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[Display omitted] • Various carbon nanotube-based devices are developed for solar energy utilization. • The water evaporation system can generate freshwater (1.28 kg m−2h−1). • The solar-thermoelectric system can output a voltage and charge a cellphone. • The supercapacitor performs an areal specific capacitance of 19.6 mF cm−2. • The hybrid energy system can produce freshwater, generate and store electric power. Nowadays, multi-functional systems driven by solar energy have been explored to alleviate the crisis of energy and freshwater scarcity. However, it remains a great challenge to integrate multi-functions into one hybrid system with a monolithic material, which can harvest, convert and store solar energy synergistically. Here, we firstly propose a multi-functional carbon nanotube paper, which starts from a material level to solve these problems. The carbon nanotube paper is fabricated by vacuum filtration. It exhibits high efficiency of solar-thermal conversion. Secondly, three types of energy conversion/storage systems (e.g., solar-thermal evaporation system, solar-thermoelectric generation system, and supercapacitor) are constructed based on the carbon nanotube paper, which extend the research to a device level. The solar-thermal evaporation system shows an evaporation rate of 1.28 kg m-2h−1 under simulated sunlight irradiation of 1 kW m−2. The solar-thermoelectric generation system demonstrates a stable electric power generation with an output voltage of 100 mV under light irradiation of 1 kW m−2. The supercapacitors perform the energy storage function with an areal specific capacitance of 19.6 mF cm−2. These devices and systems can be used in freshwater generation (0.84 kg m-2h−1, sunlight irradiation of 1 kW m−2), water purification/desalination (inorganic ions rejection larger than 99.9%) and portable solar charging system (maximum output voltage of 5 V). Finally, a hybrid energy system is innovatively proposed from the system level to simultaneously produce freshwater, generate and store electric power. Through the synergetic coupling of solar conversion and storage technologies, the hybrid energy system can supply sustainable freshwater and electricity for remote areas in daily life, highlighting the superiority of multi-energy (thermal energy, electrical energy, and electrochemical energy) complementary. [ABSTRACT FROM AUTHOR]

• An improved model DWTimesNet based on dilated convolution and WN is proposed. • RF was used to reduce the effect of missing data on the proposed model. • To eliminate the effect of some variables, MIC is used for feature selection. • The PBT algorithm is used to efficiently parameterize the proposed model. • Two cases with different data quality are used to verify the proposed model. The share of wind power in global electricity generation is increasing year by year, and the prediction of wind power is a practical and necessary scientific research. In this paper, the TimesNet model is used for multistep prediction of wind power. It is observed that the prediction error of the TimesNet model could be improved by replacing the original convolutional structure with the dilated convolution and weight normalization (WN). And in addition, the population-based training (PBT) algorithm is introduced to guide the model tuning. Missing values in the raw data are imputed to enhance data integrity. And the maximal information coefficient (MIC) method is chosen to select features for the different influences on wind power, which reduces the computational effort of the model. In order to demonstrate the effectiveness of the proposed model MIC-PBT-DWTimesNet, nine models are arranged in this paper as a control group and compared with their predicted values with each other. It can be observed that the RMSE of the proposed model MIC-PBT-DWTimesNet is decreased by 17–33% compared to the base TimesNet method. [ABSTRACT FROM AUTHOR]

• A long-term analysis of the United Kingdom steel sector's efficiency is undertaken. • The sector is evaluated using both conventional and exergy-based metrics. • The indicators quantify the trade-offs between energy and material flows. • The effect of by-products and electricity generation on efficiency is considered. • The sector's overall resource efficiency went from 19% to 32% over the period. Resource efficiency is a key component of sustainable policies and practices, particularly in industries with high energy demands. Using empirical data, this paper evaluates the long-term performance (1960–2009) of the United Kingdom steel sector through the exergy-based metrics of "resource efficiency" and "useful exergy efficiency". The analysis is broken down into two production pathways: the basic oxygen furnace and the electric arc furnace. The scope includes electricity generation and steel refining. It incorporates energy and material inputs, as well as by-products as useful outputs. The exergy-based indicators demonstrate the benefit of measuring both the quality and quantity of resources. The results are contextualised to gain insights into the long-term impact of political and socioeconomic transitions on resource consumption trends. Over the period, the sector's overall resource efficiency went from 19% to 32%. Between 2% and 4% of this improvement results from the reincorporation of by-products into production processes. The basic oxygen furnace route's resource efficiency increased by 9% whilst the electric arc furnace route rose by 20%. These improvements occurred via the promotion of successful energy saving policies rather than the diversion of large amounts of scrap inputs into the furnaces. This paper shows that both the resource efficiency and useful exergy efficiency indicators are a valuable complement to the benchmark metrics (energy intensity and material efficiency). This is because they can quantify the interactions and trade-offs between energy and material flows. [ABSTRACT FROM AUTHOR]

• Comparison for the first time of FEM and RC in TEM transient simulation. • RC replicates results of FEM under steady state with deviations lower than 3 % • RC replicates also values, trends and rates of variation under transient conditions. • RC presents negligible computational cost. This paper demonstrates that resistance–capacitance models provide equal results than models based on finite-element software when predicting the performance of a thermoelectric module under transient-state conditions. Previous papers on this topic fall short as comparing finite-element models with simplified versions of resistance–capacitance models. It was confirmed that resistance–capacitance models replicate results of finite-element models in the simulation of a thermoelectric module under steady-state conditions. Deviations lower than 3 % in electric power and efficiency (ratio of electric power to heat input) are obtained for temperature differences between heat source and heat sink as large as 200 K. Similarly, deviations lower than 3 % are obtained for simulation of a thermoelectric module under transient-state conditions. Resistance-capacitance models not only replicate values, trends and rates of variation predicted by finite-element models under step, linear and sinewave variations in the boundary conditions, but they also do this with negligible computational cost. [ABSTRACT FROM AUTHOR]

The increase of power plants’ conversion efficiencies, together with the high share of renewable energy sources in the electricity production for some countries, pushes for the use of heat pumps for space heating when aiming at reducing the associated primary energy consumption. However, the effective reduction of primary energy consumption should be supported by careful evaluations, as a number of parameters influence the heat pumps performance, including outdoor temperature, supply temperature, heat load and electricity primary energy factor. The variability of such parameters increases the complexity of the analysis, and annual or monthly average calculations might lead to incomplete evaluations and thus to sub-optimal solutions. This paper performs a hourly simulation of the operation of an air-source heat pump for space heating, relying on the available heat demand data of real buildings currently connected to a district heating network. In addition, the paper proposes the calculation of the hourly primary energy factor of the electricity supplied by the power grid, as the variability of the generation sources plays a key role in the global analysis of the energy system’s conversion efficiency. The results show that in all the considered cases the heat pumps provide potential primary energy savings compared to natural gas boilers, thanks to the combined effect of their high coefficient of performance and the low electricity primary energy factor in the analyzed context. The primary energy consumption reduction obtained in each case is in the range 10–40%, with a median value close to 30%. Moreover, the comparison between average and high-resolution calculations of primary energy factors shows the possible underestimation of the potential primary energy savings when yearly or monthly data are adopted. [ABSTRACT FROM AUTHOR]

