Foreword

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A dynamic model of an innovative high-temperature solar heating and cooling system

In this paper a new simulation model of a novel solar heating and cooling system based on innovative high temperature flat plate evacuated solar thermal collector is presented. The system configuration includes: flat-plate evacuated solar collectors, a double-stage LiBr-H2O absorption chiller, gas-fired auxiliary heater, a closed loop cooling tower, pumps, heat exchangers, storage tanks, valves, mixers and controllers. The novelty of this study lies in the utilization of flat-plate stationary solar collectors, manufactured by TVP Solar, rather than concentrating ones (typically adopted for driving double-stage absorption chillers). Such devices show ultra-high thermal efficiencies, even at very high (about 200°C) operating temperatures, thanks to the high vacuum insulation. Aim of the paper is to analyse the energy and economic feasibility of such novel technology, by including it in a prototypal solar heating and cooling system. For this purpose, the solar heating and cooling system design and performance were analysed by means of a purposely developed dynamic simulation model, implemented in TRNSYS. A suitable case study is also presented. Here, the simulated plant is conceived for the space heating and cooling and the domestic hot water production of a small building, whose energy needs are fulfilled through a real installation (settled also for experimental purposes) built up close to Naples (South Italy). Simulation results show that the investigated system is able to reach high thermal efficiencies and very good energy performance. Finally, the economic analysis shows results comparable to those achieved through similar renewable energy systems

Ist die Haftung wegen existenzvernichtenden Eingriffs auch auf andere juristische Personen als die GmbH anwendbar?

Das Problem des Mißbrauchs von Gesellschaften ist nahezu so alt wie das Gesellschaftsrecht selbst. Es liegt darin begründet, daß der Gesetzgeber seinerzeit von einem Gleichlauf von Gesellschafter- und Gesellschafts-interessen ausging und deshalb keine Regeln für ein atypisches Verhalten schuf, sondern auf eine Lösung durch die Rechtsprechung im Wege der Rechtsfort-bildung vertraute. Die Praxis zeichnete aber bald ein anderes Bild, die vorerst letzte Rechts-figur um den Mißbrauch von Gesellschaften entgegenzutreten schuf der BGH mit dem existenzvernichtenden Eingriff. Diese für das GmbH-Recht geschaffene Rechtsfigur begründet eine unbeschränkt persönliche Haftung der Gesellschafter gegenüber den Gesellschaftsgläubigern analog §§ 105, 128 HGB falls sie ihrer Gesellschaft das zur Gläubigerbefriedigung zweckgebundene Vermö-gen entziehen und sie damit in die Insolvenz treiben � �kalt liquidieren�. Auch wenn das Schutzniveau in der GmbH hierdurch erhöht worden ist, so ist der Mißbrauch von Gesellschaften überall dort anzutreffen, wo es Haftungsbeschrän-kungen gibt. Daher beschäftigt sich diese Arbeit mit der Untersuchung, ob der ex. Eingriff auch auf andere juristische Personen insbesondere die AG aber auch den e.V. anwendbar ist. Hierzu ist zunächst die Rechtsfigur des existenzvernichtenden Eingriffs und ihre Tatbestandsvoraussetzungen dargelegt worden. Die Übertragbarkeit auf andere juristische Personen habe wurde in drei Schritten geprüft: Zunächst ist im gesetzlichen Schutzsystem der juristischen Person eine Regelungslücke hin-sichtlich existenzvernichtender Eingriffe festgestellt worden. Dann wurde die Regelungslücke auf ihre Planwidrigkeit untersucht Schließlich durften keine Besonderheiten der juristischen Person der Übertragung entgegenstehen

Variable-volume Storage Systems for Solar Heating and Cooling System: A Case Study for Different Italian Climates☆

