Svend Svendsen

Svend Svendsen
Technical University of Denmark | DTU · Department of Civil Engineering

MSc in Civil Eng., PhD

About

184
Publications
45,197
Reads
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6,175
Citations
Citations since 2016
58 Research Items
4858 Citations
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
Additional affiliations
July 1974 - present
Technical University of Denmark
Position
  • Professor (Full)

Publications

Publications (184)
Article
With regard to the green transition toward 4th generation district heating (4GDH), a critical element is ensuring low operating temperatures in networks. This can help leverage the technical and economic potential of connecting renewable energy sources and recovering excess local heat. Poorly controlled and operated heating systems in existing buil...
Article
Full-text available
Storage tanks are commonly used for domestic hot water (DHW) preparation in large buildings supplied by district heating (DH), especially to cope with peak demand. The charging control of DHW tank systems is often suboptimal, increasing return temperatures and harming the overall DH operation efficiency. This paper presents two novel control concep...
Article
Full-text available
The digitalization of the demand side increased significantly in the last few years. This was mainly due to the impulse of the European Energy Efficiency Directive (EED 2012/2018), binding member states to have all energy meters remotely readable by January 2027. In collaboration with the Danish industrial partners and the local district heating (D...
Article
Future low-temperature district heating systems (LTDH) require supply and return temperatures as low as 55 °C and 25 °C, respectively. In this direction, the use of night setbacks in heating of office buildings is a problem. This article investigated in a typical office building with large distribution system by tests and simulations the energy and...
Article
Low-temperature district heating (LTDH) networks can integrate sustainable energy sources and waste industrial heat towards decarbonisation goals by 2050. LTDH networks can be realised through the low-temperature operation of heating systems in buildings. However, the low-temperature operation of heating systems is obstructed by inefficient radiato...
Article
Modernization of the existing district heating systems is a necessary activity to improve their energy efficiency in the field of generation, distribution and use of the heat. This paper presents the results of several years of field research carried out for 13 multi-family buildings supplied from the district heating network. The benefits associat...
Article
Full-text available
District heating networks increasingly rely on heat pumps, condensing biomass boilers, and excess heat in the transition to sustainable energy systems. Accordingly, district heating operators seek to reduce their networks’ supply and return temperatures to maximise production efficiencies, minimise heat losses from distribution pipes and allow grea...
Article
Full-text available
Automated hydronic balancing in space heating systems is crucial for the fourth-generation district heating transition. The current manual balancing requires labor- and time-consuming activities. This article presents the field results of an innovative electronic radiator thermostat tested on two Danish multi-family buildings. The prototypes had an...
Article
Full-text available
With international awareness of the need to decrease greenhouse gas emissions, the Danish government set a target to be fossil fuel-free by 2050. To achieve that, existing buildings will need to be retrofitted with energy-saving technologies such as improved thermal insulation. In Denmark, a larger mass of the building stock from around 1850 to the...
Article
Full-text available
The study proposed and investigated a new concept for hydronic floor heating in dwellings with the aim of reducing hot water temperatures toward a more robust and energy efficient operation. Modern heating systems often rely on low return temperatures to improve operation efficiencies through reduced heat losses from return pipes, greater utilisati...
Article
With increasing focus on the performance of district heating systems, a concept is developed to obtain low district heating return temperatures from domestic hot water systems with a high share of circulation loss. For these systems, it is challenging to realize a low district heating return temperature by direct heat exchange only, due to the high...
Technical Report
Full-text available
Edited by Kristina Lygnerud and Sven Werner This guidebook was written between 2018 and 2021 by seventeen authors that used approximately 15 000 hours of work within the IEA DHC TS2 annex. The content is based on more than 250 literature references and 165 inspiration initiatives to obtain lower temperatures in buildings and heat distribution netw...
Article
Full-text available
The operation of typical domestic hot water (DHW) systems with a storage tank and circulation loop, according to the regulations for hygiene and comfort, results in a significant heat demand at high operating temperatures that leads to high return temperatures to the district heating system. This article presents the potential for the low-temperatu...
Article
The low-temperature operation of existing radiator systems connected to district heating is hindered by various factors, including non-ideal local control by users. The use of only a few of the available radiators to provide the necessary thermal comfort in an apartment is a common example. This requires a higher supply temperature and results in a...
