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Smart Energy and Grid: Novel Approaches for the Efficient Generation, Storage, and Usage of Energy in the Smart Home and the Smart Grid Linkup: Foundations, Principles, and Applications
Abstract
This chapter presents novel approaches for the efficient generation, storage, and usage of energy in the smart home environment and their link to the smart grid. It also demonstrates innovative concepts and their feasibility for these purposes. The generation of renewable energy on the level of individual homes and housing estates is achieved by aerodynamically and aeroacoustically optimized small wind turbines as well as combined heat and power (CHP) micro plants using organic Rankine cycles (ORCs) to complement solar energy. The chapter further discusses the intelligent distribution of electric energy between the smart home and the smart grid. In order to tackle the transition of the electric power supply toward a renewable-based generation plant system, it is necessary to fully exploit locally available energy sources and to generate production surpluses in rural areas for the supply of urban agglomerations and industrial centers.
... Similarly, a recent survey is presented by Fallah et al. [15] with coverage of 52 papers in the range of 2001~2019. The energy forecasting methods during the given tenure [16,17] lack focusing on the usage of resourceconstrained devices, which are emerging due to their computational capabilities and instant decision support system. The subsequent sections discuss these methods in a classified format i.e., statistical and deep learning based load forecasting methods. ...
Green energy management is an economical solution for better energy usage, but the employed literature lacks focusing on the potentials of edge intelligence in controllable Internet of Things (IoT). Therefore, in this article, we focus on the requirements of todays’ smart grids, homes, and industries to propose a deep learning based framework for intelligent energy management. We predict future energy consumption for short intervals of time as well as provide an efficient way of communication between energy distributers and consumers. The key contributions include edge devices based real-time energy management via common cloud-based data supervising server, optimal normalization technique selection, and a novel sequence learning based energy forecasting mechanism with reduced time complexity and lowest error rates. In the proposed framework, edge devices relate to a common cloud server in an IoT network that communicates with the associated smart grids to effectively continue the energy demand and response phenomenon. We apply several preprocessing techniques to deal with diverse nature of electricity data, followed by an efficient decision-making algorithm for short-term forecasting and implement it over dependable resource-constrained devices. We perform extensive experiments and witness 0.15 and 3.77 units reduced MSE and RMSE for residential and commercial datasets, respectively.
Recent advances in energy conversion, information technology, the internet, new types of web, and communication technologies have enabled the interconnection of all physical objects, including sensors and actuators. Web‐enabled smart objects have paved the way for smart homes by enabling innovative services. In this work, the idea of using time series analysis based on machine learning and forecasting considering the weather conditions is discussed, to enhance automation and improve intelligence. The proposed Prophet model is used to predict the future net energy consumption and generation for improving energy efficiency and enabling power backup. Energy efficiency is the need of the hour, wherein major utilization of energy is in the residential sector, it is gravely important to analyze current generation and consumption and act accordingly for the future predicted results. Moreover, smart homes are dependent on web technologies and telecommunication for the operation of every action, which makes it crucial to have necessary power backup. The Prophet forecasting model, after parameter tuning and logistic growth pattern with additional regressors, gives only 0.27 mean absolute error and 0.13 mean squared error for predicting future energy consumption as compared to other models.
This paper discusses the concept of Urban SUNstainability and its importance for territorial sustainable development. Generically understood as a process for attaining sustainable development in urban areas, via the intense production and use of solar energy, Urban SUNstainability is presented as a convincing urban policy strategy for a greener, sustainable and prosperous world. Based on existing experiences in areas with abundant levels of solar radiation, it was found that, by now, the use and production of solar energy in urban areas starts to be economically viable, and should be regarded as an adequate solution to implement a greener and sustainable territorial development process in urban areas. As a way to assess the potential and current levels of Urban SUNstainability in urban areas, the paper proposes a multi-dimensional policy evaluation framework, based on five crucial aspects: the solar energy generation capacity, the direct and indirect environmental, economic and social benefits from implementing Urban SUNstainability strategies, and the soundness and effectiveness of the urban planning and governance processes related to the implementation of this process.
