Stationarity and cycles in the energy consumption in the United States.

The purpose of this paper is twofold: analyzing stationarity of energy consumption by source in the United States and studying their cycles and pairwise synchronization. We study a panel of nine time series of monthly energy consumption for the period 1973-2022. Four of the series (namely coal, natural gas, petroleum, and nuclear electric power consumption) are non-renewables, whereas the remaining ones (hydroelectric power, geothermal, biomass, solar, and wind energy consumption) are renewable energy sources. We employ a nonparametric, panel stationarity testing approach. The results indicate that most of the series may be trend-stationarity, with nuclear and geothermal energy consumption being the only exceptions. Additionally, a study on potential cycles in the series of energy consumption by source is carried out, and subsequently we analyze pairwise concordance between states of different energy sources and between states of energy sources and the business cycle. Significant correlations are detected in the latter analysis, which are positive in the case of fossil fuel sources and negative for two renewable sources, namely geothermal and biomass energy consumption.

IoT Sensor Challenges for Geothermal Energy Installations Monitoring: A Survey.

Geothermal energy installations are becoming increasingly common in new city developments and renovations. With a broad range of technological applications and improvements in this field, the demand for suitable monitoring technologies and control processes for geothermal energy installations is also growing. This article identifies opportunities for the future development and deployment of IoT sensors applied to geothermal energy installations. The first part of the survey describes the technologies and applications of various sensor types. Sensors that monitor temperature, flow rate and other mechanical parameters are presented with a technological background and their potential applications. The second part of the article surveys Internet-of-Things (IoT), communication technology and cloud solutions applicable to geothermal energy monitoring, with a focus on IoT node designs, data transmission technologies and cloud services. Energy harvesting technologies and edge computing methods are also reviewed. The survey concludes with a discussion of research challenges and an outline of new areas of application for monitoring geothermal installations and innovating technologies to produce IoT sensor solutions.

Geothermal energy integrated multi-effect evaporator (MEE) and multi-effect distillation (MED)-based desalination systems: an ecofriendly and sustainable solutions.

Desalination is a tried-and-true method for obtaining clean water from the ocean's brackish waters and recycling and reusing water. It requires a fair amount of energy, so it is necessary to create sustainable energy systems to lessen energy use and environmental impact. For thermal desalination procedures, thermal sources can be great heat sources. This paper's research focuses on thermoeconomically optimized multi-effect distillation and geothermal desalination systems. Collecting hot water from subsurface reservoirs is a well-established method of generating electricity through geothermal sources. Low-temperature geothermal sources, which have a temperature of less than 130 °C, can be utilized for thermal desalination systems, for example, multi-effect distillation (MED). Geothermal desalination is affordable, and it is possible to produce power simultaneously. Because it only uses clean, renewable energy and produces no greenhouse gasses or other pollutants, it is also safe for the environment. The viability of any geothermal desalination plant will be influenced by the location of the geothermal resource, feed water supply, cooling water source, water market, and concentrate disposal site. Geothermal energy can directly supply heat for a thermal desalination system or indirectly give electrical power to reverse the osmosis (RO) membrane-based desalination plant.

Return connectedness and multiscale spillovers across clean energy indices and grain commodity markets around COVID-19 crisis.

The aim of this paper is to examine the return connectedness and multiscale spillovers between the Clean Energy Index and the grain commodity market around COVID-19. Using daily data from January 4, 2017 to July 1, 2022, a time-varying parametric vector autoregressive (TVP-VAR) connectedness approach is first used to reveal connectedness patterns before and during COVID-19. We further used Baruník and Krehlík (2018)'s frequency domain spillover method to assess connectedness in different domain horizons. Our results show spillover effects over time and frequency, with COVID-19 significantly affecting the connectedness of the whole system. Dynamic connectedness peaks significantly after sudden bursts of COVID-19, validating the reported uncertainty. We also documented higher spillover levels in the short term than in the medium and long term. In addition, We find that (i) most clean energy indices are positively affected by the COVID-19 outbreak; (ii) the NASDAQ OMX Bio/Clean Fuels Index and NASDAQ OMX Geothermal Index send spillovers to all grain commodities throughout the sample period, while the WilderHill Clean Energy Index and NASDAQ OMX Wind Energy Index indices are the largest recipients of spillovers from other markets regardless of time horizon; (iii) the OMX Bio/Clean Fuels and OMX Geothermal Energy indices dominate spillover shocks to grain commodity markets. This is the first study to analyse the connectedness and time-frequency dynamics of returns in the green energy index and the grain commodity market. These results provide valuable insights to investors and key policymakers, especially at a time of more significant uncertainty.

