1,721,007 research outputs found
Optimising low-temperature district heating networks: A simulation-based approach with experimental verification
No full textFifth generation district heating and cooling systems are becoming increasingly popular due to their ability for working with low temperature of heat transfer fluids. Among the other benefits, this characteristic allows for a better exploitation of renewable energy sources. On the other hand, these networks require a fine design and precise management to exploit their full potential. Both these requirements can be met by using advanced simulation and optimisation tools. This research proposes a simulation tool purposely conceived for the design and the optimisation of fifth-generation district heating and cooling systems. This tool is capable of assessing the effects of each building-plant system on the whole district heating and cooling water loop, and to evaluate the effectiveness of diverse network morphology. These capabilities are due the level of detail of the mathematical modelling which takes into account the thermohydraulic characteristics of the network, each building thermo-physics properties, and the heat pump/chiller detailed operation. The described tool has been adopted to simulate an existing experimental network prototype (consisting of a central heat pump, behaving as thermal energy balancing station, and eight users), and the achieved results were compared to those experimentally obtained for validation aims. The capabilities of the validated tool have been demonstrated by investigating an innovative control logic (representing a further novelty of this research) for a “proof-of-concept” fifth-generation district heating and cooling network. In particular, by adopting a predictive control logic, the water loop temperature is dynamically optimised to minimise the entire network energy demand. The adopted control strategy has yielded significant primary energy savings, amounting to 10.3 MWh/year, with a rate of 6.5 % compared to the reference case characterised by a fixed network temperature. These results underscore the potential of the proposed method and demonstrate the effectiveness of the developed tool
Energy recovery through natural gas turboexpander and solar collectors: Modelling and thermoeconomic optimization
No full textThis paper presents a novel dynamic simulation model for the analysis of a hybrid turboexpander systemcoupled with innovative high-vacuum solar thermal collectors. The model is developed in MatLab and itis able to dynamically calculate the energy, exergy, environmental, and economic performances of theinvestigated system, by taking into account the hourlyfluctuation of thermodynamic and economicparameters (e.g. electricity cost, natural gas temperature, andflow rates, etc.). In addition, a computer-based Design of Experiment (DoE) approach was implemented for achieving the optimal design of theproposed system.A suitable case study is presented in order to show the capabilities of the developed simulation tool.Conventional and non-conventional decompression systems located in the weather zone of Messina(South-Italy) are investigated with the aim of assessing the optimal system configuration. By means ofthe computer-based DoE analysis, the optimal values of several design parameters (such as the numberof solar thermal collectors, the volume of the hot water storage tank, and the size of the water looppump) are calculated. Numerical results show significant primary energy savings (1.36 TWh/year) andavoided carbon dioxide emissions (348 tCO2/year). From the economic point of view, a feasible simplepay-back period of 4.51 years is achieved. The destroyed exergy of the system components are calculated,obtaining the highest value for the turbo-expander, equal to 12.0 TWh/year
Photovoltaic thermal collectors: Experimental analysis and simulation model of an innovative low-cost water-based prototype
No full textThis paper presents an innovative water photovoltaic thermal collector prototype. One of the main novelties of such system is its economic affordability, obtained through low-cost materials. The collector, constructed and experimentally tested at the University of Patras (Greece), is composed of a polycrystalline photovoltaic module coupled to eleven plastic pipes for water heating, located under the PV panel in an aluminium box. The prototype, suitable for building architectonical integration, can provide domestic hot water and electricity to the building. In order to assess the energy, economic and environmental performance of the system under different weather conditions and for diverse building uses, a suitable dynamic simulation model was developed and validated vs. experimental data. To investigate the convenience of the presented prototype and the potentiality of the developed software, a suitable case study is presented. In particular, the photovoltaic thermal collector is coupled to a stratified hot water storage tank for supplying domestic hot water to a single-family house located in three different European weather zones: Freiburg, Naples and Almeria. The system layout optimization was also performed through an energy and economic sensitivity analysis to some design and operating parameters. Useful design criteria and interesting energy and economic results were obtained
Solar heating and cooling systems for residential applications: a comparison among different system layouts and technologies