Due to the expanding ubiquity of distributed computing, more proprietor of the information is roused to outsource their information to cloud servers for incredible comfort and diminished cost in information administration. Nonetheless, touchy information ought to be encoded before outsourcing for security necessities, which obsoletes information usage like catchphrase based report retrieval. In this paper, we display a hybrid secure searchable encryption in cloud with privacy management, which all the while bolsters dynamic upgrade operations like cancellation and inclusion of reports. In particular, the vector space show and the generally utilized term frequency–inverse record recurrence model are consolidated in the index development and question era. Authors build an exceptional tree based spatial directory structure and proposes a recurrent depth search calculation to give effective multi-keyword sorted secure inquiry. The secure approximate nearest neighbors calculation is used to encode the registry and request, and in the interim guarantee exact importance score figuring between scrambled index and inquiry vectors. Keeping in mind the end goal to oppose factual assaults, apparition terms are added to the index vector for blinding list items. Broad analyses are directed to exhibit the productivity of the proposed conspire. Reflected from the experimental simulation, the proposed model outperforms.
This book describes the wind resources in the built environment that can be converted into energy by a wind turbine. It especially deals with the integration of a wind turbine and a building in such a way that the building concentrates the available wind energy for the wind turbine. The three different ways to concentrate wind power are examined: wind turbines on the roof or at the sides of a building; wind turbines between two airfoil shaped buildings; wind turbines in ducts through buildings.
The author's analysis leads him to conclude that wind energy conversion in the built environment, making use of the concentrator effect of buildings, is a promising renewable energy source.
The present study investigates the type of temperature sensor that best represents the operative temperature, i.e., the type of sensor that will integrate the influence of air and mean radiant temperature in the same way as a person. Size, shape and colour of the sensor will have an impact on the relative influence of air and mean radiant temperature in a space. In an experimental chamber different combinations of air temperature and radiant heated or cooled surfaces were tested. Several types of sensor (flat, sphere, ellipsoid, half-sphere, grey, black, white) were used to measure the operative temperature. Besides comparing the type of sensor, the influence of the sensor position in the room was experimentally investigated. The results show that a grey sensor of 3-5 cm diameter is the best size. The best shape, however, depends on the position of the sensor in the space.
Vertical Axis Wind Turbines (hereafter VAWT) are one of the useful renewable energy systems. They have several advantages in comparison with the conventional, propeller-typed, horizontal axis wind turbines. VAWTs operate independently of the wind direction. Moreover, maximum power coefficient can be obtained at lower tip-speed ratio compared to the conventional wind turbines. Flow induced noise is therefore smaller than that of the conventional ones. In this paper, we attempt to simulate an unsteady flow filed and aerodynamic noise radiated from VAWT by using the discrete vortex method and Ffowcs Williams-Hawkings equation. The result shows that the power coefficient is almost the same as the conventional typed wind turbines. Moreover, the predicted noise level of the developed VAWT is about 70dB, which is 10 dB lower than that of the horizontal axis wind turbine. We also attempted to estimate noise spectrum by using three dimensional vortex methods. However, the applied vortex methods can not simulate turbulent eddy motions such as the combination process and vortex break down process. Aerodynamic noise simulation by using discrete vortex methods is therefore limited to overall noise level estimation. However, vortex methods are useful to estimate aerodynamic noise from VAWT with small-scale computers.
