Specific Power Demand Research Articles

Electric DQ0 Library Model for Smart Grid Simulation

This paper addresses the pressing need for advanced simulation tools in electric phasor modeling and Smart Grid-Power to X systems. The motivation for this study stems from the critical importance of enhancing the balance between performance and the detailed dynamic representation of the system behavior in the simulations. The identified problem lies in the absence of a comprehensive framework that seamlessly integrates electric phasor DQ0 components into a multi-purpose object-oriented environment. The primary objective of this research is to develop and introduce two simulation libraries, centered around the core component, Electric_DQ0. These libraries aim to establish a robust phasor-based framework, incorporating essential electric components such as sources, loads, branches, power converters, and electric machines. The main goal is to enable dynamic frequency and voltage simulations, particularly focusing on transients in alternators and facilitating Voltage and Frequency Rate of Change analysis during power production-demand imbalances. The libraries were developed within a versatile object-oriented environment, employing the Electric_DQ0 components as the foundation. Through ports, these components transmit turning frequencies, supporting the simulation of dynamic frequency and voltage. The libraries are designed to comprehensively support monophasic and triphasic systems, encompassing delta and wye connections, with a flexible neutral configuration under both balanced and unbalanced conditions. A validation case is presented to demonstrate the tool’s ability to accurately reproduce predictions when compared to one of the most widely used electrical modeling tools in the market. A study case is also presented to evaluate the toolkit’s capabilities. The study sets a specific power demand to fulfill, utilizing diverse energy sources. The obtained results showcase the libraries’ effectiveness in addressing the identified problem, providing valuable insights into their performance and applicability in real-world scenarios. The results demonstrate the efficacy of the proposed framework, delivering accurate outcomes within a reduced execution time.

Evaluation of Real-World Fuel Consumption of Hybrid-Electric Passenger Car Based on Speed-Specific Vehicle Power Distributions

Fuel consumption differs between the hybrid electric vehicle (HEV) and the conventional vehicle (CV). However, traditional fuel consumption models developed for CVs are commonly applied to HEVs, which leads to uncertainties in the quantitative evaluation of energy consumption for passenger cars in traffic road networks. Considering the internal combustion engine (ICE) operating modes of hybrid vehicles among varying vehicle specific power (VSP) demand, we present a method to incorporate the HEV ICE speed to develop speed-specific VSP distributions for real-world driving conditions. Using vehicle trajectory and fuel consumption data in real traffic conditions, the results of this study show that the application of methods developed for CVs leads to a significant underestimation of fuel consumption for HEVs when the average speed is in the high-speed range (over 50 km/h) and a significant overestimation of fuel consumption when the average speed is in the low-speed range (below 30 km/h). The average relative error of the measured fuel consumption factor in each speed bin is 7.1% compared with real-world observations, which is an unacceptably large error. This paper proposes a method to develop the speed-specific VSP distribution, considering whether the internal combustion engine (ICE) of HEVs is on or off. This approach reduces the average relative error of the obtained fuel consumption compared with real-world observations to 2.2%, and the measuring accuracy at different average speeds is significantly improved. This method enhances the functionality and applicability of the VSP theory-based traffic energy model for HEVs.

An Efficient Stochastic Reconfiguration Model for Distribution Systems With Uncertain Loads

Active power losses of distribution systems are higher than transmission ones, in which these losses affect the distribution operational costs directly. One of the efficient and effective methods for power losses reduction is distribution system reconfiguration (DSR). In this way, the network configuration is changed based on a specific power demand that has been already predicted by load forecasting techniques. The ohmic loss level in distribution system is affected by energy demand level, this is while an error in load forecasting can influence losses. Accordingly, including load uncertainty in DSR formulation is essential but this issue should not lead to change of the reconfiguration results significantly (i.e. the model should be robust). This paper presents a robust and efficient model for considering load uncertainty in network reconfiguration that is simple enough to implement in available commercial software packages and it is precise enough to find accurate solutions with low computational time. The analysis of results shows high efficiency and robustness of the proposed model for reconfiguration of distribution systems under demand uncertainty.

