Energy Resources Research Articles

Game Theoretic Approach for the Synthesis and Optimisation of Economically Optimal Coalitions in Integrated Renewable Energy and Polygeneration Networks

This study presents the generation of an integrated resource network that encompasses a bioenergy supply chain and a polygeneration hub. The resource network is designed using a superstructure that comprises 3 layers. The first layer is a supply chain network of seasonally available renewable and non-renewable energy sources and is connected to the second layer by a transport system comprised of rail, road, and pipeline. The second layer, which is the polygeneration hub, comprises a boiler to produce high-pressure steam, steam turbines for generating power, a multi-effect evaporation system for desalinating salt-water and an absorption refrigeration system to produce chilled water. The option of connecting the boiler to a solar-thermal and heat storage subnetwork for feedwater pre-heating is included in the second layer. Piping and electrical cables connect the polygeneration layer to the third layer, which comprises industrial heat demand, represented by heat exchanger network, and electrical power demand. The model is applied to a case study in which the subnetworks in the overall integrated superstructure layers are considered as individual players in an industrial symbioses network with the possibility to be in a cooperative game. The objective function of the model, which is represented as a mixed integer nonlinear programming model, involves the minimization of the summation of the players’ marginal contribution, with equal weighting applied for each player, to the coalition’s total annual cost. The result obtained involves preference for a coalition among participating subnetworks that include combined heat and power, multi-effect evaporation, and heat exchanger network.

Continuously stirred tank reactor for oil-suspended thermochemical energy storage systems for CuSO4·5H2O

Thermochemical energy storage can be used for heating applications, thereby helping to cut down on greenhouse gases from burning non-renewable fuels by offering a solution for seasonal heat storage. In the scope of the EU project RESTORE, a thermochemical energy storage is used to store low temperature waste heat and use it for district heating. This study presents the thermochemical energy storage as a new continuously stirred tank three-phase suspension reactor for storing heat from renewable sources or waste heat with almost no losses, in reaction. Therefore, the reactor was built of glass, where process parameters, such as the mean residence time, have been varied to obtain optimized results for thermochemical energy storage operating at the fixed temperature of 125 °C chosen due to project restrictions. The heat is used to dehydrate CuSO4·5H2O in the charging step and recovered by rehydrating CuSO4·3H2O or CuSO4·H2O, respectively, while generating heat in the discharging step. Using a mixture of silicone and mineral oil to prevent foaming, conversion rates of over 94 % to CuSO4·H2O were reached in the charging step with the continuously stirred tank reactor, with 1 kW thermal power, 150 mm diameter and 900 mm height in continuous operation. In discharging operation, 100 % conversion from CuSO4·H2O to CuSO4·5H2O was measured. This paper lays the groundwork for a new technology for thermochemical heat storage in low temperature application.

Mechanisms underlying variations in pore structures and permeability in response to thermal treatment and their implications for underground coal utilization

Coal remains a predominant energy source in today's society. However, the coal mining process is associated with severe environmental hazards, and combustion for power generation leads to pollution and carbon dioxide emissions. As a result, many countries have imposed restrictions on underground coal mining. Underground coal gasification, direct combustion for heat recovery and thermal treatment provides serval promising way for cleanly and safely utilizing coal resources. However, the successful operation of these technologies needs to comprehensively understand the physical and chemical properties of coal responding to high temperature. In particular, the pore structures and permeability of coal which are closely related to the transport of gas and liquid in coal seams. Therefore, serval advanced instruments were employed to investigate the variation of the functional groups, pore structures, permeability from room temperature to 500 °C. Their connection was discussed in detail to reveal the mechanism of thermal treatment on the pore structures and permeability of coal. The variations of all physical properties with temperature demonstrated a trend of gradual change followed by a sudden change. This indicated that coal samples possess relatively good stability up to 300 °C. Experimental results revealed significant alterations in the pore structure and permeability of the coal at 400 °C and 500 °C. Correspondingly, the mass of coal samples and the CC functional groups, which constitute the main molecular structure of coal, underwent significant changes at these temperatures. This suggested that the pyrolysis of coal beyond 400 °C led to an increase in both pore volume and permeability. Moreover, observations through scanning electron microscopy indicated that the increase in pore volume at 400 °C and 500 °C also resulted from the thermal stress induced cracks between minerals and organic matters. These mechanisms significantly enhance the pore volume and permeability of coal seams, facilitating the transport of coalbed gases and liquids during the production process of underground coal utilization.