The analysis, modeling and design of the lift-driven Vertical Axis Wind Turbine (VAWT) has challenged the wind energy community for many decades; this limited progress in knowledge has severely impaired the development of the VAWT, giving rise to the myth that the VAWT rotor is inherently inefficient (in comparison with the more conventional Horizontal Axis Wind Turbine - HAWT) or too complex for commercial implementation. In this research work, we take a new path on the analysis of the VAWT: instead of considering a rotor that creates a perturbation on the flow (wake and induction field), we consider an unsteady wake, to which a rotor energy-conversion system is associated, obtaining the loading on the blade by better understanding the flow. The research aims at understanding the wake and its relation with energy conversion and the loading on the rotor system. Four main questions drive this research: • What is the relation between blade loading and energy conversion? • How does the near wake of the VAWT develop? • What is the difference between the 2D and the 3D wake? • How does understanding the near wake improve our design? At the end of this dissertation we achieve a clear and insightful view on the 2D and 3D aerodynamics from the point of view of the wake, that significantly improves the aerodynamic design and optimization of new VAWT rotors for energy conversion and propulsion, opening a new design space and methodology. The results and discussion presented in this dissertation are organized in five steps (see thesis outline, Chapter 1): • Part I: understand the fundamental VAWT aerodynamics and how these relate with the research presented in this dissertation. • Part II: understand the energy exchange process in the 2D plane by understanding the shedding of the wake over the rotation, and the wake expansion in 2D. Analyze the impact of dynamic stall on the near wake evolution, and how to extract blade load information from the near wake in dynamic stall. • Part III: understand the impact of the spanwise dimension of the rotor and the role of the consequent trailing vorticity. Investigate the little known skewed flow. • Part IV: understand better the energy exchange process, the wake’s generation and the decoupling between loading and energy conversion. Propose new approaches and guidelines for the aerodynamic rotor design. • Part V: discuss the main results and conclusions of the research, and its impact on new aerodynamic research and design approaches, both for 2D and 3D VAWT rotors. In Part I (Chapter 2) we frame our research approach, analyzing the VAWT from a wake perspective, by considering both 2D and 3D aerodynamics of the VAWT at two different scales: aerofoil/blade scale and rotor scale. We divide the rotor in windward (315◦ < θ < 45◦), upwind (45◦< θ < 135◦), leeward (135◦ < θ < 225◦) and downwind (225◦ < θ < 315◦) regions of the rotation. This approach obsolesces the conventional division of the rotor into upwind and downwind halves; while the upwind/downwind division is driven by angle of attack considerations (blade loading problem), this new segmentation is determined by the shedding of vorticity (energy conversion problem), a more useful and effective approach. The wake is also split into shed vorticity due to the time gradient of the bound circulation, and trailing vorticity due to the spatial gradient of the bound circulation; this division leads to our 2D and 3D analysis of the flow. In Part II, we analyze the 2D rotor and wake at two scales: rotor and blade. The two flow scales are obviously related, in the sense that the rotor’s aerodynamics are the result of the wakes generated at the several blades and the blade experiences an induction field due to the vorticity distributed over the wake at the rotor scale. The separation in blade and rotor scale is in fact a separation of two views on the total system: • The rotor, as an energy exchange system, where the energy exchange results in a wake and streamline expansion. • The blade, as an aerodynamic loading system, where the design-objective loading is associated with an equivalent bound circulation. The time variation of this bound circulation results in a shed wake. The 2D potential-flow analysis (Chapter 3) shows that: • the conventional breakdown of the VAWT into upwind and downwind actuator systems is incorrect, leading to an overestimation of energy conversion on the upwind half of the rotation and an underestimation in the downwind half. • contrary to the HAWT, the induction is not a function of the total loading, but only of the load component associated with the azimuthally varying circulation. • it is possible to significantly improve Double Multiple Streamtube models by incorporating a better description of the flow. The proposed improved model clearly surpasses conventional models on the prediction of the induction and loading. • the impact of the blade bound-circulation constant-term is small in comparison to the time-varying bound-circulation term; therefore, the induction field of the 2D VAWT in potential flow can be defined by only the number of blades, rotor solidity and tip-speed ratio. This allows for the obsolescence of streamtube momentum models, replaced by faster and more accurate potential flow vortex models. In Chapters 4 and 5 we visualize and quantify, experimentally and numerically, the flow field in the near wake of the blade during the upwind and leeward segments of the motion, at tip-speed ratios λ = 2, 3 and 4, using Particle Image Velocimetry (PIV). An interesting physical aspect of the vortical flow in dynamic stall, especially at low tip-speed ratios, is the transport of the shed vorticity with the blade. This transport of the vortical structures with the blade means that the geometry of the wake, due to viscous effects, differs from what is obtained with potential flow. A different spatial distribution of the shed vorticity implies a different induction field, which might imply a reduction of the