Performance of ultra low temperature district heating systems with utility plant and booster heat pumps

Ommen, Torben Schmidt; Thorsen, Jan Eric; Markussen, Wiebke Brix; Elmegaard, Brian

doi:10.1016/j.energy.2017.05.165

Cited by 70 publications

(33 citation statements)

References 23 publications

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“…Although they found the mixed working fluids resulting in a higher investment cost, the economic performance was comparable to the pure fluids while the mixtures showed similar performance as the pure fluids at off-design conditions. Ommen et al [18] analyzed the performance of ULTDH systems with utility plant and booster heat pumps, observing a performance improvement of 12% for the reference calculations when the system was supplied by central heat pumps. In another work, they designed a new heat pump furnished substation configuration for multifamily buildings in ULTDH systems, finding it energetically and economically interesting [19].…”

Section: Introductionmentioning

confidence: 99%

Thermal-Hydraulic Performance Analysis of Twin-Pipes for Various Future District Heating Schemes

Khosravi

Arabkoohsar

2019

Energies

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Future energy systems will come with a 100% share of renewable energy and high integration of energy systems. District heating and cooling systems will be undeniable parts of the future energy systems, as they pave the bed for high-efficiency, low cost, and clean production. District heating systems may come into a wide range of designs in the future. Currently, most of the world’s district heating systems are based on the third generation design while everything in this framework is on the verge of a transition to the fourth generation. A large number of technologies for the future district heating systems has been proposed so far, among which low-, ultralow- and variable-temperature systems seem more of qualification. This study employs computational fluid dynamics to make a comprehensive examination of the compatibility of regular twin-pipes with various potential district heating schemes for future energy systems. The results show that both low- and ultralow-temperature systems could efficiently use regular twin-pipes commonly used in the third generation district heating systems, though the insulation of the pipe could be proportionally strengthened based on a techno-economic trade-off. In contrast, the results show that the thermal inertia of the pipe does not allow the variable-temperature district heating system to effectively operate when the transmission pipeline is longer than a limited length. Therefore, a regular heat distribution network may not be an appropriate host for a variable-temperature district heating scheme unless decentralized heat production units come into service.

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Section: Introductionmentioning

confidence: 99%

Thermal-Hydraulic Performance Analysis of Twin-Pipes for Various Future District Heating Schemes

Khosravi

Arabkoohsar

2019

Energies

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“…Elmegaard et al [19]compare the performances of different system configurations with supply temperature at 45 °C, and find the R134a HP system with hot water tank on the primary side reach the highest exergy efficiency. Ommen et al [20] conduct theoretical investigation on the optimal use of booster HP in ULTDH for new buildings, and find the booster HPs can improve the system performance if the central HP is used for heat supply. Torio et al [21] concluded that the geothermal heat pump is a low exergy energy sources.…”

Section: Introductionmentioning

confidence: 99%

Ultra-low temperature district heating system with central heat pump and local boosters for low-heat-density area: Analyses on a real case in Denmark

Yang

Svendsen

2018

Energy

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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 lower temperature level for the heat-sparse area where the distribution losses accounts for a large proportion in the total heat supply. In this study, the actual performance of a case ultra-low temperature district heating (ULTDH) system in Denmark was investigated based on long-term measurements. The system combines the central heat pump and local boosters, while the impact of such configuration on the overall system performance was analysed. The energy, exergy and economy performances of the case system were compared to medium temperature district heating system (MTDH) and low-temperature district heating system (LTDH). The results show that the LTDH system without supplementary heating has the highest energy and exergy efficiency. While the ULTDH system has better performance compared to the

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“…Yang found that a decentralized substation system with an instantaneous heat exchanger was the best exergo-economic solution in the case that the district heating temperature is high enough for SHW heating. Ommen et al [15] investigated the optimal integration of a heat-pump booster in an ultra-low-temperature district heating system. Analyzing two possible heat sources, i.e., combined heat and power (CHP) and a central heat pump, the study was made for an energy-efficient, multi-family residential building where heating and SHW accounted for equal shares of the demand.…”

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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Performance of ultra low temperature district heating systems with utility plant and booster heat pumps

Cited by 70 publications

References 23 publications

Thermal-Hydraulic Performance Analysis of Twin-Pipes for Various Future District Heating Schemes

Thermal-Hydraulic Performance Analysis of Twin-Pipes for Various Future District Heating Schemes

Ultra-low temperature district heating system with central heat pump and local boosters for low-heat-density area: Analyses on a real case in Denmark

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

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