A new waste heat district heating system with combined heat and power (CHP) based on ejector heat exchangers and absorption heat pumps

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.

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Energy performance assessment of a complex district heating system which uses gas-driven combined heat and power, heat pumps and high temperature aquifer thermal energy storage

Energy and Buildings ◽

10.1016/j.enbuild.2014.07.061 ◽

2014 ◽

Vol 84 ◽

pp. 142-151 ◽

Cited By ~ 22

Author(s):

Răzvan Mihai Zeghici ◽

Andrei Damian ◽

Rodica Frunzulică ◽

Florin Iordache

Keyword(s):

High Temperature ◽

Energy Storage ◽

Performance Assessment ◽

Thermal Energy ◽

District Heating ◽

Heating System ◽

Energy Performance ◽

Combined Heat And Power ◽

Heat Pumps ◽

District Heating System

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New low temperature industrial waste heat district heating system based on natural gas fired boilers with absorption heat exchangers

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2017.07.134 ◽

2017 ◽

Vol 125 ◽

pp. 1437-1445 ◽

Cited By ~ 9

Author(s):

Fangtian Sun ◽

Lijiao Cheng ◽

Lin Fu ◽

Junwei Gao

Keyword(s):

Low Temperature ◽

Natural Gas ◽

Heat Exchangers ◽

Industrial Waste ◽

Waste Heat ◽

District Heating ◽

Heating System ◽

District Heating System ◽

Industrial Waste Heat

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Exergoeconomic Analysis of New High-Temperature District Heating System Based on Absorption Heat Pump Technology in Combined Heat and Power

Volume 5: Energy Systems Analysis, Thermodynamics and Sustainability; NanoEngineering for Energy; Engineering to Address Climate Change, Parts A and B ◽

10.1115/imece2010-38014 ◽

2010 ◽

Author(s):

Fangtian Sun ◽

Lin Fu ◽

Shigang Zhang

Keyword(s):

Heat Exchanger ◽

Heat Pump ◽

Waste Heat ◽

District Heating ◽

Heating System ◽

Combined Heat And Power ◽

Space Heating ◽

Exergetic Efficiency ◽

District Heating System ◽

Absorption Heat Pump

Space heating area of district heating system of combined heat and power (CHP) accounts for approximately one third of total space heating area in Chinese northern cities. In the extraction condensing turbine combined heat and power system based on district heating network, there are a large number of low-grade waste heat in the condenser, and exergy loss in the steam-water heat exchanger and water-water heat exchanger. Based on absorption heat pump technology, a new high-temperature district heating technology (DHSAHP) was presented to improve the current district heating system of CHP. Absorption heat pumps are used to recycle low-temperature waste heat in condenser. Absorption heat pump type heat exchanger is used to reduce temperature of return water in primary heat network, and decrease irreversible loss. Where, DHSAHP was analyzed by thermodynamics and economics method, and evaluated by exergetic efficiency, exergetic output cost, exergetic cost difference and exergoeconomic factor. Compared with current district heating system of CHP, DHSAHP can decrease about 31.3% steam consumption, increase about 75% transmission and distribution capacity of the primary heating network. The evaluation results show that the exergetic efficiency of new district heating system of CHP based on the absorption cycle technology is higher 10.41% than that of current district heating system of CHP, whereas its exergetic cost is lower 36.6¥/GJ than that of the conventional district heating system. With the increase of annual heating time, economy efficiency of new district heating system of CHP becomes better. The DHSAHP has higher energy utilization efficiency and better economic benefits and provides a kind of better technological method to solve the main problems of cuurent district heating with CHP in China.

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Upgrading a District Heating System by Means of the Integration of Modular Heat Pumps, Geothermal Waters, and PVs for Resilient and Sustainable Urban Energy

Energies ◽

10.3390/en14092347 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2347

Author(s):

Elżbieta Hałaj ◽

Jarosław Kotyza ◽

Marek Hajto ◽

Grzegorz Pełka ◽

Wojciech Luboń ◽

...

Keyword(s):

District Heating ◽

Heating System ◽

Upper Jurassic ◽

Heat Pumps ◽

Water Levels ◽

Energy Potential ◽

Geothermal Waters ◽

District Heating System ◽

Heating And Cooling ◽

The City

Krakow has an extensive district heating network, which is approximately 900 km long. It is the second largest city in terms of the number of inhabitants in Poland, resulting in a high demand for energy—for both heating and cooling. The district heating of the city is based on coal. The paper presents the conception of using the available renewable sources to integrate them into the city’s heating system, increasing the flexibility of the system and its decentralization. An innovative solution of the use of hybrid, modular heat pumps with power dependent on the needs of customers in a given location and combining them with geothermal waters and photovoltaics is presented. The potential of deep geothermal waters is based on two reservoirs built of carbonate rocks, namely Devonian and Upper Jurassic, which mainly consist of dolomite and limestone. The theoretical potential of water intake equal to the nominal heating capacity of a geothermal installation is estimated at 3.3 and 2.0 MW, respectively. Shallow geothermal energy potential varies within the city, reflecting the complex geological structure of the city. Apart from typical borehole heat exchangers (BHEs), the shallower water levels may represent a significant potential source for both heating and cooling by means of water heat pumps. For the heating network, it has been proposed to use modular heat pumps with hybrid sources, which will allow for the flexible development of the network in places previously unavailable or unprofitable. In the case of balancing production and demand, a photovoltaic installation can be an effective and sufficient source of electricity that will cover the annual electricity demand generated by the heat pump installation, when it is used for both heating and cooling. The alternating demand of facilities for heating and cooling energy, caused by changes in the seasons, suggests potential for using seasonal cold and heat storage.

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