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In this research, the simulation of an existing 31.5 MW steam power plant, providing both electricity for the national grid and hot utility for the related sugar factory, was performed by means of ProSimPlus® v. 3.7.6. The purpose of this study is to analyze the steam turbine operating parameters by means of the exergy concept with a pinch-based technique in order to assess the overall energy performance and losses that occur in the power plant. The combined pinch and exergy analysis (CPEA) initially focuses on the depiction of the hot and cold composite curves (HCCCs) of the steam cycle to evaluate the energy and exergy requirements. Based on the minimal approach temperature difference (∆Tlm) required for effective heat transfer, the exergy loss that raises the heat demand (heat duty) for power generation can be quantitatively assessed. The exergy composite curves focus on the potential for fuel saving throughout the cycle with respect to three possible operating modes and evaluates opportunities for heat pumping in the process. Well-established tools, such as balanced exergy composite curves, are used to visualize exergy losses in each process unit and utility heat exchangers. The outcome of the combined exergy–pinch analysis reveals that energy savings of up to 83.44 MW may be realized by lowering exergy destruction in the cogeneration plant according to the operating scenario. [ABSTRACT FROM AUTHOR]

The paper presents the process of electricity and thermal energy production in a cogeneration plant and the process of wood pellet production. The aim of this study was to analyze the energy gain—EROI for energy products that are created as a product contained in electrical and thermal energy and the energy contained in wood pellets. According to the obtained results, the production of only electrical energy from wood biomass in a cogeneration plant was not sustainable from an energy point of view, since the obtained electrical energy was only 1.46 times greater than the input wood energy (EROIel = 1.46), while the obtained energy of the produced wood pellets was 4.82 (EROIpel = 4.82). According to the results of equivalent carbon emission, positive net value was achieved only with cogeneration plant and pellet plant working in synergy. Wood is a renewable source of energy, and its economic use can create a significant energy gain. However, due to the trend of using renewable energy sources and the increasing need for electricity, such a process of obtaining electricity is financially profitable, although it is not justified from the energy profitability and environmental sustainability point of view. [ABSTRACT FROM AUTHOR]

Active noise control (ANC) aims to reduce a noise source at a listening point by destructive interference with a reverse phase noise emitted by one or more control devices. ANC systems cover a wide range of applications, such as industrial plants, vehicle cabins, headphones. Usually, in these applications the control devices are loudspeakers, and the error signals come from microphones. In outdoor applications, this solution comes with some limitations, such as the ageing of the loudspeakers due to humidity, temperature, rain and dust, and the presence of wired connections between the error sensors and the control system. This paper presents a noise reduction solution for a cogeneration plant, consisting of an Active Vibration Control (AVC) system applied to the cogenerator enclosure. To overcome the above limitations, electrodynamic shakers are used as controllers and an accelerometer as error signal. The control algorithm is a single reference, Single Input, Multiple Output (SIMO) Filtered-X Normalized Least Mean Square (FxNLMS), implemented in a Virtual Studio Technology (VST) plugin. VST plugins work in real-time in Digital Audio Workstation (DAW) software installed on personal computers, therefore without the need for low-level implementation on dedicated electronic boards, thus reducing the development time and the cost of the equipment. First, the effectiveness of the solution is demonstrated in a laboratory experiment. Subsequently, the results obtained on the cogenerator are presented, which show remarkable performance, with a noise reduction up to −17.5 dB on the main disturbing frequencies.