The solar energy share in Sweden will grow up significantly in next a few decades. Such transition offers not only great opportunity but also uncertainties for the emerging solar photovoltaic/thermal (PV/T) technologies. This paper therefore aims to conduct a techno-economic evaluation of a reference solar PV/T concentrator in Sweden for building application. An analytical model is developed based on the combinations of Monte Carlo simulation techniques and multi energy-balance/financial equations, which takes into account of the integrated uncertainties and risks of various variables. In the model, 11 essential input variables, i.e. average daily solar irradiance, electrical/thermal efficiency, prices of electricity/heating, operation & management (OM) cost, PV/T capital cost, debt to equity ratio, interest rate, discount rate, and inflation rate, are considered, while the economic evaluation metrics, such as levelized cost of energy (LCOE), net present value (NPV), and payback period (PP), are primarily assessed. According to the analytical results, the mean values of LCOE, NPV and PP of the reference PV/T connector are observed at 1.27 SEK/kW h (0.127 €/kW h), 18,812.55 SEK (1881.255 €) and 10 years during its 25 years lifespan, given the project size at 10.37 m 2 and capital cost at 4482–5378 SEK/m 2 (448.2–537.8 €/m 2 ). The positive NPV indicates that the investment on the selected PV/T concentrator will be profitable as the projected earnings exceeds the anticipated costs, depending on the NPV decision rule. The sensitivity analysis and the parametric study illustrate that the economic performance of the reference PV/T concentrator in Sweden is mostly proportional to solar irradiance, debt to equity ratio and heating price, but disproportionate to capital cost and discount rate. Together with additional market analysis of PV/T technologies in Sweden, it is expected that this paper could clarify the economic situation of PV/T technologies in Sweden and provide a useful model for their further investment decisions, in order to achieve sustainable and low-carbon economics, with an expanded quantitative discussion of the real economic or policy scenarios that may lead to those outcomes. [ABSTRACT FROM AUTHOR]

This paper aims to present a futuristic review on the potential of photovoltaic-thermal or PV/T systems in a wide spectrum for the efficient utilization of solar radiation through well engineered hybrid PV/T systems. These hybrid PV/T system based technology is just 30 years old which had gained significant attention from the researchers and academicians all over the world in a recent decade. The word PV/T is composed of [PV (photovoltaic) + T (thermal)] i.e. the simultaneous production of heat and electricity in an integrated manner thus paving the way towards improving the overall energy efficiency of the system. It is a sort of co-generation technology so that the issue of low efficiency associated with existing PV technology can be impact fully addressed. It provides an opportunity for the efficient utilizing of solar radiation which is eventually dissipated as waste heat in the PV cells causing decrease in the efficiency of the PV cells. This paper covers an extensive overview of the most recent trends and useful technologies available for thermal management in PV/T collectors in a categorical manner i.e. air based, liquid based, phase change material (PCM) based and heat pipe based along with wide range of possible applications in building, solar distillation /desalination and thermoelectric generators & heat pumps. The paper also covers economical aspects like payback period, concept of Net Present Value (NPV) and exergo-economic & enviro-economic parameters for the economic assessment of the PV/T systems. The results are being tabulated for visual understanding of the different techniques being reviewed. The paper also identifies the potential role of PV/T systems to mitigate emission challenges particularly with respect to building applications. [ABSTRACT FROM AUTHOR]

The impact of carbon capture and storage (CCS) technology on the coal-fired power generation was evaluated in this paper. The impact was measured through the cost of conserved water (CCW) as an indicator. This indicator was estimated by combining water demand coefficients and levelized cost of electricity (LCOE). CCW was calculated based on a reference case for each of the developed 66 generic pathways of coal-based power generation with CCS. The current existing mix of power generation in the Province of Alberta, Canada was taken as the reference case in this paper. Water consumption coefficients for coal-based power generation with CCS were found in the range 1.01–4.85 m 3 /MWh based on the complete life cycle and 0.15–3.65 m 3 /MWh for the power generation stage. Based on the complete life cycle boundary, pathways involved ultra-supercritical configuration and oxyfuel combustion CCS technology offer the lowest CCW, with values less than 0.89 USD per m 3 of water saved for consumption and less than 0.66 USD per m 3 of water saved for withdrawals. In the sensitivity analysis, LCOE for the pathways involved dry cooling was increased by 6.00 USD/MWh over the base case value, and the resulted corresponding increase in the CCW was found in the range 9–33% compared to the base case. [ABSTRACT FROM AUTHOR]

This paper presents an optimized ethanol phase-change immersion cooling method to obtain lower temperature of dense-array solar cells in high concentrating photovoltaic system. The thermal performances of this system were compared with a conventional active water cooling system with minichannels from the perspectives of start-up characteristic, temperature uniformity, thermal resistance and heat transfer coefficient. This paper also explored the influences of liquid filling ratio, absolute pressure and water flow rate on thermal performances. Dense-array LEDs were used to simulate heat power of solar cells worked under high concentration ratios. It can be observed that the optimal filling ratio was 30% in which the thermal resistance was 0.479 °C/W and the heat transfer coefficient was 9726.21 W/(m 2 ·°C). To quantify the quality of energy output of two cooling systems, exergy analysis are conducted and maximum exergy efficiencies were 17.70% and 11.27%, respectively. The experimental results represent an improvement towards thermal performances of ethanol phase-change immersion cooling system due to the reduction in contact thermal resistance. This study improves the operation control and applications for ethanol phase-change immersion cooling technology. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present an improved way of collection and compilation of data about solid biomass consumption in households in order to improve accuracy of official energy statistics data. The accurate, timely and reliable energy data significantly contribute to the consistency in national energy statistics, energy balance, as well as for many other obligatory reporting procedures which are requested and prescribed by national and international standards. When compiling energy statistics, statistics on renewables, particularly biomass consumption, it is often the most questionable as little or no available official data exists in the country. According to the international standards and definitions, solid biomass covers organic, non-fossil material of biological origin which may be used as fuel for heat production or electricity generation. In households, the most commonly used biomass are fuelwood and wood residues. In the process of compiling national energy statistics, national institutions responsible for official energy statistics usually estimate biomass consumption based on the reports on fuelwood cuts in state forests and official biomass production, although it is known that consumption is much higher. Over the past two decades, Energy Institute Hrvoje Požar worked intensively on the energy consumption data collection and particularly on the development of the tailored-made surveying methods for different final energy consumption sectors, particularly for the household sector. The similar methods were recommended to national statistics institutes in the countries in the region when providing technical assistance in developing energy statistics. This paper describes the survey results and methods applied for the determination of energy consumption in households and particularly biomass consumption in three selected countries: Croatia, Bosnia and Herzegovina and Macedonia, and recommendations for the further improvements. [ABSTRACT FROM AUTHOR]

In this paper, an alternative renewable energy concept, i.e. concept of solar power plant with short diffuser (SPD) was investigated through the development of a numerical model with simplifications due to general complexity. The mentioned alternative energy concept is based on the possibility of utilizing an artificially created and maintained convective vortex system in the surrounding atmosphere. Finally, it is assumed that the specific vortex system would able to deliver useful mechanical work which then can be used to produce carbon-free electricity via turbine assembly. Preliminary numerical results were presented as a case study for SPD plants using a solar collector diameter of 600 m with a diffuser of 30 m in maximal and 25 in minimal diameter. According to the obtained numerical simulations, for the considered case, it was found that pressure potential should be below 5 kPa in general (with mass air flow rates less than 31 t/s) in order to enable reasonable operating conditions for commercial wind turbine technologies (a specific pressure potential range was defined in order to provide reasonable parameters related to the vortex system). Namely, for pressure potentials ranging between 3.5 kPa to 5.0 kPa, and mass air flow rates from 26 to 31 t/s, the plant would be able to deliver between 5.17 MW to 16.95 MW of nominal electric power output with an associated range of wind turbine operating air velocities from 30 m/s to 50 m/s. A comparison of the numerical results was obtained by using available observation data and reasonable matching was achieved, i.e. partial validation of the developed numerical model due to the non-existence of an experimental plant. Current research related to SPD concept development is still in the stage of numerically based experiments, which are crucial and important towards the consideration of a prototype plant. Therefore, the gained and presented findings in this paper are certainly valuable for the further development of the herein analyzed alternative renewable energy concept and provide a base for the final experimental realization of a prototype plant. [ABSTRACT FROM AUTHOR]

