter, from results obtained after processing it can be concluded that the higher the heat loss value, better the efficiency value, Explains that performance Demister arguably had no problems in a year.

Analysis of Global Warming’s Influence on the Dimensioning of Borehole Heat Exchangers at a Climate-Exposed Site

A borehole heat exchanger (BHE) presents the most reliable source of geothermal energy for any object where the heat pump system is to be installed. The main objective of BHE optimization in a specific rock massive and for calculated heat consumption is to design a BHE with proper capacity and sustainable performance. One of the most important inputs for the preparation of such a model is the average outer air temperature on the site during the year. While the properties of the local rock massive are from the heat project lifetime view (tens of years) stable, the local average outer temperature fluctuates according to global climate changes. This article presents a study of the impact of climate changes on the dimensioning process of a BHE and consequently on its performance using data from a real installation at a highly climate-exposed site in the Czech Republic. During the dimensioning of a BHE, this study could help to better quantify the objective risks that result from climate changes. However, the results of this study show that the currently calculated impact of an increase in outer temperature is not crucial, but it is advisable to take this new fact into account during the design and dimensioning process, especially for large installations. To study the ground in terms of usable energy potential at climate-exposed locations properly, the available data were critically analyzed and the results were then synthesized in an appropriate way for the needs of the data simulations.

Underground heat mine – potential for large scale production and storage of thermal energy

We have studied possibilities to utilize the 1.4 km deep Pyhäsalmi mine as a source of geothermal energy. Measured thermal conductivities of the Precambrian (1.9 Ga) crystalline bedrock hosting the massive Cu-Zn sulphide deposit vary between 2.5 and 3.5 W/m·K, depending on the rock type, and the bedrock temperature increases with depth by 12–14 K/km. The design concept for heat utilization studied in this project is based on an underground borehole field exchanging heat between the bedrock and the water circulation loop, which then transfers thermal energy to the heat pumps. In the borehole heat exchanger (BHE) performance evaluations, we focused on a coaxial configuration, in which formation water circulates down in contact with borehole wall and returns inside a pipe. The borehole field modelled has a hemispherical geometry, so that all boreholes start from a central hall at the bottom of the mine (where the temperature is 21 °C) and would be directed radially outwards. Our reference case consists of 136 boreholes having length of 300 m, thus covering a rock volume of 57 million cubic meters. Simulations indicate that this BHE fields can sustain heating power of 1 MW for at least 44 years, but the average temperature of the borehole field would decrease by about 10 degrees. Thermal power can be increased substantially by increasing the borehole density, but the lifetime of the BHE field decreases.