Exergy-based investigation of a coal-fired allam cycle

The Allam cycle is a novel cycle that capitalizes on the unique thermodynamic properties of supercritical CO2 and the advantages of oxy-fuel combustion for power generation and CO2 capture. This study aims to confirm the outstanding performance of a coal-fired Allam cycle and with the aid of an exergetic analysis to provide detailed important information on the real thermodynamic inefficiencies within the cycle. The results show that the overall exergetic efficiency is 40.6%, with near 100% carbon capture. The highest exergy destruction occurs within the gasifier, which contributes 29.1% to the overall exergy destruction, followed by the combustion chamber (17.4%), the air separation unit (7.4%) and the turbine (4.1%). In addition, the results obtained from the exergetic analysis in this study are compared to those of a gas-fired Allam cycle. The contribution of the exergy destruction of the combustor in the gas-fired Allam cycle is higher than the total share of the gasifier and the combustor of the coal-fired Allam cycle in the system exergy destruction. The sensitivity analysis shows that the specific power demand of the air separation unit, as well as the turbine inlet pressure, outlet pressure and isentropic efficiency have significant impacts on the overall exergetic efficiency.

The roticulating concept air compressor: experimental and numerical investigation

This paper documents the first prototype tests of the FeTu bare-shaft oil-free air compressor, conducted over a one-year study at the University of Bath, with funding support from Innovate UK. Giving feasibility to the concept and to provide an initial indicator of its performance, in terms of pressure capability, isentropic efficiency and specific power demand as an oil-free air compressor.A range of 6 units in total were validated on a continuous flow test-rig, with variations on internal sealing, internal clearance, and Non-Return Valve (NRV) settings, to assess their impact on volumetric efficiency, in pursuit of an optimal design.Tests covered a speed range of 100 rpm-1500 rpm and reached discharge pressures up to 6 barg, results indicated that the compressor can maintain a 50% torque-based efficiency between a pressure ratio (PR) of 1.5 to 2.8. Tests reveal low compressed gas temperature of 125ºC at 2.8PR, which gave rise to a high isentropic efficiency of over 80%, therefore specific power was adopted as the main Key Performance Indicator (KPI).

Membrane-assisted Cryogenic Distillation for Energy-efficient Argon Production from Air

High-purity argon is produced from air by cryogenic distillation; the process is energy intensive because of the similar volatilities of oxygen and argon. This work investigates the potential to reduce the energy consumption of argon production by using membrane-assisted distillation in the crude argon column of an air separation unit (ASU). Membrane-assisted distillation flowsheets are developed and simulated in Aspen Plus®. A customised model for the membrane separation is implemented in Aspen Plus as a user-defined unit. The built-in optimisation tool in Aspen Plus is used to optimise process operating conditions and the location of the membrane unit along the distillation column with the objective of minimising the overall power demand of the process. The performance of ambient polymeric membrane separations and low-temperature carbon molecular sieve membranes separations is evaluated.Detailed simulation and optimisation results show that membrane-assisted distillation offers considerable power savings when the membrane is placed in parallel to the distillation column. For both types of membrane material, the reduction in specific power demand (i.e. per unit of argon produced) is greatest when the membrane is placed close to the feed stage of the distillation column. A reduction in specific power demand of 12 %, relative to conventional distillation, is found for commercially available polymeric membranes. The decrease in specific power demand would be even greater (up to 32 %), if carbon molecular sieve membranes operating at low temperatures could be used.

Comparative power demand of mechanical and aeration imposed shear in an immersed membrane bioreactor

The power demanded for the application of mechanically-imposed shear on an immersed flat sheet (iFS) membrane bioreactor (MBR) has been compared to that of conventional membrane air scouring. Literature correlations based on the Ostwald model were used to define the rheological characteristics of an MBR sludge. The correlation of specific power demand (P'¯, in Watts per m2 membrane area) with shear rate γ in s−1 was developed from first principles through a consideration of the force balance on the system in the case of mechanically-imposed shear. The corresponding aeration imposed shear correlation was interpreted from literature information.The analysis revealed the energy required to impose a shear mechanically through oscillation (or reciprocation) of the membrane to be between 20 and 70% less than that demanded for providing the same shear by conventional aeration of the immersed membrane. The energy saving increases with decreasing shear in accordance with a power demand ratio (aeration:mechanical) of 1400γ−1.4 for a specific sludge rheology. Whilst the absolute P'¯ value is dependent on the sludge rheology, the aeration:mechanical power demand ratio is determined by the difference in the two exponents in the respective correlations between P'¯ and γ. Consequently, aeration-imparted shear becomes energetically favoured beyond some threshold shear rate value (∼180 s−1, based on the boundary conditions applied in the current study). The outcomes qualitatively corroborate findings from the limited practical measurement of energy demand in MBRs fitted with reciprocating immersed membranes.

