District Heating Network Modelling for the Analysis of Low-Exergy Sources

2017 ◽  
Author(s):  
Vittorio Verda ◽  
Elisa Guelpa
Keyword(s):  
Power Plants ◽  
Waste Heat ◽  
Fluid Dynamic ◽  
Renewable Energy Sources ◽  
Variable Mass ◽  
District Heating ◽  
Conservation Equation ◽  
Operating Conditions ◽  
Heat Sources ◽  
District Heating System

One of the main advantages of district heating system technology is the possibility of integrating multiple heat sources for domestic heating. In particular, it is often possible exploit low-exergy sources, such as waste heat recovered from industry or from renewable energy sources, that are often affected by time variation of the temperature. A very convenient and useful opportunity for predicting and analyzing district heating network behavior is modelling. Modelling allows to quantify opportunities related to changes in DH (district heating) network design or management, before real implementation. Therefore an important point is the creation of models able to simulate network, also very large and linked to many power plants, working at variable heat production conditions (i.e. variable mass flow rates and temperatures). The goal of this work is to propose a novel approach which combines exergy analysis with a DH network model for evaluating the best DH operating conditions. A thermo-fluid dynamic model based on conservation equation has been adapted for the discussed aims and applied to a network involving different low-exergy heat sources with variable temperatures. An evaluation of the implementation of these sources is provided for the Turin district heating network, which is the largest network in Italy.

scholarly journals Analysis of Different Strategies for Lowering the Operation Temperature in Existing District Heating Networks

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 321 ◽  
Author(s):  
Francesco Neirotti ◽  
Michel Noussan ◽  
Stefano Riverso ◽  
Giorgio Manganini
Keyword(s):  
Energy Efficiency ◽  
Power Plants ◽  
Waste Heat ◽  
Control Strategies ◽  
Renewable Energy Sources ◽  
District Heating ◽  
Heating System ◽  
Heat Pumps ◽  
Critical Parameters ◽  
District Heating System

District heating systems have an important role in increasing the efficiency of the heating and cooling sector, especially when coupled to combined heat and power plants. However, in the transition towards decarbonization, current systems show some challenges for the integration of Renewable Energy Sources and Waste Heat. In particular, a crucial aspect is represented by the operating temperatures of the network. This paper analyzes two different approaches for the decrease of operation temperatures of existing networks, which are often supplying old buildings with a low degree of insulation. A simulation model was applied to some case studies to evaluate how a low-temperature operation of an existing district heating system performs compared to the standard operation, by considering two different approaches: (1) a different control strategy involving nighttime operation to avoid the morning peak demand; and (2) the partial insulation of the buildings to decrease operation temperatures without the need of modifying the heating system of the users. Different temperatures were considered to evaluate a threshold based on the characteristics of the buildings supplied by the network. The results highlight an interesting potential for optimization of existing systems by tuning the control strategies and performing some energy efficiency operation. The network temperature can be decreased with a continuous operation of the system, or with energy efficiency intervention in buildings, and distributed heat pumps used as integration could provide significant advantages. Each solution has its own limitations and critical parameters, which are discussed in detail.

Reduction of Primary Energy Consumption Through Distributed Thermal Storage in Buildings Connected With a District Heating Network

2014 ◽  
Author(s):  
Giorgia Baccino ◽  
Sara Cosentino ◽  
Elisa Guelpa ◽  
Adriano Sciacovelli ◽  
Vittorio Verda
Keyword(s):  
Energy Consumption ◽  
Thermal Load ◽  
Waste Heat ◽  
Distributed Storage ◽  
Fluid Dynamic ◽  
District Heating ◽  
Thermal Storage ◽  
Primary Energy ◽  
Operating Conditions ◽  
Primary Energy Consumption