Abstract This paper analyzes different control strategies for the thermal storage management in Solar Heating and Cooling systems (SHC) for different Italian climates. This novel thermal storage system consists in a variable volume storage tank system, which includes three separate tanks and a number of mixers and diverters. Such devices are managed through two different control strategies, based on combinations of series/parallel charging and discharging approaches. Thus, it is possible to vary the thermal storage capacity as a function of the combinations of solar radiation availability and user thermal/cooling energy demands. The system allows one to either increase or reduce the number of active tanks when the occurring mismatch between the solar energy supply and the user demand is either high or low, respectively. In addition, the surplus of solar energy is used through a heat exchanger included in the solar loop for the production of Domestic Hot Water (DHW). This novel variable-volume storage system, in all the proposed configurations, is also compared with a constant-volume storage system from the energetic and economic points of view. In addition, in order to determine the set of the synthesis/design variables which maximize the system profitability, a parametric analysis is implemented. A case study developed for an office building located in different Italian climatic areas is also presented. Simulation results show that the analyzed SHC systems system configurations may be profitable for all those cases and weather locations in which a sufficiently high solar fraction is achieved

Technical and economic analysis of a cogeneration plant fueled by biogas produced from livestock biomass

AbstractThis technical report illustrates an anaerobic digestion plant for the production of biogas designed to be powered by livestock biomass, combined with a 330 kWe CHP unit co-generator, installed in a cattle farm located in the province of Reggio Emilia. The plant consists essentially of a pre-treatment system of the effluents to the load, two anaerobic continuously stirred tank reactors and heated under mesophilic regime sheltered with gasometric coverings with double membrane; at the end of the process of fermentation, the digestate converges in a solid-liquid separation system with helical compression and a storage tank of the clarified fraction, sheltered with a covering for the containment of residual gaseous emissions into the atmosphere. The produced biogas is collected in gasometers placed above the tanks and, after desulfurization, dehumidification and cooling, it fuels the co-generator. The report is determined to illustrate the experimental results for the first 12 months of operation of the plant that confirmed, both in terms of energy and from a financial perspective, the efficiency of biogas plants fueled only by livestock effluents

Design and Dynamic Simulation of a Combined System Integration Concentrating Photovoltaic/Thermal Solar Collectors and Organic Rankine Cycle

This study presents the design of a novel ultra-high efficient solar power system. The system is equipped with a concentrating PhotoVoltaic/Thermal (CPVT) solar collectors bottomed by an Organic Rankine Cycle (ORC). The basic idea is to use a high temperature CPVT device producing simultaneously electricity and hot diathermic oil. Then, this hot fluid is used to supply heat to the Organic Rankine Cycle producing additional electricity. The collector is based on a combination of a parabolic dish concentrating solar thermal collector and a high efficiency solar photovoltaic collector. Among the possible high-temperature PVT systems, this paper is focused on a system consisting in a dish concentrator and in a triple-junction PV layer. In particular, the prototype consists in a parabolic dish concentrator and a planar receiver. The system is equipped with a double axis tracking system. The bottom surface of the receiver is equipped with triple-junction silicon cells whereas the top surface is insulated. Similarly, the ORC subsystem is equipped with tube and shell heat exchangers, a pump and an expander. In order to analyze the performance of the CPVT collector and ORC cycle, detailed mathematical models were implemented. These models are based on zero-dimensional energy balances on the control volumes of the system. The simulation model allows one to calculate in detail the temperatures of the main components of the system and the main energy flows. Both CPVT and ORC models are integrated in a more complex dynamic simulation model, developed in TRNSYS environment. Here, additional components are included in the system: Pump, tank, controllers, valves, etc. The input parameters of the model include weather conditions (temperature, insolation, wind velocity, etc.) and the geometrical/material parameters of the systems. This novel system was compared with a more conventional one, consisting of a concentrating PV collector equipped with III-V cells. Results showed that such second system (only CPVT) is more profitable from an economical point of view, with a 20 years Net Present Value 15% higher than the novel system (CPVT+ORC). Conversely, the novel (ORC+CPVT) system produces 6% more electrical energy

design and parametric optimization of an organic rankine cycle powered by solar energy

