Use Of Organic Rankine Cycle Research Articles

Investigation and thermodynamic analysis of hydrogen liquefaction cycles: Energy and exergy study

The use of hydrogen as a clean fuel has drawn the attention of many scientists due to the problem of energy and environmental pollution caused by fossil fuels. One of the important requirements for expanding the use of hydrogen is the investigation and thermodynamic analysis of liquefaction cycle; this includes the thermodynamic investigation of different cycles of hydrogen liquefaction in pre-cooling and cryogenic cooling. Thermodynamic analysis comprises an examination of the cycle's energy and exergy, as well as the equipment employed. In this research, three liquefaction cycles with different pre-cooling cycle and cryo-cooling cycle have been evaluated. The use of organic Rankine cycle (ORC) and liquefied natural gas (LNG) has also been applied in the cycles and the arrangement of the equipment. Simulations and analyzes have been done in Aspen HYSYS V12. The results show that in the pre-cooling process of cycles 1, 2, and 3, the amount of useful exergy is 49.87 %, 58.87 %, and 61.21 %, respectively, which means that the third cycle uses the input exergy better. Also, in the pre-cooling process of cycles 1, 2, and 3, the amount of exergy loss is 33.86 %, 26.77 %, and 19.73 %, respectively, which means that the third cycle has less exergy loss in the pre-cooling process. The findings indicate that in each of the three cycles, over 50 % of the input exergy is wasted in the cryo-cooling process. Value of specific energy consumption (SEC) for cycle 1,2, and 3 is equal to 6.605 kWh/kgLH2 , 6.601 kWh/kgLH2 and 6.618 kWh/kgLH2, respectively. The three cycles under examination had COP values of 0.19945, 0.19936, and 0.19884, in that order. Also, the values for EXE cycles 1, 2, and 3 are 45.816 %, 45.883 %, and 45.797 %, respectively. Analyzing the energy and exergy of liquefaction cycles is a good step toward increasing cycle efficiency, identifying weak places, and altering cycles to improve efficiency.

Analytical study on hybrid thrust foil bearing, structural characterization and measurement of static performance

This work presents a novel hybrid foil thrust bearing (HFTB) with an outer diameter of 154 mm, along with simulation and test results. The HFTB incorporates a high-pressure air/gas injection to the taper portion of the thrust foil bearing, boosting the hydrodynamic effect on the main bearing surface and hydrostatic load capacity at zero speed. The bearing has high load capacity, low power loss, and no friction/wear during startup and shutdown. Firstly, push-pull tests were conducted on a double-acting HFTB configuration to evaluate the nonlinear structural stiffness of the bump foil structure. The measured nonlinear stiffness model was adopted to predict the overall bearing performance under various speeds and loads. The simulation uses an advanced model which predicts the 2D plate top foil deflection with physical bump locations mapped from the actual hardware. The simulation confirms that the hybrid operation significantly increases the load capacity compared to hydrodynamic bearing due to the boost effect of hydrostatic pressure in the main film. Tests were conducted at 10krpm, 15krpm, and 20krpm to measure load capacity, power loss, and average film thickness. At 20krpm, a maximum axial load of 1711 N was achieved before bearing failure. Ultimately, the novel HFTB shows excellent static performance with potential for use in Organic Rankine Cycle (ORC) generators and other large oil-free turbomachines.

Organic Rankine Cycle (ORC) Systems: A fundamental Overview of Small-scale Applications Fuelled by Low-grade Heat Sources