No full textA purposely developed dynamic simulation model for different Solar Heating and Cooling (SHC) systems including adsorption and absorption chillers driven by Evacuated Tube solar Collectors (ETC) and Concentrating PhotoVoltaic/Thermal (CPVT) collectors is presented. The modelled system layouts are capable to simultaneously produce electricity, space heating/cooling and domestic hot water. A case study focused on a representative cluster of two buildings, including office and residential spaces, located in cold and temperate European climate zones, is developed. A comprehensive parametric analysis is carried out in order to find out the design and operating conditions for the optimal energy performance of systems
Building to vehicle to building concept toward a novel zero energy paradigm: Modelling and case studies
No full textThis paper proposes and analyses a novel energy management system for buildings connected in a micro-grid, by considering electric vehicles as active components of such energy scheme. Renewable energy sources, PV, energy storage systems and bidirectional electricity exchange with the buildings and the grid are taken into account. The considered energy scheme, Building to Vehicle to Building, is analysed by including both buildings and mobility consumptions in the energy balance. Three different management system scenarios, designed to analyse the role of electric vehicles as electricity vector among buildings integrating PV panels and electrical storages, are analysed through a case study analysis. To this aim, a dynamic simulation model, implemented in MatLab, is suitably developed for the assessment of the energy demands and loads of the building, as a function of the considered electric vehicles energy use patterns. Simulation results show that the proposed energy management systems improves the building grid reliance and the grid electricity consumption is remarkably reduced up to 45% and 77% depending on the proposed scenarios. Their energy exchange options also enhanced the energy-matching indexes. The economic analysis highlights the economic viability of the system, as well as the need of suitable funding policies to support the development of such micro-grid systems
Enhancing trains envelope – heating, ventilation, and air conditioning systems: A new dynamic simulation approach for energy, economic, environmental impact and thermal comfort analyses
No full textNowadays, due also to high hygrothermal comfort requirements, the energy consumption for heating/cooling of modern trains can reach 30% of the related overall electricity demand. Energy-saving of train Heating, Ventilation and Air Conditioning systems can be suitably assessed through dynamic simulation approaches. Specifically, the weather solicitation has to be dynamically accounted for by considering the actual moving train location and orientation. Through such methodology different innovative actions for energy efficiency, environmental impact reduction and comfort enhancement can be analysed by also assessing their economic feasibility. In this paper, a novel simulation tool for the complete performance analysis of trains was developed in TRNSYS environment. To show the capabilities of the considered approach, a novel case study referred to an existing medium-distance train operating in South Italy is presented. Heating/cooling loads and demands, and the related electricity requirements, are dynamically assessed for the standard and revamped train. Several energy saving actions are considered for the coupling between the envelope and the Heating, Ventilation and Air Conditioning systems enhancement. The obtained results return significant benefits in terms of energy saving, avoided CO2 emissions and comfort. Paybacks depend on operating conditions. Useful design and operating criteria for trains manufacturers and users are provided
Dynamic simulations of an adsorption chiller using low-temperature heat from Building Integrated PhotoVoltaic and Thermal system
No full textThis paper is focused on a novel thermo-economic dynamic simulation model for the energy performance analysis of Building Integrated PhotoVoltaic Thermal (BIPVT) system. The investigated BIPVT system is obtained by flat-plate PVT collectors, integrated in the building roof of a typical 3-floors office building, in order to provide Domestic Hot Water (DHW), electricity and space heating/cooling. Space heating is obtained by BIPVT collectors thermal energy supplying a radiant floor system, designed for the top building floor only. Space cooling energy is provided through an adsorption chiller, driven by the low-temperature fluid produced by the BIPVT collectors. The chilled water produced by the adsorption chiller is used to supply a fan coil unit system, installed at third floor of the building. Suitable auxiliary systems for heating and cooling energy integration and DHW production are: electric air-to-water heat pump/chiller, gas-fired condensation boiler. Dynamic simulations were carried out by the simulation model purposely developed in TRNSYS environment in order to analyse the effects due to the use of BIPVT collectors and the adsorption chiller on the building heating and cooling energy demands, on the electricity and DHW production. The obtained results are compared with those of a traditional building considered as reference system. Here, energy demand for DHW, space cooling and heating is achieved by the same auxiliary units, whereas electricity is provided by the national grid. In order to mitigate the effects of intermittency of renewable sources and obtain a virtually grid-independent system, the use of an electrical energy storage system (lead-acid batteries) is also taken into account. A suitable economic analysis is also carried out by calculating the simple payback period, with the aim to evaluate the economic feasibility of the proposed BIPVT system