In past centuries, men have mainly looked to increase their production of energy in order to develop their industry, means of transport and quality of life. Since the recent energy crisis, researchers and industrials have looked mainly to manage energy in a better way, especially by increasing energy system efficiency. This context explains the growing interest for thermoelectric generators. Today, thermoelectric generators allow lost thermal energy to be recovered, energy to be produced in extreme environments, electric power to be generated in remote areas and microsensors to be powered. Direct solar thermal energy can also be used to produce electricity. This review begins with the basic principles of thermoelectricity and a presentation of existing and future materials. Design and optimization of generators are addressed. Finally in this paper, we developed an exhaustive presentation of thermoelectric generation applications covering electricity generation in extreme environments, waste heat recovery in transport and industry, domestic production in developing and developed countries, micro-generation for sensors and microelectronics and solar thermoelectric generators. Many recent applications are presented, as well as the future applications which are currently being studied in research laboratories or in industry. The main purpose of this paper is to clearly demonstrate that, almost anywhere in industry or in domestic uses, it is worth checking whether a TEG can be added whenever heat is moving from a hot source to a cold source. [ABSTRACT FROM AUTHOR]

The use of zeotropic fluid mixtures in refrigeration cycles and heat pumps has been widely studied in the last three decades or so. However it is only in the past few years that the use of zeotropic mixtures in power generation applications has been analysed in a large number of studies, mostly with low grade heat as the energy source. This paper presents a review of the recent research on power cycles with zeotropic mixtures as the working fluid. The available literature primarily discusses the thermodynamic performance of the mixture power cycles through energy and exergy analyses but there are some studies which also consider the economic aspects through the investigation of capital investment costs or through a thermoeconomic analysis. The reviewed literature in this paper is divided based on the various applications such as solar energy based power systems, geothermal heat based power systems, waste heat recovery power systems, or generic studies. The fluid mixtures used in the various studies are listed along with the key operation parameters and the scale of the power plant. In order to limit the scope of the review, only the studies with system level analysis of various power cycles are considered. An overview of the key trends and general conclusions from the various studies and some possible directions for future research are also presented. [ABSTRACT FROM AUTHOR]

Solar pond undoubtedly has been a reliable source of low grade heat supply by acting as both collector and storage for the incoming solar radiation. The thermal efficiency of the solar ponds is between 15 and 25% of the incoming horizontal solar radiation. Meanwhile, the thermoelectric technology enables the conversion of heat into electricity using thermoelectric modules. In this paper, the feasibility of the system by combining solar pond and thermoelectric modules is presented. This system can be achieved by using a thermoelectric modules-embedded heat exchanger module that will able to extract the heat available from the lower convective zone of the solar pond. The analysis in this paper was conducted by investigating the solar ponds operating in different climate conditions, which are Group A (Kuala Lumpur), Group B (Riyadh) and Group C (Melbourne and Granada) base on Köppen climate classification. The theoretical feasibility draws the limit on the performance and cost of the solar pond-thermoelectric system under commercially available thermoelectric technology at the present state. Later, the result was contrasted against the performance of the power generation units operate under realisable operating condition with solar pond. The result in this study revealed that, under ideal condition, the system is at least 10 times costly compared to other renewable energy sources like off-grid solar photovoltaic system with storage. Meanwhile, at its best operating climate, this system will be able to achieve annual carbon dioxide reduction of 2.38 kg/m 2 -year in a practical case. [ABSTRACT FROM AUTHOR]

If all the resources in power supply side, transmission part, and power demand side are considered together, the optimal expansion scheme from the perspective of the whole system can be achieved. In this paper, generation expansion planning and transmission expansion planning are combined into one model. Moreover, the effects of demand response in reducing peak load are taken into account in the planning model, which can cut back the generation expansion capacity and transmission expansion capacity. Existing approaches to considering demand response for planning tend to overestimate the impacts of demand response on peak load reduction. These approaches usually focus on power reduction at the moment of peak load without considering the situations in which load demand at another moment may unexpectedly become the new peak load due to demand response. These situations are analyzed in this paper. Accordingly, a novel approach to incorporating demand response in a planning model is proposed. A modified unit commitment model with demand response is utilized. The planning model is thereby a bi-level model with interactions between generation-transmission expansion planning and operation simulation to reflect the actual effects of demand response and find the reasonably optimal planning result. [ABSTRACT FROM AUTHOR]

This paper presents a piezoelectric energy harvester for rotational motion applications. The piezoelectric energy harvester is mounted on a rotating system in which the axis of rotation is more or less parallel to the Earth’s surface. As the harvester rotates, the piezoelectric elements in the energy harvester are repeatedly deformed to generate electrical power. A novel design of the harvesting structure is proposed in this paper and analyzed theoretically. Experiments were conducted to validate the concept and analysis. Power output of 83.5 – 825 μW is achieved at the rotating frequencies of 7 – 13.5 Hz with a prototype of rotational energy harvester. Results show that the harvester can offer sufficient power for low-power wireless transmitters. [ABSTRACT FROM AUTHOR]

A transition in the electricity market is required to manage the volatility of increasing renewable energy generation. These fluctuations can be faced with flexible consumption through Demand Side Management (DSM), establishment of further centralized storage capacities and provisioning of dynamic back up generation capacities. At least the latter two options can impose large establishment and operation costs upon the electricity market. Therefore, the feasibility and the resulting potential of coupling the electricity grid with the thermal supply of residential buildings is analysed in this paper. Thereby, inexpensive and widespread thermal storage capacities could be used to improve the integration of dynamic renewable electricity generation. In this paper the technical and economical key impact factors for such thermal DSM approach are elaborated. Based on a literature review, the identified key factors are aggregated to form consistent scenarios of the German “Energiewende” (turnaround in energy policy). The practicability and possible magnitude of the intended DSM is then analysed based on the identified scenarios. All resulting scenarios highlight the growing demand for a flexible electricity market. Especially in scenarios with strong growth of renewable electricity generation, up to 45 GW of flexible electric capacities would be required in Germany by the year 2030. Furthermore, the analysis demonstrates that independently of the energy market development, it is very likely that electricity coupled supply systems will continuously have installed capacities of at least 14 GW. It is found that especially the strong dissemination of smart metering and smart control infrastructure is crucial to incorporate these capacities into DSM activities. Furthermore, the necessity and the resulting benefits of residential end-user participation in the electricity market need to be communicated to all stakeholders to ensure the availability and acceptance of dynamic pricing schemes in the future. [ABSTRACT FROM AUTHOR]

This paper mainly focuses on the modeling and simulation of the doubly fed induction generator (DFIG) based wind turbine generation system. In this paper, a new method which combines the mechanical part and electrical part is presented to model the wind turbine generation system. The turbine rotor blade is modeled by the lifting line model and the aerodynamic forces are solved by the improved free vortex wakes method with the supplementary of two dimensional aerodynamic data (three dimensional corrected). The control system of pitching and generator with voltage oriented control (VOC) are established in Matlab/Simulink. The drive train is also modeled with two mass model. In order to realize the coupling computation of the wind turbine model, a data link is built to transfer the parameters between aerodynamic part and electrical part. In this way, the interaction between turbine rotor and generator could be predicted. The validations are firstly made to ensure the reliability of the model. Then the performance of a 1.5 MW wind turbine is investigated with this integrated model under different wind and symmetrical grid voltage dip condition. [ABSTRACT FROM AUTHOR]