Environmental issues shift energy production from conventional methods to new and more efficient alternatives. One of these alternatives is the use of organic Rankine cycles (ORC) in low-grade heat sources to generate both heat and power at small scales. Among different technologies available for this purpose, ORC-based systems seem to be the most suitable and promising option due to their simplicity and versatility. Thus, such systems have been investigated intensively. However, current studies often focus on only one aspect of these systems due to the massive research scale in this field. Therefore, this study aims to provide a fundamental and holistic overview to evaluate ORC-based low-heat sourced and small-scale applications from multiple perspectives. As a result, the basic operating principles and application areas of ORCs, selection and design criteria of their working fluids and all other system components, methods of improving their performance, and other thermodynamic cycles that can be ORC alternatives are examined in detail. The results of this study show that ORC applications can enable small-scale combined heat and power generation, while geothermal and solar energy sources have the potential to scale the size of such applications up to kW capacities. The results also showed that dry & isentropic fluids and vane & scroll expanders are the most suitable refrigerant and expander types, respectively, for small-scale ORC applications. Furthermore, the implications of all findings are critically discussed.

Enhancing sustainable energy conversion: Comparative study of superheated and recuperative ORC systems for waste heat recovery and geothermal applications, with focus on 4E performance

This study investigates the 4E performance of small-scale (<100 kW), low-temperature (<179 °C) Organic Rankine Cycle (ORC) technology, comparing two distinct configurations using different working fluids and heat sources. The work utilizes experimental methods to analyse the efficiency of the ORC systems, focusing on variables such as evaporation temperature and pressure drop across the heat exchanger. Various working fluids and heat sources are tested to evaluate their impact on performance using CoolProp libraries.The results reveal that the ideal evaporation temperature for maximizing overall performance and efficiency is between 140 and 150 °C. Higher pressure drop across the heat exchanger improves heat transfer, thermal efficiency, and power output, but increases pumping requirements and reduces overall effectiveness. Among the tested heat sources, the Dynalene SF exhibits the best performance, followed by therminol T72, T66, geothermal water, and Paratherm HE. The most suitable working fluids for commercial ORC units are R245fa and hexamethyldisiloxane (MM), providing excellent thermodynamic properties and low environmental impact. Comparatively, the superheated ORC system using R245fa outperforms the MM, achieving higher net efficiency (7.29%), greater network generation (20.29%), and improved exergy efficiency (20.54%). The economic viability of the recuperative system is evident from the Levelized Cost of Electricity (LCOE) range of 12.4–14.5 (cents/kWh), with an average Total Installed Cost (TIC) of 354.5 k$. These results showcase the system's competitiveness in providing cost-effective electricity generation, reaffirming its potential as a financially viable option for sustainable energy solutions.The objective is to explore the use of Organic Rankine Cycle (ORC) technology as an alternative to steam Rankine cycle for low-power and lower-temperature applications. Specifically, the study focuses on ORC systems with external heat sources, including geothermal, solid fuels and waste heat recovery (WHR).The novelty of this article lies in its updated analysis of the techno-economic-environmental feasibility of ORC systems for different applications, which goes beyond previous studies. It provides a systematic evaluation and comparison specifically tailored to small-scale and low-temperature operating conditions. The aim is to promote the integration of these two systems in various sectors, particularly for countries undergoing an energy transition. This emphasis on the technical aspects and the specific focus on small-scale and low-temperature conditions make this study unique and valuable in advancing the understanding and application of ORC technology.

Effect of tooth head modification on the performance of a scroll expander for ORC waste heat recovery system

In order to cope with the energy crisis and improve energy efficiency, the use of organic Rankine cycle (ORC) to convert low-quality heat energy into electricity and use it is an effective method. Based on the ORC waste heat recovery system of vehicle engine, this paper explores the flow heat transfer and deformation law of the core component scroll expander under different tooth head corrections. Deformation has a significant impact on the performance of the expander. In this study, several flow-thermal-solid coupling models based on double circular arc correction and double circular arc plus straight-line correction are established. The effects of tooth head correction on the strength and stiffness of tooth head, flow field distribution of suction chamber and deformation characteristics of tooth head are studied. Finally, the deformation law of scroll tooth head with different correction angles was discussed. The results show that the EA-SAL correction makes the wall curvature of the tooth head change greatly, and the flow field in the center of the tooth head becomes more uneven and complicated. The tooth head area under EA-SAL modification is larger, and the tooth head strength and stiffness are improved by about 6%. Within a certain angle range, the tooth head deformation after EA-SAL correction is slightly larger than that after PMP correction, but the difference between them decreases and even reverses with the increase of angle. The maximum deformation of the EA-SAL modified tooth head under internal pressure is about 20% smaller than that of PMP. With a given initial correction angle ∅, the deformation of the corrected tooth head caused by a pressure or temperature load reduces when the correction angle γ is reduced, Therefore, reducing the correction angle properly is helpful to reduce the deformation of the tooth head.

