| 1. |
- Abugabbara, Marwan, et al.
(författare)
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A simulation model for the design and analysis of district systems with simultaneous heating and cooling demands
- 2022
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 261, Part A
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Tidskriftsartikel (refereegranskat)abstract
- Latest generations of district heating and cooling systems are characterised by low network temperature with uninsulated pipes, decentralised heat pumps and chillers to modulate the network temperature, and shared energy flows between interconnected buildings. This paper presents a simulation model for the design and analysis of these systems. The model was developed using the Modelica language and it consists of component models from thermal, fluid, and control domains. The model was employed to simulate and analyse the first existing Swedish district system with simultaneous heating and cooling demands and bidirectional energy flows. The system currently connects nine buildings with total respective annual heating and cooling demands of 4.2 and 1.2 GWh. Simulation results revealed several benefits for integrating district and heat pump technologies, including (1) sharing energy flows between interconnected buildings to cover 40 % of the total carried heat in the network, (2) reducing the total purchased energy by 69 % compared to a traditional four-pipe district system, and (3) reducing distribution losses by 28 % compared to traditional networks with insulated pipes. The model can be utilised to support future research and development of new advanced district heating and cooling systems.
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| 2. |
- Abugabbara, Marwan, et al.
(författare)
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Bibliographic analysis of the recent advancements in modeling and co-simulating the fifth-generation district heating and cooling systems
- 2020
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788. ; 224
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Forskningsöversikt (refereegranskat)abstract
- District heating and cooling systems have evolved through several development stages in order to improve their energy efficiency. The latest development reached the fifth generation where customers can be producers and/or consumers of thermal energy flows towards the network. The variety and complexity of system configurations and interactions between connected customers poses a challenge in adopting a suitable modeling paradigm capable of simulating each design case. Modelica language and the Functional Mock-up Interface standard are computational tools opted by the International Energy Agency for simulating building and community energy systems. This work aims to analyze the current status in literature where these tools are utilized in building and energy simulation with focus on district heating and cooling systems. Bibliographic maps and networks are presented to analyze the literature based on different bibliometrics. Among others, the analysis shows that coupled simulation between district and building energy models is a novel research area and can benefit in reducing the oversizing of space heating and cooling systems. In addition, the analysis demonstrates that the fifth generation district heating and cooling systems require advanced control strategies. These strategies need accurate and upfront specifications to decide a proper control strategy for each design case.
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| 3. |
- Abugabbara, Marwan, et al.
(författare)
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Comparative study and validation of a new analytical method for hydraulic modelling of bidirectional low temperature networks
- 2024
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Ingår i: Energy. - 0360-5442. ; 296
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Tidskriftsartikel (refereegranskat)abstract
- Bidirectional Low Temperature Networks (BLTNs) are an innovative technology of district heating and cooling systems. Because of their intrinsic feature of supplying simultaneous heating and cooling either directly from an energy source/sink or through distributed heat pumps and chillers, circulation pumps installed at each building extract water from the network and a distinct pressure cone is subsequently created. Variations in the amount (and direction) of the extracted water call for accurate hydraulic design and analysis to ensure safe and adequate network operation. This paper proposes a new analytical solution method for fast hydraulic modelling of BLTNs. The analytical method was compared against three numerical solution methods and validated using different current and future operating scenarios of a real-world bidirectional network. In all modelled cases, the calculated mass flows and pressure drops using the new analytical method yielded very small Normalised Mean Bias Error (NMBE) and Coefficient of Variation of the Root Mean Square Error (CV(RMSE)), suggesting excellent agreement between the analytical and numerical solution methods. The new analytical method offers better performance over its numerical counterparts due to its explicit nature, ease of implementation, and quick modelling time.
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| 4. |
- Abugabbara, Marwan, et al.
(författare)
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How to develop fifth-generation district heating and cooling in Sweden? : Application review and best practices proposed by middle agents
- 2023
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Ingår i: Energy Reports. - : Elsevier Ltd. - 2352-4847. ; 9, s. 4971-4983
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Tidskriftsartikel (refereegranskat)abstract
- Sweden has an ambitious plan to fully decarbonise district heating by 2030 and to contribute with negative emissions of greenhouse gases in 2050. The vagaries of the energy market associated with climate, political, and social changes entail cross-sectoral integration that can fulfill these national targets. Fifth-generation district heating and cooling (5GDHC) is a relatively new concept of district energy systems that features a simultaneous supply of heating and cooling using power-to-heat technologies. This paper presents best practices for developing 5GDHC systems in Sweden to reach a consensus view on these systems among all stakeholders. A mixed-method combining best practice and roadmapping workshops has been used to disseminate mixed knowledge and experience from middle agents representing industry professionals and practitioners. Four successful implementations of 5GDHC systems are demonstrated and the important learned lessons are shared. The best practices are outlined for system planning, system modeling and simulation, prevailing business models for energy communities, and system monitoring. A roadmap from the middle agents’ point of view is composed and can be utilised to establish industry standards and common regulatory frameworks. © 2023 The Author(s)
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| 5. |
- Abugabbara, Marwan, et al.