The need to modernize existing district heating systems is due to increased requirements for their flexibility, energy efficiency, and environmental friendliness. The technical policy on district heating pursued in different countries centers on the listed goals and takes account of historical, climatic, and regional features of the resource, technology, and economic availability of various thermal energy sources. This study aims to analyze methods designed to improve the flexibility, energy efficiency, and environmental friendliness of district heating systems. The focus of the study is district heating system, which provides heating and hot water supply to consumers and consists of various types of thermal energy sources. The work shows the possibility for the heating system to transition from the third generation to the fourth one, which differ in their level of intellectualization. The establishment of an intelligent control system will ensure the interaction of various heat sources, but this is a separate strand of research. In this study, a model and a methodology were developed to optimize the structure of thermal energy sources and their operating conditions when covering the heat load curve of a territory with a predominance of household consumers. Gas-reciprocating and gas-turbine cogeneration plants are considered as the main thermal energy sources, whose efficiency is boosted through their joint operation with electric boilers, thermal energy storage systems, low-grade heat sources, and absorption chillers. The primary emphasis of the study is on the assessment of the environmental benefit to be gained by using cogeneration plants as a factor of enhancing the investment appeal of the district heating systems. The findings suggest that the transition of district heating systems to the next generation is impossible without changing the institutional environment, strengthening the role of active consumers, and introducing intelligent control for district heating systems. [ABSTRACT FROM AUTHOR]

In this research, the simulation of an existing 31.5 MW steam power plant, providing both electricity for the national grid and hot utility for the related sugar factory, was performed by means of ProSimPlus® v. 3.7.6. The purpose of this study is to analyze the steam turbine operating parameters by means of the exergy concept with a pinch-based technique in order to assess the overall energy performance and losses that occur in the power plant. The combined pinch and exergy analysis (CPEA) initially focuses on the depiction of the hot and cold composite curves (HCCCs) of the steam cycle to evaluate the energy and exergy requirements. Based on the minimal approach temperature difference (∆Tlm) required for effective heat transfer, the exergy loss that raises the heat demand (heat duty) for power generation can be quantitatively assessed. The exergy composite curves focus on the potential for fuel saving throughout the cycle with respect to three possible operating modes and evaluates opportunities for heat pumping in the process. Well-established tools, such as balanced exergy composite curves, are used to visualize exergy losses in each process unit and utility heat exchangers. The outcome of the combined exergy–pinch analysis reveals that energy savings of up to 83.44 MW may be realized by lowering exergy destruction in the cogeneration plant according to the operating scenario.

This study aims to develop, and examine a cogeneration system for electric power, hydrogen, and ammonia production. A modified Rankine cycle is configured to supply power. An electrolyze unit and an ammonia synthesis reactor are used to provide hydrogen and ammonia. The system is investigated from technical and economic aspects. The inquiry outcomes disclose that the reaction pressure and hydrogen to nitrogen molar ratio have mainly affected the ammonia production rate increment. The system energy and exergy efficiencies as well as the total unit cost of the product are at about 50.47 %, 51.41 %, and 638.3 $/GJ, respectively. The results show that the exergy destruction rate of the system is 89.797 MW. Moreover, 6.438 kg/h of hydrogen and 6.528 kg/s of ammonia are attainable. The sweeping sensitivity investigation on the economic aspect reveals that the reaction pressure, input hydrogen molar ratio, and hydrogen to nitrogen molar ratio have a positive effect on the sum unit cost of the product's decrement. Finally, the thermodynamic sensitivity examination outcomes affirm that altering reaction temperature leads to technical inefficiencies in the proposed cogeneration system. [ABSTRACT FROM AUTHOR]

Electricity–water cogeneration power plants are an important tool for advancing sustainable water treatment technologies because they provide a cost-effective and environmentally friendly solution for meeting the energy and water needs of communities. By integrating power and water production, these technologies can reduce carbon emissions and help mitigate the impact of climate change. This work deals with the energy and exergy analysis of a cogeneration plant for electrical power generation and water desalination using real operational data. The power side is a pressurized water reactor (PWR) nuclear power plant (NPP), while the desalination side is a multi-effect distillation (MED) system with a thermo-vapor compressor (TVC) plant coupled with a conventional multi-effect plant (ME-TVC-MED). A mathematical model was implemented in MATLAB software and validated through a comparison with previously published research. The exergy analysis was carried out based on the second law of thermodynamics to evaluate the irreversibility of the plant and the subsystems. In this study, the components of the sub-systems were analyzed separately to identify and quantify the component that has a high loss of energy and exergy. According to the energy and exergy analyses, the highest source of irreversibility occurs in the reactor core with 50% of the total exergy destruction. However, turbines, steam generators, and condensers also contribute to energy loss. Further, the thermodynamic efficiency of the cogeneration plant was obtained as 35.38%, which is more effective than other systems. In the ME-TVC-MED desalination unit, the main sources of energy losses are located in the evaporators and the thermo-compressor (about 50% and 36%, respectively). Moreover, the exergetic efficiency of the ME-TVC-MED unit was found to be low at 6.43%, indicating a high degree of technical inefficiency in the desalination process. Therefore, many opportunities exist to improve the performance of the cogeneration system. [ABSTRACT FROM AUTHOR]