Integration of geothermal-driven organic Rankine cycle with a proton exchange membrane electrolyzer for the production of green hydrogen and electricity.

Engineers and scientists are increasingly interested in clean energy options to replace fossil fuels in response to rising environmental concerns and dwindling fossil fuel resources. There has been an increase in the installation of renewable energy resources, and at the same time, conventional energy conversion systems have improved in efficiency. In this paper, several multi-generation systems based on geothermal energy are modeled, assessed, and optimized which employ an organic Rankine cycle and a proton-exchange membrane electrolyzer subsystem in five different configurations. Based on the results, the evaporator mass flow rate and inlet temperature, turbine efficiency, and inlet temperature are the most influential parameters on system outputs, namely, net output work, hydrogen production, energy efficiency, and cost rate. In this study, the city of Zanjan (Iran) is selected for a case study, and the results of system energy efficiency for changes in ambient temperature are examined during the four seasons of the year. To determine the optimal values of the objective functions, energy efficiency, and cost rate, NSGA-II multi-objective genetic algorithm is employed, and a Pareto chart is derived. The system's irreversibility and performance are gauged by energy and exergy analyses. At the optimum state, the best configuration yields an energy efficiency and cost rate of 0.65% and 17.40 $/h, respectively.

Internal radiation exposure from TENORM for workers conducting cleaning activities on equipment used at geothermal energy plant.

Geothermal energy is predicted to be one of the most important renewable energy sources in the near future. In geothermal energy plants, the secondary products such as the scale containing naturally occurring radioactive material (NORM) and adhering to the surface of equipment produce radiation fields. The workers who maintain and clean such equipment are at a risk to be exposed by the technically enhanced NORM (TENORM). To estimate the risks of radiation exposure to the workers, we assessed internal doses resulting from the cleaning activities on 150 heat exchanging boards used at a geothermal energy plant, focusing on 222Rn, 226Ra, 210Pb, 228Ra and 228Th. The experiment was performed with the subjects of workers and office workers as control, supplying prepared foods and drinks. Using the analytical results of 210Pb, 226Ra, 228Ra, and 228Th in the excretions of subjects, committed effect doses were determined. The annual internal dose for the workers with protective clothing due to the cleaning activities on removing scale, assuming the cleaning activities requires 170 h (standard monthly working time) a year, was obtained as 26 µSv/y and the total dose including 222Rn inhalation dose was calculated as 323 µSv/y. The additional dose for the cleaning workers was less than the dose limit of 20000 µSv/y for radiation workers, even less than for general population (1000 µSv/y) recommended by International Commission on Radiological Protection (ICRP). However, the elevated inhalation dose for workers conducting cleaning activities may present a health hazard to workers if they deal with excessive materials containing TENORM, work for excessive time or are under inappropriate safety measures.

Does geothermal energy and natural resources affect environmental sustainability? Evidence in the lens of sustainable development.

Climate change and global warming have been driven by a rise in carbon dioxide (CO2) concentrations in recent decades, posing a danger to environmental sustainability. Thus, this research scrutinizes the effects of two types of energy (coal and geothermal) and natural resources on CO2 emissions in 10 newly industrialized countries (NICs). The study also considers the role of financial globalization using a data between 1990 and 2019. This research applied a fresh nonparametric econometric technique termed "method of moments quantile regression (MMQR)." This approach is resistant to outliers and produces an asymmetric connection between variables. Furthermore, the long-run estimators (AMG and CCEMG) are employed as a robustness check. The findings reveal that natural resources, coal, and economic growth contribute to the degradation of the environment in the NICs in all quantiles (0.1-0.90). However, geothermal energy aids in enhancing environmental sustainability at all quantile distributions (0.1-0.90). Our findings are robust with alternative methods (AMG and CCEMG). The research's outcomes have the potential to help NICs nations design policies. Finally, based on the research results, a policy framework is proposed to solve the objectives of SDGs 7 and 13.