One of the possible options for increasing the primary energy efficiency in district heating networks (DHNs) consists in flattening the thermal load diagram of the plants. This can be obtained through thermal storage. Storage generally allows one to increase the percentage of heat produced through CHP plants, waste heat or renewable systems. In this work, a numerical approach to analyze possible effects of distributed storage on the primary energy consumption is presented. This is based on the availability of detailed information about the thermal substations that connect the users to the DHN and a thermo-fluid dynamic model of the network. First, the analysis of a user of the district heating network is proposed in order to show the operating conditions of the heat exchanger in the thermal substation. Then the model of the network is presented and an application is proposed. This application allows us to discuss how the thermal request of a user modifies along the network because of the heat capacity of the network itself and mixing with the mass flow rates at different temperatures. Therefore, the thermal load that the plants should fulfill is different than the simple summation of the thermal request of the users. This tool allows one to link the thermal thermal request of the users to the thermal load of the plant and thus to the global primary energy consumption. It can be then applied to the evaluation of possible variation of thermal request profile of the users.

Development of a Design Approach for the Optimization of Steam Turbine Exhaust System Performance Through CFD Modelling

2021 ◽  
Author(s):  
Tommaso Diurno ◽  
Stella Grazia Tomasello ◽  
Tommaso Fondelli ◽  
Antonio Andreini ◽  
Bruno Facchini ◽  
...  
Keyword(s):  
Power Plants ◽  
Fluid Dynamic ◽  
Renewable Energy Sources ◽  
Computational Cost ◽  
Great Influence ◽  
Computational Effort ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Geometrical Parameters ◽  
Exhaust Hood

Abstract Nowadays, the ever-increasing world electricity generation by renewable energy sources has brought about changes in conventional power plants, especially in those ones where large steam turbines work, which were widely used to meet the world’s energy needs by operating mostly at fixed conditions. Now, instead, they have to be capable to operate with greater flexibility, including rapid load changes and quick starts as well, in order to make the most of the renewable resources while guaranteeing the coverage of any shortcomings of the latter with traditional fossil fuel systems. Such service conditions are particularly challenging for the exhaust hoods, which have a great influence on the overall turbine performance, especially at off-design conditions. In fact, the complex and high rotational 3D flow generated within the diffuser and the exhaust hood outer casing can cause an increase in aerodynamic losses along with the detriment of the hood recovery performance. For these reasons, an optimized design and adequate prediction of the exhaust hood performance under all the machine operating conditions is mandatory. Since it has been widely proven that the exhaust hood flow strongly interacts with the turbine rear stage, the necessity to model this as well into a CFD modeling becomes crucial, requiring a remarkable computational effort, especially for full transient simulations. Even if adopting simplified approaches to model the last stage and exhaust hood interfaces, such as the so-called Frozen Rotor and the Mixing Plane ones, helps to keep the computational cost low, it can be not for an exhaust hood optimization process, which requires a significant number of CFD simulations to identify the most performing geometry configuration. For these reasons, a simplified model of the exhaust hood must be adopted to analyse all the possible design variants within a feasible time. The purpose of this work is to present a strategy for the exhaust hood design based on the definition of a simplified CFD model. A parametric model has been developed as a function of key geometrical parameters of both the exhaust hood and the diffuser, taking into account the strong fluid-dynamic coupling between these components. A periodic approximation has been introduced to model the exhaust hood domain, thus allowing to augment the number of the geometrical parameters of the DOE, while keeping the computational effort low. A response surface has been achieved as a function of the key geometrical parameters, therefore an optimization method has allowed identifying the best performing configuration. A 3D model of the optimized periodic geometry has been then generated to assess the effectiveness of the procedure here presented. Finally, the presented procedure has been applied in several off-design operating conditions, in order to find out an optimal geometry for each operating point, evaluating how much they differ from that one got for the design point.