Recovery of waste heat from proton exchange membrane fuel cells – A review

This work discusses the novel application of proton exchange membrane fuel cells (PEMFC) in the transport sector as well as portable applications. This kind of fuel cell produces a considerable quantity of heat while in operation. This quantity of heat is about 45–60% of entire energy composition of the hydrogen that is introduced into the cell. A correctly built cooling system must be used to efficiently eliminate produced heat from the stack to extend the stack's life and preserve its efficiency throughout its entire lifespan. Using appropriate thermal management techniques coupled with exploiting possibilities for fuel cell heat recovery may significantly improve size, cost, etc., while also reducing its total energy consumption. It is possible to collect and utilise the heat produced by PEMFC in other applications. A thorough analysis of heat recovery possibilities in this type of fuel cells is presented in this investigation. Similarly, the study further touched on the need for experimental studies into waste heat recovery from proton exchange membrane fuel cells as most of the recent work being championed are modelling based and does not really present a real life scenario of the system investigated. The need for investigations into the environmental performance of the waste heat recovery unit coupled to the proton exchange fuel cell system is also another important research direction that must be considered in future studies. Finally most of the studies on waste heat recovery from fuel cells have largely employed the use of organic Rankine cycle but other types of thermodynamic cycles like Kalina cycle is however recommended for further investigations due to their range of operation hence making them suitable for low and high temperature proton exchange membrane fuel cells.

Mapping the potential for a combined generation of electricity and industrial process heat in the northeast of Brazil - Case study: Bahia

Industrial Process Heat represents a large part of the energy demands of industries. A parabolic trough solar plant with cogeneration can meet the thermal and electric demand of these industries, mainly at medium and low temperatures.In this work, a linear parabolic solar plant for generation of electricity (1 MWe) and industrial process heat (1 MWt) were simulated at a small industry situated in the State of Bahia. The levelized costs of heat (LCOH) for an evacuated tube solar plant resulted, for extensive regions west and north (Carinhanha (IGR 10, Guanambi), Barra (IGR 4, Feira de Santana), Bom Jesus da Lapa (IGR 10, Guanambi), Santa Rita de Cássia (IGR 8, Barreiras), Paulo Afonso (IGR 3, Paulo Afonso), Remanso (IGR 6, Juazeiro) and Correntina (IGR 8, Barreiras) of the State of Bahia, in the range of 2.85–2.97 ¢/kWh-t. When compared to the medium LCOH produced by the combustion of natural gas in the United States (2.8 ¢/kWh-t) and in European Union (between 3.5 and 5.9 ¢/kWh-t), have shown to be quite competitive. Even in the case of using non-evacuated tubes collectors, the region mentioned has a LCOH in the range of 3.93 ¢/kWh-t to 4.19 ¢US$/kWh-t and still competes with costs in Europe.The levelized costs of electricity (LCOE), considering a linear parabolic solar power plant with evacuated tube collectors and ORC cycle, resulted in minimum and maximum values of 0.225 US$/kWh-e and 0.591 US$/kWh-e for the State of Bahia. In 2019, commercial enterprises of CSP technology reached LCOE values in the range of 0.10 US$/kWh-e to 0.243 US$/kWh-e and, therefore, the LCOE for the most promising regions of Bahia (west and north) have shown to be competitive in the current market. The study also showed that is indifferent to the use of Organic Rankine Cycle (ORC) or Vapour Rankine Cycle (VRC) for the generation of solar energy in the promising regions identified in the State of Bahia. The explanation is that, although the ORC is more efficient than the VRC for operational temperatures of this power plant, its cost is still very high, both for still being under development and for its small scale of production. As consequence, the recommendation of this study is the use of VRC turbines, which are already manufactured in the country and are routinely used to convert biomass to electricity.