effectiveness of momentum models and simple potential-flow models and change the rotor’s performance. The results show two important effects: • At the rotor scale, the transport of vorticity with the blade, rolled in the leading edge/trailing edge separated vortices. • At the blade scale, the importance of the small scale vortices for the oscillations on pressure distribution and loads. In Chapter 6 we use the experimental and numerical data from the previous chapters to evaluate the feasibility of extracting information from the flow/wake measured with PIV, even in dynamic stall, for improving flow analysis and model validation. In Part III we introduce the fourth dimension of our problem: the spanwise direction. The finite span leads to a non-constant spanwise distribution of circulation on the blade, and this distribution leads to the release of trailing vorticity, of which the blade tip vortex is the most prominent component. In Chapter 7 we measure the wake at the tip-vortex region of the VAWT; in Chapter 8 we combine these experimental results with 3D unsteady free-wake potential-flow simulations to: • experimentally and numerically observe, quantify and analyze the generation and convection of the 3D tip vortex of the VAWT. • experimentally, numerically and analytically investigate the effect of blade-tip shape on the generation and convection of the tip vortex, with focus on the added circulation due to the motion of the blade. • combine experimental measurements and numerical simulations to analyze: the 3D wake of the VAWT; the interaction between shed and trailing vorticity; the roll-up and expansion of the wake in the leeward and windward regions; the in-rotor convection and inboard/outboard motion of the tip vortex; the 3D induction field; the 3D blade wake interaction during the downwind blade passage; and the effect of trailing vorticity in the spanwise distribution of circulation, including the 2D to 3D load direction reversal in the downwind blade passage. The spanwise dimension of the flow also gives rise to a new form of misalignment between the flow and the axis: skewed flow. In Chapter 9 we analyze the physics of skewed flow, flow asymmetry, near wake development, blade-wake interaction and impact on energy conversion. The analysis of the VAWT from the point of view of the 2D and 3D near wake is shown to be very effective in understanding: the physics of the flow; the energy exchange process; how the total energy exchange over one rotation actually relates to the local aerodynamic loading on the blade; the impact of implementing an essentially 2D energy conversion process into a 3D aerodynamic system; and the resulting inefficiencies due to the finite span and trailing vorticity. In Part IV (Chapter 10) we show that it is possible to decompose the VAWT design problem into designing for loading and designing for energy conversion, opening a large design space and proposing a new methodology, impacting both 2D and 3D flow. We also show that, although the 2D wake does not vary significantly with variation in the pitching axis location and blade camber, the 3D wake and performance are significantly affected by these variations. This is due to the impact that varying the bound circulation has on the release of trailing vorticity; a larger trailing vorticity generated during the upwind blade passage implies a larger induction due to trailing vorticity, and a worse interaction at the downwind blade passage. The effects of variation of camber and/or pitching axis in 2D and 3D performance are contradictory and complementary and can be simultaneously optimized. In Part V (Chapter 11) we further develop these and other main conclusions, discussing their impact on VAWT aerodynamics. The research here presented implies a break from conventional approaches to the VAWT aerodynamics, allowing for the development of new research and models, both in 2D flow (aerofoil design, rotor energy conversion optimization) and 3D flow (blade and rotor shape, non-uniform flows).
Im Kontext der Energiewende sind Energiespeicher ein zentrales technisches, wirtschaftliches und energiepolitisches Thema.Die Autoren dieses kompakten Werkes geben einen umfassenden Uberblick Uber die verschiedenen Aspekte der Energiespeicherung. Sie beschreiben zunachst die Bedeutung von Energiespeichern in der Energieversorgung und definieren ihre Rolle darin. Dann gehen sie auf den Speicherbedarf in der Strom-, Warme- und Kraftstoffversorgung im Kontext der Energiewende ein. Im Hauptteil werden die verschiedenen Speichertechnologien ausfUhrlich vorgestellt sowie ihre Vor- und Nachteile diskutiert. Praktische Anwendungsbeispiele und die Integration von Speichern Uber alle Energiesektoren hinweg runden das Buch ab. Zahlreiche Grafiken und Beispiele veranschaulichen das gesamte Feld der Energiespeicher und sind als Erganzung samt Animationen online in Farbe verfUgbar.Die ZielgruppenDas Lehr- und Fachbuch wendet sich an Ingenieure, Wissenschaftler, Energieplaner und Energiewirtschaftler in Forschung und Industrie sowie an Studierende an Hochschulen und Universitaten in den Bereichen Maschinenbau, Verfahrenstechnik, Elektrotechnik und Energietechnik.Die AutorenProf. Dr.-Ing. Michael Sterner erforscht und lehrt an der Technischen Hochschule Regensburg in der Fakultat Elektro- und Informationstechnik die Bereiche Energiespeicher, Energiewirtschaft und Integration erneuerbarer Energien. Zuvor war er am Fraunhofer IWES in leitender Funktion verantwortlich fUr die Bereiche Systemanalyse und Energiewirtschaft und hat mit Kollegen die Speichertechnologie Power-to-Gas entwickelt. Der Ingenieur arbeitet ehrenamtlich in der Energietechnischen Gesellschaft des VDE, dem bayerischen Wirtschaftsministerium und dem Weltklimarat (IPCC), leitet Speicherkonferenzen von VDI und OTTI, ist beratend fUr die Bundesregierung tatig und im wissenschaftlichen Beirat der International Renewable Energy Storage Conference der Eurosolar sowie der Energy Storage Düsseldorf.
