In the Republic of Croatia there is some medium temperature geothermal fields (between 100 and 180 °C) by means of which it is possible to produce electricity. However, only recently concrete ...initiatives for the construction of geothermal power plants have been started. In previous papers, the possible cycles for geothermal fields in the Republic of Croatia are proposed: ORC (Organic Rankine Cycle) and Kalina cycle. Also for the most prospective geothermal fields, energy and exergy analysis for the proposed cycles are performed, on the basis of which the most suitable cycle is proposed. It is ORC which in all cases has better both the thermal efficiency (the First Law efficiency) and the exergy efficiency (the Second Law efficiency). With aim to further improving of geothermal energy utilization in this paper the replacement of a basic ORC with a dual-pressure ORC is analysed. A dual-pressure cycle reduces the thermodynamic losses incurred in the geothermal water-working fluid heat exchangers of the basic ORC, which arise through the heat transfer process across a large temperature difference. The dual-pressure cycle maintains a closer match between the geothermal water cooling curve and the working fluid heating/boiling curve and these losses can be reduced. Now, on the example of the most prospective geothermal field, Velika Ciglena (175 °C), energy and exergy analysis for the proposed the dual-pressure cycle are performed. As a conclusion, in case of Geothermal Power Plant Velika Ciglena, a dual-pressure ORC has slightly lower thermal efficiency (13.96% vs. 14.1%) but considerably higher both exergy efficiency (65% vs. 52%) and net power (6371 kW vs. 5270 kW).
•In Croatia there are several medium temperature geothermal sources (100–180 °C).•Electricity production is possible in binary plants with ORC (Organic Rankine Cycle) or with the Kalina cycle.•In all cases ORC has better thermodynamic characteristics than Kalina cycle.•The replacement of a basic ORC with a dual-pressure ORC is analysed.•A dual-pressure ORC achieves higher net power.
The expander is the key element of an organic Rankine cycle (ORC) and has a significant influence on the cycle efficiency. Therefore, in this study, an innovative small axial multistage turbine with ...partial admission for a bottoming ORC (ORBC) is investigated. The ORBC was used for the waste heat utilization of exhaust gases and jacket cooling water from a 537 kW biogas internal combustion engine (ICE) .
The initial design of the turbine flow part was developed using a mean diameter two-dimensional (2D) preliminary design (PD) method. The high rotational speed of the axial turbine, which is its most critical characteristic, was overcome by employing partial admission. To achieve high isentropic efficiency, new (nonstandard) profiles of the nozzle and moving blades were designed using an analytical method. The initial full flow part of the turbine was further investigated by three-dimensional (3D) computational fluid dynamics (CFD) simulations, with the aim of improving its design. The simulations also provided a better insight into the physics of flow than the mean diameter 2D method. Both the 2D PD calculations and 3D CFD simulations were performed using real gas properties.
The innovative axial action–reaction turbine with partial admission has 8 stages, a mean diameter of 140 mm, and a rotational speed of 9000 rpm. According to the CFD simulation results, a mass flow of isopentane as the working fluid of 1.171 kg/s achieves an effective power of 60.35 kW and isentropic efficiency of 74.8%. These represent an 11.2% increase in the overall power and a 4.5% increase in the overall thermodynamic efficiency by employing an ORBC on a 537 kW biogas ICE.
Therefore, the new turbine is competitive with other expanders in this power range.
•Review of methods used for heat integration of Organic Rankine Cycle.•Integration of Organic Rankine Cycle with industrial waste heat.•Influence of working fluid selection, architecture and low ...temperature waste heat.•Problems in integration with continuous and batch industrial processes.