Review on available biogas upgrading technologies and innovations towards advanced solutions

Biogas from anaerobic digestion of organic wastes or energy crops has proven to be a valuable alternative energy source both climate-neutral and sustainable on a global scale. The alternate valorization path of cleaning the biogas for the production of biomethane to be injected into the natural gas grid or to be used as a local vehicle fuel has gained significant importance in the last years. Considerable efforts in contemporary research are undertaken in order to improve efficiency and flexibility of biogas upgrading to enhance economic viability of biogas plants in times of expiring green-electricity feed-in tariffs, rising or strongly fluctuating costs for substrates and the currently low global energy prices. Current work tries to contribute to these questions suggesting and introducing innovative and highly effective technologies along the whole chain of biomethane production. A novel technique to separate high and fluctuating amounts of hydrogen sulphide from raw biogas is presented that relies on a highly intensified method of chemical-oxidative scrubbing. Single-stage separation efficiencies of 92% have been identified with this technology. A recently commissioned three-staged demonstration plant with an expected separation efficiency >99% is presented briefly. Furthermore, membrane-based gaspermeation is presented as a capable and economic method of CO2 removal and drying of raw biogas. While this technique is not new, authors try to demonstrate the huge potential for further development and exploitation peculiar to this method. Specific power demand for upgrading of 0.26 kWh/m3 biogas and specific upgrading costs of less than 0.15 €/m3 biomethane can be achieved. Today and in the future similar concepts and systems will be able to increase economic and ecologic performance of biogas plants thus contributing to strengthen biogas industry within the renewable energy sector.

Introducing a novel air separation process based on cold energy recovery of LNG integrated with coal gasification, transcritical carbon dioxide power cycle and cryogenic CO2 capture

An integrated coal gasification process with a novel double-column cryogenic air separation unit (ASU) based on the LNG (liquefied natural gas) cold energy recovery is proposed and analyzed. The process consists of a trans-critical carbon dioxide power generation cycle, a shift converter unit and cryogenic CO2 capturing system. ASU is used to produce high purity oxygen (99.99%) and nitrogen (99.99%). The specific power demand per flow rate of pure oxygen is 0.11 kWh/kg. Due to effective integration between two distillation columns in the ASU, the latent heat of the condenser in high pressure column is exchanged with reboiler of the low pressure column. The outlet LNG stream from ASU is utilized as cold source of the condenser in the trans-critical CO2 power cycle. The results show energy saving in the ASU and trans-critical power generation are 2301.6 kW and 14,217.6 kW respectively. The produced high purity gaseous oxygen is sent to the coal gasification unit to participate in the gasifier reactions. In this process, 99.83% of carbon dioxide with 99.80% purity, is captured and the required power is about 0.10 kWh/kg CO2.

Specific energy consumption of cake dewatering with vacuum filters

The energy consumption of vacuum filtration operations in cake filtration depends on the properties of the cake, the filtration conditions applied, and the progress of the cake dewatering process. Operating a vacuum filter at a high pressure difference requires a high air flow rate and thus has high energy consumption. By taking the filtered solids content into consideration together with the power demand and energy consumed at a certain pressure difference level, it is possible to investigate the specific power demand and energy consumption relative to the filtered cake solids content. When the mother liquor in the void space of the filter cake is replaced by air, the flow rate of air through the cake increases, which has a dramatic influence on the specific energy consumption. In this study, dewatering of calcite mine tailings is investigated with respect to the specific power demand and energy consumption of vacuum generation calculated using the assumption of an ideal isentropic process. The results of this study demonstrate clearly that both the air flow rate and the specific energy consumption in dewatering increase sharply after a certain solid content of the cake is reached. The results suggest that pumping costs in vacuum filtration can be reduced substantially by allowing a slight increase in the residual moisture content of the filter cake.

