Search

Abstract The clean transition of traditional coal-dominated GenCos plays critical role in national energy transition. However, the formulation of strategy is dominated by qualitative analysis, which lacks the ability to quantify key operation indicators in a complex transition process. This paper develops a computer simulation tool for the study of medium and long-term transition of GenCo to simulate the dynamic process of its clean transition. Under the background of clean transition in China's power sector, it quantitatively analyzes the dynamic performance such as business structure, profit, and carbon emission of a traditional GenCo according to its 2020 and 2030 clean development strategic targets, and compares the differences between different pathways under the same strategic targets. And then, this paper analyzes the impact of uncertainties such as coal prices and renewable energy subsidies. [ABSTRACT FROM AUTHOR]

Abstract For the sustainable development of the environment, the Fuel cell is more and more popular in power generation because of its high efficiency and high capacity. Among them, the Solid Oxide Fuel Cell (SOFC) own the highest efficiency and is one of the best potential in the Fuel Cell. To optimize and control the SOFC system, building a detailed model of SOFC is very important. Thus, a SOFC stack model which includes transport processes, the electrochemical and chemical reactions is simulated and evaluated in this paper. This model is used on the Bond Graph theory, so it can simulate the energy conservation and flow in different physical domains. It is a transient model and has a rough distribution along the gas channel. First, the theory and dynamics of SOFC model were proposed. Second, the Bond Graph theory was briefly introduced and SOFC Bond Graph model was proposed. Finally, the SOFC stack was simulated in this paper. Characteristics of SOFC stack along gas channel with a load current was dynamic simulated. Power and Fuel utilization curves of SOFC at different H 2 flow rate were simulated in this paper as well. The model and simulation are useful to the control of SOFC for the high efficiency of the SOFC system. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a hierarchical scheduling framework is proposed to dispatch electricity and thermal in CHP system with thermal energy storage for the consumption of wind power. An optimization mathematical model is proposed to demonstrate the characteristics of the whole system. The modified PSO algorithm is used to solve the coordinated dispatching problem. The traditional way of working between electricity and thermal is independent while the proposed mathematical model combined electricity and thermal, it's more accurate to take the relationship between electricity and thermal into consideration. This model has good performance in solving the cross coupling problem. The simulation results indicate that the proposed optimization mathematical model has good dispatching performance on reducing coal consumption. The most important contribution of this paper are accelerating the consumption of wind power in Northern China and saving coal consumption, which can save plenty of money and prevent air pollution. Further work will be reflected in the demonstration project. [ABSTRACT FROM AUTHOR]

Abstract As pollution has become a significant issue in China, developing clean energy power generation is one of the main strategies to promote the sustainable economy. Based on the partially closed input-output model corresponding to 29 industries in 2012, this paper categorized power generation sectors to coal-fire power generation, gas power generation, wind power generation, photovoltaic generation, biomass energy power generation, and nuclear power generation to analyze the impacts on environment and social-economic developments. The results showed that improving single clean energy technology would lead to different degrees of positive impacts on environment, but the effects of GDP development and employment are highly correlated with the various generating costs. For the high generating costs, the clean-energy technologies would contribute to the positive effects; however, the drawbacks of social economic development could overweight the benefits for the low generating costs in short run. In addition, improving diverse clean energy generating approaches could promote GDP growth, reduce pollution, and increase employment. Finally, this paper provided some policy suggestions for the green-energy power supply and low-carbon economic developments. [ABSTRACT FROM AUTHOR]

Abstract Co-pyrolysis of coal and lignocellulosic biomass can reduce the consumption of non-renewable fossil fuel and improve the proportion of renewable energy. Products distribution and kinetic analysis can provide fundamental information about the process design and facility development. In this paper, kinetic analysis on the main gaseous products during co-pyrolysis of low-rank coal with lignocellulosic biomass model compound was explored via a drop tube furnace combined with process mass spectrometer. Lignin was selected as the typical model compound, which is also the main content of black liquor from the paper industry. Releasing properties of the main volatile products from individual and mixing materials under various lignin mixing ratios were obtained. Iso-conversional method was applied to calculate the kinetic parameters, including reaction order, frequency factor, and activation energy. The activation energy about forming of CO 2 , CO, CH 4, and H 2 from low-rank coal was 40.23 kJ/mol, 20.39 kJ/mol, 48.39 kJ/mol and 37.37 kJ/mol. The frequency factor were 1.48, 0.12, 6.43 and 0.43 respectively. The activation energy about forming of CO 2 , CO, CH 4, and H 2 from lignin was 15.42 kJ/mol, 32.28 kJ/mol, 12.94 kJ/mol and 35.21 kJ/mol. [ABSTRACT FROM AUTHOR]

Abstract Due to its flexible power regulation capability, energy storage is been considered as an efficient technology to reduce wind curtailment. However, since the fluctuation characteristics and low energy density characteristics of wind power, energy storage might be inefficient when reducing the wind curtailment from a single wind farm and the regulation capability of energy storage system (ESS) may not be fully utilized. Based on theoretical analysis the externality effect of energy storage is revealed in this paper, the control strategy of energy storage externality for reducing wind curtailment from wind farm cluster is established. By simulating analysis, the feasibility of the energy storage externality is verified. Moreover, by comparing with the conventional ESS control method, the paper evaluates the efficiency of the control strategy. The simulation results prove it can expand the influence scope of ESS and reduce more wind curtailment from wind farm cluster, the utilization of ESS is also promoted significantly. [ABSTRACT FROM AUTHOR]

Abstract Currently, a serious operation security problem of wind power plant has caused by the massive wind power integration, which has increased the difficulty of the operation in large scale wind power plant. Energy storage system (ESS) is thought the best choice to solve the operation scheduling problem of large-scale wind power plant, therefore, under the premise of ensuring the reliability of power supply and network constraints, it is particularly significant to select the proper capacity with both economy and feasibility, aiming at the problems above, this paper constructs capacity configuration of storage which is of statistical significance by studying the probability distribution characteristics, aiming at the deviation load during the operation of wind power plant, utilized Monte Carlo simulation, through whole lifetime NPV, payback period PBP and operation scheduling deviation OOD to verify the reliability and economy of the capacity. Finally, the actual operation data from a wind power plant installed 99MW in Northwest of China is utilized as a case study, simulation result shows that it could get the best storage capacity under the standard of the characteristics of economic and reliability criteria, which proves the validity and feasibility of the method in this paper. [ABSTRACT FROM AUTHOR]