Prof. Dr.-Ing. habil. Ingo Stadler forscht und lehrt an der Fachhochschule Köln und ist dort für die Erneuerbaren Energien und Energiewirtschaft verantwortlich. Er habilitierte an der Universität Kassel. Seine Arbeiten umfassen die Netzintegration Erneuerbarer Energien und Energiesysteme mit hohen Anteilen an Erneuerbaren Energien und konzentriert sich auf die über die Elektrizität hinausgehenden, nichtelektrischen Speicher und das Lastmanagement. Er ist Mitglied des Beirats der International Renewable Energy Storage Conference sowie des International Centre for Sustainable Development of Energy, Water and Environment Systems. Über ein Jahrzehnt arbeitete er im Photovoltaik-Programm der Internationalen Energieagentur IEA.
Please note: this is an erroneous citation for an article, the actual source is the book of the same title published by Butterworth-Heinemann (Elsevier) - see separate reference in ResearchGate.
In electric energy systems based on renewable generation plants supply and demand often do not occur in the same period of time. Consequently demand side management is gaining importance whereby decentralized automation offers opportunities in industrial environments. Compressed air systems on industrial plants consist of air compressors, compressed air reservoirs and compressed air lines. With suitable dimensioning those industrial compressed-air systems can be used for demand side management purpose. As power consumption of industrial air compressors ranges between a few and several hundred kilowatts each, swarms of communicatively connected air compressors can contribute to the stabilization of power grids. To avoid costly production downtime it is to ensure, that a reliable, non-disruptive supply of compressed air can be maintained at all time. Industrial compressed air systems equipped with automation technology and artificial intelligence, which hereinafter are referred to as Cyber-Physical Compressed Air Systems (CPCAS), allow new business models for utilities, industrial enterprises, compressor manufacturers and service providers. In addition to basic operating parameters like current air pressure and status, those systems can process further information and create, for example, profiles on compressed air consumption over time. By enriching those profiles with data on pressure, volumes, system restrictions and current production requirements (plans), the CPCAS can identify the available potential for demand side management. Ipso facto predictive power on electricity consumption is increasing. By providing the information obtained to the power company or a service provider, savings in electricity costs may be achieved. Expenses within the industrial company may be lowered further as compliance with agreed load limits is being improved by automatic shutdown of air compressors upon reaching the load limit. Within this article the structure of the aforementioned Cyber-Physical Compressed Air Systems is presented in more detail, relations between the major actors are being shown and possible business models are being introduced.
The objective of this paper is to validate two different numerical methods for noise prediction of the H-Darrieus wind turbine using a complementary approach consisting of experimental measurements and numerical simulations. The acoustic measurements of a model scale rotor were performed in an anechoic wind tunnel. This data is the basis for the validation of the computational aeroacoustic simulations. Thereby, we have applied two different numerical schemes for noise prediction using hybrid methods. As usual in hybrid aeroacoustic approaches, flow field and acoustic calculations are carried out in separate software packages. For both schemes the time-dependent turbulent flow field is solved with Scale-Adaptive Simulation. The two schemes then differ in how the location of the acoustic sources and their propagation is calculated. In the first scheme the acoustic source terms are computed according to Lighthill's acoustic analogy which gives source terms located on the original CFD grid. These source terms are projected onto a coarser acoustic grid on which Lighthill's inhomogenous wave equation is solved by the Finite Element (FE) method. The second scheme uses the Ffowcs Williams-Hawkines (FW-H) method which is based on a free field Green's function. The scheme uses a porous integration surface and implements an advanced time formulation. Both methodologies are compared with experimental data.