Unveiling the impacts of geothermal energy growth on food security in EU27 region: an empirical analysis.

There are many advantages of geothermal energy, as an environmental friend resource. This heat radiation emanating from beneath the earth's surface presents man with good opportunities to harness it and makes a good level of agricultural food production and its processing in the EU region. The primary objective of this research is to examine the impact of geothermal energy on agri-food supply among the 27 European countries (EU27), within the time frame 1990 to 2021. The study adopted the autoregressive distributed lag (ARDL), and the findings from this study revealed that agri-food supply can increase significantly among the 13 European countries (EU13 emerging economies), leveraging on geothermal energy and economic growth variables than in the EU14 emerged economies. Furthermore, the outcome of this study showed that there could be a significant decrease in the food products coming from agricultural practices among the 13 European countries (EU13 emerging economies), due to an ineffective population density than in EU14 emerged economies. Furthermore, fossil fuel and institutional quality contribute more positively to the agri-food supply in the EU14 emerged economies than in the EU13 emerging economies. This results in an outcome that means that the agri-food supply among the EU13 emerging economies could be greatly boosted by replacing fossil fuel consumption with geothermal energy, and this facilitates the attainment of the European energy goals by the year 2030. Substituting fossil fuels with geothermal will also assist in minimizing the risks of environmental pollution and climate change. All projected calculations were seen as valid in this study, and this was confirmed by the three estimators adopted which are the pooled mean group, the mean group, and the dynamic fixed effect. This study, therefore, recommends that the 27 European countries should lay more emphasis on geothermal energy production as this will help in ensuring food security in the region. Policymakers and other government authorities as well as local and foreign investors should make more investments in geothermal energy resources as this study has proven that this will lead to agri-food security and sustainability. Not only this, it will as well curb the incidence of climate change and environmental pollution.

Toward a sustainable environment: nexus between geothermal energy growth and land use change in EU economies.

There are many advantages of geothermal energy as an environmentally friendly resource; however, there are quite a several challenges that need to be overcome to completely harness sustainable and renewable energy that is also natural. The primary aim of this study is to examine what influence geothermal energy will have on land use changes among the considered 27 states in the European Union from the time being 1990 to 2021. The study adopts the auto-regressive distributed lag (ARDL); the findings show that geothermal energy growth could be leveraged to achieve remarkable growth in land use change among the 13 European developing economies than among the 14 EU developed economies. On the other hand, results from analysis further show that a remarkable decrease in land use change could be better attained among the 14 EU developed economies that among the 13 EU developing economies as a result of institutional quality. Furthermore, the result suggests that through economic growth, there could be a remarkable increase in land use change among the 14 EU developed economies than among the 13 EU developing economies. It was further revealed by the study that the level of land use change among the 27 EU nations could be remarkably increased, boosting the level of geothermal energy production that will assist in attaining the aims behind the 2030 energy union. This will eventually help in curbing the incidence of climate change and pollution in the environment; the projected calculations are observed to be valid, as confirmed through the chosen three estimators for this research. The chosen estimators are the pooled mean group, mean group, and dynamic fixed effect. The regulations and governors in 27 European Union countries should give priority to using geothermal in their renewable energy mix to reduce the incidence of changes in land structures. Also, an increased level of efficiency and effectiveness should be made to the generation of geothermal energy by state actors and investors to prompt sustainability and attainability with no further depreciation in agricultural and forest natural states.

A review on geothermal energy resources in India: past and the present.