The dwindling and scarcity of fossil energy sources is the basis of the energy transition, where renewable resources are increasingly valued. The purpose of the cogeneration system studied in this article is to recover the residual heat from the gases coming out of the chimneys of the cement kilns, to produce at the same time the electricity and the heat required for offices and residential houses of cement workers. Cement kilns are reputed to be energy-intensive, generating excessive heat losses. These heat losses are found mainly in the conduction–convective and radiative modes, representing about 26% of the overall heat input to the system. Nevertheless, the gases at the chimney outlet can still have temperatures between 250 and 350 °C, which presents a non-negligible potential for a cogeneration system. This study compares the thermal performance of different cogeneration plant configurations (KCA, KCB, and KCC systems) using the Kalina cycle to determine the best one. Several assumptions were made to reduce the complexity of the model. MATLAB and Excel software were used to solve the system of equations. After extensive analysis of the results, the KCA system showed the best performance, compared to the KCB and KCC systems, with a thermal efficiency of 22.15%, an exergy efficiency of 45.12%, and a net electrical capacity of 2565.03 kWe. Model sensitivity to concentration, temperature, and pressure variations also gave the KCA system the best-performing system. Evaluation of the excess heat flux removed from the process yields values of 7368.20 kW, 7421.86 kW, and 8094.15 kW for the KCA, KCB, and KCC systems. The results of this article serve as a decision support tool for installing the cogeneration system via the Kalina cycle in cement installations. [ABSTRACT FROM AUTHOR]

The need to modernize existing district heating systems is due to increased requirements for their flexibility, energy efficiency, and environmental friendliness. The technical policy on district heating pursued in different countries centers on the listed goals and takes account of historical, climatic, and regional features of the resource, technology, and economic availability of various thermal energy sources. This study aims to analyze methods designed to improve the flexibility, energy efficiency, and environmental friendliness of district heating systems. The focus of the study is district heating system, which provides heating and hot water supply to consumers and consists of various types of thermal energy sources. The work shows the possibility for the heating system to transition from the third generation to the fourth one, which differ in their level of intellectualization. The establishment of an intelligent control system will ensure the interaction of various heat sources, but this is a separate strand of research. In this study, a model and a methodology were developed to optimize the structure of thermal energy sources and their operating conditions when covering the heat load curve of a territory with a predominance of household consumers. Gas-reciprocating and gas-turbine cogeneration plants are considered as the main thermal energy sources, whose efficiency is boosted through their joint operation with electric boilers, thermal energy storage systems, low-grade heat sources, and absorption chillers. The primary emphasis of the study is on the assessment of the environmental benefit to be gained by using cogeneration plants as a factor of enhancing the investment appeal of the district heating systems. The findings suggest that the transition of district heating systems to the next generation is impossible without changing the institutional environment, strengthening the role of active consumers, and introducing intelligent control for district heating systems.