Article
In order to reach targeted 4th generation district heating temperatures around 55 °C supply and 25 °C return, it is necessary to ensure that heating installations inside buildings are designed and operated properly. In this study we investigated the best-case of current design and operation of building installations with the aim of identifying whet...
Article
Full-text available
Industrial exhausted heat can be used as the heat source of central heating for higher energy efficiency. To recover more industrial exhausted heat, a new low-temperature central heating system integrated with industrial exhausted heat using distributed electric compression heat pumps is put forward and analyzed from the aspect of thermodynamics an...
Article
Full-text available
This study investigated a double loop network operated with ultra-low supply/return temperatures of 45/25 °C as a novel solution for low heat-density areas in Denmark and compared the proposed concept with a typical tree network and with individual heat pumps to each end-users rather than district networks. It is a pump-driven system, where the sep...
Article
Thermal treatment for sterilising domestic hot-water systems requires a circulation temperature higher than 50 oC, which is not suitable for low-temperature district heating systems. Chemical treatment is a temperature-independent sterilisation method for hot-water systems. This study demonstrates that the heat exchanger-based domestic hot-water sy...
Article
In the district heating (DH) systems, the thermal storage tank is widely used for domestic hot water (DHW) preparation to shave the peak load. Compared to the space heating, the domestic hot water demand exists for all seasons, and the variation of which is more dramatic within short time span. Therefore, the well-controlled storage tank is of grea...
Article
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 meth...
Technical Report
Full-text available
The IEA EBC Annex 64 – LowEx Communities was a three year international research project which aims to demonstrate the potentials of low exergy thinking on a community level as energy and cost efficient solutions to achieve 100 % renewable and GHG emission-free energy systems. Central challenges are the identification of promising and efficient tec...
Article
Full-text available
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 e...
Article
This paper aims to provide an overview of the costs and benefits of preparing existing space heating systems for low-temperature district heating. Necessary heating system improvements were assessed based on previous work carried out on the topic. This included evaluating the necessity of installing larger heating elements and improving heating sys...
Article
Proper heating system operation in buildings is a vital area for the realization of low-temperature district heating with supply and return temperatures of 55 °C and 25 °C respectively. But the operating area of the district heating companies usually only extends to the substations at the entry of the buildings, and very little is known about the a...
Article
This study analyses the heat load in a total of 11,584 rooms in 1645 Danish houses and the heat output of the radiators in them to evaluate whether typical radiators are over-dimensioned. The aim was to find out whether radiators in existing houses are suited for low-temperature district heating. We found that new houses are generally more likely t...
Article
This review article presents a description of contemporary developments and findings related to the different elements needed in future 4th generation district heating systems (4GDH). Unlike the first three generations of district heating, the development of 4GDH involves meeting the challenge of more energy efficient buildings as well as the integ...
Article
Low temperature district heating (DH) system gives easier access to the renewable energy as heat sources and improves the heat distribution efficiency. From the exergy point of view, low DH supply temperature also better matches the exergy demand of space heating and domestic hot water. It is more beneficial to operate district heating system under...
Article
The efficiency of district heating systems is greatly affected by network supply and return temperatures. However, the opportunities to lower the temperatures and thereby increase network efficiency are restricted by customer installations. Very little is known about the customer installations, because heating system operation is only rarely monito...
Code
This Excel add-in involving of user-defined-functions that calculate the friction pressure loss in circular pipes with full flow water, with options to select through different solver types ('Darcy-Weisbach' or 'Hazen-Williams') and various Darcy friction factor algorithms ('Moody', 'Colebrook-White', 'Clamond', 'Swamee-Jain', 'Zigrang-Sylvester',...
Code
This Matlab tool calculates the friction pressure loss in circular pipes with full flow water, with options to select through different solver types ('Darcy-Weisbach' or 'Hazen-Williams') and various Darcy friction factor algorithms ('Moody', 'Colebrook-White', 'Clamond', 'Swamee-Jain', 'Zigrang-Sylvester', and 'Haaland'). Besides, there are othe...
Article
Full-text available
The large price drop in solar PV and electrical batteries offer new opportunities for optimizing district energy plants, but requires a more complex daily operation of these plants. Solar PV production used locally by a ground source heat pump (GSHP) with a minimal use of the national grid is one opportunity. Even if, for the benefit of the GSHP, t...