By 2040, India hopes to have completed its energy supply to fulfill the country's rising energy demands. Renewable and conventional sources must be used in an environmentally acceptable manner to achieve sustainable growth. India must enhance its use of renewable and clean energy sources, including geothermal, wind, and solar, to satisfy its growing demand. While solar and wind energy output has increased significantly, geothermal energy has yet to be fully harnessed. Among the many forms of geothermal energy found on the surface are volcanoes, fumaroles, erupting geysers, steaming fields, and hot springs. A total of about 340 geothermal springs may be found in India, spread throughout both orogenic (in the Himalayas) and non-orogenic (in the Peninsula). There were 31 places extensively evaluated, and deep drilling was performed in sixteen of them. Average temperatures range from 35.0°C to the boiling point of water in these springs. Medium (100.0-200.0°C) and low (100°C) enthalpy geothermal energy resources/systems are found in India, with the latter being the most abundant. The essential component of a geothermal system is understanding the heat source and harnessing it. Studies so far have indicated that some geothermal areas have sufficient geothermal potential for direct heat usage and power generation. If the Puga (J&K) field is explored to a depth of at least 500 m, reservoir simulation studies have shown that it might produce more than 3 MW of power. India's diverse geothermal sites and the current status of exploration for future research are discussed in the paper.

Conceptual Modelling of Two Large-Scale Mine Water Geothermal Energy Schemes: Felling, Gateshead, UK.

A conceptual model is presented of two MW-scale low enthalpy mine water geothermal heat pump schemes that are being developed in Tyneside, UK. The Abbotsford Road scheme (54.955° N 1.556° W) is operating (as of May 2021) at 20-30 L/s, abstracting groundwater (and heat) from an unmined Coal Measures Upper Aquifer System (UAS) and reinjecting to the deeper High Main Aquifer System (HMAS), associated with the High Main (E) coal workings and the overlying High Main Post sandstone. A similar scheme, 700 m away at Nest Road (54.959° N 1.564° W), abstracts at 40 L/s from the HMAS, recovers heat from the mine water and reinjects the thermally spent water to deeper workings associated with the Hutton (L), Harvey-Beaumont (N) (and possibly other) coal seams, termed the Deep Mined Aquifer System (DMAS). The three aquifer systems are vertically discontinuous and possess different hydraulic (storage, transmissivity and continuity) properties that would have been near-impossible to predict in advance of drilling. At the sites, 10 boreholes were drilled to obtain five usable production/reinjection boreholes. Development of mine water geothermal energy schemes thus carries a significant project risk, and also a potential ongoing maintenance burden related to iron hydroxide scaling. These do not preclude mine water geothermal as a useful low carbon heating and cooling technology, but the involvement of skilled hydrogeologists, hydrochemists, mining and groundwater engineers is a pre-requisite.

A Monte Carlo based approach to the resource assessment of Jamaica's geothermal energy potential.

The Eastern Caribbean chain of islands is commonly known to exhibit high-enthalpy systems for geothermal energy exploitation. The northernmost Caribbean Community member state of Jamaica possesses physical manifestations of 12 hot springs across the island. Previous investigations indicate that of the potential 12 hot springs, Bath, Windsor and Milk River springs have cogent geothermometry of their thermal fluids with estimated temperature ranges of (80-102°C), (128-156°C), and (158-206°C), respectively. The paper provides numerical findings for each geothermal system of interest and performs Monte Carlo simulations to optimize calculated findings. The determined quantitative findings are considered under the context of environmental savings and policy regime conditions for driving geothermal energy development. The three areas of interest are situated within the Rio Minho Basin, the Dry Harbour Mountains and the Blue Mountain South Basin. Through the consideration of a 25-year lifetime for production, a collective total of 94.81 MWe of geothermal power reserves can be absorbed into the national energy mix, displacing an estimated 0.38 million barrels of oil imports, resulting in approximately 0.44 million tonnes of carbon dioxide emissions being avoided per year. This article is part of the theme issue 'Developing resilient energy systems'.

Environmental benefits from geothermal energy use with a well doublet located in the Szczecin Trough (NW Poland).