This study presents the simulation and performance analysis of a regenerative and superheated Organic Rankine Cycle (ORC). To this scope, anew simulation model has been developed. The model is based on zero-dimensional energy and mass balances for all the components of the system. Shell and tube heat expanders with single shell and double tube pass have been chosen. Pump and expander have been considered only form a thermodynamic point of view, with constant compressor and expansion efficiency. The simulations havebeen carried out in order to find different optimization criteria to use as preliminary design tools,especially for the organic fluid choice and the heat exchanger design. Firstly, the ORC performances have been evaluated for different organic medium, varying the temperature of the heat source. The global efficiency of the plant, the net electric power generation and the volumetric expansion ratio has been considered as evaluation parameters. The simulation results show that two hydrocarbons demonstrate good performance for low, medium and high heat source, namely Isobutene, n-Butene; R245fa can add to them for the exploitation of heat source up to 170°C. Additional simulations have been carried out to discover an optimization criterion for the heat exchanger design. The plant performances have been first evaluated varying one by one the following parameters: tube length, tube number and shell diameter. Then a global optimization was also performed using the Golden Search technique. The total cost of the plant has been considered as objective functions. With respect to the objective function, higher the boiling heat transfer area higher the electric power generation and the economical benefit. The optimal configuration, compared to the initial one, shows an increase of incomes and mechanical power equal to 60.1 and 48.2% respectively, against a decrease of global efficiency equal to 10.9%

Recent Advances in Technology, Strategy and Application of Sustainable Energy Systems

The global COVID-19 pandemic has had strong impacts on national and international freight, construction and tourism industry, supply chains, and has resulted in a rapid decline in the demand for traditional energy sources. In fact, research has outlined that urban areas depend on global supply chains for their day-to-day basic functions, including energy supplies, food and safe access to potable water. The disruption of global supply chains can leave many urban areas in a very vulnerable position, in which their citizens may struggle to obtain their basic supplies, as the COVID-19 crisis has recently shown. Therefore, solutions aiming to enhance local food, water and energy production systems, even in urban environments, have to be pursued. The COVID-19 crisis has also highlighted in the scientific community the problem of people’s exposure to outdoor and indoor pollution, confirmed as a key element for the increase both in the transmission and severity of the contagion, on top of involving health risks on their own. In this context, most nations are going to adopt new preferential policies to stimulate the development of relevant sustainable energy industries, based on the electrification of the systems supplied by renewable energy sources as confirmed by the International Energy Agency (IEA). Thus, while there is ongoing research focusing on a COVID 19 vaccine, there is also a need for researchers to work cooperatively on novel strategies for world economic recovery incorporating renewable energy policy, technology and management. In this framework, the Sustainable Development of Energy, Water and Environment Systems (SDEWES) conference provides a good platform for researchers and other experts to exchange their academic thoughts, promoting the development and improvements on the renewable energy technologies as well as their role in systems and in the transition towards sustainable energy systems. The 14th SDEWES Conference was held in Dubrovnik, Croatia. It brought together around 570 researchers from 55 countries in the field of sustainable development. The present Special Issue of Energies, specifically dedicated to the 14th SDEWES Conference, focuses on four main fields: energy policy for sustainable development, biomass energy application, building energy saving, and power plant and electric systems

Recent Advances in Technologies, Methods, and Economic Analysis for Sustainable Development of Energy, Water, and Environment Systems

Sustainability has become a broad societal goal, aiming to ensure that human beings coexist safely and harmoniously with nature over a longer time. The influence of the COVID-19 pandemic on the global economy is coming to an end. The development and merits of sustainable energy supply, advanced technology, and economic features have received significant attention over the last few decades. However, significant gaps still exist with respect to how to design, construct, and implement hybrid and optimal energy systems with the lowest investment and cost. Since 2002, the Sustainable Development of Energy, Water, and Environment Systems (SDEWES) conferences have become a significant meeting venue for researchers to introduce, discuss, share, and disseminate novel concepts and ideas. This paper presents an overview of published articles in the Special Issues (SIs) dedicated by the series SDEWES conferences, especially those published in Energies recommended by the 16th SDEWES Conference, which was held on 10–15 October 2021 in Dubrovnik, Croatia. This SI in Energies focused on four main topics, including the application of renewable bioenergy, component enhancement in renewable systems, sustainable development for buildings and economic analysis and evaluation for sustainability. The collected papers provide insight into the topics related to recent advances in improving sustainable efficiency, including studies on waste-to-wealth techniques, utilization of hybrid bioenergy systems, heat exchangers and other components for performance enhancement, energy supply and demand analysis, low-temperature DHC systems, techno-economic assessment, and environmental evaluation