Surface Subsidence Modelling Induced by Formation of Cavities in Underground Coal Gasification

Underground coal gasification (UCG) is an efficient method for the conversion of deep coal resources into energy. The scope of this work is to model the subsidence of four gasification cavities with a size of 30 m × 30 m × 15 m, separated by 15 m wide pillars. Two scenarios of gasification sequence are modelled, one with the gasification of cavities 1 and 2 followed by 3 and 4, and the other one with the sequence of cavities 1 and 3, followed by 2 and 4. The results show that the final surface subsidence after gasification of four cavities is 9.8 mm and the gasification sequence has an impact only on the subsidence at the intermediate stage but has no impact on the final subsidence after all four cavities are formed, when only the elasticity regime is considered. Additionally, the maximum surface subsidence for the studied cavities of different sizes ranges from 0.016 mm to 7.14 mm, and the relationship between the subsidence and the cavity volume is approximately linear. Finally, a prediction model of surface subsidence deformation is built up using the elastic plate theory, and the formula of surface deformation at a random point is given. The maximum difference between measured and calculated deformation is 4.6%, demonstrating that the proposed method can be used to predict the ground subsidence induced by UCG.

From hydratable alumina bonded high chrome castables to shaped product for coal water slurry gasifier

The gasifier is a key equipment of coal gasification technology, enabling efficient and clean utilization of coal resources. However, the aluminum phosphate bonded high chrome brick lining in the gasifier experienced premature failure due to the migration of phosphate in reducing gases such as H2 and CO, as well as increased slag penetration and thermal spalling. In this study, a high chrome castable was prepared using hydratable alumina as a binder and fired at 1600 ℃ to replace the traditional phosphate bonded high chrome brick. The impact of curing temperatures (25℃, 40 ℃, and 60 ℃) on the properties of the high chrome castable was investigated, with corresponding hydrates examined through XRD, FTIR, TG-DSC, and SEM analyses. Results revealed that higher curing temperatures accelerated the hydration process of hydratable alumina. At higher curing temperatures, more well-developed micro-nano sized boehmite and bayerite phases were formed within the castables, filling their pores effectively and enhancing their properties after drying at 110 ℃. Moreover, during heat treatment these micro-nano sized hydrates decomposed into submicron/nano sized alumina which readily reacted with Cr2O3 to form (Cr-Al)2O3 solid solution. This phenomenon facilitated the sintering of castables fired at 1600 ℃ and optimized internal structure, ultimately leading to the enhanced mechanical properties and improved slag resistance.

Control strategies applied to distribution networks with the integration of distributed energy resources - A review

The continuous integration of distributed energy resources (DERs) in power systems has opened the need to propose control strategies that tend to mitigate the possible impacts that an unlimited integration can produce. Authors have presented studies that present different control strategies that take advantage of the devices already present in the network or of new elements added, such as DERs. Also, different control architectures that can take full advantage of the capabilities that DERs can offer are studied. Therefore, this article focuses on reviewing the recent literature related to control strategies and architectures applied to distribution networks with DERs as protagonists. The control strategies that exploit the characteristics of DERs to perform control actions are described, and the control architectures adapted to the integration of DERs in distribution networks are detailed. Device modeling approaches are also mentioned, considering that some DERs depend on random variables and can introduce uncertainty in the analyses if their behavior is not modeled correctly. Finally, current and future trends in this area are discussed. Keywords. Control architectures, control strategies, deterministic approach, Distributed Energy Resources, stochastic approach.