The Use of Organic Rankine Cycles for Recovering the Heat Lost in the Compression Area of a Cryogenic Air Separation Unit.

The use of organic Rankine cycles (ORCs) is a viable solution for the recovery of waste heat. For an air separation unit (ASU) with a production of operating in Romania, the value of utilization of the heat transferred to the cooling system of the compression area represents 21% of the global system electrical energy input. To recover this thermal energy and transform it into mechanical energy, an ORC system was proposed. To maximize the production of mechanical power, an exergy analysis was performed. Exergy analysis was used to choose the most suitable organic fluid and find the optimum constructive structure of the Rankine cycle. The calculation of the exergy destruction in the key apparatuses of the system allowed investigation into the optimization search procedure. The large exergy destruction in the liquid preheater suggested the decrease in the temperature difference in this part of the evaporator by increasing the inlet temperature of the liquid; and an internal recuperative heat exchanger was used for this purpose. When permitted, the overheating of the vapors also reduced the temperature difference between the heat source and the organic fluid during the heat transfer process. The analysis was comparatively performed for several organic fluids such as R-245fa, R123, n-pentane and R717. The use of ammonia, that offered the possibility of superheating the vapors at the turbine inlet, brought a gain of mechanical power corresponding to 6% economy in the electrical energy input of the global plant.

Technical and Environmental Feasibility Study of the Co-Production of Crude Oil and Electrical Energy from Geothermal Resources: First Field Trial in Colombia

In the oil and gas industry, there has not been a consistent, concerted effort to reduce global greenhouse gas (GHG) emissions across the supply chain. In addressing this challenge, this study evaluates the potential GHG emissions reduction that may be realized through deployment of a geothermal power co-production system in two Colombian oil fields, compared to a base case where energy needs are derived through non-renewable sources such as gas and diesel. These geothermal power co-production systems make use of organic Rankine cycle (ORC) engines to convert the heat from produced oilfield fluids into electrical energy. The energy potential of this resource is evaluated through the exergy concept, and a life cycle analysis is implemented to calculate the carbon footprint using the Intergovernmental Panel on Climate Change (IPCC) 2013 methodology. In the two oil fields of interest, OFA and OFB, the results show a maximum potential energy production of 2260 kWe for OFA and 657 kWe for OFB. The co-production of crude oil and electrical energy from geothermal resources suggests a possible a carbon footprint reduction of 19% and 11% for OFA and OFB, respectively, when compared to conventional power systems. In addition, four emissions scenarios are assessed where the current energy sources in these oil fields are substituted by gas, diesel, co-generated geothermal power, or a combination of the three while maintaining the average power output in each field. The highest carbon footprint reduction is found in Scenario 1, which replaces 100% of the liquid fuel consumption with purchased gas (gas provided by a third party and treated outside the system’s limits), thereby achieving carbon footprint reductions up to 54% for OFB. This research opens the prospect for the use of renewable energies in the oil and gas industry.

Performance analysis and optimization of a trilateral organic Rankine powered by a concentrated photovoltaic thermal system

The growing demand for energy encourages the use of organic Rankine cycles powered by renewable energies. This work introduces the novel renewable system combining a high performance concentrated photovoltaic thermal and a trilateral organic Rankine cycle for power generation. The high performance concentrated photovoltaic thermal system is sized to meet the heat requirements of a trilateral organic Rankine cycle at high evaporation temperatures of the working organic fluid. Mathematical models are developed for different components of the combined system. The differences between current and previous work models did not exceed 3%. The results showed that the electric power generated by the combined system varied between 70 and 273 kW and the overall efficiency ranged from 29 to 38.55%. Effect of some parameters such as the incidence angle, the aperture area and the condensing temperature of the working organic fluid on the system efficiency are investigated. The results demonstrated that production performance decreased as the incidence angle and the condensing temperature of the working fluid increased. The results also showed that the levelized cost of electricity of the combined system ranged from 0.047 to 0.099U$/kWh. The overall results highlighted that the production performance of the renewable system was very high compared to other solar technologies presented in the literature review.