The article presents environmental aspects related to the use of geothermal waters of the Lower Jurassic in the area of the Szczecin Trough. The research area located in the north-western part of the country has been successfully using underground waters of the Lower Jurassic since the 1990s to generate thermal energy at two geothermal heating plants located in Pyrzyce and Stargard. In the case of the area in question, it was proposed a hypothetical geothermal doublet located in the vicinity of the city of Choszczno, for which numerical simulations were carried out for different variants of the locations of the wells and the intake capacity. On the basis of the obtained results, the environmental effect that could be achieved in the case of the analyzed investment was estimated. Reduction in pollutants emission might be expected on the global scale. Even taking into account the emission linked to the electricity consumed (more than 81% of electricity in 2020 in Poland was produced based on fossil fuels, the share of had coal is about half of them). Local reduction in emission is obvious, and it is strictly related to the amount of reduction of fuels consumption. Taking into account the health resorts and thermal pools that utilize groundwater operating in the Polish Lowlands, the chemical composition of the underground waters extracted in the region of Choszczno was also analyzed, and the possibilities of their use for therapeutic and balneotherapeutic purposes were indicated.

Arsenic-rich geothermal fluids as environmentally hazardous materials - A global assessment.

Arsenic-rich geothermal fluids are hazardous materials of global impact, affecting different environments (groundwater, surface water, seawater, sediments, soils, atmosphere) and human and animal health. They can be released naturally or through human activities. For the first time, a systematic global assessment of geothermal arsenic (As) in fluids of the six principal types of geothermal reservoirs and their environmental impact (e.g. freshwater sources used for drinking and irrigation), distinguishing between different uses (if any), was performed based on research of the geochemical characteristics and geotectonic setting of the formation of natural geothermal reservoirs worldwide. This will assist to further improve the sustainability of geothermal energy use, which can be an excellent environmental friendly renewable energy resource for electric power production and direct heat use. Arsenic in geothermal fluids (up to several tens of mg/L) originates especially in deep seated (several kilometers) reservoirs. Proper management of geothermal fluids during exploration, exploitation, use and disposal of resulting waste products through sustainable As mitigation strategies are essential. However, more research about As speciation and volatile As is necessary to fulfil this aim. Therefore As (and its principal species) needs to be included as parameter for standard analysis and monitoring program in any project using geothermal fluids from exploration to management of resulting wastes as base to define appropriate mitigation actions.

Environmental and social impacts of the increasing number of geothermal power plants (Büyük Menderes Graben-Turkey).

The use of renewable energy is critical to the long-term development of global energy. Geothermal power plants (GPPs) differ in the technology they use to convert the source to electricity (dual, single flash, double flash, back pressure, and dry steam) as well as the cooling technology they use (water-cooled and air-cooled). The environmental consequences vary depending on the conversion and cooling technology used. Environmental consequences of geothermal exploration, development, and energy generation include land use and visual impacts, microclimatic impacts, impacts on flora-fauna and biodiversity, air emissions, water quality, soil pollution, noise, micro-earthquakes, induced seismicity, and subsidence. It can also have an impact on social and economic communities. As geothermal activity progresses from exploration to development and production, these effects become more significant. Before beginning geothermal energy activity, the positive and negative aspects of these effects should be considered. The number of GPPs in the Büyük Menderes Graben (BMG) geothermal area is increasing rapidly. According to the findings, in order to reduce the environmental and social impacts of the GPPs in the BMG, resource conservation and development, production sustainability, and operational problems should be continuously monitored.

Impacts of hydrogeological characters of fractured rock on thermodynamic performance of ground-coupled heat pump.