Assessing the environmental footprint of alternative green biorefinery protein extraction techniques from grasses and legumes

The significant grasslands of Europe and its member states represents a significant feedstock opportunity for circular bioeconomy development. The development of green biorefineries (GBR), to supply protein for the feed industry from grass, could help many European member states to address significant deficits in protein availability and reduce imports. The current study assesses the environmental footprint of alternative GBR protein extraction techniques from grasses and legumes using life cycle assessment. The focus is on comparing feedstock and technology pathways that could displace soya bean imports. The study finds that leaf protein concentrate (LPC) produced from grass had an improved environmental performance when compared to soya bean meal (SBM), across the assessed feedstock (perennial ryegrass or grass-clover mixtures) and technology pathways (one-stage maceration versus multi-stage maceration). For example, in the case of Climate Change the emission intensity for LPC was 57–85 % lower per tonne of crude protein (CP) compared with SBM. Acidification burdens were 54–88 % lower, and Eutrophication: Freshwater burdens 74–89 % lower. Some scenarios of GBR produced LPC with a larger Energy Resources: Non-Renewable burden than SBM, though this could be mitigated with higher renewable energy (biogas and wind energy) integration within the scenario. Grass-clover scenarios generally achieved a lower intensity of emissions compared to ryegrass scenarios, particularly in the category of Climate Change, where feedstock cultivation represents a significant contributor to impacts. Overall, GBR can produce quality protein with a lower environmental burden than SBM, but choice of feedstock and system design are critical factors for overall environmental performance.

Impact of phase selection on accuracy and scalability in calculating distributed energy resources hosting capacity

Hosting capacity (HC) and dynamic operating envelopes (DOEs), defined as dynamic, time-varying HC, are calculated using three-phase optimal power flow (OPF) formulations. Due to the computational complexity of such optimisation problems, HC and DOE are often calculated by introducing certain assumptions and approximations, including the linearised OPF formulation, which we implement in the Python-based tool ppOPF. Furthermore, we investigate how assumptions of the distributed energy resource (DER) connection phase impact the objective function value and computational time in calculating HC and DOE in distribution networks of different sizes. The results are not unambiguous and show that it is not possible to determine the optimal connection phase without introducing binary variables since, no matter the case study, the highest objective function values are calculated with mixed integer OPF formulations. The difference is especially visible in a real-world low-voltage network in which the difference between different scenarios is up to 14 MW in a single day. However, binary variables make the problem computationally complex and increase computational time to several hours in the DOE calculation, even when the optimality gap different from zero is set.

Investigation of solid waste generation rate and biogas production

Anaerobic Digestion (AD) of organic waste is one of the most promising processes and is the ideal solution for the disposal of organic waste (OW) and at the same time, the production of methane gas which may be used as a sustainable energy resource. An anaerobic biodigester with a volume of (20) liters has been used to digest organic waste and to trace the changes that occur during the AD process. Operating parameters such as temperature, pH, total solids, and volatile solids (TS, VS) have been measured which have a significant impact on the rate and quality of biogas production. Experiments on anaerobic biodegradation of OW-SS were monitored under mesophilic conditions (temperature 37 °C, retention time 30–31 days). The pH value varied between (4.2–5.8) for OW-SS. During 30 days of the detection period, the maximum methane production (corrected) occurred on day 21 which was equal to 254.3-ml. The cumulative volume of the produced methane was recorded as (3409 ml), OW-SS, and these results were corrected to the standard conditions, where after correction, it became (2929 ml). The highest rate of methane concentration was estimated at (52 %) for OW-SS, while the rate of decrease in the TS and VS was (54 %, and 45 %), respectively. It is recommended to examine the changes that occur if a larger digester is used than the one used in the current study, such as 50 L, 100 L …. Etc. To compare the data obtained in this study with the results of larger digestions to allow for the opportunity to build anaerobic digesters at the plant level with the benefit of renewable energy production. It is also recommended to investigate the impact of some types of pretreatments on biogas production such as the use of alkali, enzymatic, ultrasonic treatment or acid ton the solid waste feed.