Purpose. To determine the contribution of emissions of the state enterprise ‘Severodonetsk Cogeneration Plant’ to the air basin pollution level in Severodonetsk and the risks to public health. Methods. Modelling of the pollutants spread from a single point source and assessment of chronic carcinogenic and toxic risks by using EOL-2000 [h] automated system with the ‘Risk Indicator’ utility for calculating the dispersion of emissions in the atmosphere. Risk Calculator (EPA US) helped to assess the risk levels for workers of different occupations, namely, outdoor workers, indoor workers, and builders. The seasonal wind rose was determined based on the Copernicus Climate Change Service (European Commission). Results. According to the adopted modelling scenario (stable operation of the plant, a seasonal wind rose), the contribution of emissions from SE ‘Severodonetsk СP’ to the level of air pollution in Severodonetsk is extremely small, since the contents of all components are less than normal. However, the plant emits toxic compounds of manganese, vanadium, mercury as well as xylene and hydrogen fluoride, which are combined with background substances in the summation group. According to the modelling results, the sanitary protection zone of Severodonetsk СP does not require modification or adjustment. Among all the emissions, chromium (VI) and nickel demonstrate oncogenic properties with a unidirectional effect on the lungs and nasal cavity. The individual carcinogenic risk of 6.01´10-6 generated by gas emissions of the plant is acceptable. Manifestation of chronic toxic effects from emissions of Severodonetsk СP is unlikely as indicated by the minimum (target) levels of non-carcinogenic risks. Conclusions. Emissions from the planned activities of the СP during the cold period do not exceed MPC, and the risks to the health of the population living nearby residential areas and employees of enterprises are minimal. At the same time, the air quality in Severodonetsk is not satisfactory and requires measures to reduce risks. To perform this task, it is necessary to identify all sources of air pollution with the maximum contribution to the risks to the urban population health.

In this article, the preliminary routing, sizing, and cost structure of a heat network that supplies energy, in an agrarian district, to greenhouses located around a cogeneration plant in the municipality of El Ejido (Almería) is presented. A genetic algorithm is employed to select a set of points of consumption (plots of land)–which indirectly determine the network routing over the road network–resulting in a project with a better net present value. To obtain the routing, the Steiner tree problem is solved through an approximation that involves several algorithms derived from graph theory and the use of georeferenced information. The design is constrained to ensure technical feasibility, so that the available thermal power from the plant, averaged for hourly periods over a year, is greater than the demand from the greenhouses. The said demand is calculated through an empty-greenhouse climate model, considering temperature setpoints compatible with the most common crops in the region. According to the results, a network of total length equal to 1.3464 km and an average pipe diameter of 0.1532 m would be required to annually supply 8621.4 MWh of heat to 12 points of consumption. The net present value of the project would be 6 417 900 € , considering a 3% discount rate and useful life of 30 years, with an initial investment cost of 1 723 300 € and an annual operation cost of 15 800 € year − 1 . A sensibility analysis of the variables with greater economic impact is also presented. • Refined heat network design using a multi-staged genetic algorithm. • Precise georeferenced data integration for routing. • Greenhouses as heat consumers for enhanced crop growth. • Promising economic viability for waste heat reuse. [ABSTRACT FROM AUTHOR]

This article is devoted to optimization of parameters and structure of the industrial-heating vapor-gas facilities (HVGF). The aim of the study is determination of the optimal initial parameters of two-circuit utilization HVGF. The set goal is achieved based on the methods of the mathematical modeling of the thermal schemes, using the elements of thermodynamic economic analysis. As the optimization criterion, the index of a relative fuel economy is used upon the combined generation of the energy and heat. The most significant result of the research consists in revealing a tendency to an increase in the optimal vapor pressure of the HVGF high pressure circuit, compared to a similar parameter of the condensation vapor gas device (VGD CEPP). For the two-circuit HVGF, the optimal initial pressure is 9.8—10 MPa (for the CEPP it is 8 MPa). The tendency is revealed for an increase of the relative fuel economy upon the complication of the HVGF thermal scheme. It was established that for the identic HVGF located in different energy systems, the relative fuel economy differ greatly. The relative fuel economy for the HVGF under consideration compared to analogous VGD CEPP is 27.35 %, and compared to the vapor turbine CEPP, the relative fuel economy will increase by 8.8 %. The importance of the results obtained consists in that their application will make it possible to increase the energy efficiency of the HVGF being constructed, and optimize the structure of the energy systems of separate regions and states.