Abstract The three-port DC/DC converter can connect two different energy storage devices, and can reduce the number of DC/DC converters used, optimize the system structure, and achieve low volume quality, high integration, and high efficiency of energy storage systems. This paper proposes a new three-level and three-port DC/DC converter, which has the advantages of small voltage resistance and high efficiency of the switch tube. This paper focuses on the analysis of the topological structure and working principle of the new converter. A novel control strategy for dynamically determining the duty cycle is proposed for the novel converter's flying capacitor voltage equalization control. Finally, the feasibility of the working principle and the control strategy are verified by DSPACE and Typhoon real-time simulation platform. [ABSTRACT FROM AUTHOR]

Abstract This paper constructed an energy configuration model with economic optimization in distributed energy system. On this basis, we carried out the sensitivity analysis of the price of large power grid, natural gas, cooling, heating and secondary power for the economic optimized results. And then, we have analyzed the critical value point of new energy conversion technologies appear or old disappear with the change of those energy price. In this paper, the secondary power price is same with the price of large power grid. In this study, an economic analysis of a distributed energy station project has been completed, which is a commercial complex in Shanghai. The results show that the power price have a biggest impact to -F value, and the influence of heating price is minimum, and supposing that self-generating electricity is grid-connected with no power injection. And at last, we find that the energy conversion technologies appear in different place of different scenario. [ABSTRACT FROM AUTHOR]

Abstract Due to high variability of energy demand in a whole year, optimizing the configuration and operation of a CCHP system will take very high and unfeasible computational time expenses. To overcome this problem, this paper presents a new and creative method to get few representative days that adequately preserve significant demand characteristics. Typical demand days are selected based on the use of k -means clustering algorithm and average method. A hypothetical CCHP system is optimized with mixed-integer linear programming algorithm (MILP) in order to confirm the selection of typical days in this paper. This paper also imitates traditional method. A case study of a Qingdao office building is discussed to demonstrate the proposed method. The results illustrate that the magnitude of Mean Absolute Percentage Errors (MAPE) between actual demand load and typical days load can affect actual operational effect. In conclusion, optimal number of typical days for actual CCHP operation can obtain very low MAPE and lowest annual total cost. [ABSTRACT FROM AUTHOR]

Abstract If the UK wishes to decarbonise its energy supply, it should consider a wider uptake of district heating. Currently, district heating only accounts for 2% of the country's total heat supply. This paper considers the initial stages of designing a district heating network, the energy mapping in the local area, using a case study of Darley Dale, England. Energy mapping techniques are used to estimate the local area energy demand, a basis on which the district heating network design will rely on. The areas in the case study that are found to be profitable for possible district heating and where the rest of the district heating design work should focus on are Matlock, Bakewell and Darley Dale. The results of the mapping technique presented in this paper are found to agree with heat mapping work carried out by the UK Government. The agreement between the two mapping techniques shows that the mapping technique outlined in this paper is accurate enough for use. [ABSTRACT FROM AUTHOR]

Abstract Due to the ability to obtain energy from direct connection to the electricity grid, plug-in hybrid electric vehicles benefit both society and drivers environmentally and economically by reducing energy consumption and emissions. To extend the travel range, existing studies focus mostly on optimizing the power split of the internal combustion engine and battery without considering the impact of the transmission system. This paper deals with the optimization of a continuously variable transmission (CVT) operation for a parallel pre-transmission hybrid powertrain. The novelty of this paper is that the operation of both engine and CVT transmission are optimized together, resulting in a better fuel efficiency. Simulation work has been carried out to compare the performance of the optimized CVT transmission with a fixed transmission, showing that the fuel consumption is reduced and hence the range is increased for the optimized CVT, which makes the engine to operate in higher efficiency points. A key advantage of the formulation proposed is that the result of the optimization process may be expressed in terms of a 2D map that for any pair of vehicle speed and traction force gives the optimal value of the CVT transmission ratio. Such a map may be easily implemented in real vehicular applications. [ABSTRACT FROM AUTHOR]

Abstract District heating and cooling (DHC) networks play a fundamental role in the transition towards a sustainable supply of heating and cooling, due to their ability to integrate any available source of thermal energy and to distribute it to the buildings. However, the use of renewable non-constant sources together with the variable heat demand of the buildings creates instable and pronounced transient operating conditions. In order to analyse the hydraulic and thermal behaviour and the dynamics occurring within these networks, several physical models based on different methods were proposed by previous researchers. Numerical thermal models based on finite difference methods (FDM) were pointed out to suffer from artificial diffusion when simulating the propagation of heat through the network. However, due to a wide and well-known literature on these methods, they are still used by many researchers and are therefore worth being investigated. The present paper analyses the effects of artificial diffusion using two models based on two different first-order approximation schemes. An ideal temperature wave and a dataset from a real DH network were used to evaluate the accuracy of the models using different discretization levels in time and space. As a result, the paper provides a framework to set a proper discretization when simulating a DHC network with FDM-based models considering both the expected accuracy and the computation time as criteria. [ABSTRACT FROM AUTHOR]