Experimentation, modelling and applications of a novel low-cost air-based photovoltaic thermal collector prototype
No full textThis paper focuses on the design of an innovative low-cost air-based photovoltaic/thermal collector prototype, for which a novel dynamic simulation model is suitably developed in order to investigate its energy performance and economic feasibility under different operating conditions. The main novelty of this photovoltaic/thermal collector is the low-cost heat extraction system, implemented to reduce the photovoltaic cells temperature and to recover thermal energy. The prototype is tested under different operating conditions and the experimental data are used to validate the presented simulation model. The developed tool, implemented in a MatLab code, is used for analysing a suitable case study. The photovoltaic/thermal collectors are coupled to an air-to-air heat pump for space heating of a sample building. A novel performance map of such a coupled system is built with the aim of linking the heat pump coefficient of performance to both the outdoor air temperature and incident solar radiation. In addition, the system energy effectiveness and economic feasibility, compared to those of a traditional system, are assessed for the climate of 8 different European weather zones. Simulation results highlight the effectiveness of the proposed system, estimating primary energy savings (11.0 - 19.7 MWh/year corresponding to 52 - 80%), avoided carbon dioxide emissions (4.64 - 10.4 tCO2/year), and simple pay-back periods (3.2 - 4.8 years)
Sustainable energy design of cruise ships through dynamic simulations: Multi-objective optimization for waste heat recovery
No full textModern cruise ships are energivorous systems and their design is challenging due to stringent restrictions on the environmental impact recently imposed by the International Maritime Organization. Nowadays, energy saving technologies and strategies for ships can be selected and analysed by means of system dynamic simulations. In this paper this innovative goal is obtained through TRNSYS where the ship-envelope and the related energy system are modelled and simulated by means of new customized weather data with the aim to optimize the system energy performance by considering different objective function (maximum energy saving, minimum payback, etc.). To show the effectiveness of the proposed approach, a novel case study is presented. It refers to a modern cruise ship fuelled by liquefied natural gas cruising in Mediterranean and Caribbean seas. Novel hourly weather files are developed for accounting actual locations and orientations of the moving ship. Low-, medium- and high-temperature engines waste heat recoveries are exploited for supplying different thermally activated energy saving devices. Results of the conducted optimization procedure show significant reductions of fuel consumption (between 0.1 and 1.9 kt/y), operating costs (up to 615 k€/y), and pollutant emissions with respect to traditional systems. Short paybacks are obtained (lower than 5 years), depending on the considered innovative system layouts. Finally, useful design and operating criteria for ship manufacturers and users are provided
A novel dynamic simulation model for the thermo-economic analysis and optimisation of district heating systems
No full textThis paper presents a novel dynamic simulation tool able to assess and optimize the energy, environmental and economic performance of standard and innovative district heating/cooling systems. To this aim, several design and operating parameters (e.g.: weather conditions, heat selling price for users, national unitary price of electricity, etc.) are dynamically taken into account. The heating and cooling demands and loads of the buildings to be fed by the network working fluid are dynamically calculated. The system pipeline network is modelled through a suitable plug-flow approach. Fluid temperatures are calculated in each network node. The optimization of several system design and operating parameters is achieved for different objective functions. A suitable analysis is considered for selecting the most convenient urban zones for system application. The whole simulation model is implemented in a suitable computer code written in MatLab. By such tool useful design criteria and feasibility analyses can be obtained. To show the capabilities of the presented simulation tool, a novel case study, referred to a district heating system supplied by an existing thermoelectric power plant, was developed. The conducted analysis is based on system optimizations focused on the number of users, the selling heat/electricity prices and system geometric features. As for example, for minimizing the system payback to about 14.0 year, the optimal number of users and network length are 5 × 103 and 2.7 km, respectively. In this case the primary energy savings and the avoided carbon dioxide emissions are about 11.0 GWh/y and 16.1 ktCO2/y, respectively
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