Efficiency Of Electricity Production Research Articles

Structural and Parametric Optimization of S-CO2 Nuclear Power Plants.

The transition to the use of supercritical carbon dioxide as a working fluid for power generation units will significantly reduce the equipment′s overall dimensions while increasing fuel efficiency and environmental safety. Structural and parametric optimization of S–CO2 nuclear power plants was carried out to ensure the maximum efficiency of electricity production. Based on the results of mathematical modeling, it was found that the transition to a carbon dioxide working fluid for the nuclear power plant with the BREST–OD–300 reactor leads to an increase of efficiency from 39.8 to 43.1%. Nuclear power plant transition from the Rankine water cycle to the carbon dioxide Brayton cycle with recompression is reasonable at a working fluid temperature above 455 °C due to the carbon dioxide cycle′s more effective regeneration system.

The influence of electrode spacing on the performance of bioretention cell coupled with MFC.

In order to explore the influence of electrode spacing on the performance of the enhanced bioretention system, four bioretention cells with microbial fuel cell (BRC–MFC) systems with different electrode spacing were designed, and the effect of electrode spacing on system performance was revealed by analysing its water treatment capacity and electricity production efficiency. The results showed that BRC–MFC had good water treatment capacity and could produce electricity simultaneously. Compared with other BRC–MFC systems with spacing, the BRC3 system (with an electrode spacing of 30 cm) had significant water treatment capacity under different organic loads, especially under high organic load (C/N = 10) operation, COD removal rate was as high as 98.49%, removal rate was as high as 97%, and it had a higher output voltage of 170.46 ± 6.17 mV. It could be seen that proper electrode spacing can effectively improve the water treatment capacity of the BRC–MFC system. This study provided a feasible method for improving the performance of the BRC–MFC system, and revealed the relevant mechanism. A proper electrode spacing with sufficient carbon sources could effectively improve the water treatment capacity of the BRC–MFC system.

Evaluating the urban metabolism sustainability of municipal solid waste management system: An extended exergy accounting and indexing perspective

In this study, Extended Exergy Accounting was adopted to develop an accounting model to evaluate the performance of a Municipal Solid Waste Management System. Furthermore, urban metabolism sustainability index for waste was also proposed to represent the unified society-economy-environment impacts of the MSWMS under the framework of a comprehensive sustainability evaluation. A detailed analysis of wood and horticultural waste treatment scenarios in Singapore was done as a case study. It was found that the gasification scenario theoretically performs significantly better than the incineration scenario, in terms of energy carrier consumption, emissions, thermodynamic efficiency and sustainability. Analysis results show that, if extrapolated to Singapore’s total wood and horticultural waste, gasification technology has potential to reduce energy consumption and increase electricity output. An uncertainty analysis was carried out and it was found that the main extended exergetic parameters of the two scenarios considered were in the range of 3–8%, thus confirming the reliability of the accounting results. A sensitivity analysis of the urban metabolism sustainability index for waste was conducted for the gasification scenario to identify key influencing factors and seek potential improvements; this was done by considering changes in four variables: transportation distance, electrical efficiency, working hour increment and gross capital cost per ton waste treated. It was found that, to ensure the feasibility and sustainability of gasification scenario, the following are required: keeping the electricity production efficiency greater than 21.33%; the transportation distance between the gasification power plant and source of wood and horticultural waste should be kept within 17.08 km; employment of per kton annual treatment capacity should be less than 0.14 workers; wood and horticultural waste source should control the waste collection frequency of no more than 3 times per day and the number of workers participating in the collection each time is less than 4 persons, totaling to 12 workers per day.

Energy, exergy, exergoenvironmental, and economic assessments of the multigeneration system powered by geothermal energy

In this article, a new geothermal powered multigeneration system is proposed and analyzed via energy, exergy, economic, and exergoenvironmental points of view as well as parametric study to see the effects of main parameter variations. This multigeneration system includes a new configuration of the organic Rankine cycle with two evaporators and expanders, heater, NaClO system, and reverse osmosis. The products of this proposed system are electricity, hydrogen, heating, potable water, and salt. Due to theoretical analysis, this system produces 1.264 GWh of electrical energy, 15.93 GWh heating, 1919 Ton salt, 86400 m3 of potable water, and 4.397 × 107 m3 of hydrogen, annually with 60% and 21% of the system energy and exergy efficiencies. The organic Rankine cycle and reverse osmosis systems have the highest and lowest percentage of exergy destruction rates. The economic analysis reveals that the system payback period is 5.3 years. The system's net present value is 668.2 million US$. The exergoenvironmental analysis shows that the exergoenvironmental, environmental damage effectiveness, and the exergy stability factors for the proposed system are 0.86, 4.414, and 0.8, respectively. The parametric study shows that increasing the geo-fluid mass flow rate, increases the system's electrical power production and exergy efficiency while decreases the system exergy efficiency.