Machine based energy-saving tool path generation for five-axis end milling of freeform surfaces

Energy consumption in five-axis machining can be extremely large, especially for processing large-sized parts such as blades and dies, which often take hundreds of hours to machine. Once the specific machine tool configuration is given, one important objective in planning a five-axis machining operation is to reduce the total amount of energy consumption, which is not only particularly pertinent for mass production type operations but also plausible in today's energy-conscientious environment. While past research in this subject has been mainly focusing on finding better machining or processing parameters such as the cutting depth, feed rate, spindle speed, etc., in this paper, we study the fundamental problem of how to plan a five-axis tool path for machining an arbitrary free-form part surface on a given type of machine tool so that the total amount of energy consumption can be reduced, as compared to a traditional tool path, with everything else – e.g., the cutting depth, feed rate, spindle speed, maximum scallop-height, etc. – being equal. Towards this goal, an algebraic model called machine dependent energy potential field is formulated on the part surface, which encapsulates the specific power demand at any cutter contact point and along any feed direction. With this potential field, a simple tool path generation method is proposed that strives to find a good balance between the best fitting to the potential field (to minimize the total energy consumption) and the desired streamline patterns of the tool path. Experiments of the proposed method are carried out in both computer simulation and physical cutting, and the results are compared with that of some popular tool path generation methods such as the iso-scallop height method. The remarkable more than 25% savings in total consumed energy by the proposed method confirm the original motivation – designing better tool paths adaptive to the given specific machine tool is a powerful approach to reducing the total consumed energy, perhaps in general more effective than the passive selection of machining parameters which often have little room to adjust due to many constraints (e.g., the feed rate is highly regulated by the machine's controller during the cutting).

Commodity Dynamic Pricing and Inventory Joint Decision-Making Model Based on Specific Power Demand Function

Commodity Dynamic Pricing and Inventory Joint Decision-Making Model Based on Specific Power Demand Function

Operational energy use and power demands in European HVAC components

This paper is presented in the context of a gradual move from energy management at a Building level to energy management at Component level. This move requires specific energy consumption and power demand benchmarks to allow measured component energy use and power demands to be put into context. The paper presents a methodology for collecting and collating the data needed for producing these benchmarks from measured operational data. This methodology was tested in the European iSERVcmb project. Example benchmarks from iSERVcmb are provided along with links to the full published data. The paper concludes that large scale measurement and comparison of detailed operational data are possible and useful in support of achieving operationally low energy buildings. Practical application: The explosion of low-cost operational data availability at the level of individual components can be used to improve understanding of their operational energy efficiency in the context of the overall efficiency of a building. The paper shows this data can: Be collected from all types of buildings across all EU Member States Produce benchmark ranges of operational energy consumption and power demands at the level of individual components serving given activities Applying this benchmarked data in the design and operation of buildings will: Improve their operational energy efficiency, Enable legislation using this data to show compliance

Soil disturbance index as an indicator of seed drill efficiency in no-tillage agrosystems

In no-tillage agroecosystems, furrow openers prepare the seed line to place the seeds and fertilizers, and this event represents a unique opportunity to disturb the soil in this kind of crop system. Shanks are used to promote an appropriate soil physical condition, and, in case of soil compaction problems, shanks are used more frequently and at deeper layers of the soil profile. However, this deeper use causes greater draught and does not appropriately disturb the soil because narrow shanks have limited depth performance (“critical depth”). Here, we tested the operation of shanks in Oxisol and Alfisol. We assessed the shank performance 6–18 cm of depth, and we evaluated several soil disturbance parameters, such as area of groove, effective depth, and volume, as well as the demand of power force. Based on this evaluation, we calculated the specific power demand and the disturbance index, which is obtained from the ratio of disturbed area and maximum depth. With increasing depth of operation, the specific power demand increased in both soil types, while the disturbance index remaining approximately constant in the Oxisol and decreasing in the Alfisol. In the latter soil type, the shanks operated at more than 12 cm deep, and the lower disturbance index indicated a loss of efficiency in the soil disturbance. Therefore, the disturbance index is an efficient indicator of both the performance of seed drill shanks and the soil disturbance in no-till systems.