Pumping Cost Minimization in an Existing District Heating Network

2013 ◽  
Author(s):  
Adriano Sciacovelli ◽  
Elisa Guelpa ◽  
Vittorio Verda
Keyword(s):  
Control Strategy ◽  
Urban Areas ◽  
Cost Minimization ◽  
Fluid Dynamic ◽  
District Heating ◽  
Primary Energy ◽  
Operating Conditions ◽  
Waste To Energy ◽  
District Heating System ◽  
Partial Load

District heating is expected to significantly contribute to the reduction of primary energy needs for heating in urban areas. This result is obtained through use of such as CHP systems, residual heat from industries or waste-to-energy plants, as well as the integration of renewable energies. The pumping system plays a crucial role and may significantly affect its performances. In this paper a large district heating system is considered. Various operating conditions corresponding with partial load operation are analyzed through a thermo-fluid dynamic model of the network. For each condition, the optimal set point of the various pumps is obtained. The set of optimal operating conditions is finally used to obtain a control strategy for the network. Results show that with respect to conventional control strategy significant reductions in primary energy consumption can be achieved.

Thermal Storage Systems for District Heating Networks

2010 ◽  
Author(s):  
Vittorio Verda ◽  
Francesco Colella
Keyword(s):  
Electricity Market ◽  
Thermal Load ◽  
Storage Systems ◽  
Fluid Dynamic ◽  
District Heating ◽  
Heating System ◽  
Maximum Load ◽  
Operating Conditions ◽  
District Heating System ◽  
The Impact

District Heating is an efficient way to provide heat to residential, tertiary and industrial users. Heat is often produced by CPH plants, usually designed to provide the base thermal load (40–50% if the maximum load) while the rest is provided by boilers. This choice is made on the basis of economic criteria, in fact the investment cost of a CHP plant is much higher than the cost of boiler, thus its use is convenient when it operates for a large number of hours. The use of storage tanks would permit to increase the annual operating hours of CHP: heat can be produced when the request is low (for instance during the night), stored and then used when the request is high. The use of boilers results partially reduced, thus the thermal load diagram is flattered. Depending on the type of CHP plant this may also affect the electricity generation. All these considerations are crucial in the free electricity market. In this paper, the use of storage systems connected to the district heating systems, is examined. A thermo fluid dynamic model of the tanks is considered in order to calculate the amount of energy actually provided, taking the real operating conditions into account. These considerations are applied to the Turin district heating system, in order to determine the impact of storage systems on the primary energy consumption required to supply heat to the users over the entire heating season.

scholarly journals Possibilities of Using Industrial Waste Heat for Heating Greenhouses in Northern Greece

2018 ◽  
Vol 10 (4) ◽  
pp. 116 ◽  
Author(s):  
John Vourdoubas
Keyword(s):  
Industrial Waste ◽  
Heat Recovery ◽  
Power Plants ◽  
Waste Heat ◽  
District Heating ◽  
Economic Benefits ◽  
Hot Water ◽  
Northern Greece ◽  
District Heating System ◽  
Industrial Waste Heat

The possibility of using the rejected heat from lignite-fired power plants for heating greenhouses in northern Greece has been examined. Although currently industrial waste heat is used for district heating in a few towns in Greece, its use in agriculture has not been reported so far. Due to many environmental and economic benefits symbiosis of industrial and agricultural activities is promoted in many countries. Greenhouses in northern Greece utilize mainly natural gas as heating fuel. However heat recovery from the existing power plants and its use in greenhouses could increase their energy efficiency and reduce the thermal pollution. It will also decrease the use of fossil fuels in greenhouses and the resulting carbon emissions as well. Their heating requirements have been estimated at 170 W/m2 and the required hot water temperatures are 50-60 oC below the required water temperature in district heating systems, at 120 oC. Currently the price of heat sold in the district heating system in the town of Kozani is 0.0435 €/KWh, which is very attractive for heating greenhouses compared with other existing methods or fuels. It has been estimated that the heat recovery from the power plants at 70 MWth could cover the heating needs of 41.2 ha of modern agricultural greenhouses in northern Greece. Recycling of industrial waste heat in greenhouses in northern Greece, apart from the resulting environmental benefits, will offer a competitive advantage, increasing the profitability of those enterprises.