Study on a passive concentrating photovoltaic-membrane distillation integrated system

The traditional photovoltaic-thermal desalination systems generally need to consume produced electricity to power their pumps and fans, thus fail to provide users sufficient household electricity. This paper presents a concentrating photovoltaic-thermal membrane distillation integrated system, innovatively combining concentrating photovoltaic and membrane distillation. Besides producing electricity and fresh water, it is designed with cultivation chambers to directly use the produced water for growing crops. The system could be fully embedded underground and operating passively when tempered glasses are used as its top transparent cover, which can also serve as pavement. In such a way, it has strong resistance to typhoons and saves land sources as well. Here, the system design scheme is introduced. An experimental setup is developed, during which the structural design and optimization method for the concentrator is given, to verify the system’s feasibility. Mathematical models for the photovoltaic and thermal processes are established and well-validated via testing. The maximal overall efficiency is about 42% under solar radiation of 900 W/m2, in which the system’s electrical and water production efficiency is 10% and 32%, respectively. The system also performs well during the whole-day testing. There is more than 40% of solar energy can be utilized on sunny days.

The role of electricity mix and production efficiency improvements on greenhouse gas (GHG) emissions of building components and future refurbishment measures

PurposeAn estimation of the environmental impact of buildings by means of a life cycle assessment (LCA) raises uncertainty related to the parameters that are subject to major changes over longer time spans. The main aim of the present study is to evaluate the influence of modifications in the electricity mix and the production efficiency in the chosen reference year on the embodied impacts (i.e., greenhouse gas (GHG) emissions) of building materials and components and the possible impact of this on future refurbishment measures.MethodsA new LCA methodological approach was developed and implemented that can have a significant impact on the way in which existing buildings are assessed at the end of their service lives. The electricity mixes of different reference years were collected and assessed, and the main datasets and sub-datasets were modified according to the predefined substitution criteria. The influence of the electricity-mix modification and production efficiency were illustrated on a selected existing reference building, built in 1970. The relative contribution of the electricity mix to the embodied impact of the production phase was calculated for four different electricity mixes, with this comprising the electricity mix from 1970, the current electricity mix and two possible future electricity-mix scenarios for 2050. The residual value of the building was also estimated.Results and discussionIn the case presented, the relative share of the electricity mix GHG emission towards the total value was as high as 20% for separate building components. If this electricity mix is replaced with an electricity mix having greater environmental emissions, the relative contribution of the electricity mix to the total emissions can be even higher. When, by contrast, the modified electricity mix is almost decarbonized, the relative contribution to the total emissions may well be reduced to a point where it becomes negligible. The modification of the electricity mix can also influence the residual value of a building. In the observed case, the differences due to different electricity mixes were in the range of 10%.ConclusionsIt was found that those parameters that are subject to a major change during the reference service period of the building should be treated dynamically in order to obtain reliable results. Future research is foreseen to provide additional knowledge concerning the influence of dynamic parameters on both the use phase and the end-of-life phase of buildings, and these findings will also be important when planning future refurbishment measures.

