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Svend Svendsen - One of the best experts on this subject based on the ideXlab platform.
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Transformation Roadmap from High to Low Temperature District Heating Systems
2020Co-Authors: Helge Averfalk, Svend Svendsen, Hongwei Li, Sven Werner, Clemens Felsmann, Karin Rühling, Robin Wiltshire, Jérôme Faessler, Floriane Mermoud, Loic QuiquerezAbstract:The condensed Transformation Roadmap can be expressed as: 1. Eliminate Temperature errors in existing distribution networks and substations in order to make existing systems more efficient. This will reduce existing Temperature levels. 2. Avoid these Temperature errors in new network parts and in new substations. 3. Use heat exchangers with longer thermal lengths in substations for indirect connection of customer heating systems and closed hot water preparation. This will reduce the Temperature differences between the warmer distribution waters and the colder fluids to be heated. 4. Reduce existing customer Temperature demands by elimination of local Temperature errors, reduction of heat demands by means of energy efficiency measures, and by installation of larger heating surfaces in radiator and ventilation systems. 5. New low Temperature network parts in conjunction with existing systems can be connected by concurrent operation of these parts as secondary networks. 6. The long-term vision is to deliver heat to substations with a supply Temperature of 50°C, while obtaining a Return Temperature of 20°C as annual average. However, the technical solutions for obtaining this low Return Temperature have yet not been defined.
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multi mode control method for the existing domestic hot water storage tanks with district heating supply
Energy, 2020Co-Authors: Tao Huang, Xiaochen Yang, Svend SvendsenAbstract:Abstract The hot water tank is widely used for domestic hot water (DHW) preparation. When supplied by district heating (DH), the operation of DHW tanks directly influences the DH Return Temperature, thereby affecting the DH system efficiency, supply capacity and the realization of the low Temperature district heating. However, the conventional charging method often results in high DH Return Temperature. This study develops a new charging method aiming at reducing the DH Return Temperature without violating the comfort or hygiene requirements. The concept uses the multi-mode charging method considering the periodical characteristics of the load pattern. Multi scenarios are simulated by dynamic models using the practical DHW load profiles from a case study. Moreover, the impacts of the tank configuration, the location of the Temperature sensor, and the distribution heat loss are investigated. The results show that the new control method can reduce the primary Return Temperature by 5–8 °C compared to the conventional control method. The distribution heat loss imposes great impact on the DH Return Temperature. In addition, the tank with the external heat exchanger performs better than the tank with the internal heating coil if the circulation heat loss is less than 50% of the DHW demand.
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Improved Control of Radiator Heating Systems with Thermostatic Radiator Valves without Pre-Setting Function
Energies, 2019Co-Authors: Theofanis Benakopoulos, Robbe Salenbien, Dirk Vanhoudt, Svend SvendsenAbstract:Low-Temperature district heating will play an important role in a future free of fossil fuels. This will only be able to be realized through the low-Temperature operation of heating systems in existing buildings. Existing radiator systems can operate with low Temperatures for most of the year because they are designed for extremely cold days, but errors have to be corrected and the control of the radiator systems needs to be improved. In this paper, we present a strategy to achieve low-Temperature operation from the radiator system of a multi-family building in Denmark without a pre-setting function in the thermostatic radiator valves. The strategy is based on operating the system with a combination of a minimum supply Temperature and small Temperature differences over the radiators. The operation of the system is analyzed through a thermal-hydraulic model. A minimum supply Temperature weather compensation curve was calculated and implemented in the central supply Temperature control. Return Temperature measurements in the substation, the risers, and several critical radiators were performed before and after the implementation of the strategy. The measurements confirm that a lower supply Temperature results in a reduction of the Return Temperature. However, the system operator needs to be supported by a tool package to correctly maintain the system’s operation.
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Improving thermal performance of an existing UK district heat network: a case for Temperature optimization
Energy and Buildings, 2017Co-Authors: Michele Tunzi, Svend Svendsen, Rabah Boukhanouf, Hongwei Li, Anton IanakievAbstract:This paper presents results of a research study into improving energy performance of small-scale district heat network through water supply and Return Temperature optimization technique. The case study involves establishing the baseline heat demand of the estate’s buildings, benchmarking the existing heat network operating parameters, and defining the optimum supply and Return Temperature. A stepwise Temperature optimization technique of plate radiators heat emitters was applied to control the buildings indoor thermal comfort using night set back Temperature strategy of 21/18 °C. It was established that the heat network Return Temperature could be lowered from the current measured average of 55 °C to 35.6 °C, resulting in overall reduction of heat distribution losses and fuel consumption of 10% and 9% respectively. Hence, the study demonstrates the potential of operating existing heat networks at optimum performance and achieving lower Return Temperature. It was also pointed out that optimal operation of future low Temperature district heat networks will require close engagement between the operator and the end user through incentives of mutual benefit.