Increasing interest in low rank coal pyrolysis (LRCP) polygeneration has resulted in the development of a number of different technologies and approaches. Evaluation of LRCP processes should include not only conventional efficiency, economic and environmental assessments, but also take into consideration sustainability aspects. As a result of the many complex variables involved, selection of the most suitable LRCP technology becomes a challenging task. This paper applies a House of Quality method in comprehensive evaluation of LRCP. A multi-level evaluation model addressing 19 customer needs and analyzing 10 technical characteristics is developed. Using the evaluation model, the paper evaluates three LRCP technologies, which are based on solid heat carrier, moving bed and fluidized bed concepts, respectively. The results show that the three most important customer needs are level of technical maturity, wastewater emissions, and internal rate of return. The three most important technical characteristics are production costs, investment costs and waste emissions. On the basis of the conducted analysis, it is concluded that the LRCP process utilizing a fluidized bed approach is the optimal alternative studied. [ABSTRACT FROM AUTHOR]

In the manuscript “Comment on ‘A hybrid multi-objective cultural algorithm for short-term environmental/economic hydrothermal scheduling’ by Youlin Lu et al. [Energy Convers. Manage. 52 (2011) 2121–2134]”, Abdollah Ahmad et al. reported that there were some inaccuracies made by Youlin Lu et al. in the paper [Energy Convers. Manage. 52 (2011) 2121–2134] while presenting the solutions. By detailed analysis and checking, the different results in the two papers are caused by taking the storage volume at different moments of one period during hydro generation calculation. Abdollah Ahmad et al. take the final storage volume of the period when doing the calculating, while Youlin Lu et al. take the initial storage volume of the period. The checking results indicate that the schemes in the two papers are correct and reasonable only they are obtained by taking different storage volumes. These schemes have less fuel cost and emission while satisfying various constraints. Moreover, the key references cited in the original paper also take the initial storage volume of the period to calculate hydro generation, which are suitable for the comparison of the optimal results. Finally, few inaccurate expressions in the original paper [Energy Convers. Manage. 52 (2011) 2121–2134] are modified. [ABSTRACT FROM AUTHOR]

This paper investigates the energy distribution and the waste heat energy characteristics of a compression ignition engine for micro-cogeneration applications, at different engine speeds and loads. The experimental activity was carried out on a three-cylinder, 1028 cc, common-rail engine. Tests were performed with diesel fuel and a 20% v/v biodiesel blend (B20). The quantity and the quality of the waste heat energy were studied through energy and exergy analyses, respectively. Combustion characteristics were investigated by means of indicating data. Gaseous emissions were measured and particles were characterized in terms of number and size at exhaust. It was found out that the addition of 20% v/v of RME to diesel fuel does not affect significantly the brake fuel conversion efficiency and the energetic flows. On the other hand, biodiesel blend allows to reduce the combustion noise and the pollutants emissions in most of the operating conditions. A proper phasing of the injection strategy for the biodiesel blend could further reduce the exhaust emissions, mainly at high engine speeds. The results presented in this paper could be useful for the development of diesel engine based micro-cogeneration systems working at different engine speeds and loads. [ABSTRACT FROM AUTHOR]

As an important means of demand-side response, the reasonable formulation of the electricity price mechanism will have an important impact on the balance between the supply and demand of electric power. With the introduction of Chinese intelligence apparatus and the rapid development of smart grids, real-time electricity pricing, as the frontier electricity pricing mechanism in the smart grid, will have great significance on the promotion of energy conservation and the improvement of the total social surplus. From the perspective of system dynamics, this paper studies different real-time electricity pricing mechanisms based on load structure, cost structure and bidding and analyses the situation of user satisfaction and the total social surplus under different pricing mechanisms. Finally, through the comparative analysis of examples under different real-time pricing scenarios, this paper aims to explore and design the future dynamic real-time electricity pricing mechanism in China, predicts the dynamic real-time pricing level and provides a reference for real-time electricity price promotion in the future. [ABSTRACT FROM AUTHOR]

• Optimization of a green water, Hydrogen, Methane, and power generation system. • Carbon capture from diesel units and green hydrogenation for Methane production. • Use of solar-wind-diesel-hydro units for water, gas, and power generation. • Present mathematical model of water, Hydrogen, Methane, and power generation processes. This paper proposes a novel water, gas and power generation system using wind turbines, solar photovoltaic panels, hydro and diesel units. A power to gas technology composed of a carbon capture unit, an electrolizer, a hydrogen storage, and a methanation process, is used to supply the natural gas demand of an industrial microgrid. The electricity is consumed by a desalination unit to procure the water demand, electrolizer inflow, and charge the water storage. A mixed integer nonlinear optimization problem is developed to minimize daily operation cost of hydro units, fuel cost of diesel engines, and cost of electrical power purchased from local grid. A 1-year study with 12 extreme operational conditions is carried out to validate its resiliency and flexibility in warm and windy coastal area of Kish. Minimum and maximum objective functions are 2320 and 6797 $ during April and August, respectively. Maximum values of power purchased/sold from/to local grid are obtained as 6.12/9.18 MW at hours 3 and 15 of April as well as 1.2/3.55 MW at hours 22 and 14 of August, respectively. Lower renewables products and higher loads are caused to lower power selling to distribution company during summer days of August, and vice versa during April with higher wind and solar products and lower demands. Electricity consumption of desalination, carbon capture, electrolizer and pump under peak water (1.866 million Liter) and gas (1.827 MW) loads during August are higher than those of April with light loads (maximum 841.1 m3 water and 875.6 kW gas demand). [ABSTRACT FROM AUTHOR]

[Display omitted] • Two hydrogen liquefaction cycles are compared thermodynamically & economically. • Waste heat is used to generate both refrigeration & power in two distinct scenarios. • Waste heat recovery in the form of refrigeration is more appropriate than power. • Energy consumption & exergy efficiency for best scenario are 4.32 kWh/kgLH 2 & 53.34%. • Payback period & net benefit for best scenario are 5.942 years & 26.25 MMUS$/year. One of the main problems of hydrogen storage by the liquefaction method is the high specific power consumption. Waste heat recovery from different industries can be used to reduce the power consumption of hydrogen liquefaction cycles. In this paper, industrial waste heat is applied for two distinct purposes: to generate refrigeration using the diffusion-absorption refrigeration cycle (the first scenario), and to produce electricity with the support of the organic Rankine cycle (the second scenario). The diffusion-absorption refrigeration integrated structure generates 0.5786 kg/s liquid hydrogen. Two new integrated scenarios have been compared regarding energy, exergy, and economic analyses to use waste heat. The specific power consumption in the first and second scenarios are 4.320 and 4.359 kWh/kgLH 2 , respectively. The results of the exergy analysis show that the exergy efficiency of the first and second structures are 53.35 and 50.82 %, respectively. Economic analysis of integrated structures developed based on the annualized cost of system method shows that the annualized cost of the product in the first and second systems are calculated at 88.53 MMUS$/year and 82.68 MMUS$/year, respectively. Also, the prime cost of the product in the first and second processes are computed at 4.401 US$/kgLH 2 and 4.320 US$/kgLH 2 , respectively. The findings indicate that utilizing wasted heat for refrigeration production, as opposed to electricity generation in the liquid hydrogen pre-cooling system, is a thermodynamically preferable choice, but it may not be economically viable. The sensitivity analysis of the integrated diffusion-absorption refrigeration structure shows that the payback period and prime cost of liquid hydrogen decrease to 5.041 years and 4.115 US$/kgLH 2 , respectively when the price of electricity decreases from 0.400 to 0.040 US$/kWh. The payback period and levelized cost of liquid hydrogen decrease to 2.886 years and 4.295 US$/kgLH 2 , respectively with a reduction in capital cost from 374.4 to 93.60 MMUS$. [ABSTRACT FROM AUTHOR]