The Effect of Plants on the Energy Output of Green Roof Photovoltaic Systems in Tropical Climates

The rapid rise in the number of fossil fuel uses over the last few decades has increased carbon dioxide (CO2) emissions. The purpose of implementing renewable energy solutions, such as solar, hydro, wind, biomass, and other renewable energy sources, is to mitigate global climate change worldwide. Solar energy has received more attention over the last few decades as an alternative source of energy, and it can play an essential role in the future of the energy industry. This is especially true of energy solutions that reduce land use, such as off-grid and on-grid solar rooftop technologies. This study aims to evaluate the energy conversion efficiency of photovoltaic (PV) systems in tropical environments. It also explores the effect of growing plants beneath PV panels. Two identical grid-connected PV systems—each containing five solar panels—were installed. The overall power production of each PV system was about 1.4 kWp. All the collected data were processed and analysed in the same way and by the same method. The PV systems were installed in two different environments—one with the possibility of growing the plants beneath the PV panels (PViGR module) and one with no possibility of growing the plants beneath the PV panels (PViSR module). The experiments were conducted in the Bo Yang District of Songkhla, Thailand over a 12-month period. Our findings indicate that green roof photovoltaic (GRPV) systems can produce around 2100 kWh of electricity in comparison to the 2000 kWh produced by other solar energy systems. Thereby, growing plants beneath PV panels increases electricity production efficiency by around 2%. This difference comes from the growing of plants underneath GRPV systems. Plants do not only help to trap humidity underneath GRPV systems but also help to cool the PV panels by absorbing the temperature beneath GRPV systems. Thus, in the production of electrical energy; the system was clearly showing significant differences in the mentioned results of both PV solar systems, which are evident for great energy efficiency performances in the future.

Life cycle assessment of molten carbonate fuel cell system for power plants

This study evaluated the environmental impacts of a 2.5 MW molten carbonate fuel cell (MCFC) system on impact categories such as climate change (CC), abiotic resource depletion (ARD), acidification (AC), and eutrophication (EU) using a life cycle assessment (LCA) methodology with the functional unit of 1 kWh electricity. Because MCFC systems produce electricity and heat simultaneously, the allocation was performed based on the amounts of exergy contents between electricity and heat (0.636 and 0.364, respectively). The impact on CC, expressed in global warming potential (GWP), was estimated as 3.53E-01 kg CO2 eq./kWh, while the impact on ARD was 1.90E-03 kg Sb eq./kWh, the impact on AC was 3.05E-04 kg SO2 eq./kWh, and the impact on EU was 1.35E-05 kg PO43− eq./kWh. The main cause for the impact on CC was found to be the reforming of liquefied natural gas in the operation stage. For the other categories (ARD, AC, and EU), the contributions of the operation stage were also over 80%. A comparison of the MCFC system with the Korean grid mix showed that the environmental impacts of the grid mix were larger than those of the MCFC system. Several improvement strategies were simulated to reduce the GWPs. First, to improve the efficiency of the heat exchanger, instead of using the heat generated by the MCFC system to produce high-temperature steam as is currently done, the generated heat was proposed to be used to produce medium or low-temperature water. This change reduced the GWPs of the MCFC by approximately 1.72E-02 kg CO2 eq./kWh. Second, this study simulated with an improved electricity production efficiency, with an increase from its current level (45%) to the theoretical maximum value of 60%. This improvement achieved a reduction of approximately 4.00E-02 kg CO2 eq./kWh. Finally, the electricity production efficiency was further increased using unreacted hydrogen, resulting in a reduction of 2.70E-02 kg CO2 eq./kWh.

Oxygen transport membrane unit applied to oxy-combustion coal power plants: A thermodynamic assessment

The oxy-combustion process is one of the alternatives which have been evaluated to counteract the increase in CO2 emissions over recent years. This technology consists of a combustion process with oxygen instead of air, which facilitates the capture of CO2 after the flue gas treatment process. Nowadays, oxy-combustion has not been implemented full-scale because of the high energy and economic requirements of the air separation unit to provide oxygen to the process. This paper proposes to ion transport membranes as a replacement for the air separation unit in order to minimize their high energy penalty of the overall system power. In particular, this work presents four processes based on the oxygen-fired plant with an oxygen transport membrane unit. As benchmark cases used to quantify the energy penalties for CO2 capture, the correspondent air combustion process without CO2 capture and a cryogenic oxygen-fired process (Case1) were considered. The thermodynamic comparison between the proposal alternatives has been conducted through simulation models based on Aspen Plus tools. The net electric power and the net efficiency of electricity production have been used as key parameters, which have allowed achieving an optimal system design that provides reduces the power consumption related to separate oxygen from the air. As the results show, the oxygen transport membranes concept exhibits better net electrical efficiency (35.7% vs. 30.6%), lower efficiency drop (2.5% vs. 7.6%) and lower specific captured CO2 (986 gCO2/hkWnet vs. 1140 gCO2/hkWnet) compared to the cryogenic oxygen-fired process.