Abstract When it comes to the design of new district heating networks, different design guidelines of different countries and pipe manufactures occur. All guidelines are aiming to restrict the specific pressure drop per meter pipe length to avoid uneconomic network operation. This paper evaluates the impact of different design guidelines from Sweden, Germany and Austria, as well as pipe manufacture recommendations on the total distribution costs. The analysis was conducted for a 4th generation district heating network for a new housing development (3 km trench length). The resulting district heating networks were compared in terms of total distribution costs. The results state that designing small networks at maximum heat load by allowing high specific pressure drops of 300 Pa/m shows the most economic results in terms of capital costs and variable costs. Compared to 70 to 100 Pa/m recommendations, 6 – 8 % investment costs for transportation pipes can be saved designing the network with 300 Pa/m pressure drops of short duration. Regarding distribution heat loss costs, the smaller the average diameter of the network the lower the heat distribution losses. Optimal network design leads to a 7 % heat loss reduction for the whole network. Furthermore, the paper compares total costs of the networks designed for two different design temperatures: 70°C supply with 40 °C return and 40°C supply temperature with 25 °C return. In terms of total distribution costs, both networks are very similar, which shows that ultra-low temperature networks have no economic disadvantages compared to state of the art 70°C networks, as often believed. [ABSTRACT FROM AUTHOR]

Abstract The integration of heat production from solar energy technologies can be realized by feeding in energy both at centralized or at multiple decentralized locations from the consumer side. As distribution networks serve as thermal transmission grids, the interaction between the energy feed in (i.e. production) and withdrawal (i.e. consumption) at multiple locations within distribution networks should be incorporated. Modelling the interactions between these subsystems is challenging. This paper aims to study the potential of district heating system with solar thermal based prosumers, by developing a modelling framework for design and simulation of such networks. Quantitative comparisons are made on the system performances, by addressing key technical configurations and constraints of thermal networks and temperature dynamics of energy sources. In this paper, a comprehensive design and simulation model is built to assess the performance of different scenarios of district heating system designs with solar thermal based prosumers. Design variations are carried out by selection of different buildings in the district as prosumers. The simulation model framework is setup in Matlab, with hourly time step. The distribution network model is formulated as a thermal hydraulic model representing detailed information on thermal and hydraulic losses on each pipe. It enables bidirectional flow from multiple sources integrated into the district heating network. Energy conversion technologies (solar thermal collectors) and heat demand are connected with the network model as source and sink. A natural gas boiler acts as an additional base load heat source. The design and simulation framework is applied to an artificial case study, composed of 20 buildings with mixed building stocks including office and residential buildings. [ABSTRACT FROM AUTHOR]

Abstract In Europe buildings account for 40% to 50% of total energy consumption and the largest greenhouse gases emitters and urgent measures and valid instruments are therefore required to improve energy saving, use of renewable sources in moving towards a sustainable materials management where waste becomes a "resource". In this context, there is an increase in research into development and manufacturing of new eco-friendly building envelope components from recycled and waste materials as high value-added good circular economy practice. Waste management may have significant effects in the sector of sustainable building the ultimate objective being the alternative construction materials replacing traditional materials: the development of innovative techniques aims to incorporate wastes into the production of building materials – for examples rubber, fly ash and sludge, etc. – to enhance thermal insulation properties. An effort in the sustainability in building design process is to develop researches aimed at enhancing thermal performance of components using materials capable of reusing a high waste content. The goal of this paper is to examine the technical feasibility of using inert waste materials from the combustion of municipal solid waste or solid recovered fuel and highlight changes in thermal characteristics (thermal conductivity, specific heat and density) by adding recycled and waste materials to the construction materials. The paper explores the potential of the use of thus obtained materials for the energy-refurbishment of existing buildings or with the challenge of meeting stringent energy consumption limits which are typical of a NZEB (net-zero energy building). [ABSTRACT FROM AUTHOR]

Abstract Hybrid vehicles are one of the most important choices to improve efficiency and reduce CO2 production of vehicles. Benefits in using hybrid powertrains are generally found in urban environment where lower average speeds, higher accelerations make the internal combustion engine run at lower efficiency points. The originality of the present paper consists in the data elaboration and analysis collected in a measurement campaign on road in real driving conditions, on an ad hoc path planned according to the average national daily mileage in metropolitan urban context, which thus acquires a significance generalizable in that specific context, which led to the consumption quantification and an analysis of the main factors that determine the reduction in consumption of full-hybrid vs conventional vehicles. Another important and original aspect of this paper is the analysis of the operating times in ZEV mode of hybrid vehicles, which shows how this solution leads to a significant reduction of pollutant emissions in urban contest. An on-road experimental campaign has been done by comparing two different versions of the same model (Toyota Yaris Hybrid and a conventional one, Toyota Yaris 1.5 gasoline) and a hybrid vehicle with different characteristics (the hybrid born - Toyota Prius), like size, traction battery capacity, generator/motor electric power. Thirty drivers on a fixed path have done this experimental campaign and in this paper, the results are reported. The results show that a strong influence on consumption is due not only to the type of vehicle, but also to driving style and speed. The comparison between the two versions of Yaris, shows a strong reduction in consumption using hybrid vehicle for low and medium speeds (for 20 km/h about 50%), such benefit decreases with the increasing speed and for values higher than 90 km/h both the vehicles have the same consumption. The reduced consumption of the hybrid vehicle at low speeds is due, on the one hand, to the greater efficiency of the hybrid vehicle engine compared to the conventional one and on the other hand to the high functioning in ZEV mode, with the engine off, (63% of time) thanks to the use of the electric motor. The comparison between the two hybrid vehicles with different characteristics (YarisHy and Prius) shows that the consumption trend vs. speeds is similar but the Prius has lower consumption due above all to the high efficiency of the braking energy recovery system, despite the greatest mass. This lead then to significant consumption reduction, but also lower emissions in places where such parameters have an important role: the urban environment. [ABSTRACT FROM AUTHOR]