Ground-coupled heat pump (GCHP) is used to recovery shallow geothermal energy, a widely distributed green energy source. Due to the imbalance between heat rejection and extraction, heat buildup underground is commonly associated with the long-term operation of GCHPs, which undermine system performance. Heat buildup intrinsically results the irreversibilities (entropy production) in subsurface heat sink, in which thermodynamic and transport properties are largely influenced by hydrogeologic properties, especially the existence of fractures and groundwater. This study investigates the influence of water flow in fractures on the thermodynamic performance of a single borehole heat exchanger (BHX) and heat buildup in the underground heat exchange zone (UHXZ). Potential influence factors were screened out, and new terms were proposed to quantify the scale of fractures and available heat and cold in the heat sink. Governing equations were established to calculate the impacts of vertical and horizontal fractures on the heat exchange rate in BHX as well as on the heat flow across the UHXZ. The analysis results show that water flow in fractures can significantly enhance heat transfer, reduce required number of boreholes, mitigate heat buildup and reduce irreversibilities underground. The results also suggest that the role of fracture scales and water velocity in GCHP operation should be carefully evaluated. Therefore, detailed hydrogeological survey is necessary. The study results provide a guide on more accurately evaluating the risk of heat buildup and how to take advantage of hydrogeological characters to improve the performance of GCHPs.

A numerical study on heat transfer performances of horizontal ground heat exchangers in ground-source heat pumps.

Horizontal ground heat exchangers (HGHEs) have advantages such as convenient construction and low cost; however, their application and popularization are restricted owing to traditional linear HGHEs occupying large space and presenting low total heat transfer capacity. Spiral-coil and slinky-coil HGHEs have been proposed, but currently a comprehensive comparison and evaluation for these types of HGHEs are still needed. In this study, a three-dimensional heat transfer model of the three types of HGHEs for ground source heat pumps (GSHPs) was established. Based on the simulation results, the long-term heat transfer performances were investigated, including the temperature field of surrounding energy-storage soils, outlet working fluid temperature, coefficient of performance (COP) of units, and surplus temperature of the energy-storage soils. A new concept named heat transfer capacity per heat-affected area was proposed in this paper. It is found that the spiral-coil HGHEs have the best performances in terms of working-fluid outlet temperature, unit COP, total heat transfer capacity, heat transfer rate heat-affected area. The linear HGHEs shows the best performances in terms of mitigating heat imbalance risk and heat transfer rate per length. The results provide a reliable basis for selection of HGHE types in engineering practice and improvement guide in the future.

Is thermal use of groundwater a pollution?

Thermal use of the shallow subsurface and its aquifers (< 400 m) is steadily increasing. Currently, more than 2800 aquifer thermal energy storage (ATES) systems are operating worldwide alongside more than 1.2 million ground source heat pump (GSHP) systems in Europe alone. These rising numbers of shallow geothermal energy (SGE) systems will put additional pressure on typically vulnerable groundwater systems. Hitherto, suitable criteria to control the thermal use of groundwater in national and international legislations are often still at a preliminary state or even non-existing. While the European Union (EU) Water Framework Directive (WFD) defined the release of heat into the groundwater as pollution in the year 2000, the cooling of groundwater for heating purposes is not explicitly mentioned yet. In contrast, some national legislations have stricter guidelines. For example, in Germany, detrimental changes in physical, chemical and biological characteristics have to be avoided. In the Swiss water ordinance, it is even recommended that the groundwater biocenosis should be kept in natural state. However, exact definitions of 'detrimental changes' and 'natural state' are still missing. Hence, the current study provides an overview on natural and affected thermal groundwater conditions and international and national legislations of the thermal use of groundwater. Also, it presents recent studies on groundwater ecosystems and proposes a sustainable policy framework for the thermal use of groundwater. In addition to geothermal heat sources, other anthropogenic heat sources such as climate change, underground car parks, heated basements, district heating systems, land fills, wastewater treatment plants and mining are considered, although no legislation on these anthropogenic heat sources and their impact on groundwater is currently in place. Finally, we intend to answer the above question and provide recommendations for the further discussions on the joint use of shallow groundwater systems for drinking water production and thermal use.

A breath of deadly air.

Air pollution kills many more people every year than COVID-19 has in its first year but is receiving less attention. India is facing a pollution crisis from multiple sources, while European cities have mainly their motor vehicles to blame. Mounting evidence suggests that particle pollution may harm every organ of the body. Michael Gross reports.