Wind of change: Small-scale electricity production and distribution-grid efficiency in Sweden

In this paper, we measure the technical efficiency for local electricity distribution firms in Sweden, and in particular how small and micro-scale generation affects efficiency scores. Using a two-stage data envelopment analysis to model the technical efficiency and a double bootstrap approach to estimate the determinants of inefficiencies, we show that firms are heterogeneous in terms of inefficiency, but that a large share of small and micro-scale generation is not associated with more inefficient operations.

Energy, exergy, economic, and environmental (4E) analyses and optimization of a CCHP system with steam turbine

AbstractDue to finding solutions to reduce energy consumption and improve the electricity production efficiency in the power cycles, using the waste heat of power cycles in the combined generation systems can be a useful approach. Also, by using the wasted energy of the power generation cycles, the cooling and heating demands can be met. Therefore, this study presents energy, exergy, economic, and environmental evaluations of a new configuration of combined cooling, heating, and power (CCHP) or tri‐generation system with a steam turbine. This CCHP system includes a steam boiler, a steam turbine, a heat exchanger, a single‐effect absorption chiller, and pumps. Some important performance parameters such as electrical efficiency, combined electrical and cooling efficiency, combined electrical and heating efficiency, and tri‐generation efficiency, as well as exergy efficiency, are considered. Also, various output and environmental performance parameters such as percentage of operational cost reduction, percentage of fuel consumption reduction, percentage of pollutant emission reduction, and economic and technical issues based on different inlet temperatures and pressures of the steam turbine are investigated. In addition, the performance of the absorption chiller at different operating conditions has been investigated. This study shows that the usage of the CCHP system leads to reduction of 24.91% in carbon dioxide emission, 15.83% in fuel consumption, and 35.34% in operating costs compared with conventional systems. Also, the results show that there is a good improvement in the overall performance of the system with the tri‐generation efficiency of 82.46%.

Microalgae and cyanobacteria as biological agents of biocathodes in biofuel cells.

Biofuel cells (BFCs) are an environmental friendly technology that can simultaneously perform wastewater treatment and generate electricity. Peculiarities that hinder the widespread introduction of this technology are the need to use artificial aeration and chemical catalysts, which make the technology expensive and cause secondary pollution. A possible solution to this issue is the use of biocathodes with microalgae and cyanobacteria. Microalgae in the biocathodic chamber produce oxygen as the terminal electron acceptor. Various BFC technologies with algal biocathode (microbial fuel cells, microbial desalination cells, and plant microbial fuel cells) can address a variety of issues such as wastewater treatment, desalination, and CO2 capture. The main technological parameters that influence the performance of the biocathode are light, pH, and temperature. These technological parameters affect photosynthetic production of oxygen and organic compounds by microalgae or cyanobacteria, and hence affect the efficiency of electricity production, wastewater treatment and production of added-value compounds in microalgae biomass like lutein, violaxanthin, astaxanthin. The ability to remove carbon, nitrogen, and phosphorus compounds; antibiotics; and heavy metals by pure cultures of microalgae and cyanobacteria and by mixed cultures with bacteria in the cathode chamber can be used for wastewater treatment.

Design and optimization of photovoltaic systems in a parking garage - a case study

This paper deals with the design of photovoltaic (PV) systems in the roof plane of a parking garage for passenger cars. The selected type of PV system is optimized in terms of maximum efficiency of electricity production. A model solution for a parking house is being located on the outskirts of Žilina. The facade and roof of the parking house is without external shading by the surrounding buildings and vegetation. PV technology is located on the flat roof of the garage house. The optimization of the layout and inclination of the photovoltaic panels was performed in several variants. The energy produced is stored in batteries, which are located in the engine room. It is situated on the roof of the garage house above the charging stations of passenger cars, which are at the level of the 1st floor. In terms of economic efficiency, the optimal solution of PV technology from the analyzed variants for the climatic conditions of the Žilina locality was assessed. By economic analysis, we found that by installing PV panels, we can ensure the production of electricity for 6 charging stations and cover energy consumption related to the operation of the building.