Approximate Dynamic Programming With Enhanced Off-Policy Learning for Coordinating Distributed Energy Resources

Approximate Dynamic Programming With Enhanced Off-Policy Learning for Coordinating Distributed Energy Resources

Sustainable valorisation of sewage sludge via carbon dioxide-assisted pyrolysis

The escalating volume of sewage sludge (SS) generated poses challenges in disposal, given its potential harm to the environment and human health. This study explored sustainable solutions for SS management with a focus on energy recovery. Employing CO2-assisted pyrolysis, we converted SS into flammable gases (H2 and CO; syngas). Single-stage pyrolysis of SS in a CO2 conditions demonstrated that CO2 enhances flammable gas production (especially CO) through gas phase reactions (GPRs) with volatile matter (VM) at temperatures ≥520 °C. Specifically, the CO2 partially oxidized the VM released from SS and concurrently underwent reduction into CO. To enhance the syngas production at temperatures ≤520 °C, multi-stage pyrolysis setup with additional heat energy and a Ni/Al2O3 catalyst were utilized. These configurations significantly increased flammable gas production, particularly CO, at temperatures ≤520 °C. Indeed, the flammable gas yield in the catalytic pyrolysis of SS increased from 200.3 mmol under N2 conditions to 219.2 mmol under CO2 conditions, representing a 4.4-fold increase compared to single-stage pyrolysis under CO2 conditions (50.0 mmol). By integrating a water-gas-shift reaction, the flammable gases produced from CO2-assisted catalytic pyrolysis were expected to have the potential to generate revenue of US$4.04 billion. These findings highlight the effectiveness of employing CO2 in SS pyrolysis as a sustainable and effective approach for treating and valorising SS into valuable energy resources.

New Technique to enhance Hybrid Renewable Energy Resources Operational Flexibility and Reliability

In this research four integrated strategies proposed and discussed for increasing the flexibility of hydropower operations. This initiative seeks to understand, enable, and improve the contribution of hydropower, including pumped storage hydropower (PSH) to reliability, resilience, and integration in the rapidly evolving U.S. electricity system. Hydropower’s flexibility is central to enhancing all these contributions. Four KFA (key focus areas) listed below to maintain and reliable operations. These KFAs will develop a suite of advancements that improve hydropower flexibility at multiple scales: improved components within the plant, improved hybridized capabilities at the plant interconnection, and improved operations across the fleet.[1],[2],[3] 1. HSE in Hydropower Hybrids 2. Reliable productivity 3. Technologies to Increase Flexibility 4. Operational Flexibility Key words. Novelty, Corrective Maintenance and Preventive maintenance and Intelligent module.

Impact of the 2022 energy crisis on energy transition awareness in Latvia

Citizens, businesses, and governments faced energy scarcity, skyrocketing costs, and a high degree of unpredictability due to the Russian invasion of Ukraine in 2022. This situation has forced the European Union and national governments to switch to local energy resources and increase energy efficiency more strictly. But has society's attitude changed in the same way? Two separate public opinion surveys and network analyses were carried out to gain an understanding of energy efficiency practices prevalent in Latvia before and after the war erupted. In addition, the energy community simulation tool has been used to quantify the economic indicators under various conditions.The household survey results show that there, in fact, have been relatively few measures adopted to increase energy efficiency among the population during the energy crisis. The developed policy energy community simulation tool shows, that the energy costs in existing multi-family buildings have increased from around 61 EUR/m2 to 83.5 EUR/m2. However, it is still not motivating households to seek solutions toward more efficient energy use and RES generation due to the governmental subsidies to cover steep cost increases. Interventions targeting efficient energy communities through building managers would give higher strength and long-term effects.