A Control-Oriented ANFIS Model of Evaporator in a 1-kWe Organic Rankine Cycle Prototype

This paper presents a control-oriented neuro-fuzzy model of brazed-plate evaporators for use in organic Rankine cycle (ORC) engines for waste heat recovery from exhaust-gas streams of diesel engines, amongst other applications. Careful modelling of the evaporator is both crucial to assess the dynamic performance of the ORC system and challenging due to the high nonlinearity of its governing equations. The proposed adaptive neuro-fuzzy inference system (ANFIS) model consists of two separate neuro-fuzzy sub-models for predicting the evaporator output temperature and evaporating pressure. Experimental data are collected from a 1-kWe ORC prototype to train, and verify the accuracy of the ANFIS model, which benefits from the feed-forward output calculation and backpropagation capability of the neural network, while keeping the interpretability of fuzzy systems. The effect of training the models using gradient-descent least-square estimate (GD-LSE) and particle swarm optimisation (PSO) techniques is investigated, and the performance of both techniques are compared in terms of RMSEs and correlation coefficients. The simulation results indicate strong learning ability and high generalisation performance for both. Training the ANFIS models using the PSO algorithm improved the obtained test data RMSE values by 29% for the evaporator outlet temperature and by 18% for the evaporator outlet pressure. The accuracy and speed of the model illustrate its potential for real-time control purposes.

Exergo-economic assessment of OTEC power generation

Ocean Thermal Energy Conversion is an important renewable energy technology aimed at harvesting the large energy resources connected to the temperature gradient between shallow and deep ocean waters, mainly in the tropical region. After the first small-size demonstrators, the current technology is focused on the use of Organic Rankine Cycles, which are suitable for operating with very low temperatures of the resource. With respect to other applications of binary cycles, a large fraction of the output power is consumed for harvesting the resource – that is, in the case of OTEC, for pumping the cold and hot water resource. An exergy analysis of the process (including thermodynamic model of the power cycle as well as heat transfer and friction modelling of the primary resource circuit) was developed and applied to determine optimal conditions (for output power and for exergy efficiency). A parametric analysis examining the main design constraints (temperature range of the condenser and mass flow ratio of hot and cold resource flows) is performed. The cost of power equipment is evaluated applying equipment cost correlations, and an exergo-economic analysis is performed. The results allow to calculate the production cost of electricity and its progressive build-up across the conversion process. A sensitivity analysis with respect to the main design variables is performed.

Condensation of zeotropic mixtures of low-pressure hydrocarbons and synthetic refrigerants

Zeotropic mixtures are under consideration to replace pure working fluids for use in Organic Rankine Cycles for power generation from low-grade heat sources. An experimental investigation of the condensation heat transfer and frictional pressure drop of a zeotropic mixture of R245fa and n-pentane in smooth horizontal tubes was conducted. These measurements were made over mass fluxes ranging from 150 to 600 kg m−2 s−1, operating pressures from 122 to 610 kPa, and nominal vapor qualities ranging from 0.05 to 0.95. Results from this experimental study are compared with the common zeotropic modeling approaches using various correlations from the literature.