Article
The renovation of single-family houses in Denmark is progressing only slowly. Changes in current policy are needed if the political goal of a fossil-free building sector as part of a fossil-free society is to be achieved. Known barriers and motivators for energy renovation are identified, and arranged in a framework with three main fields (Informat...
Article
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...
Article
Full-text available
District heating is predicted to play a large role in the future fossil free energy system. Apart from providing energy savings by utilizing surplus heat, the district heating system also provides flexibility to fluctuating electricity generation by bridging the electricity and the heating sector. These benefits can be maximized if district heating...
Article
Full-text available
The building sector is responsible for more than one third of the final energy consumption of societies and produces the largest amount of greenhouse gas emissions of all sectors. This is due to the utilisation of combustion processes of mainly fossil fuels to satisfy the heating demand of the building stock. Low temperature district heating (LTDH)...
Article
Full-text available
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 t...
Article
Building renovation is too often carried out with only one objective: necessary maintenance, updating design and functions, or reducing energy consumption. But, if a necessary maintenance is exploited as an opportunity for renovation, energy improvements can be implemented, house functions can be updated, and indoor climate improved with minimal nu...
Article
One way of reducing the use of fossil fuels in Denmark is to explore possible energy savings in the building stock, especially the large number of single-family houses built from 1960 through 1980. Energy renovation in this housing segment is progressing slowly. The aim of this project was to determine how a one-stop-shop (OSS) or full-service conc...
Article
Full-text available
Roof windows are efficient and flexible daylight sources that are essential in certain types of houses if they are to achieve sufficient daylighting throughout. Previous studies have indicated that, for such buildings to meet nearly zero-energy targets in an easy and robust way without compromising on daylighting and thermal comfort, the thermal pr...
Article
Densely occupied spaces such as classrooms can very often have problems with overheating. It can be difficult to cool such spaces by means of a ventilation system without creating draughts and causing discomfort for occupants. The use of a wall radiant cooling system is a suitable option for spaces with a high occupant density. Radiant systems can...
Article
The development of DH (District Heating) is an environmentally friendly and energy-efficient strategy in China. Currently, the vast majority of DH systems are SH (Space Heating) only and do not provide DHW (Domestic Hot Water). DHW is mainly produced by individual water heaters due to the cost-effective issues of the centralized DHW systems. From t...
Article
Full-text available
Dynamic solar shading is commonly suggested as a means of reducing the problem of overheating in well-insulated residential buildings, while at the same time letting daylight and solar irradiation in when needed. To critically investigate what dynamic shading can and cannot do compared to permanent alternatives in buildings with very low space-heat...
Article
This study presents a method to adapt existing hydronic systems in buildings to take advantage of low temperature district heating (LTDH). Plate radiators connected to double string heating circuits were considered in an optimization procedure, based on supply and return temperatures, to obtain the required logarithmic mean temperature difference (...
Conference Paper
Full-text available
Current research and development shows that it is technical feasible to change high/medium temperature district heating system to low temperature district heating system for both new and existing building areas. We collect and identify promising technologies in low-temperature district heating application to meet the goals of future renewable based...
Conference Paper
District heating is predicted to play a large role in the future fossil free energy system. Apart from providing energy savings by utilizing surplus heat, the district heating system also provides flexibility to fluctuating electricity generation by bridging the electricity and the heating sector. These benefits can be maximized if district heating...
Article
This study investigated the performances of five different substation configurations in single-family houses supplied with ULTDH (ultra-low-temperature district heating). The temperature at the heat plant is 46 °C and around 40 °C at the substations. To avoid the proliferation of Legionella in the DHW (domestic hot water) and assure the comfortable...
Article
Hydraulic unbalance is a common problem in Chinese district heating (DH) systems. Hydraulic unbalance has resulted in poor flow distribution among heating branches and overheating of apartments. Studies show that nearly 30% of the total heat supply is being wasted in Chinese DH systems due to a lack of pressure and flow control. This study investig...
Article
A common problem with Chinese district heating systems is that they supply more heat than the actual heat demand. The reason for this excess heat supply is the general failure to use control devices to adjust the indoor temperature and flow in the building heating systems in accordance with the actual heat demand. This results in 15–30% of the tota...
Conference Paper
Full-text available
By introducing better interfaces between the demand and supply, district heating and cooling (DHC) systems can be transformed into a smart grid energy system on a district level. In the IEA DHC Annex TS1 project, the Subtask C collects and identifies promising models, concepts, and technologies to meet the goals of future renewable based community...