Eine thermodynamische Analyse zum Einsatz von Kältespeichern und der Abwärmenutzung bei Kühl- und Gefrieranwendungen wird vorgestellt. Die Energieeffizienz der betrachteten Systeme steht dabei im Fokus. Zudem wird die Umgebung als unendliche Wärmesenke zur direkten Ableitung der Wärme aus dem Kühlschrank untersucht. Es werden fünf verschiedene Konzepte beschrieben und anhand ihres Jahresenergie- und Jahresprimärenergiebedarfs verglichen.A thermodynamic analysis of cold storage systems and waste heat usage for refrigeration and freezing applications is presented. The focus is set mainly on the energetic efficiency of the systems. The environment is considered as an infinite heat sink to which the heat from the refrigeration compartment can be transported directly. Five different concepts are presented and evaluated based on the annual electric energy and primary energy demand.
Plasmadust® is a new technology using cold active plasma for additive metallization of different substrate materials. For electronics production, in particular Molded Interconnect Devices (MID), thermoplastic materials can be structured with copper as power electronic conductive pattern. The main advantages of Plasmadust® are the controllable process temperature range between about 90°C and 180°C, the good adhesion of the metallization, the fast process speed of about 100 mm/s and the fast growing conductor tracks with about 15 microns thickness per cycle. Plate specimens were made of PA, a thermoplastic commonly used in automotive applications, with different process parameters. Conductor tracks applied onto the substrates consist of one line with different electrical and mechanical properties according to the process temperature and process speed. Additionally, the thickness and the width of the conductor track depend on the process parameters. The setting of the process speed turns out to be an important influence on the thickness and roughness of the conductor track that can be achieved on thermoplastic substrates. The investigated combination of thermoplastic and copper shows a constant bonding performance during thermal shock testing for 1000 cycles in the range of -40°C and +125°C. An exposure to humidity heat (85% r.h / 85°C) for 500 h has only marginal effects on the adhesion of the printed structures on the thermoplastic substrates, too. This highly promising results provide the base for further investigations to achieve a sufficient ampacity related to standard chemical PCB metallization processes.
Since millenaries humans have attempted to harness the wind energy through diverse means. Vertical axis wind turbines (VAWTs) were originally considered as very promising, before being superseded by the present, horizontal axis turbines. For various reasons, there is now a resurgence of interests for VAWTs, in particular Darrieus turbines. Using modern design tools and computational approaches, it should be possible to increase considerably the performance of traditional VAWTs, reaching a level almost comparable to that of horizontal axis turbines. Since VAWTs show many specific advantages (compact design, easier connection to gears/generator, easier blade control if needed, lower fatigue…), it is important to check quantitatively the efficiency of such turbines. This is the purpose of the present work, starting from the standard, straight Darrieus turbine (H-rotor). The aerodynamic investigation will be carried out for 20 different airfoils (Symmetric and Non-symmetric) by two-dimensional Computational Fluid Dynamics in order to maximize output torque coefficient and output power coefficient (efficiency). A considerable improvement of the H-rotor Darrieus turbine performance can be obtained in this manner.
This article presents an experimental investigation of substituting R134a with R436A (a mixture of R290 and R600a with a mass ratio of 56/44) in a 238 L single evaporator domestic refrigerator without any modification in refrigeration cycle. The refrigerator’s compressor was charged with different amount of R436A, and in addition to refrigerator’s power consumption during operation, the temperatures in different sections of the refrigerator were measured. Results showed that in comparison to the base refrigerator working with R134a, the ON time ratio and the energy consumption per day were reduced by 13% and 5.3%, respectively. Although the original R134a charge for this refrigerator was 105 g, the optimum charge for R436A was reduced to 55 g that exhibits 48% reduction in refrigerant charge. Also replacing R134a charge with R436A raised the energy efficiency index of the refrigerator from label “E” to label “D” according to Iranian National Standard No. 4853-2.
Das Wrme-Wohlbefinden des Menschen wird von der Temperatur der Umgebungsflchen, der Lufttemperatur, der Bewegung der Luft sowie der Luftfeuchte wesentlich bestimmt.