The thawing process within fish processing is one of the most essential steps in manufacturing. Various processes of thawing can be used where efficiency varies between companies depending on such characteristics as energy consumption, the price of resources, etc. The main aim of the research is to increase the efficiency of thawing processes. Firstly, to analyse various thawing methods and to find the most efficient one by using multi-criteria decision making analysis method. Secondly, analysing data of thawing of existing company to find opportunities for improvements, including the change of existing technology. Results showed that the most suitable method for thawing is the air blast method. Case study showed that current thawing technology is outdated, thus suggested improvement would be to replace the current boiler house with a cogeneration plant. A sensitivity analysis for the cogeneration plant has been performed.

The dwindling and scarcity of fossil energy sources is the basis of the energy transition, where renewable resources are increasingly valued. The purpose of the cogeneration system studied in this article is to recover the residual heat from the gases coming out of the chimneys of the cement kilns, to produce at the same time the electricity and the heat required for offices and residential houses of cement workers. Cement kilns are reputed to be energy-intensive, generating excessive heat losses. These heat losses are found mainly in the conduction–convective and radiative modes, representing about 26% of the overall heat input to the system. Nevertheless, the gases at the chimney outlet can still have temperatures between 250 and 350 °C, which presents a non-negligible potential for a cogeneration system. This study compares the thermal performance of different cogeneration plant configurations (KCA, KCB, and KCC systems) using the Kalina cycle to determine the best one. Several assumptions were made to reduce the complexity of the model. MATLAB and Excel software were used to solve the system of equations. After extensive analysis of the results, the KCA system showed the best performance, compared to the KCB and KCC systems, with a thermal efficiency of 22.15%, an exergy efficiency of 45.12%, and a net electrical capacity of 2565.03 kWe. Model sensitivity to concentration, temperature, and pressure variations also gave the KCA system the best-performing system. Evaluation of the excess heat flux removed from the process yields values of 7368.20 kW, 7421.86 kW, and 8094.15 kW for the KCA, KCB, and KCC systems. The results of this article serve as a decision support tool for installing the cogeneration system via the Kalina cycle in cement installations.

As a result of the lack of flexible capacities and an increase in the fraction of nuclear power plants in European Russia, the combined heat and power (CHP) plants currently need offloading during the off-peak hours of electric power demand. The adjustment of electric power demand necessitates additionally increasing the electric power of the power-generating units in the on-peak hours and decreasing it at nighttime. The existing methods for increasing the power of combined heat and power plants suffer from a number of serious drawbacks. The reduction in the electric power in the heating period is restricted, as a rule, by high heat demand. In this work, we show the possibility of extending the control range of the electric power output at CHP plants through the use of the heat-accumulation properties of the heat-supply networks and buildings and, accordingly, through the changeover of the operating modes of the cogeneration plant. Several operating-mode variants of the cogeneration plant are considered. The calculations conducted show that the consideration of the heat-accumulation properties of the heat-supply networks and buildings allows, having reduced the electric output of the CHP plant at nighttime, for an increase in the thermal output to increase the electric output in the day reducing the thermal output. An important requirement for the heat supply to buildings is the maintenance of comfortable indoor conditions. The optimal permissible temperature range for living space in the cold period of the year is 20–22°C. The possibility of ensuring the comfortable conditions indoors is confirmed by the calculations of the indoor air temperature by the method previously proposed by the authors that considers the heat-accumulation properties of the heat-supply networks and buildings. The indoor air temperature decreases by the end of the discharge period, i.e., the time when the accumulated heat has been consumed, to approximately 19°C; consequently, it does not go down below the permissible range. It should be noted that this is predominantly due to the heat-accumulation properties of the buildings. The material of the main heating system pipelines has a low accumulation capacity, i.e., the pipe walls transfer heat rapidly to the water that enters the pipeline at a temperature lower than that of the pipes. However, due to the considerable length of the heat system's pipelines, the temperature of the heating-system water that arrives at the consumer remains constant at the time moment after the temperature perturbance on the heat source. [ABSTRACT FROM AUTHOR]