Abstract The increasing penetration of intermittent and aleatory RES such as photovoltaics and wind power poses new challenges in terms of grid stabilization. Surplus electric energy needs to be stored, if not curtailed. From this point of view, chemical storage can pave the way for a long-term shift between demand and production, together with sector interconnection. Hydrogen as an energy vector has been deeply studied but it has difficulties in asserting itself due to its low energy density at environmental conditions and lack of infrastructure. In previous papers, an innovative plant for the conversion of biomass and fluctuating electric power into substitute natural gas and stable electricity has been designed and analysed in terms of its overall performances. The adoption of an electrolyser for hydrogen production allows to use part of the oxygen for the biomass gasification and the syngas oxy-combustion. The resulting combustion products have high carbon dioxide concentration, which avoids energy consuming separation equipment. This paper analyses in detail the plant performances in terms of energetic and exergetic efficiencies, components by components. The plant is simulated with the commercial software AspenONE® V9. Losses allocation and optimum operating conditions are identified. The proposed heat recovery strategies allow consistent energy savings, making this plant competitive with other energy storage conversion devices in terms of energy efficiency. [ABSTRACT FROM AUTHOR]

Abstract In the last decades, European countries have provided for stringent energy requirements for new buildings. In improving the energy performance of buildings, windows play a significant role as they largely influence the energy need. The windows design should base on the balanced trade-off between the solar heat gains and the heat transfer by transmission. In the paper, for some Italian climatic zones, the relation between the optimal window-to-wall ratio (WWR) and the energy need in residential nearly zero-energy buildings (nZEBs) is investigated. In the case studies, the envelope thermo-physical properties are consistent with the nZEB requirements established at national level. The energy performance assessment is carried out by means of a detailed dynamic simulation tool (EnergyPlus). The influence of different orientations and sizes of windows on the energy performance and the peak power are studied. The paper analyses the effect of WWR in the design of nZEBs. [ABSTRACT FROM AUTHOR]

Abstract In this paper technical-economic feasibility is analyzed about a gas-steam combined-cycle, fueled by syngas produced in a local downdraft gasifier. At first, the downdraft gasifier model is briefly described, where a biomass mix of Refused-Derived Fuel, RDF, and sewage sludge is transformed into syngas; then, the economic model is introduced with the graph about the economic trends of the most important plant components. Starting from the Design of Experiment (DOE) analysis, this paper proposes a multi-objective optimization methodology to obtain the Pareto Frontier of micro gas turbine technologies. In particular, this study allowed us to determine which micro gas turbine technology is more suitable to attract investment capital. The considered performance parameters are: the nominal power of the cycle; the total plant efficiency; the net revenues; the pay back period. On the other hand, the input design variables are represented by the turbine intake temperature, the compression ratio and the biomass chemical composition. [ABSTRACT FROM AUTHOR]

Abstract The paper focuses on the analysis of inline water piston pumps, by means of simulation of the fluid-dynamic behaviour and experimental characterization. These pumps are commonly used on the car wash systems, industrial washes systems and fire protection systems. They possess a robust architecture, made of a typical rod-crankshaft mechanism, which transforms the circular motion of the pump shaft in the reciprocating displacement of the piston. The pump analyzed in the paper, in particular, moves three pistons, shifted one another of 120°; each piston sucks from a tank and delivers water to a hydraulic line via automatic, spring loaded, poppet valves. The shaft, rod and other movable components are lubricated with mineral oil; the three ceramic pistons are isolated from this environment using opportune seals and work with water. This pump is robust and durable but suffers of some problems: the instantaneous pressure trend within each piston is ideally a square wave: the pressure is equal to the tank pressure during suction, while it is equal to the delivery pressure during the delivery phase. Instead, non –ideal behaviour of the poppet valves, leakages, fluid properties make the pressure trend more critical: during the pressure transient between the two high and low levels, pressure peaks and de-pressurization till aeration and cavitation occurrence may happen. These phenomena generate vibrations and noise and can damage the pump components. In order to study this, a lumped parameter fluid dynamic model of the pump has been realized, later compared with experimental results coming from the test rig to validate it. The model has been used to explore the dynamic pump behaviour in several operating conditions (various speed values and delivery pressure levels), calculating the flow irregularity, the pressure and forces instantaneous trends. The design characteristics of the poppet valves have been explored, in particular the spring characteristics, to discuss the trend of the previous variables. [ABSTRACT FROM AUTHOR]

Abstract The present paper is aimed at the energetic analysis of a solar hot water system performed on a dwelling located in different cities in Italy, precisely, from north to south: Bolzano, Turin, Bologna, Rome, Brindisi and Trapani. The study is focused on a group of apartments, where the domestic hot water is provided by a solar system coupled with a storage tank and a recirculation loop; it is worth to mention that the recirculation loop is obligatory on this kind of plants. Therefore, a dynamic energetic study is carried out, assigned the hot water load profiles and the set parameters of the solar collectors with reference to the configurations here tested (flat plane and evacuated tube). Thus, dynamic simulations have been performed by means of TRNSYS simulations tool, setting different parameters: collector configuration and mass flow rate. Several ideas and results emerged from this study, such as the sizing process of the whole system, according to the variation of the solar fraction for all the analyzed scenarios. A digression with simulation results regarding a specific case concludes the paper. More specifically, the study of water temperature oscillations in winter and summer time with reference to the climatic data of Bologna has been carried out under particular operating conditions: i) the pump of the recirculation loop is powered all time (24 hours a day) ii) the pump is switched off during the night, except when the water temperature in the loop falls below a certain threshold temperature. [ABSTRACT FROM AUTHOR]

Abstract The most commonly used interventions for energy requalification of buildings aim to increase the thermal resistance of the perimeter walls and ceiling and the efficiency of the HVAC system. Windows replacement is also usually foreseen. Moreover, the energy saving strategies have to reduce the energy consumption of the building, taking into account economic aspects and thermo-hygrometric comfort conditions of the occupants. In the case of historic buildings, some architectonical and urban planning restrictions impose to adopt only a few solutions that are well suited with the valuable architectural qualities of the building. In Italy, there are many historic buildings. They are often located in small towns, such as the case study of this paper, a public historic building, the library "G. Pascoli" placed in S. Severo (FG). In this paper, the authors propose an energy saving intervention, which consists in the application of a green wall on the back side of the building, being the principal façade subjected to architectural restrictions. The most suitable technological solution for the building considered has been proposed and a numerical analysis of the building's energy performance has been carried out by the software DesignBuilder. The results are satisfactory, being the energy consumptions significantly reduced both in summer and winter conditions. [ABSTRACT FROM AUTHOR]