НЕВІДВОРОТНІСТЬ ПЕРЕХОДУ УКРАЇНИ ДО ВІДНОВЛЮВАНОЇ ЕНЕРГЕТИКИ

В статті розглянуто суттєві проблеми сучасної української електроенергетики. Зношеність енергетичного обладнання ТЕС і АЕС перевищує допустимі проектні ліміти, що зменшує стійкість постачання електроенергії споживачам, збільшує обсяги локальних і глобальних шкідливих викидів, збільшує питомі витрати палива на ТЕС і АЕС, а з цим – збільшує собівартість і ціну продажу електроенергії. Ще одним з викликів для електроенергетики України є залежність від імпорту палива. Пріоритетний розвиток виробництва електроенергії з відновлюваних джерел енергії, обраний європейськими країнами, дозволив подолати проблеми фізичного і морального зносу обладнання, доступу до енергоносіїв, екологічної чистоти роботи електростанцій, ефективності виробництва електроенергії для інвесторів і для держави. Для України є дуже важливим цей позитивний європейський досвід подолання кризи в електроенергетиці.
 За даними International Energy Agency в період 2014-2035 рр. інвестиції у відновлювані технології виробництва електроенергії в країнах ЄС перевищать інвестиції в галузі традиційної енергетики (ТЕС і АЕС) разом взяті, більше ніж у три рази.
 Результати функціонування європейської електроенергетики за новим “низьковуглецевим” курсом засвідчують, що стратегічні рішення в європейській електроенергетиці були вдалими – країни Європи подолали всі перешкоди розвитку. 
 Зважаючи на подібність багатьох нагальних проблем української і європейської електроенергетики, а також на значний енергетичний потенціал відновлюваних джерел енергії України, зокрема енергії сонця та вітру — 2273 млрд кВт∙год у рік, стратегічні рішення для української електроенергетики мають враховувати відповідний європейський досвід пріоритетного розвитку виробництва електроенергії з відновлюваних джерел енергії. Крім того, проведений аналіз дає обґрунтований висновок, що відновлювані технології виробництва електроенергії найбільш привабливі для інвесторів. 
 Бібл. 19, табл. 8, рис. 12.

Review of ways to increase efficiency of energy generation at TPP at the account of additional energy carriers

The problem of increasing the efficiency of generation facilities through the use of additional energy carriers is considered. Presented are the modern achievements of ways to increase the efficiency of energy production at TPPs: 1) transition to super-critical parameters of steam and 2) multigeneration. Increasing the parameters of steam increases the energy efficiency of electricity production, and multigeneration allows to produce additional energy carriers (hydrogen, oxygen, compressed air, cold, etc.) due to the unclaimed capacity of the equipment used or the utilization of flows inside the generating facility. The additional energy carriers produced as a result of such processes can be centrally supplied to external consumers or used inside the production cycle, for example, to switch to super-critical steam parameters. The transition to over critical parameters is possible when using high-temperature over heaters or when using new boiler units.

Solar hybrid steam-injected gas turbine system with novel heat and water recovery

For concentrating solar power, Brayton cycle offers a more attractive method than Rankine cycle to improve the flexibility and the efficiency of electricity production and peak-load regulation. Therefore, in this study, a solar hybrid steam-injected gas turbine system with novel heat and water recovery is proposed. The new system injects steam at the inlet of a turbine and recovers waste heat and water from exhaust gas. Thermodynamic models of the novel system are built to analyze main factors that affect the performance and characteristics. The system efficiency is improved by 17% under an optimal steam injection rate of 0.065. Water recovery rates reach up to 98%, which is associated with a high waste heat recovery rate from the exhaust gas. Compared with a single-stage absorption refrigeration unit, the heat recovery rate and refrigeration capacity of the system with a double-stage absorption refrigeration unit are increased by 109% and 63%, respectively. Furthermore, the models are applied to analyze the annual performance and environmental sustainability of the novel system in Lhasa and Dunhuang, western China. The maximum efficiency and peak power output of the novel system are increased by 21.8% and 37.9%, respectively. The consumption of fuels and emissions of CO2 is lower than conventional gas turbine. These results indicate that the proposed system shows high efficiency possibility and environmental sustainability with a near-zero water consumption.