In this study, an innovative cogeneration system is developed and investigated which aim is to produce electrical power, ammonia, and hydrogen. A Kalina cycle is designed for electricity supply. An ammonia synthesis reactor and an electrolyzer are utilized for production of ammonia and hydrogen. The projected system is examined from economic and technical viewpoints. The analysis reveals that the ammonia production rate growth has been primarily influenced by the hydrogen to nitrogen molar ratio and pressure of reaction. For the system, the efficiencies of energy and exergy as well as the products' total unit cost achieve 50.47 %, 51.41 % as well as 638.3 $/GJ, each. The outcomes underscore that the rate of the destructed exergy is 89.797 MW for the system. Furthermore, 6.528 kg/s of ammonia and 6.438 kg/h of hydrogen are achievable. From a purely economic point of view, the comprehensive sensitivity examination deduces that 3 factors, namely the reaction pressure, hydrogen to nitrogen molar rate, and input hydrogen molar rate, do exercise a positive impact on the products' total unit cost lessening. Lastly, results of thermodynamic sensitivity evaluation confirm that the offered system technical inefficiencies are correlated to the reaction temperature changes. [Display omitted] [ABSTRACT FROM AUTHOR]

In most large cities of Russia, the annual heat consumption exceeds the annual electricity consumption more than twice as a rule. On the contrary, the electric power of the combined-cycle cogeneration heat-power plant (CCCHPP) with heat-recovery steam generators (HRSG) is much higher than the thermal power of the cogeneration extraction of its steam turbine plant. This necessitates equipping combined-cycle gas turbine–combined heat and power plants (CCGT–CHPP) with additional heat sources to cover the heat loads of the heating season, which exceed the heat capacity of the cogeneration extractions of the combined-cycle gas turbines. The article shows that the use of water-heating boilers in this capacity has a number of serious disadvantages. These disadvantages can be eliminated by equipping HRSGs with afterburner units (ABUs), which burn the gas fuel in the residual oxygen of the exhaust gases of the gas turbine engine (GTE) directly in the HRSG. The range of thermal loads can be expanded, and the efficiency of the ABU application can be significantly increased by mounting the ABUs in the HRSG downstream from the high-pressure steam superheater upstream from the high-pressure evaporator. Furthermore, it is necessary to integrate a number of new components into the HRSG configuration, such as a water low-pressure steam superheater (WLPSSH) used instead of the gas LPSSH, a reduction device, and a peak network heater included in the heating plant of the steam turbine unit as the third stage of the network water heater at high (peak) thermal loads. By the example of the PGU-450T CCCHPP, the fundamental possibility of implementing the proposed modernization of its complete HRSG without making any changes to the design of the steam turbine is shown. Since the low-pressure drum of this HRSG is additionally equipped with a deaeration unit, the upgraded HRSG of the PGU-450T plant had also to be equipped with a water condensate heater upstream from the deaerator and additional shut-off and control valves that maintain the pressure in the deaerator and assure the subcooling of the water condensate at the deaerator inlet within the permissible range of all operating modes as well as under changing thermal loads all the year round. [ABSTRACT FROM AUTHOR]

In this research, Abadan combined cycle power plant (CCPP) has been thermodynamically modeled and the obtained results have been compared with the information obtained from the design conditions of the system. By introducing a multi-effect desalination cycle and several parabolic solar collectors, the CCPP, and the effects of these changes on its performance have been investigated. In this study, the exergy efficiency, carbon dioxide emission, and the cost of electricity generation have been considered based on the SPECO model. The results show that the thermal and exergy efficiency of the cogeneration of power and water with the parabolic solar collectors (CPWSC) depends on the design parameters. The efficiency of the power plant after using multi effect desalination (MED) system and parabolic solar collector increases from 48.71% to 50.91% and the exergy efficiency enhances from 45.95 to 50.03. The heat loss in the steam cycle is reduced by 29%. Also, a reduction in the cost of exergy destruction in the condenser is observed to be 13.56%. The CPWSC produces 20,000 tons of freshwater per day. Also, CO2 emissions have decreased from 58.05 to 54.97 kg per megawatt hour of electricity. [ABSTRACT FROM AUTHOR]