Condensation heat transfer and pressure drop of low-pressure hydrocarbons and synthetic refrigerants

Synthetic refrigerant R-245fa is an alternative to R-134a in HVAC systems and is being considered for use in Organic Rankine Cycles (ORCs) for power generation from low-grade heat sources. Pentane, in combination with R245fa, is being considered for use in geothermal heat generation. An experimental investigation of condensation heat transfer and frictional pressure drop for pure R-245fa and pentane flowing through smooth horizontal tubes with internal diameters of 7.75 mm and 14.45 mm was conducted. These measurements were made over mass fluxes ranging from 100 to 600 kg m−2 s−1, operating pressures from 122 to 610 kPa, and nominal vapor qualities ranging from 0.05 to 0.95. Results from this experimental study are compared with predictions from correlations in the literature, and agreement and differences are interpreted and discussed. The measured frictional pressure drops ranged from 0.25 to 100 kPa m−1, and heat transfer coefficients from 1.5 to 15 kW m−2 K−1 were observed. Heat transfer and pressure drop models that apply specifically to these low pressure fluids, tube diameters, and operating conditions are developed. These models provide significant statistical improvements in the predictions of the heat transfer coefficient and pressure drop over existing correlations.

An experimental study of an Organic Rankine Cycle utilizing HCFO-1233zd(E) as a drop-in replacement for HFC-245fa for ultra-low-grade waste heat recovery

The use of Organic Rankine Cycles (ORCs) for waste heat recovery can reduce energy consumption in data centers, which in turn benefits the environment through the reduction of carbon-based fuels. However, data center applications exist in the ultra-low temperature range (40 − 80℃), making efficient and economical operation challenging. The operating fluids that are viable in this temperature range are limited, so it can be a challenge to identify a suitable drop-in replacement for a proven fluid. In this study, the use of HCFO-1233zd(E) is explored to determine its suitability as a low Global Warming Potential and zero Ozone Depletion Potential alternative to the more common HFC-245fa in ultra-low temperature data center applications. This study features the first known comprehensive comparison between the alternative working fluid HCFO-1233zd(E) and HFC-245fa in a lab-scale experimental ORC under ultra-low-grade waste heat temperatures. The results of this study show that the lower HFCO-1233zd(E) saturated pressures impact the ORC operation by reducing the mass flow rate by 3–21%, thereby reducing the heat transfer across the evaporator and condenser. However, the peak thermal efficiency of the lab-scale system is seen to increase with the use of HCFO-1233zd(E) to a high of 5.0% from 4.6% with HFC-245fa. This work also identifies the minimum feasible waste heat temperature as 55 °C for a successful ORC application with both working fluids.

ТЕРМОДИНАМИЧЕСКИЕ ХАРАКТЕРИСТИКИ КОМБИНИРОВАННЫХ ЦИКЛОВ ВАКУУМНЫХ МИКРОГАЗОТУРБИННЫХ УСТАНОВОК ТЕПЛОЭЛЕКТРОСНАБЖЕНИЯ ЛОКАЛЬНЫХ ОБЪЕКТОВ

The subject of this article is the use of organic Rankine cycle (ORC) plants to improve the efficiency of vacuum cycles of micro-gas turbine engines (VMGTE). Combined installations VMGTE with ORC of a simple cycle and with heat regeneration have been investigated. The optimal parameters of the plants in the mode of the switching heat flow are found for various working fluids of the ORC. It has been established that the combination of VMGTE with ORC allows to increase the efficiency of plants by 4.2 ... 12.5%, while maintaining cogeneration capabilities. Due to the design features, the combined plant based on a simple cycle can be used for the utilization of secondary energy resources of any potential.

A novel combined cooling-heating and power (CCHP) system integrated organic Rankine cycle for waste heat recovery of bottom slag in coal-fired plants