Abstract: Recently, due to technology improvements and governmental incentives for using the green energies, Fuel Cell Power Plants (FCPPs) seem to be a promising approach for electricity generation. FCPPs, as Distributed Generation (DG) units, can be considered as Combined sources of Heat, Power, and Hydrogen (CHPH). CHPH operation of FCPPs improves system efficiency because of produced hydrogen which can be stored for future use of FCPPs or can be sold for profit. Using 2m +1 Point Estimate Method (2m +1 PEM), a probabilistic load flow approach is employed to model the uncertainties in electrical and thermal load demands, pressure of input oxygen and hydrogen importing to FCPPs, and temperature of FCPPs. Minimizing the operation costs of electrical energy generated by distribution substation and FCPPs, minimizing the voltage deviation, and minimizing total emissions produced by distribution substations and FCPPs are selected as objective functions. This paper just considers the placement of CHPH FCPPs without assuming the devices investment cost. A powerful optimization technique, θ-Self Adaptive Gravitational Search Algorithm (θ-SAGSA), is proposed to achieve the optimal places for FCPPs and daily optimal active powers of distribution substation and FCPPs. For solving the proposed multi-objective problem, this paper utilizes the Pareto Optimality idea to obtain a set of solutions in the multi-objective problem instead of a sole solution. The proposed method effectiveness is validated on a 69-bus distribution system. [Copyright &y& Elsevier]

Abstract: This paper presents an approach for solving the generation scheduling problem of a complex system consisted of conventional and renewable energy sources (RES). Wind power plants are integrated into the system in order to minimize the total thermal unit fuel costs. The gained results for wind farm power production are used as input in the system to determine the optimal amounts of generated power for the thermal generating units and hydro generating units over the study period. The optimization problem consists of minimizing the total production costs, respecting power balance equations for each time interval and all operational system constraints. The proposed approach is applied on a specific system consisted of thermal power plants (TPPs), storage hydro power plants (HPPs), pumped-storage hydro power plant (PSHPP) and wind power plant (WPP). The benefits of energy production from WPP, in terms of reducing the production costs of conventional thermal power plants are also investigated. In the proposed paper two cases are analyzed. In the two analyzed cases power unit’s generation, thermal unit’s fuel costs and stream flows of hydro units are calculated over the study period. [Copyright &y& Elsevier]

Abstract: The present paper investigates the potential of wind energy in selected areas in Jordan. The aim of this work is to set up promising wind farms that are able to feed electricity to the Jordanian distribution authority with excellent percentage of clean energy. There are some particular locations in Jordan where the wind potential is very promising for economical electrical power generation. Four of these promising locations are investigated in this paper for the possibility of building and investing 100MW wind turbine in each of these four locations. The environmental data needed to perform the present study are obtained from the local Meteorological department. The suggested wind turbines to be implemented in each of the four locations are selected from the international rating and specification catalogues of wind turbine manufacturers. This study reveals that the total rated wind power that can be generated from the four selected wind farms is 136MW. On the other hand, the expected total energy that can be produced from the four selected wind farms is 18.9×103 GWh. [Copyright &y& Elsevier]

Abstract: This paper addresses generation of electricity in the specific aspect of finding the best location and sizing of biomass fueled gas micro-turbine power plants, taking into account the variables involved in the problem, such as the local distribution of biomass resources, biomass transportation and extraction costs, operation and maintenance costs, power losses costs, network operation costs, and technical constraints. In this paper a hybrid method is introduced employing discrete particle swarm optimization and optimal power flow. The approach can be applied to search the best sites and capacities to connect biomass fueled gas micro-turbine power systems in a distribution network among a large number of potential combinations and considering the technical constraints of the network. A fair comparison among the proposed algorithm and other methods is performed. [Copyright &y& Elsevier]

Abstract: Prompted by the need for clean energy sources, increasing amounts of photovoltaic (PV) generator is connected to the power system around the world, hence, affects many aspects the dynamic and operational characteristics of synchronous generator dominated power system. In this paper, the impact of large-scale PV generation on power system oscillation, especially the inter-area oscillation is studied. The effect of PV on inter-area mode is investigated in New England–New York test system for different level of penetrations and operating conditions. Analysis in the paper reveals that increased PV penetration could affect the critical inter-area mode detrimentally. A trajectory sensitivity based rotor angle norm is evaluated to explore the reason why PV generators are interacting negatively on critical inter-area mode. The primary basis of the method is to convert the PV generator with equivalent sized synchronous generator and evaluate the sensitivity by real power perturbation. The analysis reveals that integration of PV to the system creates higher angular separation among synchronous generators, results inter-area oscillations. A generator ranking based operating point adjustment method is proposed in this paper to minimize the angular separation. The results obtained indicate that the proposed method can effectively minimize the angular separation, hence, enhance the damping of inter-area mode. [Copyright &y& Elsevier]

Abstract: In this paper, a new security-constrained self-scheduling framework incorporating the transmission flow limits in both steady state conditions and post-contingent states is presented to produce efficient bidding strategy for generation companies (GENCOs) in day-ahead electricity markets. Moreover, the proposed framework takes into account the uncertainty of the predicted market prices and models the risk and profit tradeoff of a GENCO based on an efficient multi-objective model. Furthermore, unit commitment and inter-temporal constraints of generators are considered in the suggested model converting it to a mixed-integer programming (MIP) optimization problem. Sensitivity of the proposed framework with respect to both the level of the market prices and adopted risk level is also evaluated in the paper. Simulation results are presented on the IEEE 30-bus and IEEE 118-bus test systems illustrating the performance of the proposed self-scheduling model. [Copyright &y& Elsevier]

The main purpose of this paper is to investigate the contribution of iron to the energy requirements of a process for producing magnesium hydroxide {Mg(OH)2} from alkaline-earth Mg–silicate rock that contains iron, such as serpentinite. Once produced Mg(OH)2 could be used to sequester carbon either by direct mineralization at a power plant or from the air, or as a means to deliver alkalinity to the ocean thus tending to restore oceanic pH and sequester atmospheric carbon. Fe-containing by-products obtained from producing Mg(OH)2 are considered to be beneficial as secondary raw materials for iron-and steel-making industries. It has been proposed that this could further reduce CO2 emissions as well as raw material costs. However, this study hypothesized that the extent of this benefit, if any, would depend on energy intensity of reactions involving iron compounds. Using Aspen Plus® software, the contribution of iron to the energy input requirement of CO2 sequestration was modeled. Results obtained showed that the extraction of iron from Mg–silicate minerals could present a significant energy penalty to the mineralization process. Exergy analysis shows that at the experimental optimal temperature of 400°C, the energy penalties of having iron oxide (FeO), hematite (Fe2O3) and magnetite (Fe3O4) as dominant iron compounds results are (for 10wt.% Fe in the rock) an increase of 0.3 GJ/t CO2 (7%), 0.7GJ/t CO2 (20%) and 2.2GJ/t CO2 (60%) respectively when compared to an iron-free base case. Recovery of input raw material, ammonium sulfate (AS) by evaporative crystallization is a major energy intensive step in this process. However, our model applied mechanical vapor recompression (MVR), which resulted in a significant reduction in energy demand. It can be concluded that the benefit of producing useful Fe by-products comes with an energy penalty, the extent of which varies with the form of Fe compound in the mineral. The findings in this paper are useful in determining which Mg–silicate-based rocks would be energy efficient for use. [Copyright &y& Elsevier]