大功率白光LED路灯照明系统模拟设计

Using high-power white LEDs as light source,a design proposal of simulative model of street lamp lighting system satisfying specific illumination and power demand was introduced,with the help of the optical software named Trace Pro. The feasibility of the proposal was validated through an experiment. The simalative proposal can provide guiding significance for actual development.

A methodology of computation, design and optimization of solar Stirling power plant using hydrogen/oxygen fuel cells

The objective of this paper is to develop a methodology to determine how many houses could be fueled from the solar energy captured by a number of solar Stirling modules (with a fixed dish area per module) and also to determine the minimum necessary area of the fuel cell to ensure the amount of power needed to meet daily energy use requirements. The detailed method includes the effect of the fuel cell efficiency function on the power consumption of the user. Experimental data from our laboratory are used to determine the fuel cell efficiency as a function of the electric current density for a specific power demand. As an illustrative example, the analysis is applied to a residential area having a specific electrical demand. Using the developed method, the number of houses that could be fueled directly by the stored hydrogen is determined, and also the minim fuel cell area required.

Energy Conservation in Urban Areas

AbstractThis article outlines the energy conservation measures in the civilian sector from a few different viewpoint regarding energy conservation in cities. First, the energy consumption trends in the business and residential sectors are discussed, focusing the importance of energy conservation measures in applications such as home heating, water heating and specific power demand. Second, as a measure to reduce energy demand itself, energy conservation by way of applying heat insulating materials to buildings and changing the life style of residents is considered. And from the viewpoint of improving the energy system efficiency, additionally discussed here are the measures to improve the efficiency of each energy equipment such as air‐conditioners and co‐generation equipment, and the characteristics of District heating and cooling systems such as the local energy infrastructures. Lastly, from the knowledge obtained through model analyses by the authors, a scheme is recommended that would be one of the most efficient city‐energy schemes where the energy systems including heat pumps, co‐generators or equipment using solar power are utilized for their best‐suited applications for business and residential customers. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A simple model for fruit tree shaking harvest

A tree structure model was composed of trunk and main roots. It included a mass, spring and damping element, all of them reduced to the external end of the main roots. The model parameters, such as virtual turning centre, reduced mass, spring constant and clamping coefficient were measured on a real cherry tree. The model was than virtually shaken at 80 cm trunk height and acceleration and displacement amplitudes versus shaking frequency were calculated. The real cherry tree was shaken also at 80 cm trunk height by an inertia type shaker machine and the same data were recorded. The acceleration amplitude vs. frequency and displacement amplitude vs. frequency functions were similar for the virtual and real tree which proves the ability of the model. Power demand and specific power demand was then calculated in function of shaking frequency. The diagrams show that the shaking frequency of 12-14 Hz, of the practice is not the most efficient concerning amplitude, but is probably necessary from the point of view of acceleration needed to detachment of fruits.

Effect of impeller circumferential velocity on the specific power demand of water-ring vacuum pumps

Effect of impeller circumferential velocity on the specific power demand of water-ring vacuum pumps

A new sputter cleaning system for metallic substrates

In an experimental set-up for the gas discharge pretreatment of moving metallic substrates the efficiency of sputter cleaning was investigated with respect to planar magnetron discharges (PMDs) and conventional glow discharges (GDs). The substrate temperatures needed to deposit adhesive Ni films (5 μm) on steel in a high vacuum were taken as a measure of efficiency. As far as the substrate temperature, the sputtering of surface material, the processing speed, the specific power demand and the length of cleaning zones are concerned, the PMD pretreatment was shown to be superior to the GD treatment. To obtain films of good adhesion, the PMD treatment requires only 15% of the energy demanded by GD systems. This is attributed to the fact that, in a magnetron discharge, the ions are of low energy content and therefore they generate activated centres of enhanced bonding energy that are most prevalent in the surface region of the substrate. The initial drawbacks with reference to the uniformity of the PMD pretreatment have now been eliminated almost entirely. The results suggest that PMDs may be used to advantage in the pretreatment of metallic strip-type substrates.