The extensive use of organic Rankine cycle (ORC) in waste heat recovery motivates the employment of ORC technique to recover the waste heat in coal-fired plants. A novel combined cooling-heating and power (CCHP) system integrated Organic Rankine Cycle (CCHP-ORC) for recovering the waste heat of bottom slag in coal-fired plant is first proposed in this paper. A MATLAB procedure with REFPROP database is developed for the proposed system based on the mass, energy and exergy balances of each component. With the application of Analytic Hierarchy Process (AHP) method, R1234ze(E) and heptane/R601a are adopted as the optimal working fluids for the Sing Fluid CCHP-ORC and Dual Fluid CCHP-ORC systems, respectively. Parametric studies are conducted to investigate the effect of superheat degree of turbine inlet temperature, chilled water mass flow rate and condenser temperature on the coefficient of performance, thermal efficiency, heat exergy, cooling exergy, total exergy production and exergy production rate. The results show that the superheat degree of turbine inlet temperature benefits the enhancement of the exergy production rate. The enhancement of chilled water mass flow rate leads to an increase in coefficient of performance and refrigerating capacity while the cooling exergy, total exergy production and exergy production rate decrease. Except for exergy production rate in Dual Fluid CCHP-ORC system, the rise of condenser temperature leads to a decrease of performance parameters. As the condenser temperature rises from 25 °C to 40 °C, the thermal efficiency of Cycle2 declines 19.4% and 18.3% respectively in the Sing Fluid CCHP-ORC system and Dual Fluid CCHP-ORC system.

Feasibility study of using organic Rankine and reciprocating engine systems for supplying demand loads of a residential building

ABSTRACTIn this paper, the potentials of the combined use of organic Rankine cycle (ORC) and reciprocating engine for supplying electric power, as well as heating and cooling loads of a residential building in Tehran, are discussed. The studied building is a 10-floor building with a total area of 8000 m2. The type of reciprocating engine and ORC was selected based on CHP (cooling, heating and power) data and consequently, the number of required engines and ORC systems was calculated. It was concluded that, at most, three reciprocating engines with a rated power of 145 kW and three ORCs with a nominal power of 35 kW should be used to meet all loads of studied building. The cost of electricity is about 0.18 (US$/kWh). This system is not economical in comparison with electricity cost incurred by IC (internal combustion) engine employing natural gas as a fuel, but it is more economical than using micro gas turbine.

Promising Direction of Perfection of the Utilization Combine Cycle Gas Turbine Units

Issues of improving the efficiency of combined cycle gas turbines (CCGT) recovery type have been presented. Efficiency gas turbine plant reaches values of 45 % due to rise in temperature to a gas turbine to 1700 °C. Modern technologies for improving the cooling gas turbine components and reducing the excess air ratio leads to a further increase of the efficiency by 1-2 %. Based on research conducted at the Tomsk Polytechnic University, it shows that the CCGT efficiency can be increased by 2-3 % in the winter time due to the use of organic Rankine cycle, low-boiling substances, and air-cooled condensers (ACC). It is necessary to apply the waste heat recovery with condensation of water vapor from the flue gas, it will enhance the efficiency of the CCGT by 2-3 % to increase the efficiency of the heat recovery steam boiler (HRSB) to 10-12 %. Replacing electric pumps gas turbine engine (GTE) helps to reduce electricity consumption for auxiliary needs CCGT by 0.5-1.5 %. At the same time the heat of flue gas turbine engine may be useful used in HRSB, thus will increase the capacity and efficiency of the steam turbine.

Greenhouse gas reduction potential by producing electricity from biogas engine waste heat using organic Rankine cycle

Organic Rankine cycles have been identified as a suitable technological option for converting low-grade heat into electricity with relatively high efficiency, and the organic Rankine cycle technology has been successfully implemented in different power production systems and in recovering heat in industrial processes. This paper studies the greenhouse gas emission reduction potential by using organic Rankine cycles for recovering exhaust gas heat of biogas engines. The study concentrates especially on the biogas engine power plants in Europe. Life cycle assessment methods are used and various waste heat utilization scenarios are compared. According to the results, greenhouse gas emissions can be reduced significantly if the thermal energy of the exhaust gases, otherwise lost in the process as waste heat, is utilized for additional electricity production by means of organic Rankine cycle. However, there may already be use for the exhaust gas heat in biogas plants in the form of heat power. In these cases, the use of organic Rankine cycle does not necessarily lead to greenhouse gas emission reductions. The results also indicate, that the working fluid leakages and production as well as the organic Rankine cycle construction materials and production have only marginal effects on the results from greenhouse gas perspective.