Space heating with ultra-low-temperature district heating – a case study of four single-family houses from the 1980s

Østergaard, Dorte Skaarup; Svendsen, Svend

doi:10.1016/j.egypro.2017.05.070

Cited by 61 publications

(41 citation statements)

References 7 publications

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“…Modern low-temperature systems require low supply temperatures and allow for low return temperatures [6]. Due to there being several positive impacts of lowering the supply and return temperatures of such a district heating system (DHS), especially concerning the energy efficiency, DHSs with low supply temperatures down to 35 • C are undergoing pilot testing [7]. They can be supplied from waste-heat recovery systems or renewables, but although these can provide the low temperatures suitable for low-temperature district heating (LTDH) systems, they are insufficient for sanitary hot-water (SHW) production.…”

Section: Introductionmentioning

confidence: 99%

Exergy Analyses of Low-Temperature District Heating Systems With Different Sanitary Hot-Water Boosters

Poredoš

Kitanovski

Poredoš³

2019

Entropy

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This paper presents an exergy-efficiency analysis of low-temperature district heating systems (DHSs) with different sanitary hot-water (SHW) boosters. The required temperature of the sanitary hot water (SHW) was set to 50 °C. The main objective of this study was to compare the exergy efficiencies of a DHS without a booster to DHSs with three different types of boosters, i.e., electric-, gas-boiler- and heat-pump-based, during the winter and summer seasons. To achieve this, we developed a generalized model for the calculation of the exergy efficiency of a DHS with or without the booster. The results show that during the winter season, for a very low relative share of SHW production, the DHS without the booster exhibits favorable exergy efficiencies compared to the DHSs with boosters. By increasing this share, an intersection point above 45 °C for the supply temperatures, at which the higher exergy efficiency of a DHS with a booster prevails, can be identified. In the summer season the results show that a DHS without a booster at a supply temperature above 70 °C achieves lower exergy efficiencies compared to DHSs with boosters at supply temperatures above 40 °C. The results also show that ultra-low supply and return temperatures should be avoided for the DHSs with boosters, due to higher rates of entropy generation.

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Section: Introductionmentioning

confidence: 99%

Exergy Analyses of Low-Temperature District Heating Systems With Different Sanitary Hot-Water Boosters

Poredoš

Kitanovski

Poredoš³

2019

Entropy

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“…It is estimated that a low-temperature distribution network with 50 • C of supply water temperature and 20 • C of return water temperature should cut the current 3rd generation distribution temperature difference between average water temperature and ground by a factor 2 [20]. A further temperature reduction in the circulating water as in the CDH network can increase energy saving.…”

Section: Low Thermal Losses In the Distribution Networkmentioning

confidence: 99%

“…Further specific analysis has been carried out to identify how technical [25][26][27], legislative [28,29] and economic [30,31] barriers can be overcome. Case studies from different countries have also been reported [20,[32][33][34]. Nevertheless, the development of 4th generation systems of district heating is characterized by two strong limitations: the first is that the demand side of a district heating network consists of buildings built at different times.…”

Section: Introductionmentioning

confidence: 99%

“…A further division of 4th generation systems can be made between so-called low temperature district heating (LTDH) and ultra-low temperature district heating (ULTDH). LTDH networks are usually characterized by supply temperatures in the range 50-70 • C, while ULTDH networks have supply temperatures below 50 • C, without a common definition of lower limit [20]. In ULTDH networks, decentralized micro-heat power stations should be used to boost the domestic hot water (DHW) temperature as needed [21].…”

Section: Introductionmentioning

confidence: 99%

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The Innovative Concept of Cold District Heating Networks: A Literature Review

Pellegrini

Bianchini

2018

Energies

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Abstract:The development of sustainable and innovative solutions for the production and supply of energy at district level is nowadays one of the main technical challenges. In the past, district heating and cooling networks aimed to achieve greater energy efficiency through the centralization of the energy production process but with relevant losses related to heat transport. Moving towards a higher share of renewables and lower demand of primary energy requires redesign of the energy district networks. The novel concept of cold district heating networks aims to combine the advantages of a centralized energy distribution system with low heat losses in energy supply. This combined effect is achieved through the centralized supply of water at relatively low temperatures (in the range 10-25 • C), which is then heated up by decentralized heat pumps. Moreover, cold district heating networks are also very suitable for cooling delivery, since cold water supplying can be directly used for cooling purposes (i.e., free cooling) or to feed decentralized chillers with very high energy efficiency ratio. This paper provides a preliminary literature review of existing cold district heating networks and then qualitatively analyses benefits and drawbacks in comparison with the alternatives currently used to produce heat and cold at district level, including the evaluation of major barriers to its further development.

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“…A large number of different software types is being used in these investigations. Finite difference methods (FDM) used by TRNSYS [17,25] and IDA-ICE [26][27][28][29] are widely adopted, due to their ability to account for variable ground surface temperatures [30,31]. In some recent approaches, these can even be combined with probabilistic analysis [32].The Finite Element Method (FEM) [33][34][35] is extensively used as well, for instance with ABAQUS [36][37][38] or COMSOL Multiphysics [39][40][41][42].…”

mentioning

confidence: 99%

Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

Ferrantelli

Fadejev

Kurnitski

2019

Preprint

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As the energy efficiency demands for future buildings become increasingly stringent, preliminary assessments of energy consumption are mandatory. These are possible only through numerical simulations, whose reliability crucially depends on boundary conditions. We therefore investigate their role in numerical estimates for the usage of geothermal energy, performing annual simulations of transient heat transfer for a building employing a geothermal heat pump plant and energy piles. Starting from actual measurements, we solve the heat equations in 2D and 3D using COMSOL Multiphysics and IDA-ICE, and discover a negligible impact of the multiregional ground surface boundary conditions. Moreover, we verify that the thermal mass of the soil medium induces a small vertical temperature gradient on the piles surface. We also find a roughly constant temperature on each horizontal cross-section, with nearly identical values if the average temperature is integrated over the full plane or evaluated at one single point. Calculating the yearly heating need for an entire building we then show that the chosen upper boundary condition affects the energy balance dramatically. Using directly the pipes’ outlet temperature induces a 54% overestimation of the heat flux, while the exact ground surface temperature above the piles reduces the error to 0.03%.

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Space heating with ultra-low-temperature district heating – a case study of four single-family houses from the 1980s

Cited by 61 publications

References 7 publications

Exergy Analyses of Low-Temperature District Heating Systems With Different Sanitary Hot-Water Boosters

Exergy Analyses of Low-Temperature District Heating Systems With Different Sanitary Hot-Water Boosters

The Innovative Concept of Cold District Heating Networks: A Literature Review

Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

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