• Hourly analysis of the Italian electricity production mix is performed. • Evaluation of the electricity produced by each fossil and renewable source with a hourly time resolution. • Four power plant efficiency indicators are defined and evaluated. • Three equivalent carbon dioxide emission factors are determined. The power system has faced unprecedented challenges in the last decade caused by many factors: the introduction of the open electricity market, the diffusion of distributed generation, the growth of the electricity production from the no-programmable renewable energy sources, etc. In this framework the power generation system turned extremely varied and complex. In addition, European Union highlighted the need to increase the energy efficiency to achieve the goal of 30% savings in primary energy consumption by 2030 compared to 1990 levels. Since the goal is defined on primary energy level, the electric efficiency indicators are central issues in the assessment of energy saving measures that affect electricity demand and involve different processes. However, all European Directives set electric efficiency indicators and carbon dioxide emission factors to fixed values neglecting their intrinsic time-variability due to the primary energy source mix used in the electricity generation hour by hour. The use of a fixed value for these parameters could lead to inaccurate or wrong results in various processes. Indeed, they have an impact on the choice of electricity versus fossil-fuel based technologies. In particular, they affect both the possibility for a product to retain access to European market, and its specific rating in an energy labelling class. Moreover, in the case of the modelling of any energy system that interacts with the power grid the electric efficiency indicators are the crucial factors to assess the potential primary energy savings of the technologies. On another level, the use of an incorrect value of energy and environmental indicators in the evaluation of the primary energy savings of those energy efficiency measures supported by economic mechanisms (as white certificates, policy mechanisms supporting renewables, tax deductions), could lead to an underestimation or an overestimation of the economic support. In this context, the aim of this paper is to perform an hourly analysis of the Italian electricity production mix evaluating the contribution of each primary energy source. The novelty of this approach is related to the evaluation of the electricity produced by each fossil and renewable source with an hourly time resolution over the years 2016 and 2017. Four power plant efficiency indicators and three carbon dioxide emission factors have been also defined and determined on hourly basis for both considered years. The results of the analysis have showed the strongly variability of the considered parameters across the years, the seasons and hour by hour depending upon the hourly power generation mix. [ABSTRACT FROM AUTHOR]

• A concept of a cascade LiBr/H 2 O absorption refrigeration/transcritical CO 2 process is proposed. • The proposed system is driven by low-grade waste heat. • The low-grade waste heat is utilized in a cascade approach to produce electricity. • The proposed system is designed following two optimization strategies. • Performance and parameters are analyzed and compared. In this paper, a cascade LiBr/H 2 O absorption refrigeration/transcritical CO 2 process is proposed to recover 90–150 °C low-grade waste heat. The proposed system consists of two subsystems: LiBr/H 2 O cycle and transcritical CO 2 cycle. The low-grade waste heat is utilized by LiBr/H 2 O cycle and transcritical CO 2 cycle in a cascade approach. Two optimization strategies, following efficiency of performance (FCP) and following net electricity generation (FNG), are proposed to design the cascade LiBr/H 2 O absorption refrigeration/transcritical CO 2 process. A series processes on various refrigeration temperature (i.e., 2 °C, 3 °C, 4 °C, 5 °C, 7 °C, and 10 °C) are designed following the two optimization strategies. Key parameters in terms of refrigeration temperature, segment temperature, and high pressure are analyzed. In addition, the performance of the designed processed are compared based on the simulation results. Results show that the proposed system shows a better performance at the lower refrigeration temperature of the LiBr/H 2 O cycle. The high pressure under FCP is larger than that under FNG. The investment and profit of the optimal design under FCP are both more than that under FNG. This work provides a potential way to generate electricity using low-grade waste heat. [ABSTRACT FROM AUTHOR]

Highlights • Feasibility of the electrification of offshore oil and gas platforms with energy from waves analysed. • Scaling of wave energy converters to match local wave resource and increase power performance. • Wave farm optimization considering both the life cycle costs and the electricity production. • Hydrodynamic performance of the technologies not directly linked to its economics attractiveness. • Levelized Cost of Energy ranged from 188 to 471 €/MWh and was benchmarked against reference values. Abstract Offshore oil and gas platforms have very high-power demands, being the electric power supply usually provided by gas turbines operating with natural gas extracted from the field. Since fields are ageing, the amount of gas available for electric power production is declining. One common alternative is to feed those gas turbines with fuel diesel, which is an expensive solution at remote locations and has a high carbon footprint. Since oil and gas platforms often operate in deep waters and are exposed to energetic wave climates, ocean wave energy can be used in their electrification. Even though wave energy is not yet cost competitive for suppling onshore grids, power supplying remote oil and gas platforms might be the niche market enabler to launch commercially the sector, due to the high cost of the electricity produced in those offshore facilities and the abundance of wave resource at most of their locations. This paper proposes a new techno-economic model to assess and scale wave energy converters to match the local wave climate at their deployment site, while maximizing the income of the wave farm and accounting for their life cycle costs. At the same time, the economic feasibility of providing electricity from ocean waves to remote offshore oil and gas facilities is analysed using as case study an oil and gas platform in operation at the North Sea. Seven wave energy converters were assessed at the case study site and it was proved that its hydrodynamic performance is not directly linked to its economics attractiveness. The values of the levelized cost of energy ranged from 188 to 471 €/MWh and were benchmarked against reference values. The feasibility of providing electricity from waves to offshore oil and gas facilities is also demonstrated and the exploration of this untapped market advocated. [ABSTRACT FROM AUTHOR]

Highlights • Long-term operational experiences from two ORC cogeneration plants are reported. • Variability of operational parameters including biomass quality is explained in detail. • Key performance indicators are discussed. • Current macroeconomic and project profitability issues are presented. • SWOT analysis of the technology has been performed. Abstract This paper reports on operational experiences and performance of two municipal heating plants that were converted into cogeneration plants by the installation of biomass-fired modules based on the Organic Rankine Cycle technology (ORC). Two different plants of this type are presented. The text provides a review and discussion of critical issues related to implementation of the technology. Similarities, differences and operational characteristics are substantiated by the analysis of long-term measurement data. Particular attention is paid to variability of operational parameters, problems with determination of performance indicators, equipment characteristics, system sizing and its integration with existing heating plants. A special focus is put on profitability of investment projects under variable economic conditions. Finally, the technology is evaluated using Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis. The text fills the gap between the theoretical knowledge and required practical know-how. It also indicates areas of possible improvements and helps technological risk analysis in the future investment projects. [ABSTRACT FROM AUTHOR]

Highlights • Developed and validated the detailed model of Photovoltaic/Thermal (PV/T) collector. • New correlations of series resistance and shunt resistance for better accuracy. • Compared the performance of the PV/T collector with or without air gap design. • Integration of PV/T collector with thermochemical sorption storage using SrCl 2 -NH 3. • 26 m2 PV/T collector coupled with storage covers the annual DHT demand of a household. Abstract To maximise the utilisation of solar energy and improve the solar fraction for domestic applications, this paper explored the potential of the hybrid solar Photovoltaic/Thermal (PV/T) collector integrated with a thermochemical sorption thermal storage system. The thermal output was used to provide domestic hot water or stored over seasons in the England city of Newcastle upon Tyne. The performance of the water-cooled PV/T collectors with or without an air insulation layer between the glass cover and the Photovoltaic (PV) cell was compared. The electrical power generation model of the PV cell developed in MATLAB was coupled with a Computational Fluid Dynamics (CFD) model to simulate the simultaneous generation of electrical and thermal energy. The one-diode model was used to simulate the electrical production of the PV cell with the new correlations of the series resistance and the shunt resistance proposed in this work, so that the accuracy of dynamic performance simulation can be improved especially in the cases with relatively higher PV cell temperature. The water outlet temperature was studied at 100 °C to meet the heat supply requirement of the sorption cycle using the working pair strontium chloride-ammonia. It was found that the PV/T collector with air gap could produce 28 L hot water per day per m2 collector (L/(day·m2)) with the electric efficiency of about 10% if the water outlet temperature was required at 100 °C; in contrast, around 133 L/(day·m2) was produced with the electric efficiency of 13% when the water outlet temperature at 40 °C. The PV/T collector without air gap was not competent for the applications studied in this work especially in cold regions. The application case studies suggested that an installation of 26 m2 air-gap PV/T collectors integrated with the strontium chloride-ammonia thermochemical sorption storage system can fully satisfy the annual hot water demand of an ordinary single household in Newcastle upon Tyne with 100% solar sources, and cover at least half of the annual electricity consumption. [ABSTRACT FROM AUTHOR]