District heating (DH) is an alternative technology to Individual Heating (IH) for satisfying end-user’s needs. This paper assesses the competitiveness of a DH network in the center of Italy from energy, environmental, and economic points of view considering both thermal power plant and end-users’ sides. On the thermal power plant side, the energy analysis considers the Primary Energy Saving (PES) and the specific energy (Esp) of the fuel actually exploited in the thermal power plant compared to its Low Heating Value (LHV), while the environmental analysis considers the avoided CO2 and the economic analysis considers the Energy Efficiency Certificates (EECs). Results showed that the current thermal power plant configuration with two boilers and a Combined Heat and Power (CHP) unit reaches a yearly PES of 21.3% as well as 1099 tCO2 avoided. From the economic analysis of the thermal power plant side, 829 EECs with an economic return of 207,222€ are obtained, while from the end-users’ side the DH network is cheaper than IH in 84.7% of the cases. Further technologies are also studied to enhance the CHP unit flexibility.

• The MED plant coupling increases the exergy destruction of the plant. • The RC part-load operation has a significant influence on the unit product costs. • The ambient temperature evidences only a minor effect on water costs. • The Largest MED plant sizes obtained the lowest electric and water costs. A detailed exergy cost and thermoeconomic analysis applied to a Rankine Cycle (RC) coupled to a Multi-Effect Distillation (MED) plant was performed. The aim of this work is to identify the impact of design and operating conditions on the exergy and thermoeconomic costs of the final products, electricity, and freshwater, and to assess the distribution of the destroyed exergy, the fuel, and the plant costs. The plant model considers a high disaggregation model, which includes MED plant and condenser parasitic losses, a seawater pumping system and a brine energy recovery system. It also considers solar molten salts as the RC fuel, which is the typical fluid used in solar tower plants. The impact of RC + MED plant part-load operation, ambient temperature, MED plant size, and location plant's altitude was evaluated and an analysis of operational day of the RC + MED plant was carried out. Results indicate that the plant part-load operation has a significant influence on the unit exergy and thermoeconomic product costs, while the ambient temperature evidences only a minor effect on the water costs. As well, the largest MED plant sizes (above 50,000 m3/day) offer the lowest electric and water costs, while the altitude strongly increases the water costs. [ABSTRACT FROM AUTHOR]

The oil and gas industry is usually related to environmental problems and high level of CO2 emission. This work aims to evaluate different cogeneration plants usually used in FPSOs using cold deep sea water to improve efficiency of the cogeneration plants. Petroleum production data from a given well is used to size process plant while cogeneration plants are modeled using electrical and thermal demands required by process plant. Off-design operation caused by variation in utilities demand is also considered. Optimization using the GRG (Generalized Reduced Gradient) method is performed to minimize fuel consumption by selecting the best load distribution among equipment yearly. Results reveal that the additional cooling subsystem using deep sea water increases the exergy efficiency in 2.5% for gas turbines (which is the most usual technology) and as a consequence, a reduction of 128585 t in CO2 emissions was noticed. For the steam plant, the increase in exergy efficiency was 2.9%. For reciprocating engine and combined cycle technologies there is no significant benefit. Reciprocating engines plant presented the highest exergy efficiency (∼50%), even though no benefits from the use of the additional cooling system were achieved for this technology. • Cold deep seawater is used for CO2 reduction in FPSOs power plants. • Efficiency improvements of about 2.5% are expected for gas turbines power plants. • 212873 t of CO2 can be avoided along the lifespan of the platform. • Off-design operation and parallel equipment are considered. • Utilities demand are predicted using petroleum production curve. [ABSTRACT FROM AUTHOR]