Production systems represent a significant source of waste heat. The waste heat cannot be reused often. Many optimization methods can give a solution for waste heat recovery. However, the results do not depend only on the method. The low-temperature waste heat makes difficulties for its recovery within the processes. Organic Rankine Cycle units can be used for low-temperature heat transformation into electricity. Linking the Organic Rankine Cycle within the heat integrated system is not simple. This depends on the influence of a few important factors. The process parameters of the working medium, the physical and chemical characteristics of the working fluid, the continuity of heat supply, and the temperature level of waste heat are necessary conditions that must be included in optimization. The optimization method should determine the optimal operating point of the Organic Rankine Cycle. The displacement of the operating point leads to decrease in the effective transformation of heat into electricity. These problems are analyzed through a review of the methods and approaches used for the integration of Organic Rankine Cycle in thermal process systems. These include Pinch technology, Non-Linear Programming, Multiple Integer Linear Programming, Genetic Algorithm, Artificial Neural Network and many different approaches for polygeneration systems. All methods were compared and systematized in a general scheme for integration of an Organic Rankine Cycle with low-temperature industrial waste heat supply. This work also includes experience in implemented and designed projects of an integrated Organic Rankine Cycle.
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•Heat integration of a bioprocess plant is studied.•Bioprocess plant produces yeast and ethyl-alcohol.•The design of a heat recovery system is performed by batch pinch ...analysis.•Direct and indirect heat integration approaches are used in process design.•The heat recovery system without a heat storage opportunity is more profitable.
The paper deals with the heat integration of a bioprocess plant which produces yeast and ethyl-alcohol. The referent plant is considered to be a multiproduct batch plant which operates in a semi-continuous mode. The design of a heat recovery system is performed by batch pinch analysis and by the use of the Time slice model. The results obtained by direct and indirect heat integration approaches are presented in the form of cost-optimal heat exchanger networks and evaluated by different thermodynamic and economic indicators. They signify that the heat recovery system without a heat storage opportunity can be considered to be a more profitable solution for the energy efficiency increase in a plant.
This editorial provides an overview of ten scientific articles published as
the Special paper selection in Thermal Science. The papers were selected
from almost six hundred contributions, presented ...at the 16th Conference on
Sustainable Development of Energy, Water and Environment Systems (SDEWES
2021), held on October 10-15, 2021 in Dubrovnik, Croatia. The topics covered
in the Special paper selection include economics of electricity markets,
nuclear technology, repowering of the coal-based power plant, hybrid
renewable energy system, sustainable biomass handling and conversion,
post-combustion emissions control, and efficient cooling technology. The
editorial also emphasised the papers recently published in the Special
Issues of leading scientific journals dedicated to the series of SDEWES
Conferences.
During the last decade, a design of an energy efficient and cost effective geothermal plant represents a significant and on-going technical challenge in all the Western Balkan countries. In the ...Republic of Croatia, the geothermal field Velika Ciglena is identified as one of the most valuable geothermal heat sources and probably the location where the first geothermal plant in the Western Balkan area will be built. The purpose of this work is the conceptual design and performance analysis of the binary plants–the one which operates under the Organic Rankine Cycle (ORC) and the other under Kalina (KLN) cycle–which can be used for geothermal energy utilization in Velika Ciglena. A conceptual plant design is performed by the equation-oriented modelling approach and supported by the two steady-state spreadsheet simulators. The performance analysis of all design solutions is conducted through energy and exergy analysis, and by the estimated total cost of operating units in the plant. The results of the analysis indicate that the plant design based on the ORC cycle has a higher thermodynamic efficiency and lower cost of equipment, and consequently, it is more suitable for the future geothermal plant in Velika Ciglena.
► Paper presents the analysis of binary geothermal plant for the utilization of recourses in Velika Ciglena field (Croatia). ► Thermodynamic and economical parameters of both cycles are calculated by the spreadsheet simulation software. ► The results of performance analysis indicate the advantage of electricity production based on ORC cycle.