This paper presents an experimental study on the performance of a domestic vapor-compression refrigeration system with isobutane (R600a) as the refrigerant. The input power of the compressor varied between 230 and 300 W, while the amount of the charged refrigerant was about 150 g. The expansion and heat transfer components of the system were capillary tubes and plate heat exchangers, respectively. The refrigeration temperatures were set at about 4 and −10°C to simulate the situations of the cold storage and the freezing applications. Both normal and extreme conditions were investigated in this work.In the cold storage application, two capillary tubes in parallel gave better performances than a single tube. The proper sizes of the tube are between 4 and 4.5 m in length, and 0.7 mm in internal diameter in the cold storage application, while in the freezing application they are between 4.5 and 5 m in length, and 0.6 mm in internal diameter. The coefficients of performance of the system lie between 1.2 and 4.5 in the cold storage application and between 0.8 and 3.5 in the freezing application, which are comparable with those of the system with R-12 and R-22 as the refrigerant. In general, the refrigeration capacity increases with the refrigeration loads.
Recently accepted revisions to ASHRAE Standard 55—thermal environmental conditions for human occupancy, include a new adaptive comfort standard (ACS) that allows warmer indoor temperatures for naturally ventilated buildings during summer and in warmer climate zones. The ACS is based on the analysis of 21,000 sets of raw data compiled from field studies in 160 buildings located on four continents in varied climatic zones. This paper summarizes this earlier adaptive comfort research, presents some of its findings for naturally ventilated buildings, and discusses the process of getting the ACS incorporated into Standard 55. We suggest ways the ACS could be used for the design, operation, or evaluation of buildings, and for research applications. We also use GIS mapping techniques to examine the energy-savings potential of the ACS on a regional scale across the US. Finally, we discuss related new directions for researchers and practitioners involved in the design of buildings and their environmental control systems.
The use of organic working fluids for the realization of the so called Organic Rankine Cycle (ORC) has been proven to be a promising solution for decentralized combined heat and power production (CHP). The process allows the use of low temperature heat sources, offering an advantageous efficiency in small-scale applications. This is the reason why the number of geothermal and biomass fired power plants based on this technology have been increased within the last years. The favourable characteristics of ORC make them suitable for being integrated in applications like solar desalination with reverse osmosis system, waste heat recovery from biogas digestion plants or micro-CHP systems. In this paper, the state of the art of ORC applications will be presented together with innovative systems which have been simulated in a process simulation environment using experimental data. The results of the simulation like efficiencies, water production rates or achievable electricity production cost will be presented and discussed.
In this study, a detailed thermodynamic model for a refrigerator based on an irreversible Carnot cycle is developed with the focus on forced-air heat-exchangers. A multi-objective optimization procedure is implemented to find optimal design values for design variables. Minimizations of energy consumption and material cost were the two objectives considered. Since these objectives are conflicting, no single design will satisfy both simultaneously. The result of this research is a set of multiple optimum solutions, which are called ‘Pareto optimal solutions’. Air and refrigerant side correlations were combined with an elemental approach to model the heat exchangers. This paper presents a detailed design model development. A limited validation is presented with experimental test-data obtained from a typical household refrigerator. Detailed simulation models are typically complex and computationally demanding. An optimization algorithm requires several evaluations of such models. Response surface based metamodels for objective functions were used to save computational effort. A genetic-algorithm based optimization tool is used for multi-criteria optimization.
Generalized functions have many applications in science and engineering. One useful aspect is that discontinuous functions can be handled as easily as continuous or differentiable functions and provide a powerful tool in formulating and solving many problems of aerodynamics and acoustics. Furthermore, generalized function theory elucidates and unifies many ad hoc mathematical approaches used by engineers and scientists. We define generalized functions as continuous linear functionals on the space of infinitely differentiable functions with compact support, then introduce the concept of generalized differentiation. Generalized differentiation is the most important concept in generalized function theory and the applications we present utilize mainly this concept. First, some results of classical analysis, are derived with the generalized function theory. Other applications of the generalized function theory in aerodynamics discussed here are the derivations of general transport theorems for deriving governing equations of fluid mechanics, the interpretation of the finite part of divergent integrals, the derivation of the Oswatitsch integral equation of transonic flow, and the analysis of velocity field discontinuities as sources of vorticity. Applications in aeroacoustics include the derivation of the Kirchhoff formula for moving surfaces, the noise from moving surfaces, and shock noise source strength based on the Ffowcs Williams-Hawkings equation.
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- V Fabi
- V Camisassi
- F Bellifemine
- V Bella
- S P Corgnati