scholarly journals Analysis of renewable energy sources and a heat storage tank application in a district heating substation

2021 ◽  
Vol 323 ◽  
pp. 00006
Author(s):  
Kamil Chłosta ◽  
Wiesław Zima
Keyword(s):  
Renewable Energy ◽  
Storage Tank ◽  
Heat Storage ◽  
Renewable Energy Sources ◽  
District Heating ◽  
Operating Conditions ◽  
Energy Sources ◽  
Heat Sources ◽  
Water Parameters ◽  
Air Source Heat Pump

The study verifies the potential application of renewable energy sources in a district heating substation. Different operating configurations of heat sources have been analysed, including solar collectors, PV panels and air source heat pump. Concepts of regulating the water parameters in a substation have been analysed. Moreover, the potential impact of a heat storage tank application has been calculated using a genetic algorithm to find optimal operating conditions in a district heating substation. The analysis is based on measured yearly data.

Meanline Analysis and CFD Study of a Radial Inflow Turbine With Vaneless Distributor for Low Temperature Organic Rankine Cycle

2020 ◽  
Author(s):  
M. Deligant ◽  
S. Braccio ◽  
T. Capurso ◽  
F. Fornarelli ◽  
M. Torresi ◽  
...  
Keyword(s):  
Energy Demand ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Low Grade ◽  
Heat Sources ◽  
Turbine Wheel ◽  
Good Efficiency ◽  
Low Grade Heat

Abstract The Organic Rankine Cycle (ORC) allows the conversion of low-grade heat sources into electricity. Although this technology is not new, the increase in energy demand and the need to reduce CO2 emissions create new opportunities to harvest low grade heat sources such as waste heat. Radial turbines have a simple construction, they are robust and they are not very sensitive to geometry inaccuracies. Most of the radial inflow turbines used for ORC application feature a vaned nozzle ensuring the appropriate distribution angle at the rotor inlet. In this work, no nozzle is considered but only the vaneless gap (distributor). This configuration, without any vaned nozzle, is supposed to be more flexible under varying operating conditions with respect to fixed vanes and to maintain a good efficiency at off-design. This paper presents a performance analysis carried out by means of two approaches: a combination of meanline loss models enhanced with real gas fluid properties and 3D CFD computations, taking into account the entire turbomachine including the scroll housing, the vaneless gap, the turbine wheel and the axial discharge pipe. A detailed analysis of the flow field through the turbomachine is carried out, both under design and off design conditions, with a particular focus on the entropy field in order to evaluate the loss distribution between the scroll housing, the vaneless gap and the turbine wheel.

scholarly journals Methodology for the Improvement of Large District Heating Networks

2012 ◽  
Vol 10 (1) ◽  
pp. 39-45 ◽  
Author(s):  
Anna Volkova ◽  
Vladislav Mashatin ◽  
Aleksander Hlebnikov ◽  
Andres Siirde
Keyword(s):  
Heat Generation ◽  
Large Scale ◽  
Renewable Energy Sources ◽  
District Heating ◽  
Heating System ◽  
District Heating System ◽  
Effective Operation ◽  
The Cost ◽  
Heating Networks

Abstract The purpose of this paper is to offer a methodology for the evaluation of large district heating networks. The methodology includes an analysis of heat generation and distribution based on the models created in the TERMIS and EnergyPro software Data from the large-scale Tallinn district heating system was used for the approbation of the proposed methodology as a basis of the case study. The effective operation of the district heating system, both at the stage of heat generation and heat distribution, can reduce the cost of heat supplied to the consumers. It can become an important factor for increasing the number of district heating consumers and demand for the heat load, which in turn will allow installing new cogeneration plants, using renewable energy sources and heat pump technologies

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