Integrated approaches in energy, water and environmental systems can improve the climate change reduction process. New scientific developments and advancements have provided numerous opportunities in ...the comprehensive human progress direction. In this regard, we have reviewed the 16th Conference on Sustainable Development of Energy, Water and Environment Systems presented in this editorial. Examining recent scientific developments, eight research articles on this special issue are related to eight main topics. The solar energy technology and storage section reviewed the first four articles. These articles include topics such as: 1) advanced technologies to form a new TT PS-TIM window system for adaptive daylight control and advanced thermal insulation combination, 2) using experimental data for field testing located in an area with Mediterranean climate conditions, of newly installed FPVS in these areas, 3) possibilities described in short rotation of willow type and energy crop Miscanthus cultivation dedicated to former coal mining areas, 4) using solar and geothermal energy with boiling water purification and reverse osmosis. Furthermore, the following four articles are reviewed in the energy management systems section. These articles include topics such as, 5) deep analysis of facial expression and eye tracking using samples of non-expert participants to determine emotions caused by electricity consumption graphs in different time scales, 6) studying the electric vehicles (EVs) main life cycle activities using an exploratory survey and their potential inequities, 7) the biodiesel fuel production from waste sardine fish oil using methanol, ethanol or isopropanol and a solid heterogeneous catalyst prepared using eggshell and copper oxide CaCu(OCH3)2 is analyzed. Finally, 8) biotechnology microalgae have been studied in 70-litre vertical photobioreactors that use unsupplemented secondary brewery wastewater as growth media using two collecting cells mechanically methods under hydrothermal (autohydrolysis) and dilute acid hydrolysis.
Scientific research development in energy, water and environmental systems is vital for climate change mitigation and adaptation. In this regard, the outcome of the 17th Conference on Sustainable ...Development of Energy, Water and Environment Systems was reviewed and presented in this editorial. Examining recent scientific developments, thirteen research articles on this special issue are related to specific topics. The topic of industrial energy reduction potentials and alternative fuels were discussed in the articles 1) Electricity demand reduction through waste heat recovery in olefins plants based on a technology-agnostic approach, 2) Integration of a rSOC-system to industrial processes, 3) Spray combustion of fast-pyrolysis bio-oils under engine-like conditions, 4) Complex aspects of climate change impacts on the cultivation of perennial energy crops in the Czech Republic, while residential and small scale applications were presented in 5) Experimental and theoretical analysis of a micro-cogenerative solar ORC-based unit equipped with a variable speed sliding rotary vane expander, 6) Exergy-Optimum coupling of radiant panels with heat pumps for minimum CO2 emission responsibility and 7) State-of-the-art review of micro to small-scale wind energy harvesting technologies for building integration and 8) Dynamic simulation of a 4th generation district heating network with the presence of prosumers. Potentials of renewable energy increased penetration and measures and strategies for CO2 emissions reduction presented in 9) An evaluation of the synergy between the wave and wind energy along the west Iberian nearshore, 10) Energy efficiency improvement in multi-family houses in Kosovo, 11) Natural lighting performance of vernacular architecture, case study oldtown Pasa, Ecuador, 12) Diagnosis of the building stock using Energy Performance Certificates for urban energy planning in Mediterranean compact cities. Case of study: The city of València in Spain and 13) Carbon insetting as a measure to raise supply chain energy efficiency potentials: Opportunities and challenges.
The widespread use of fossil fuels and their limitation leads to find other sources of energy. Solar thermal energy is a possible solution. There are many projects that use renewable energy. Solar ...thermal energy can be easily used for heating. However, there are problems in the efficiency of solar collectors, the loss of heat, the consistency of heat supply, temperature and weather conditions, the biggest problem being the heat storage. In this paper is provided an overview of the methodologies for thermal integration of solar heating systems implemented in various projects and research. Solar heating systems have different designs and can generate heat in different temperature ranges. The main emphasis in this comprehensive overview is the systematisation of the various methodologies used in the integration of solar heat in production. In principle, solar heating systems are directly connected to the production systems. Furthermore, a few methodologies like Pinch technology, mathematical modelling and cogeneration are included.
The use of Pinch technology is very often strongly limited by the existence of complex chemical process units (combustion, drying, scrubbing, etc.) in the energy system of the plant. Since this ...methodology, in its standard form, does not account for chemical operation inside those units, only a few process streams can be used for the creation of the heat exchanger network. The final design, in accordance with the overall mass and energy balance of the plant, will generate only slight increase in the energy efficiency.
To exceed these limitations, the plant can be reconfigured by adding the modules of virtual heat exchangers in existing physical and mathematical models of the plant. These exchangers present just fictive elements, which simulate possible heating/cooling of the streams, and their purpose is only to ensure the conservancy of balance equations. In this way, the new task enables the use of more streams in the pinch design, which can result in the solution with significant improvement of plant energy performance.
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