Abstract This paper proposes a dynamic analytical method to simulate the thermal performances of truncated cone helix ground heat exchangers (i.e., the so-called "energy baskets"). These ground-coupled devices are attractive solutions to reduce the initial cost of ground-coupled heat pump systems, as they require lower cost to be drilled and installed with respect to traditional boreholes. However, both design methodologies and performance assessment models are still not well developed, producing substantial uncertainties on final operative performances. This work presents a plain evaluation method based on the heat exchangers theory and the analytical solution of the truncated cone helix heat source in a semi-infinite medium. It can be advantageously used to simulate the thermal performance of truncated cone helix ground heat exchangers as a function of helix geometries and operative conditions evolution (e.g., inlet temperature, fluid flow rate, ground temperature...). Specifically, in this paper, we perform a sensitivity analysis of the thermal performances of a case study by varying the main geometrical parameters. Besides, we compare the heat transfer of the reference configuration with an equivalent cylindrical arrangment. The truncated coil configuration is more effective than cylindrical one as the cone aperture reduces the short-circuits between helix pitch and the equivalent thermal resistance with the ground surface. However, obtained results are notably affected by the assumption of an isothermal surface temperature, which leads to a shallow/plain helix/spiral as the best configuration: different conclusions are expected when a time dependent or adiabatic boundary condition will be accounted in the model. [ABSTRACT FROM AUTHOR]

Abstract The paper investigates the flow through a uniformly-loaded propeller by means of a free-wake ring-vortex actuator disk without wake rotation. In particular, the model represents the near wake by the superposition of N ring vortices, while the far wake is modelled by a semi-infinite vortex cylinder with uniform radius. This second part presents the iterative solution procedure of the method illustrated in the companion paper as well as the implementation of the wake boundary conditions. Then, the power coefficient, the ideal propulsive efficiency and the wake contraction ratio are presented as a function of the propeller thrust coefficient, thus revealing the relevance of the wake convergence effects. Finally, the method is used to investigate the main characteristics of the local flow field induced by such an actuator disk. [ABSTRACT FROM AUTHOR]

Abstract The paper provides a detailed methodology to perform the exergetic analysis of a Nuclear Steam Supply System (NSSS) of a Pressurized Light Water Reactor, PWR, comprised of the Nuclear Reactor and its main coolant system components (RCS). The second law analysis is carried out based on the four fundamental thermodynamic quantities: mass, Energy, Entropy and, therefore, Exergy. In particular, referring to heat exchanges within the Nuclear Reactor, the paper provides some updates of models and parameters finalized to make more and more detailed a model already developed by the authors [1]. The modeling, referring to a steady-state operational mode of the Reactor, takes into account all heat transfer phenomena between nuclear fuel UO 2 , its Zircaloy clad, cooling water, vessel material and the external environment. In the second part of the paper, the theoretical model is extended to all main RCS components (Vertical recirculating type Steam Generator, primary coolant pump and piping) to get to the Exergy Destructions and exergetic Efficiencies of all NSSS main components. A test case, applying the methodology in question, is exemplified in the Part II of the same paper. [ABSTRACT FROM AUTHOR]

Abstract Seaweed biomass is a valuable marine resource that can be used for energetic purposes or high value-added product production. Cultured locally, seaweed is considered to reduce pressure on agricultural lands and reduce eutrophication. Seaweed cultivation success is dependent from several factors which includes seaweed reproduction, where spore release takes important place. Stress induced spore release is a part of fertilization material preparation. Stress can be obtained by drying seaweed. Drying in aluminium foil and in wet paper were tested on brown seaweed Fucus vesiculosus to determine if they have an impact on the amount on released spores and on spore fertilization. Wet paper and aluminium foil were used for material drying. Drying in foil increase the number of released gametes, but do not have an impact on fertilization rate. Drying length 6 days and 2 days were tested and 6 days gave better results. [ABSTRACT FROM AUTHOR]

Abstract Chicory coffee is the most used coffee substitute due to similar properties between original coffee – coffee Arabica – and chicory coffee itself that is made out of chicory root. To increase the use of locally produced products such as chicory coffee, it should be competitive in the market with similar products which at the moment are imported from foreign countries. At the moment, the price of locally produced chicory coffee is higher than similar products that are imported. In this paper chicory coffee’s production two main energy consuming processes – drying and roasting – were analysed in different production plants and countries (including Latvia) assuming that the energy that are consumed in these two processes mostly defines the price of the chicory coffee. The purpose of this paper is to obtain the information on how much energy is consumed for material drying and roasting in various chicory coffee production plants and to compare retrieved information between Latvian and other countries production plants. [ABSTRACT FROM AUTHOR]

Abstract The paper describes the electricity balance, actual for 2005–2016 and forecast balance for 2018–2019. It has been highlighted that during the last period of country’s independence, it has positive dynamics. And within the next 10 years, it will not only be with zero deficit, but will also reach exports of 10 billion kWh of electricity. This is predicated on the basis of the existing high rates of hydraulic engineering construction in the country. The paper also analyzes exports and imports of electricity across neighboring countries and indicates great importance of energy links. To analyze the electricity balance, the authors highlight the need for taking into account the so called “hidden” and “visible” deficits. [ABSTRACT FROM AUTHOR]

Abstract The analysis proposed in this study concerns literature reviews among the ways in which insurance companies cope with climate change, natural disasters and climate risk management. The paper aims to explore the several adaptation measures against climate change adopted by insurance companies for the development of models able developing an acceptable risk forecast. The importance of the paper is substantiated in a structural analytical study of the most important literature on the adaptation of insurance companies to climate change, highlighting the methodologies and specific cases. The conclusions of the paper highlight the natural relevance and relationship between insurance companies, the mandatory interface that year after year the insurance companies have to face and especially the numerous tools that have been developed by the latter in the insurance and reinsurance field for the natural hazards. [ABSTRACT FROM AUTHOR]