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Achieving low Return Temperature for domestic hot water preparation by ultra-low-Temperature district heating
Energy Procedia, 2017Co-Authors: Xiaochen Yang, Svend SvendsenAbstract:Abstract District heating (DH) is a cost-effective method of heat supply, especially to area with high heat density. Ultra-low-Temperature district heating (ULTDH) is defined with supply Temperature at 35-45 °C. It aims at making utmost use of the available low-Temperature energy sources. In order to achieve high efficiency of the ULTDH system, the Return Temperature should be as low as possible. For the energy-efficient buildings in the future, it is feasible to use ULTDH to cover the space heating demand. However, considering the comfort and hygiene requirements of domestic hot water (DHW) preparation, supplementary heating devices should be combined, which can affect the Return Temperature in different extents. This study analysed the Return Temperatures of different types of substations for DHW preparation with ULTDH, and developed improvements in the substation for better energy efficiency. Both the instantaneous and storage-type electric heating methods were Long-term measured as supplementary heating for ULTDH in the case substations in Denmark. We analysed the seasonal impacts of the Return Temperature from the DHW loop on the overall Return Temperature of district heating. To achieve lower Return Temperature and higher efficiency for DHW supply, an innovative substation was devised, which replaced the bypass with an instantaneous heat exchanger and a micro electric storage tank. The energy performance of the proposed substation and the resulting benefits for the DH system by the lower Return Temperature were investigated
Alessandro Franco - One of the best experts on this subject based on the ideXlab platform.
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Power production from a moderate Temperature geothermal resource with regenerative Organic Rankine Cycles
Energy for Sustainable Development, 2011Co-Authors: Alessandro FrancoAbstract:Much remains to be done in binary geothermal power plant technology, especially for exploiting low-enthalpy resources. Due to the great variability of available resources (Temperature, pressure, chemical composition), it is really difficult to "standardize the technology".The problem involves many different variables: working fluid selection, heat recovery system definition, heat transfer surfaces sizing and auxiliary systems consumption. Electricity generation from geothermal resources is convenient if Temperature of geothermal resources is higher than 130. °C. Extension of binary power technology to use low-Temperature geothermal resources has received much attention in the last years. This paper analyzes and discusses the exploitation of low Temperature, water-dominated geothermal fields with a specific attention to regenerative Organic Rankine Cycles (ORC). The geothermal fluid inlet Temperatures considered are in the 100-130. °C range, while the Return Temperature of the brine is assumed to be between 70 and 100. °C. The performances of different configurations, two basic cycle configurations and two recuperated cycles are analyzed and compared using dry organic fluids as the working fluids. The dry organic fluids for this study are R134a, isobutane, n-pentane and R245fa. Effects of the operating parameters such as turbine inlet Temperature and pressure on the thermal efficiency, exergy destruction rate and Second Law efficiency are evaluated. The possible advantages of recuperated configurations in comparison with basic configurations are analyzed, showing that in a lot of cases the advantage in terms of performance increase is minimal but significant reductions in cooling systems surface area can be obtained (up to 20%). © 2011 International Energy Initiative.
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optimal design of binary cycle power plants for water dominated medium Temperature geothermal fields
Geothermics, 2009Co-Authors: Alessandro Franco, Marco VillaniAbstract:Abstract Exploitation of lower Temperature, water-dominated geothermal fields is analyzed, and a methodology for optimizing geothermal binary plants is discussed. The geothermal fluid inlet Temperatures considered are in the 110–160 °C range, while the Return Temperature of the brine is assumed to be between 70 and 100 °C. The analysis shows that the brine specific consumption, ranging from 20 to 120 kg s −1 for each net MW produced, and the efficiency of the plants, ranging from 20% to 45% in terms of Second Law efficiency, are dictated mainly by the combination of the brine inlet Temperature, the brine rejection Temperature and the energy conversion cycle being used. For given operating conditions and with correct matching between working fluid and energy conversion cycle, it is possible to obtain very similar performances in a number of different cases. It is shown that optimization of the plant can yield improvements of up to 30–40% in terms of reduction of brine specific consumption compared to conventional design.