A wayside hotbox system with fuzzy and fault detection algorithms in IIoT environment

Moving towards industrial internet of things (IIoT) concept is one of the hot issues of the management, control, and maintenance of railway transportation. The wayside hotbox systems are useful for monitoring of overheated axle bearings in the harsh dust environment. In the paper, the fuzzy-based fault detection algorithm (FDA) of the spatially distributed hotbox monitoring system (SDHMS) and its IIoT concept are presented. SDHMS consists of three stand-alone wayside hotbox monitoring systems that are installed in three distant locations: two thermal power plants and a coal mine. The system plays an important role in keeping railway safety, preventive maintenance and accident avoidance. Therefore, the IIoT concept is needed for increasing the reliability of coal transportation and the energy efficiency of electricity production. The main advantage of the presented concept is the application of the FDA at the edge and fog levels as well as the application of a complex fuzzy model for decision making at the cloud level. Edge computing involves signal processing in hotbox systems with the aim of the fault detection and quality assessment of the measured signals. Fog computing involves data processing with the aim of detecting an overheated bearing (temperature, position, axle number and train side), and alarming. Cloud computing is in charge of assessing the bearing condition and the need for replacement and maintenance planning. The proposed algorithm and fuzzy model were validated in real conditions of exploitation, successfully.

Drivers of CO2 emissions from electricity generation in the European Union 2000–2015

Carbon emissions from electricity generation in the EU have dropped from 1198 MtCO2 in 2000 to 970 MtCO2 in 2015, after an initial increase to 1304 MtCO2 in 2007. This pattern reversal is not only explained by socioeconomic drivers (an initial period of robust economic growth followed by weaker growth) but by profound shifts in the energy system. This study quantitatively evaluates the drivers of carbon emissions from EU electricity generation during two subperiods, 2000–2007 and 2007–2015. In 2000–2007 the main drivers of the decrease in carbon emissions were changes in the fossil fuel mix (replacement of coal by gas) and improvements in the efficiency of electricity use. In 2007–2015 the main drivers of the decrease in carbon emissions were the expansion of renewable electricity, improvements in the efficiency of fossil electricity production and improvements in the efficiency of electricity use. There is significant variation in the drivers of change among countries. The authors expect the continued expansion of renewables to balance economic growth in the future.

Producing electrical energy in microbial fuel cells based on sulphate reduction: a review.

Combination of the treatment of effluents with high organic loads and the production of electricity is the driving forces stimulating the development of microbial fuel cells (MFC). The increase in electricity production in MFCs requires not only the optimization of the operational parameters but also the inhibition of themetabolic pathways, which compete with electricity production, such as methanogenesis. The presence of both sulphate and sulphide ions in conventional anaerobic reactors hampers the growth of methanogenic archaea and justifies the use of sulphate and therefore sulphate-reducing bacteria (SRB) in the anodic half-cell of MFC. Most importantly, the literature on the subject reveals that SRB are able to directly transfer electrons to solid electrodes, enabling the production of electrical energy. This technology is versatile because it associates the removal of both sulphate and the chemical oxygen demand (COD) with the production of electricity. Therefore, the current work revises the main aspects related to the inoculation of MFC with SRB focusing on (i) the microbial interactions in the anodic chamber, (ii) the electron transfer pathways to the solid anode, and also (iii) the sulphate and COD removal yields along with the electricity production efficiencies.

Experimental Study on Energy Efficiency of Multi-Functional BIPV Glazed Façade Structure during Heating Season

Building integrated photovoltaics (BIPV) is technology that can significantly increase the share of renewable energy in final energy supply and are one of essential technologies for the nearly zero-energy buildings (nZEB), new build and refurbished. In the article (a) an experimental semitransparent BIPV glazed façade structure with 60% of PV cell coverage is shown; (b) energy efficiency indicators were developed based on identified impact parameters using experimental data; and (c) multi-parametric models of electricity generation, preheating of air for space ventilation, and dynamic thermal insulation features that enable prediction of solar energy utilization in different climate conditions are shown. The modeled efficiency of electricity production of BIPV was in the range between 8% and 9.5% at daily solar radiation above 1500 Wh/day, while low impact of outdoor air temperature and ventilation air flow rate on PV cell cooling was noticed. Between 35% and 75% of daily solar radiation can be utilized by preheating the air for space ventilation, and 4.5% to 7.5% of daily solar radiation can be utilized in the form of heat gains through opaque envelope walls.