Article
Low-temperature district heating is a promising technology for providing homes with energy-efficient heating in the future. However, it is of great importance to maintain thermal comfort in existing buildings when district heating temperatures are lowered. This case study evaluated the actual radiator sizes and heating demands in 4 existing Danish...
Article
Low-temperature heating provides an efficient way of heating our buildings. To obtain a high efficiency it is important that the heating systems in the buildings are operated with both low supply and return temperatures. This study set out to investigate how typical assumptions in the modelling of heat emissions from existing hydraulic radiators af...
Article
As existing buildings are renovated and energy-efficiency measures are implemented to meet requirements for reduced energy consumption, it becomes easier to heat our homes with low-temperature heating. This study set out to investigate how much the heating system supply temperature can be reduced in typical Danish single-family houses constructed i...
Article
Full-text available
Windows are central for the development of liveable nearly zero-energy homes and require careful consideration. Various studies have indicated that the effect of windows on energy consumption may change significantly with improved building insulation levels. Current guidelines on windows may therefore not apply in very well-insulated buildings, and...
Article
The use of internal insulation is investigated in a heritage building block with wooden beam construction and masonry brick walls as part of an energy renovation. Measurements were carried out and compared to results from a hygrothermal simulation model. The risk of mould growth in the wooden beams and in the interface between the insulation and th...
Article
To improve energy efficiency and give more access to renewable energy sources, low-temperature district heating (LTDH) is a promising concept to be realized in the future. However, concern about Legionella proliferation restricts applying low-temperature district heating in conventional systems with domestic hot water (DHW) circulation. In this stu...
Article
The investigation constructed and simulated moisture balance equations for single-room ventilation with a non-hygroscopic rotary heat exchanger. Based on literature, the study assumed that all condensed moisture in the exhaust subsequently evaporated into the supply. Simulations evaluated the potential for moisture issues and compared results with...
Article
Low temperature district heating (LTDH) is a cost-efficient way of supplying space heating and domestic hot water (DHW) for buildings in urban areas. However, there is concern that the potential hygiene problems (Legionella) might occur if LTDH is implemented, especially for large buildings. In this study, electric heat tracing system was investiga...
Article
District heating is a cost-effective way of providing heat to high heat density areas. Low-temperature district heating (LTDH) is a promising way to make district heating more energy-efficient and adaptable to well-insulated buildings with low heating demand in the future. However, one concern is the multiplication of Legionella due to insufficient...
Article
Full-text available
Appropriate window solutions are decisive for the design of ‘nearly zero-energy’ buildings with healthy and comfortable indoor environment. This paper focuses on the relationship between size, orientation and glazing properties of façade windows for different side-lit room geometries in Danish ‘nearly zero-energy’ houses. The effect of these parame...
Chapter
The chapter presents a method for determining the optimal capacity of a renewable-energy-based energy conversion systems for meeting the energy requirements of a given district as considered on a monthly basis, with use of a low-temperature district heating system operating at a low temperatures, as low as 55°C for supply and 25°C for return and wi...
Article
Rooms with a high density of occupants inevitably have high internal heat gains. It is possible to remove large sensible internal heat gains solely by radiant cooling systems if large areas of internal surface can be activated for radiant cooling. The ventilation system then only has to supply the small amount of fresh air required by standards to...
Article
The existing building stock will likely undergo widespread energy renovations to meet future emissions targets. Single-room ventilation may enable the process due to its simple installation, low fan power, and potential for local heat recovery. A short plastic rotary heat exchanger is developed for single-room ventilation based on thermal design th...
Article
The hypothesis investigated in this article is: it is possible to carry out moisture safe energy renovations in the old existing multi-storey buildings with heritage value and still save 50% of the building's energy consumption by use of existing technologies. A holistic energy renovation on an old multi-storey building with heritage value was carr...
Article
This paper presents a method for the dimensioning of the low-temperature District Heating (DH) piping networks operating with a control philosophy of supplying heat in low-temperature such as 55 °C in supply and 25 °C in return regularly while the supply temperature levels are being boosted in cold winter periods. The performance of the existing ra...
Article
Full-text available
Regardless of where they are in the world, people depend on a reliable and sufficient supply of domestic hot water (DHW) for daily use. Some countries that have district heating (DH) infrastructure, such as Denmark and China, combine spacing heating (SH) and DHW together, with the aim of having a smart, energy efficient and environmentally friendly...