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Optimal design of binary cycle power plants for water-dominated, medium-Temperature geothermal fields
Geothermics, 2009Co-Authors: Alessandro Franco, Marco VillaniAbstract:Exploitation of lower Temperature, water-dominated geothermal fields is analyzed, and a methodology for optimizing geothermal binary plants is discussed. The geothermal fluid inlet Temperatures considered are in the 110-160 °C range, while the Return Temperature of the brine is assumed to be between 70 and 100 °C. The analysis shows that the brine specific consumption, ranging from 20 to 120 kg s-1for each net MW produced, and the efficiency of the plants, ranging from 20% to 45% in terms of Second Law efficiency, are dictated mainly by the combination of the brine inlet Temperature, the brine rejection Temperature and the energy conversion cycle being used. For given operating conditions and with correct matching between working fluid and energy conversion cycle, it is possible to obtain very similar performances in a number of different cases. It is shown that optimization of the plant can yield improvements of up to 30-40% in terms of reduction of brine specific consumption compared to conventional design. © 2009 Elsevier Ltd. All rights reserved.
Marco Villani - One of the best experts on this subject based on the ideXlab platform.
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optimal design of binary cycle power plants for water dominated medium Temperature geothermal fields
Geothermics, 2009Co-Authors: Alessandro Franco, Marco VillaniAbstract:Abstract Exploitation of lower Temperature, water-dominated geothermal fields is analyzed, and a methodology for optimizing geothermal binary plants is discussed. The geothermal fluid inlet Temperatures considered are in the 110–160 °C range, while the Return Temperature of the brine is assumed to be between 70 and 100 °C. The analysis shows that the brine specific consumption, ranging from 20 to 120 kg s −1 for each net MW produced, and the efficiency of the plants, ranging from 20% to 45% in terms of Second Law efficiency, are dictated mainly by the combination of the brine inlet Temperature, the brine rejection Temperature and the energy conversion cycle being used. For given operating conditions and with correct matching between working fluid and energy conversion cycle, it is possible to obtain very similar performances in a number of different cases. It is shown that optimization of the plant can yield improvements of up to 30–40% in terms of reduction of brine specific consumption compared to conventional design.
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Optimal design of binary cycle power plants for water-dominated, medium-Temperature geothermal fields
Geothermics, 2009Co-Authors: Alessandro Franco, Marco VillaniAbstract:Exploitation of lower Temperature, water-dominated geothermal fields is analyzed, and a methodology for optimizing geothermal binary plants is discussed. The geothermal fluid inlet Temperatures considered are in the 110-160 °C range, while the Return Temperature of the brine is assumed to be between 70 and 100 °C. The analysis shows that the brine specific consumption, ranging from 20 to 120 kg s-1for each net MW produced, and the efficiency of the plants, ranging from 20% to 45% in terms of Second Law efficiency, are dictated mainly by the combination of the brine inlet Temperature, the brine rejection Temperature and the energy conversion cycle being used. For given operating conditions and with correct matching between working fluid and energy conversion cycle, it is possible to obtain very similar performances in a number of different cases. It is shown that optimization of the plant can yield improvements of up to 30-40% in terms of reduction of brine specific consumption compared to conventional design. © 2009 Elsevier Ltd. All rights reserved.
Janusz Wollerstrand - One of the best experts on this subject based on the ideXlab platform.