Abstract This paper presents results from the newly developed DTReM-LV model (Dynamic TRansport emission Model) for CO 2 policy mitigation analysis and design in the transport sector in Latvia. Despite the large number of studies analysing transport sector decarbonisation scenarios, previous research has focused much on the analysis of particular policy measures and/or technologies. Authors believe that there is still a gap in studies offering a complex evaluation of policy packages and their effects, especially if one looks at European countries with less advanced economies. This papers aims to fill this gap by providing a comprehensive tool for CO 2 emission reduction policy analysis in road transport sector at the country level. The overall aim of the model is to improve the knowledge-base and modelling capacity underpinning policy decision-making in the transport sector. Results from scenario studies suggest that CO 2 emission savings range from small savings up to around a third savings in 2030 compared to the baseline scenario. Best results are achieved through improving the acceptance of public transport, implementation of a combined package of policies promoting alternative fuel vehicles and by improving the fuel efficiency and reducing the average age of the car stock. [ABSTRACT FROM AUTHOR]

Abstract Refuse Derived Fuel (RDF) composed on biomass, paper, textiles, wood, synthetic polymers and other combustible materials is an alternative energy resource to implement Waste-to-Energy strategy. The aim of this study is to investigate the thermal decomposition characteristics of materials forming RDF by thermogravimetric analysis. Thermogravimetric (TG) analysis of RDF components demonstrates major differences in processes behind the thermal decomposition processes of waste components. Biomass decomposition can be divided into two distinct stages for wood, cotton, cotton wool and other biomass samples whereas three distinct stages can be distinguished for cardboard and paper samples. TG plots for synthetic polymers show two degradation steps for latex, vinyl and polystyrene sample, whereas one degradation step in nitrogen is characteristic for the rest of studied synthetic polymers. [ABSTRACT FROM AUTHOR]

Abstract The paper presents the operation mode of a ventilation chimney placed in a historical building through the use of Design Builder, a modeling and dynamical simulation software. The aim is to verify the improvement of the comfort level and energy efficiency of the simulated environments through the usage of the duct as a passive ventilation system. The method adopted to intervene in a complex system, such as that represented by historic buildings, is to enhance the preexisting architectural values through their conversion into devices able to improve the performance of the building in terms of CO 2 and energy consumption reduction. The case study is Palazzo Bruni-Riga, a valuable building located in the historic center of L’Aquila. The building has a double ventilation duct, probably also used as a light-pipe, in correspondence of two windowless rooms of similar dimensions. The dynamical simulations presented concern the analysis of the passive ventilation duct and its effects on the thermo-hygrometric well-being of the modeled rooms. The goal of this paper and this research in general, is that the wise use of such devices installed in times when there were no air conditioning systems, allows you to better use the ventilation chimneys, and have the maximum thermal indoor comfort, with the minimum effort and use of mechanical systems. Through the simulations it was possible to verify that through the use of the ventilation chimney, it is possible to have the indoor comfort conditions, by checking the Fanger indices for the data obtained from the simulations carried out. [ABSTRACT FROM AUTHOR]

Due to the increasing penetration level of tidal power in power system, the tidal turbines can provide less frequency support than conventional generators due to their small rotor mass. This makes the power system with low inertia and cause frequency problem. This paper presents a simulation model of a tidal power farm based on a MW-level variable speed tidal turbine with doubly-fed induction generator (DFIG) developed in the simulation tool of Matlab/Simulink. According to the reserve capacity required for primary frequency control, a de-loading control method is proposed in this paper to resolve the issue of primary frequency control via tidal power plant. Based on the analysis method of the frequency control characteristics of DFIGs, it is proposed by improved variable pitch control method. The control strategy, which is based on pitch control system of tidal turbine, is proposed in order to participate into primary frequency regulation of power system. Simulation results show that the proposed control strategy is effective means the tidal turbines with DFIG generators could providing frequency support for power system when they are working under the de-loading condition in this paper. [ABSTRACT FROM AUTHOR]

With the improvement of monocrystalline silicon material manufacturing technology, PV modules gradually reduce the manufacturing cost. However, the main technical difficulties for solar power system are the optimization problems of grid-connected system. This paper firstly introduced the differences between China and other countries in grid-connected PV power generation area. Furthermore, this paper also mainly researched the modulation method of PV inverter system, as two methods of SPWM and SVPWM modulation grid system modeling and then applied the methods to the three-phase grid-connected PV simulation system. According to the curve of voltage and current output, advantages of SVPWM method can be verified. [ABSTRACT FROM AUTHOR]

Security and stability control device plays a significant role in ensuring the reliable operation of power system. However, fault-operation, fail-operation, under-control and over-control could be caused by the failure of stability control devices and system. Taking SCS-500E, one kind of security and stability control device, the failure of hardware and software are discussed in this paper. According to device structure and failure data, the failure model of the device is established. The advantages of the Monte Carlo method are analyzed, and the failure probability of the device is calculated by this method. It is proved that the results worked by the method proposed in the paper are matched with the actual condition. [ABSTRACT FROM AUTHOR]

In order to evaluate the comprehensive performance of the lamps used in electric power emergency recovery system, four kinds of lamps are studied in this paper, which include metal halide lamp, induction lighting, LED lamp and XED lamp. Fuzzy Borda number analysis and maximum information coefficient method based on Grille acquisition method are combined in this paper. The evaluation index system and evaluation model of electric emergency recovery system are established to analyze the applicability, economy and reliability of different kinds of lamps. The comprehensive performances of these lamps are compared. Through the simulation studies, the applicability and reliability of the XED lamp is more prominent. [ABSTRACT FROM AUTHOR]

Based on the local energy Internet system project of State Grid Customer Service Center Northern Park, this paper introduces the general idea and system integration of local energy Internet design. In view of the system integration technology, this paper explores and studies the local energy Internet from the three aspects, namely planning and terminal access integration, equipment and system integration, system and system integration. It is found out that the integration technology can effectively gather energy sources and data to realize efficient integration between the energy flow and the data flow. [ABSTRACT FROM AUTHOR]