Integrated CO2 capture and conversion into methanol units: Assessing techno-economic and environmental aspects compared to CO2 into SNG alternative

Using carbon dioxide (CO2) as a raw-material to produce value-added chemicals has a strategic role to play in the decarbonization of energy resources and the transition to a climate-neutral economy. E-methanol, Synthetic Natural Gas (SNG) and e-kerosene are one of the most promising pathways to convert CO2. In this context, the aim of this work is to propose an optimized and integrated CO2 to methanol process and then to compare it to the CO2 to SNG process from economic and environmental points of views. An optimized reactor configuration in the CO2 to methanol conversion unit has been successfully implemented in Aspen Plus® and leads to a thermal energy self-sufficiency of this unit. A heat integration with an advanced capture unit has been performed where 5 % of the heat requirement could be provided from the conversion unit while 95 % come from external steam source. Techno-economic assessment of the optimized process showed that methanol is more profitable when it is used as a raw material to synthetize other chemicals. As an energy carrier, SNG is more interesting. Compared to the reference scenario, a net CO2 emission reduction of 70 % in the CO2 to SNG route and of 60 % in the CO2 to methanol route were obtained. Concerning the fossil depletion impact, in both cases, a reduction of more than 60 % was noticed (ca. 75 % in CO2 to SNG route and 61 % in CO2 to methanol case).

Virtual Power Plant Response Strategy Considering Dynamic Aggregation of Different Flexible Resources

Abstract Aggregate and adjust distributed resources, the virtual power plant realizes the collaborative optimization of different forms of electric energy, which greatly improves the flexibility of the power system. Considering the flexibility of distributed resources, this paper designs the active power and frequency regulation modes of virtual power plants, and proposes a response strategy for dynamic resource aggregation of virtual power plants. Firstly, the distributed energy resources of virtual power plants are classified, and their dynamic characteristics are fully considered for dynamic aggregation, and the active power and based on these characteristics, a frequency regulation model is established. Secondly, according to the real-time operation status of sampled distributed resources, a response prediction model of virtual power plant based on dynamic resource aggregation was proposed. Finally, taking the 35kV substation workbench as an example, the response effect of the virtual power plant at different times of a typical day is verified.

Dynamic impact of shadow economy and corruption on environmental sustainability: What role renewable energy consumption play in case of South Asian Economies

The South Asian region has a wide range of problems that significantly influence its path towards environmental sustainability. The region's rapid population expansion, rising urbanization rates, rising industry, and increasing resource demands primarily determine these challenges. The quest for environmental sustainability in this setting is complex and multidimensional, made more difficult by the shadow economy, corruption, and the need to improve renewable energy alternatives. Therefore, the current study examines the multifaceted and interrelated dynamics of the shadow economy, corruption, economic inequality, and environmental sustainability in South Asian nations from 2004 to 2018. We have used sophisticated methodological strategies to tackle cross-section dependence, non-stationarity, and heterogeneity issues by employing a pooled mean group (PMG). However, we use panel FMOLS and DOLS techniques for robustness checks. The findings of the PMG analysis show that the shadow economy, corruption, and industrialization significantly negatively impact environmental sustainability. On the other hand, renewable energy consumption and urbanization are positive and substantial elements that lead to improved environmental sustainability. The robust procedures applied to check the consistency of the estimators also confirmed the long-run relationship among variables. Research findings suggest that reinforcing legal frameworks for environmental rules is crucial for adherence. Incentives such as legal protection and financial rewards can encourage environmental responsibility among businesses, reducing shadow economy operations and risks. Promoting renewable energy resources and urbanization helps to support a sustainable green economy.

Enhancing sustainability of urban waste management through data envelopment analysis for municipal solid waste composting in Tehran, Iran