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adaptive control of radiator systems for a lowest possible district heating Return Temperature
Energy and Buildings, 2014Co-Authors: P. Lauenburg, Janusz WollerstrandAbstract:Abstract in Undetermined The present paper describes how the control of a radiator system connected to a district heating (DH) network via a heat exchanger can be optimized to provide the lowest possible DH Return Temperature. This can be achieved for each operating point by employing an optimal combination of radiator circuit supply Temperature and circulation flow rate. The control algorithm gradually modifies the control curve for the radiator circuit, enabling it consistently to provide an optimal cooling of the DH water. Since the heat exchanger is dimensioned for very low outdoor Temperatures, it is oversized for smaller heat loads. In addition, radiator systems are often oversized due to safety margins. Such facts render it possible to reduce the DH Return Temperature. The objective of the present study was to develop a control algorithm and to test it in practice. A description is here given of the algorithm, and, additionally, of field tests that were undertaken to practically verify it. The adaptive control method could be implemented in any modern radiator circuit control logics, and the achieved improvement was an added 2 degrees C district heating water cooling, resulting in a 3.5 per cent reduction in average district heating flow. (C) 2014 Elsevier B.V. All rights reserved. (Less)
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Adaptive control of radiator systems for a lowest possible district heating Return Temperature
Energy and Buildings, 2014Co-Authors: P. Lauenburg, Janusz WollerstrandAbstract:The present paper describes how the control of a radiator system connected to a district heating (DH) network via a heat exchanger can be optimized to provide the lowest possible DH Return Temperature. This can be achieved for each operating point by employing an optimal combination of radiator circuit supply Temperature and circulation flow rate. The control algorithm gradually modifies the control curve for the radiator circuit, enabling it consistently to provide an optimal cooling of the DH water. Since the heat exchanger is dimensioned for very low outdoor Temperatures, it is oversized for smaller heat loads. In addition, radiator systems are often oversized due to safety margins. Such facts render it possible to reduce the DH Return Temperature. The objective of the present study was to develop a control algorithm and to test it in practice. A description is here given of the algorithm, and, additionally, of field tests that were undertaken to practically verify it. The adaptive control method could be implemented in any modern radiator circuit control logics, and the achieved improvement was an added 2 C district heating water cooling, resulting in a 3.5 per cent reduction in average district heating flow. © 2014 Elsevier B.V.
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Optimum performance of radiator space heating systems connected to achieve lowest possible district heating Return Temperature
The 10th International Symposium on District Heating and Cooling, 2006Co-Authors: Patrick Ljunggren, Janusz WollerstrandAbstract:The cooling of primary water in district heating substations is largely influenced by the existing oversizing of space heating systems and its components. Performed simulations show that it is possible, with measurements of Temperatures and energy consumption, to estimate the actual oversizing of the space heating system in a specific building and, from that information, to control the supply Temperature in the system for highest possible cooling of primary water at all loads. Full optimization is possible if the indoor air Temperature can be measured or estimated with sufficient accuracy. Control of an oversized space heating system using the low circulation flow method, as well as low Temperature adjustment, results in approximately 12°C improved cooling of the primary water. Further optimization of a low Temperature adjusted system can produce another 3-4°C increased cooling. Even a perfectly sized system can be flow optimized with a gain corresponding to almost 2°C.
P. Lauenburg - One of the best experts on this subject based on the ideXlab platform.
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IMPROVED SUPPLY OF DISTRICT HEAT TO HYDRONIC SPACE HEATING SYSTEMS
2020Co-Authors: P. LauenburgAbstract:The studies presented in this thesis concern hydronic space heating systems connected via heat exchangers to a district heating network: referred to as an indirect connection. The objective has been to improve the reliability of district heat supplies and to lower the Return Temperature from consumer substations. Two of the disadvantages of an indirect connection have been addressed: the thermodynamic loss and the local dependency on electricity involved during the use of a heat exchanger. The results show that the influence of these disadvantages can be reduced by employing several variants of so-called low-flow procedures in hydronic heating systems. Concerning the reliability of district heat supplies, the present work has led to new knowledge regarding the dependence of the district heating technology on electricity. A substantial heat supply can be maintained in numerous buildings in case of an electric power failure since natural circulation can be expected to take place in the heating systems. A turbine-driven circulation pump has the potential to further reduce the dependence on electricity. Concerning a low Return Temperature from consumer substations, which is a key performance measure for district heating substations, a new method for the control of the heating system has demonstrated a potential of reducing the district heating Return Temperature. The method involves the control of both the supply Temperature and the flow rate in the heating system. The possibility of achieving a low Return Temperature from different connection schemes of the substation has also been studied. (Less)
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Små värmekällor