In view of the practical difficulties of basic data in the power grid planning work, and combined with the present situation of information systems in power grid companies, this paper puts forward the ideas about how to design planning basic data storage, and the flow of various data in the planning management information system, with the systematic analysis method and system integration mind. Firstly, the systematic analysis and multi hierarchy architecture method was employed to design and implement the power grid planning information system. Then the data flow theory was used to optimize the data flow within the panning system and the data inflow and data interfaces with external planning data source information systems. Finally, the organization architecture of the complex planning data was also designed finally. By applying the above results, a basic database and its advanced functions have been constructed. Practical application shows that the research results of this paper can integrate the existing data resources effectively, and ensure the accuracy and timeliness of the basic data for planning, so as to support the advanced planning function efficiently. [ABSTRACT FROM AUTHOR]

This paper presents a novel control strategy employing the maximum power point tracking (MPPT) and direct power control strategy (DPC) for permanent magnet synchronous generator (PMSG) based wind energy conversion system (WECS). The WECS adopts medium voltage source converter with AC-DC-AC configuration. The 10 MW wind farm is implemented in this paper which consists of 2 MW PMSG’s wind systems. The PMSG’s of the wind farm is connected to the DC collection grid through a DC/DC rectifier topology. The DC collection system is connected to the AC grid using single DC/AC inverter thus providing simple control technique which controls the number of PMSG generators. The output power fluctuations are compensated using direct torque control based maximum power point controller and direct power control. The DC link voltage and the active power injected to AC grid is controlled using grid side controller and the maximum power is extracted using the machine side controller of the wind turbine. Pitch angle control strategy is also used in order to reduce the turbine speed during high wind speed condition. The proposed controller provides aneffective solution for grid integration and constant power flow from the generator system to thegrid system. Simulation results are presented and analyzed the performance of the control strategies implemented in the system. [ABSTRACT FROM AUTHOR]

This paper is an investigation and study of how combustion characteristics appear in constant volume combustion chamber(CVCC) when biodiesel is mixed with pure gasoline. Experimental data for this study included four gasoline biodiesel fuel mixtures with concentrations of biodiesel of 5 and 20 designated GB05 and GB20 respectively. The study involves studying the positive aspects of combustion efficiency because biodiesel contains an oxygenated fraction. Through this study, we can find the most effective and efficient substitute fuel by comparing the total fuel mixture. Through these paper, you can improve your knowledge of gasoline biodiesel blended fuels and then utilize alternative fuels in high combustion efficiency and environmentally friendly modern gasoline compression ignition engines. [ABSTRACT FROM AUTHOR]

This paper proposes a multi-microgrid system reliability model which considers stochastic correlations among microgrids. Unlike traditional microgrid model, the proposed model can consider stochastic correlations among output of distributed generators and stochastic correlations among loads which is belonging to different microgrids. Using historical data, it shows that the proposed model helps to simulate the stochastic correlations among different microgrids. Furthermore, this paper also proposes a reliability assessment algorithm which incorporates the proposed model. Finally, the proposed model and algorithm are applied to a multi-microgrid system reliability evaluation case, which shows that the proposed stochastic model and algorithm can be effectively utilized by planners to conduct reliability evaluation of a multi-microgrid system. [ABSTRACT FROM AUTHOR]

With the development of smart power systems, it has become possible to adjust the operating status of aggregated air conditioning loads (ACLs) to make them trace the commands for distributed energy sources consumption. However, inevitable communication delay causes conspicuous control error. On the basis of analyzing control error of ACLs caused by communication delay, this paper proposes a communication delay compensation method based on network predictive control system. Then, aggregated ACLs are applied to consume the distributed energy sources in a microgrid, and several simulations demonstrate the compensation method proposed in this paper. The simulation results show that this method can diminish the control error caused by random communication delay to a large extent. [ABSTRACT FROM AUTHOR]

This paper exhibits varied methods for voltage security assessment in a restructured power system. This paper primarily lays emphasis on two methods that are Probabilistic Fuzzy Decision Tree (PFDT) and Case Based Reasoning (CBR). In PFDT, Decision Tree plays an integral role for classification of system. For further classification of power system security, an algorithm is developed to categorise the buses which trouble the security most. After classification of system, by using minimum amount of load curtailment of voltages on buses which made insecure to secure load. Optimization of load is done by curtailing reactive power from insecure buses. In CBR, old cases from database are used for solving the problems of new case. Hence, PFDT is re-trained in system during real operation for solving the new operating states which are found insecure in CBR approach. In case of emergency or a critical situation, structure of the power system networks changes but in such a condition CBR also gives better results by using re-training process. After re-training in real-time, CBR revises its database by accepting new conditions and stored for their further uses. These two methods are analysed on the standard test system i.e. IEEE-30 Bus along with desired accuracy. [ABSTRACT FROM AUTHOR]

Fog and haze weather has seriously affected many important aspects of human life and physical fitness. In order to improve air quality, local government has transformed coal-fired heating into clean energy heating in Beijing rural areas. This paper introduces three typical clean energy heating systems which are low temperature air source heat pump (LTASHP), thermal storage heater (TSH) and wall-mounted gas furnace (WGF), researches and tests the practical operation situation of three heating systems in the field. To compare technical and economic feasibility of three heating systems, the paper takes such residence where energy-saving standard of building palisade structure is approximately 50% as the research object, and establishes technical and economic mathematical analysis models, compares primary energy consumption and carbon dioxide emissions of three heating systems. This paper adopts annual cost approach, comprehensively takes into account power capacity increasing tariff and gas pipe network construction fee, and compares initial investment, operation cost and annual cost of three heating systems respectively from the perspective of users and government. The results show that LTASHP is the most energy-saving and its annual cost is lowest in the three heating systems. LTASHP is the most suitable alternative solutions to coal-fired heating in the three heating systems in rural Beijing. [ABSTRACT FROM AUTHOR]