The critical necessity of decreasing energy consumption and environmental effects is vital in various facets of urban life, particularly in urban waste management. This research aimed to evaluate the energy flow, CExD, and Life Cycle of a composting system for Municipal Solid Waste (MSW) in Tehran province, Iran. The initial phase entailed assessing the energy flow and effectiveness of the composting system, while the subsequent phase focused on enhancing energy efficiency through the application of Data Envelopment Analysis (DEA) to determine an optimal energy consumption strategy for conserving energy and reducing environmental impacts in Tehran's MSW composting system. Over a 90-day period, the analysis of energy usage revealed an energy input and output of 417.30 GJ (8,500 t MSW)-1, with 227.02 GJ (8,500 t MSW)-1 linked to transportation and 190.28 GJ (8,500 t MSW)-1 related to composting activities. The overall energy consumption in the composting system was determined to be 6,424.77 GJ (8,500 t MSW)-1. By applying DEA optimization, energy savings of 14.45 GJ (8,500 t MSW)-1 were accomplished in the composting process, with a significant reduction in electricity usage contributing to these savings. The environmental impact of the energy consumption patterns identified by DEA was notably lower compared to current energy practices. The most notable decrease in impact was observed in the Photochemical Oxidation category. By following the energy usage pattern recommended by DEA, the Global Warming Potential impact reduced by 500 kg CO2 eq. per 8,500 t MSW. Additionally, the optimization of energy use through DEA led to a decrease in fossil energy resource depletion by around 4 GJ (8,500 t MSW)-1 in the composting process.

Clean energy technologies and energy systems for industry and power generation: Current state, recent progress and way forward

This vision article accompanies a Special Issue of Applied Thermal Engineering dedicated to the Sustainable Development of Energy, Water and Environment Systems (SDEWES) conference series held during 2022, including the 5th SEE SDEWES Conference Vlore, 3rd LA SDEWES Conference Sao Paulo, and 17th SDEWES Conference Paphos. The article discusses a selection of papers presented at these conferences and selected for publication in Applied Thermal Engineering, all connected by a focus on clean energy technologies and systems for the advancement of sustainable thermal energy systems. This research area covers a wide range of technologies but is primarily focused on the power generation sector, energy storage and utilization, efficiency improvements, sustainable technical solutions, and the facilitation of the robust integration of renewable energy resources into wider energy systems. Additional work on previously established research topics is also present, but new directions have crystallized, especially research into thermal management for power devices and microelectronics. Based on the recent contributions to the research field presented in the included papers, this vision article discusses the development and application of cutting-edge technological solutions and identifies the challenges that require focused attention. Current shortcomings of developing and established technologies will be developed by the underlying fundamental research, reduction of prohibitively high costs, expansion of operating conditions, and the inclusion of advanced control approaches, sophisticated combinations of renewable energy sources, and modeling tools for system investigations. Scientists, researchers, and engineers can benefit from the summary of the topics at the forefront of the research field and find guidelines and ways forward for future research activities.

The Diversification of Energy Resources and Equipment Imports in the European Union

The Diversification of Energy Resources and Equipment Imports in the European Union

Фінансові перешкоди впровадженню теплових насосів в централізованому теплопостачанні

The use of powerful industrial heat pumps (HP) is a fairly effective means of rational and environmentally friendly use of energy resources both in individual households and in district heating (DH), as well as in production processes in various industries. Powerful HPs are used in Ukraine much less than in developed European countries. In fact, these are isolated cases. The post-war reconstruction of destroyed cities with their district heating systems gives Ukraine a unique chance to use modern energy-efficient technologies, including HP. As a result, efficiency will improve and DH competitiveness will increase due to the low cost of thermal energy for consumers. Almost all developed countries of the world have government financial support for the HP implementation. The purpose of this study is to determine the level and form of government financial support for projects to implement HP in DHs of Ukraine. Financial modeling of the implementation of heat pump plants shown that they are more expediently to be used in the mode of generating thermal energy than in the mode of regulating the electric load of power systems. It is shown that the projects of heat pump plants, which use the heat of flue gases as a source of low-potential heat (LPH), are the most economically attractive and practically do not require government financial support. Projects of heat pump plants, which use air, ventilation emissions, waste water, soil and groundwater, sea, rivers, and waste heat of technological processes as LPH, are not financially attractive without government financial support, and some of them are even unprofitable. The most appropriate comprehensive financial support is tax incentives and interest compensation on the loan. Sensitivity analysis showed that projects for the implementation of heat pump plants may be the most sensitive to the amount of generated thermal energy, the price of natural gas and electricity. Keywords: heat pumps, low-potential heat sources, district heating, financial obstacles, tax incentives, grants.