Зважаючи на порівняно невисоку потужність генераторів когенераційних установок та їх роботу паралельно з мережею, потужність якої може перевищувати потужність машини, виникає ряд задач пов’язаних з перерозподілом потоків енергії у результуючій схеміза умов несиметрії навантаження. Цей перерозподіл, як показано в роботі, призводить до зміни якісних показників функціонування як генератора, так і системи електропостачання. На підставі аналізу відомих прийомів щодо відображення процесів насичення сталі магнітної системи синхронної машини, з використанням теорії електричних машин, з урахуванням несиметрії навантаження розроблено модель синхронного генератора. В пакеті візуального програмування виконано моделювання системи електроспоживання малого промислового підприємства в складі якої використовується синхронний генератор. Проведено серію експериментів з імітацією роботи синхронного генератора, з урахуванням насичення сталі,на комплексне навантаження паралельно з мережею та автономно. В результаті аналізу часових залежностей параметрів режиму встановлено вплив несиметрії на динамічні показники параметрів режиму та відмічено суттєвий вплив несиметрії при паралельній роботі з системою електропостачання. Отримані результати можуть бути використані при побудові систем керування збудженням машини в умовах несиметрії навантаження.

The cogeneration plant of offshore platforms has to supply utilities following the production of the platform. This production varies yearly and also depends on the mode of operation of the platform, which varies depending on the quantity of oil, gas and water produced. The variable demand for power and heat makes the selection of cogeneration technology for offshore platforms a tricky task. A methodology for this purpose is presented and gas turbines (conventional technology), reciprocating engines, a steam plant and a combined cycle are evaluated. The design point for each cogeneration plant is defined to meet the highest heat and power demands using as much as possible of exhaust gases energy. Load distribution between boilers, internal combustion engines, steam turbines and supplementary firing is optimized for each cogeneration plant yearly. The average exergy efficiency, specific CO 2 emission and the quantity of natural gas saved are evaluated over the lifespan of the oilfield considered. It is showed that the use of reciprocating engines represents a fuel saving of up 308,300 t of natural gas in comparison with gas turbines which represents a reduction in the CO 2 released to atmosphere of about 800,000 t. [ABSTRACT FROM AUTHOR]

The paper presents a configuration of mini CHP with the methane reformer and planar solid oxide fuel cell (SOFC) stacks. This mini CHP may produce electricity and superheated steam as well as preheat air and methane for the reformer along with cathode air used in the SOFC stack as an oxidant. Moreover, the mathematical model for this power plant has been created. The thermochemical reactor with impeded fluidized bed for autothermal steam reforming of methane (reformer) considered as the basis for the synthesis gas (syngas) production to fuel SOFC stacks has been studied experimentally as well. A fraction of conversion products has been oxidized by the air fed to the upper region of the impeded fluidized bed in order to carry out the endothermic methane steam reforming in a 1:3 ratio as well as to preheat products of these reactions. Studies have shown that syngas containing 55% of hydrogen could be produced by this reactor. Basic dimensions of the reactor as well as flow rates of air, water and methane for the conversion of methane have been adjusted through mathematical modelling. The paper provides heat balances for the reformer, SOFC stack and waste heat boiler (WHB) intended for generating superheated water steam along with preheating air and methane for the reformer as well as the preheated cathode air. The balances have formed the basis for calculating the following values: the useful product fraction in the reformer; fraction of hydrogen oxidized at SOFC anode; gross electric efficiency; anode temperature; exothermic effect of syngas hydrogen oxidation by air oxygen; excess entropy along with the Gibbs free energy change at standard conditions; electromotive force (EMF) of the fuel cell; specific flow rate of the equivalent fuel for producing electric and heat energy. Calculations have shown that the temperature of hydrogen oxidation products at SOFC anode is 850 °C; gross electric efficiency is 61.0%; EMF of one fuel cell is 0.985 V; fraction of hydrogen oxidized at SOFC anode is 64.6%; specific flow rate of the equivalent fuel for producing electric energy is 0.16 kg of eq.f./(kW·h) while that for heat generation amounts to 44.7 kg of eq.f./(GJ). All specific parameters are in agreement with the results of other studies. [ABSTRACT FROM AUTHOR]