A microgrid system, be it connected to the utility grid or an independent system, usually consists of a mix of generation - renewable and non-renewable; loads - controllable or non-controllable and Energy Storage Systems (ESSs) such as batteries or flywheels. In order to determine how much power is utilized from the controllable resources such as ESS, diesel generators, micro-turbines or gas turbines, we first need to determine how much the demand is or how much the renewable energy sources are generating is which is accomplished using forecasting techniques. Due to the intermittent nature of renewable resources such as wind energy or solar energy, it is difficult to forecast wind power or solar power accurately. These forecasts are highly dependent on weather forecasts. It is evident that forecast of any data based on forecast of other parameters would lead to further inaccuracy, even if the relation between the inputs and output maybe predetermined through regression methods. Therefore, this paper illustrates an approach to use historical power data instead of numerical weather predictions to produce short-term forecast results. The concept is based on persistence method presented in [1]. This method uses the "today equals tomorrow" concept. From [2], we know that persistence technique produces results that are more accurate as compared to other forecasting techniques for a look-ahead time of 4-6 hours. Both [1] and [2] were based on wind power forecasting. In this paper, we investigate persistence method for short-term electrical demand, solar PV (Photovoltaic) power and wind power forecasting. Since the forecasts are dependent on historical averages of the data in the 'near' past, the accuracy is inversely proportional to the variation of power between the historical data and the actual data. [ABSTRACT FROM AUTHOR]

Over the past decade, building energy modelling research has increasingly focused on urban-scale models. The shortcomings of analyzing urban buildings in isolation are well known and far from negligible (mainly, the inability to account for urban heat island and shading from neighboring obstructions). The aim of this paper is to assess the impact of the urban context via urban-scale modelling and inverse parameter estimation (calibration) using metered energy consumption of each building. We describe an automated calibration method for 58 buildings in a representative downtown district of Abu Dhabi. This district has undergone a detailed energy audit and a large amount of data about the building envelopes, cooling loads and electricity consumption has been collected from 2008 to 2010. In our models, buildings are subdivided in up to three use types documented in the audit (Residential, Office and Retail). Since it is well known that, due to the urban heat island effect, the urban ambient air temperature can differ significantly from the reference rural air temperature used in most building simulations, the calibration procedure will also estimate this differential together with unknown building parameters. The main contribution of the paper is to demonstrate that the proposed district-scale calibration is, in average, more accurate than individual building calibration and informs not only on buildings but also on the outdoor environment. The calibration was performed using Genetic Algorithm, reaching an average building MAPE of 25.24%. For the district as a whole, a MAPE of 12.01% was achieved. The estimation of Urban Heat Island intensity revealed a daily maximum of 5.6°C and an average daily differential of 3°C for a typical day, showing the relevance to consider it for any building energy simulation. [ABSTRACT FROM AUTHOR]

Recent studies have shown that energy-efficient smart LED lighting systems provide a better visual comfort-working environment at a reduced energy consumption compared to existing lighting systems. Present daylighting systems are able to regulate the light intensities via communication technologies utilizing smart sensors. This paper presents implementation of a smart LED lighting system utilizing different energy-efficient techniques without compromising the visual comfort of occupants. The proposed lighting system uses ZigBee and Wi-Fi communication protocols to control the lights of commercial/residential buildings according to natural daylight, occupancy or as per the requirements of the inhabitants of the building. The lighting system can be operated in three different modes: Manual, Auto, and Hybrid to account for various applications. A wireless sensor and actuator network (WSAN) is used to collect available data, regarding the usage of personalised smart LED lights by occupants in the building. A complete design and implementation of the smart lighting system are presented in the paper. The paper also presents the detailed test-bed implementation of the proposed smart lighting technique and data management system to illustrate the impact of the proposed lighting system on energy consumption and occupants' visual satisfaction. The proposed lighting system aims to reduce energy consumption by 60-70% compared to the existing lighting system while satisfying the visual comfort of the occupants. The proposed work also suggests the guidelines to incorporate intelligence into the system such that it can automatically predict the occupant preferences in a decentralized framework for better visual comfort and improved energy utilization in existing buildings. [ABSTRACT FROM AUTHOR]

As we strive for better energy efficiency in the systems we use in buildings, this paper examines how nature can play its part in an air conditioning system. This concept is applied in a passive displacement ventilation system which distributes cooled air in a room without the use of a fan. Typically the fans consume some 15% of the total energy used in a building. Save for fans used to draw outdoor air into a building, several buildings in Singapore have been designed to use no fan to achieve thermal comfort. This paper will examine the performance of this innovative system that challenges established norms in air conditioning design. [ABSTRACT FROM AUTHOR]

In line with the strategy to position Singapore as a " Living Laboratory" to trial new technologies for a more livable and sustainable Singapore, the Land Transport Authority (LTA) has embarked on an electromobility journey since 2011 to explore the feasibility of adopting electric vehicles (EV) for local use as a key strategy to mitigate carbon emissions from the transportation sector. The paper starts with an introduction on the EV Phase 1 test-bedding which was co-led by the LTA and the Energy Market Authority (EMA). The Phase 1 test bed, which started in 2011 and completed in 2013, concluded that EVs are technically feasible in Singapore but their near-term opportunity lies in fleet electrification. Built on the findings from Phase 1, Phase 2 test-bedding, which started in 2014 and co-led by the LTA and the Economic Development Board (EDB), focuses on fleet electrification. This paper details the various pilot projects under Phase 2 including the adoption of a national public charging standard to increase the inter-operability for EV proliferation. A comparison assessment between two prevailing charging standards, namely International Electrotechnical Commission (IEC) Type 1 and Type 2, incorporating supporting literature research, is given. Local implementation needs and technical considerations, which have led to the adoption of Type 2 AC and Combo 2 charging systems as the national standard for public charging infrastructure in Singapore, are analysed. The paper concludes with some prospects for EV proliferation in Singapore's electromobility journey. [ABSTRACT FROM AUTHOR]