Highlights • Optimal design of desiccant cooling with energy generation and storage is presented. • The optimization was achieved using a neural network and a genetic algorithm. • Specific net electricity generation was used as the optimization objective. • A dimension reduction method was used to determine key design parameters. • Design solutions identified by this method outperformed a baseline design. Abstract A design optimization strategy for rotary desiccant cooling (RDC) systems integrated with a photovoltaic thermal collector-solar air heater (PVT-SAH) and a phase change material based thermal energy storage (TES) (named RDC-PVT-SAH-TES) is presented in this paper. The optimization method was developed using a multilayer perceptron neural network (MPNN) and a genetic algorithm to maximize the specific net electricity generation (SNEG) of RDC-PVT-SAH-TES systems while maintaining the required cooling demand with the assistance of an electric heater. A dimension reduction method was used to determine the main design parameters of the RDC-PVT-SAH-TES system. An RDC-PVT-SAH-TES system was simulated using TRNSYS and the simulation data were utilized for training and validation of the MPNN model and for dimension reduction analysis. A comparison of the design solution identified by this optimization method with a baseline design showed that the SNEG and the solar thermal contribution of this RDC-PVT-SAH-TES system can be increased from 3.77 kWh/m2 to 10.32 kWh/m2 and from 91.5% to 99.4%, respectively. The optimization method developed could be potentially adapted to facilitate optimal design and size of other engineering systems with onsite energy generation and thermal storage. [ABSTRACT FROM AUTHOR]

Highlights • Increasing variable renewable electricity sources has shown to lower market prices. • Researchers have investigated this effect using historical data electricity markets. • Here holistic energy system analyses are done with an energy system simulation tool. • The analyses are used to quantify the effect on a specific case. Abstract Variable renewable electricity sources have been shown to reduce wholesale electricity market prices. This is expected to reduce the incentive for investments in new electricity production capacity, and might even make these investments infeasible, if relying only on the income from trade on the current electricity market paradigms. In this paper, a novel approach for quantifying this effect in future energy systems is developed using a holistic energy system approach. The approach is applied to the case of Denmark in 2015, which is part of the Nordic and Baltic wholesale electricity market Nord Pool Spot. A holistic energy system model is created and verified according to both the Danish energy balance and the Nord Pool Spot system price in 2015. Using this verified model, the Nord Pool Spot system price is quantified at increasing amounts of onshore wind power, offshore wind power and photovoltaic in Denmark. It is found that regardless of which variable renewable electricity source is implemented, including a combination of the three, the Nord Pool Spot system price decreases as the amount of energy produced by these sources increases, and this effect occurs immediately as more is introduced. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses the design and modeling of power system for a fuel cell hybrid locomotive. Different types of fuel cells for appropriate application to locomotives were compared, fuel cell and auxiliary storage devices were modeled, and a control strategy for the overall system was developed in this paper. By using the proposed control strategy, the power control system regulates the sharing of power demand between fuel cell and auxiliary storage units including batteries and ultracapacitors. Experimental data of the power duty cycle of a typical switcher locomotive is analyzed. The proposed control system is tested using the experimental data. Results show that the control system is able to maintain output voltage from different power sources within a certain range, keep the state of charge of the batteries within an optimal range and meet power demand of the locomotive at a high efficiency. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a dynamic programming model to solve the short-term scheduling problem of a hydropower plant that sells energy in a pool-based electricity market with the objective of maximizing the revenue. This is a nonlinear and non-concave problem subject to strong technical and strategic constraints, and in which discrete and continuous variables take part. The model described in this paper determines, in each hour of the planning horizon (typically from one day to one week), both the optimal number of units in operation (unit commitment) and the power to be generated by the committed units (generation dispatch). The power generated by each unit is considered as a nonlinear function of the actual water discharge and volume of the associated reservoir. The dependence of the units’ efficiency and operating limits with the available gross head is also accounted for in this model. The application of this model to a real hydropower plant demonstrates its capabilities in providing the operation schedule that maximizes the revenue of the hydro plant while satisfying several constraints of different classes. In addition, the use of this model as a supporting tool to estimate the economic feasibility of a hydropower plant development project is also analyzed in the paper. [ABSTRACT FROM AUTHOR]

Abstract: The paper is Part 2 of the study on the thermodynamic and thermoeconomic analyses of trigeneration system with a gas–diesel engine. In Part 1, thermodynamic and thermoeconomic methodologies for such a comprehensive analysis were provided, while this paper applies the developed methodology to an actual TRIGEN system with a rated output of 6.5MW gas–diesel engine installed in the Eskisehir Industry Estate Zone, Turkey. Energy and exergy efficiencies, equivalent electrical efficiency, the Public Utility Regulatory Policies Act (PURPA) efficiency, fuel energy saving ratio, fuel exergy saving ratio and other thermodynamic performance parameters are determined for the TRIGEN system. The efficiencies of energy, exergy, PURPA and equivalent electrical efficiency of the entire system are found to be 58.97%, 36.13%, 45.7% and 48.53%, respectively. For the whole system and its components, exergetic cost allocations and various exergoeconomic performance parameters are calculated using the exergoeconomic analysis based on specific exergy costing method (SPECO). The specific unit exergetic cost of the net electrical power, heat energy in the Factory Heating Center (FHC) heating, heat energy in the Painting Factory Heating (PFH) and chilled water in the absorption chiller (ACh) produced by the TRIGEN system are obtained to be 45.94 US$/GJ, 29.98 US$/GJ, 42.42 US$/GJ and 167.52 US$/GJ, respectively. [Copyright &y& Elsevier]

Abstract: Industrial plants continuously reject large amounts of thermal energy through warm liquid or gaseous effluents during normal operation. These energy losses contribute to an inflation of production costs and also threaten the environment. This paper investigates methods of recovering the residual low grade thermal energy and converting it into higher quality mechanical energy using the thermodynamic Rankine cycle principle. For the temperature range of the available thermal energy, water was shown to be a poor working fluid for the conversion system, thus several potential working fluids, including ammonia, synthetic refrigerants, and organic compounds have been considered as alternatives. A comparative analysis led to the identification of different performance evaluation criteria. For example, the water-based Rankine cycle and, to a lesser extent, the ammonia-based Rankine cycle proved to be interesting when the power generation potential per unit working fluid mass flow rate was considered. On the other hand, Rankine-like cycles using dry hydrocarbon working fluids proved much more interesting in terms of energy conversion efficiency, as well as in terms of the net mechanical power generation potential for a given heat source. All performance indicators were low at low temperatures, and improved as the primary heat source was available at higher temperatures. This paper also discusses the influence of various external and internal operating parameters, such as heat source and heat sink temperatures, turbine and pump isentropic efficiencies and the addition of an internal heat exchanger on the overall performance of the energy recovery and conversion system. [Copyright &y& Elsevier]