Fjärrsyn for Svensk Fjärrvärme, 2016Co-Authors: Gunnar Lennermo, P. Lauenburg, Lisa BrangeAbstract:There is a huge potential to supply district heating systems with heat from small, distributed sources such as industrial surplus heat, solar thermal systems, crematories and cooling machines in offices, sport facilities and grocery stores. Prosumer is a concept that is becoming more and more common in order to describe a district heating customer that both buys and sells district heat. The district heating companies own peak load and reserve boilers are also interesting from the point of view of this study which deals with how feed-in of heat into the district heating network from a prosumer best is done. Many small heat sources have shown problems with variations in the feed-in flow. This can have a direct negative influence on the heat source’s performance – e.g. solar collectors. In a future scenario where distributed generation makes up a significant contribution to district heating, local feed-in must function satisfactorily. The objective of this study has been to examine why there are variations in the feed-in systems and how they can be avoided. The two most common variants of local feed-in is Return/Return (R/R) and Return/supply (R/S) which means that district heating water is withdrawn from the Return pipe, heated by the local heat source and then fed back into the district heating system’s Return or supply pipe. R/R is less complex but has several drawbacks, mainly that it increases the Return Temperature in the district heating system. R/S is generally the more applicable choice but it is also more complex to control. It is in R/S systems that variations in feed-in flow have been observed and the reason is the control system’s inability to account for that the largest pressure resistance to be overcome in the feed-in circuit is the differential pressure in the district heating network. The differential pressure is not dependant of the feed-in flow which means that once this pressure difference is overcome, the feed-in flow easily becomes too big. The bigger the differential pressure and the smaller the local heat source the bigger the risk for this course of events. TheThe basic principle, which is rather obvious, is that the feed-in heat power must match the available heat power. Unless a storage is used, which is generally to be avoided for practical and economic reasons, this can be done in two different ways: either through a flow-controlled or a Temperature-controlled system. In a flow-controlled system no short circuit flow (shunt) is used between the Return and supply pipe. The feed-in flow is controlled by the feed-in pump with or without assistance from a two-way valve in series with the pump. In a Temperature-controlled system there is a short circuit pipe which must never be closed, or else it will work as a flow-controlled system. The speed of the feed-in pump is controlled via a setpoint curve with the differential pressure used as input. Since the differential pressure is relatively big and constant (from a short time perspective), it is easier to balance the flow using a two-way valve rather than a tree-way valve in the short circuit. Heat sources which demand a given Return Temperature, or which cannot increase the Temperature the whole way can be connected using Temperature-control while heat sources which shall work with a Temperature as low as possible or be cooled as far as possible can be connected using flow-control, possibly with a Temperature-controlled start-up phase.
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adaptive control of radiator systems for a lowest possible district heating Return Temperature
Energy and Buildings, 2014Co-Authors: P. Lauenburg, Janusz WollerstrandAbstract:Abstract in Undetermined The present paper describes how the control of a radiator system connected to a district heating (DH) network via a heat exchanger can be optimized to provide the lowest possible DH Return Temperature. This can be achieved for each operating point by employing an optimal combination of radiator circuit supply Temperature and circulation flow rate. The control algorithm gradually modifies the control curve for the radiator circuit, enabling it consistently to provide an optimal cooling of the DH water. Since the heat exchanger is dimensioned for very low outdoor Temperatures, it is oversized for smaller heat loads. In addition, radiator systems are often oversized due to safety margins. Such facts render it possible to reduce the DH Return Temperature. The objective of the present study was to develop a control algorithm and to test it in practice. A description is here given of the algorithm, and, additionally, of field tests that were undertaken to practically verify it. The adaptive control method could be implemented in any modern radiator circuit control logics, and the achieved improvement was an added 2 degrees C district heating water cooling, resulting in a 3.5 per cent reduction in average district heating flow. (C) 2014 Elsevier B.V. All rights reserved. (Less)
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Adaptive control of radiator systems for a lowest possible district heating Return Temperature
Energy and Buildings, 2014Co-Authors: P. Lauenburg, Janusz WollerstrandAbstract:The present paper describes how the control of a radiator system connected to a district heating (DH) network via a heat exchanger can be optimized to provide the lowest possible DH Return Temperature. This can be achieved for each operating point by employing an optimal combination of radiator circuit supply Temperature and circulation flow rate. The control algorithm gradually modifies the control curve for the radiator circuit, enabling it consistently to provide an optimal cooling of the DH water. Since the heat exchanger is dimensioned for very low outdoor Temperatures, it is oversized for smaller heat loads. In addition, radiator systems are often oversized due to safety margins. Such facts render it possible to reduce the DH Return Temperature. The objective of the present study was to develop a control algorithm and to test it in practice. A description is here given of the algorithm, and, additionally, of field tests that were undertaken to practically verify it. The adaptive control method could be implemented in any modern radiator circuit control logics, and the achieved improvement was an added 2 C district heating water cooling, resulting in a 3.5 per cent reduction in average district heating flow. © 2014 Elsevier B.V.