Abstract: Wind power is a promising alternative in power generation because of its tremendous environmental and social benefits. Generation scheduling (GS) is more important in a power system integrating wind farms. Unlike conventional power generation sources, wind power generators supply intermittent power because of uncertainty in resource. This paper presents a fuzzy approach to the generation scheduling problem of a GenCo considering uncertainties in parameters or constraints such as load, reserve and available wind power generation. The modeling of constraints is an important issue in power system scheduling. A fuzzy optimization approach is an approach that can be used to obtain the generation scheduling under an uncertain environment. In this paper, a fuzzy optimization-based method is developed to solve power system GS problem with fuzzy objective and constraints. The crisp formulation of this GS problem is firstly defined and is rearranged by introduction of a membership function of some constraints and objective function. Then, this fuzzy optimization problem is converted to a crisp optimization and solved using GAMS software by mixed integer nonlinear programming. Employing the fuzzy optimization GS, it is expected that in practice a higher profit would be achieved in the operation and cost management of a real power system with large scale wind farms in different level of constraints’ satisfaction. The proposed approach is applied to a sample system (including six conventional units and two wind farms) and the results are compared with the results of crisp solution. This approach is also applied to a larger test case to demonstrate the robustness of this fuzzy optimization method. [Copyright &y& Elsevier]

Abstract: This paper presents a method that integrates deterministic approach with fault-tree analysis for reliability assessment of a composite system (generation and transmission in power systems). The contingency screening is conducted in the first step. The results are further classified into three clusters in the second step: normal, local trouble and system trouble. The fault-tree analysis is used to assess the reliability of the composite system in the third step. Finally, Risk Reduction Worth is adopted as a measure of importance for identifying the crucial element that has significant impact on the reliability. In this paper, a composite system in Taiwan serves as an example for illustrating the simulation results attained by the proposed method. The simulation results, verified by Siemens PTI PSS/E TPLAN software package, show that the proposed method is applicable for large scale power systems. [Copyright &y& Elsevier]

This paper presents the impact of technological and regulatory interventions, specifically the impact of the Renewable Energy Portfolio Standards (RPS) on the least-cost electricity generation expansion plan in a country. The case study used in the paper is the power generation system in Sri Lanka where the current policy is to have a renewable energy based generation penetration level of 10% by 2015. This study considers available renewable technologies as supply-side options together with their technical potential and economic feasibility. It also examines the impact of these interventions on overall power sector emissions including Greenhouse Gas (GHG) emissions. It has been found that the 10% RPS target by 2015 can be achieved with an additional cost burden of only 1.3% of the total cost of the plan. The results also show that small hydropower is the best non-conventional renewable energy technology needing minimum financial incentives in achieving the target. Fuelwood-fired thermal power and wind power require significant level of government incentives if they are to play a role in the declared RPS of Sri Lanka. It is concluded that small power systems like the one in Sri Lanka can still contribute to emission mitigation with regulatory interventions such as RPS without significant additional costs. It is important to select the appropriate technologies, decide on their individual allocations and the optimal timing and level of penetration of these technologies to minimize the economic impact. Further, internalizing the use of these technologies in the planning process strengthens the hands of the planners in justifying their contributions to supplying demand while mitigating emissions. [Copyright &y& Elsevier]

Abstract: This paper addresses the unit commitment (UC) in multi-period combined heat and power (CHP) production planning under the deregulated power market. In CHP plants (units), generation of heat and power follows joint characteristics, which implies that it is difficult to determine the relative cost efficiency of the plants. We introduce in this paper the DRDP-RSC algorithm, which is a dynamic regrouping based dynamic programming (DP) algorithm based on linear relaxation of the ON/OFF states of the units, sequential commitment of units in small groups. Relaxed states of the plants are used to reduce the dimension of the UC problem and dynamic regrouping is used to improve the solution quality. Numerical results based on real-life data sets show that this algorithm is efficient and optimal or near-optimal solutions with very small optimality gap are obtained. [Copyright &y& Elsevier]

Abstract: In a power system, voltage stability margin improvement can be done by regulating generators voltages, transformers tap settings and capacitors/reactors rated reactive powers (susceptances). In this paper, one of these methods, which we name “reactive power rescheduling with generator ranking”, is considered. In this method, using “ranking coefficients”, the generators are divided into “important” and “less-important” ones and then, voltage stability margin is improved by increasing and decreasing reactive power generation at the important and less-important generators, respectively. These ranking coefficients are obtained using “modal analysis”. In this paper, the method’s performance for two types of ranking coefficients has been analyzed. Also, for comparison purpose, the “usual form of optimal reactive power dispatch” method has been simulated. For all simulations, the IEEE 30 bus test system has been used. The simulation results show that in the former method, for either type of ranking coefficients, voltage stability margin is considerably improved and, usually, the system active loss and the system operating cost are increased. Also, in the latter method, voltage stability margin is improved and the system active loss and the system operating cost are decreased. [Copyright &y& Elsevier]

Abstract: In this paper, starting from previous works, further analyses on district heating cogeneration systems are proposed and particular attention is given to the NO x pollutant. In addition to the mean yearly concentrations, the hourly limit values for the protection of human health are also taken into account: the 18th maximum hourly concentration is considered. The main steps necessary to characterize a district heating plant are shown and two case-studies are discussed. As far as the energetic aspects are concerned, these new plants always offer a primary energy saving, and the global environmental effects are improved due to a reduction in CO2. Local NO x emissions of a future plant do not decrease with respect to the existing emissions, and this aspect is closely connected to the type of CHP unit that is adopted (in this paper, natural gas fuelled engines). The local environmental effects due to NO x are estimated using a dispersion model, and the NO x concentrations (annual mean value and maximum hourly value) introduced by the new plant and those avoided through the non-use of existing domestic boilers are compared. For one of the case-studies emerges that some zones do not satisfy ambient air quality limits. For these reasons, a higher stack has been assumed for this critical case and the new results show that a reduction in the frequency of the overcomings, which is in agreement with expectations, can thus be obtained. The analysed case-studies have shown that even a small CHP district heating plant can produce critical aspects and a pollutant concentration analysis is a useful tool to check local environmental aspects. [Copyright &y& Elsevier]

In this paper a hybrid energy system combining variable speed wind turbine, solar photovoltaic and fuel cell generation systems is presented to supply continuous power to residential power applications as stand-alone loads. The wind and photovoltaic systems are used as main energy sources while the fuel cell is used as secondary or back-up energy source. Three individual dc–dc boost converters are used to control the power flow to the load. A simple and cost effective control with dc–dc converters is used for maximum power point tracking and hence maximum power extracting from the wind turbine and the solar photovoltaic systems. The hybrid system is sized to power a typical 2kW/150V dc load as telecommunication power plants or ac residential power applications in isolated islands continuously throughout the year. The results show that even when the sun and wind are not available; the system is reliable and available and it can supply high-quality power to the load. The simulation results which proved the accuracy of the proposed controllers are given to demonstrate the availability of the proposed system in this paper. Also, a complete description of the management and control system is presented. [Copyright &y& Elsevier]

Abstract: In this paper, we have aimed to present a hybrid neural network model for daily electrical peak load forecasting (PLF). Since peak loads usually follow similar patterns, classification of data improves the accuracy of the forecasts. Several factors in peak load, e.g. weather temperature, relative humidity, wind speed and cloud cover, were introduced into the model in order to enhance forecast quality. Most classification attempts in the literature have been intuitive and empty of justification. In this paper, we have proposed a novel approach for clustering data by using a self-organizing map. The Davies–Bouldin validity index was introduced to determine the best clusters. A feed forward neural network (FFNN) has been developed for each cluster to provide the PLF. Eight training algorithms have also been used in order to train the proposed FFNNs. Applying principal component analysis (PCA) decreased the dimensions of the network’s inputs and led to simpler architecture. To evaluate the effectiveness of the proposed hybrid model (PHM), forecasting has been performed by developing a FFNN that uses the un-clustered data. The results proved the superiority and effectiveness of the PHM. Linear regression (LR) models have also been developed for PLF, and the results indicated that the PHM produces considerably better forecasts than those of LR models. Furthermore, the results show that the suggested clustering approach significantly improves the forecasting results on regression analysis too. [Copyright &y& Elsevier]