(författare)
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Integration of ground-source heat pumps in combined district heating and cooling networks: A holistic modeling framework
- 2022
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Ingår i: European Geothermal Congress 2022. - 9782960194623
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The integration of heat pumps in low-enthalpy district heating and cooling networks can increase the efficiency and flexibility of the network. In such systems, heat pumps are installed both locally and centrally to serve different functions. In the former case, decentralized heat pumps at each building adjust the low-network temperature to the desired supply temperature. In the latter case, a central and relatively large-scale heat pump functions as a heat source or a heat sink to the ground. The main benefits of such technology are the reduction of the network operating temperature, the ability to supply simultaneous heating and cooling by operating the heat pumps in either heating or cooling mode, and the increased potential to integrate low-enthalpy shallow geothermal energy for heat generation and heat storage. One technical challenge in accelerating the implementation of this technology is the complexity of modeling the entire district network including all its components. A holistic modeling framework based on the equation-based objected-oriented Modelica language is presented in this paper. We first describe the three component models included in the framework,namely, the building substations, the distribution pipes, and the shallow geothermal bore field. Then, an example of a campus area consisting of eight buildings with varying heating and cooling demands is presented to apply the modeling framework and to demonstrate the expected mechanism by which such systems may operate. Simulation results indicate that high system performance can be attained when 1) the building supply temperature is controlled using demand-based temperature control curves, 2) the network operates at low-temperature close to the ground temperature, and 3) the bore field is balanced with sufficient heat injection to the ground. For future investigations, the modeling framework should be extended to cover the economic and the environmental impact of such systems due to the importance of these aspects in the planning of energy systems.
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| 6. |
- Abugabbara, Marwan, et al.
(författare)
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Modelica-based simulations of decentralised substations to support decarbonisation of district heating and cooling
- 2021
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Ingår i: Energy Reports. - : Elsevier BV. - 2352-4847. ; 7:4, s. 465-472
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Tidskriftsartikel (refereegranskat)abstract
- District heating and cooling are considered effective solutions to decarbonise the energy use in the building sector. The latest generation of district heating and cooling also increases the potential of integrating heat pumps and chillers in each building substation. The benefits of such integration are the reduction of network temperature and distribution losses; the recovery of waste heat through a bidirectional network; and the decentralised production of heating and cooling. Sizing the network depends mainly on the heat flows between connected buildings. The substation performance and technical installations determine these heat flows. We present in this paper Modelica-based simulations of two design cases for substations. The first design case involves installed heat pump, chiller, and circulation pumps. Alternatively, the second design enables the heat pump to provide direct cooling through a heat exchanger. The models for these installations were developed using the Modelica language to perform continuous-time simulations. The performance in each design case was evaluated in terms of seasonal coefficient of performance and total electric energy use. An analysis on a cluster of 11 buildings suggests that the addition of the direct cooling heat exchanger can save up to 10% of the total annual electric energy use. Additional savings can be achieved by optimising the building supply temperatures and the district network temperature.
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| 7. |
- Abugabbara, Marwan, et al.
(författare)
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Validation of TEKNOsim 6 According to CIBSE TM33
- 2018
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Ingår i: Cold Climate HVAC 2018 : Sustainable Buildings in Cold Climates - Sustainable Buildings in Cold Climates. - Cham : Springer International Publishing. - 2352-2542 .- 2352-2534. - 9783030006617 - 9783030006624 ; , s. 665-676
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Bokkapitel (refereegranskat)abstract
- TEKNOsim is a simple and user-friendly program for analyzing thermal indoor climate and performing annual hourly simulations. The program was originally developed to calculate heating and cooling demands, and indoor climate conditions of a single zone building for peak winter and summer design days. However, TEKNOsim version 6 has been revised to incorporate several new features including annual energy and multi-zone simulations. These features greatly enhance the functionality and the ability of the program. Their implementation in TEKNOsim 6, however, entails a validation procedure to test the accuracy of the new algorithms. This paper presents preliminary results of the ongoing testing and validation of TEKNOsim 6 according to CIBSE TM33 tests for software accreditation and verification. The test results indicate that the new database libraries implemented in TEKNOsim 6 can be easily customized to precisely represent the actual building conditions. The results also show that the program can accurately calculate the total steady-state heat losses for all test cases of CIBSE TM33. The peak cooling loads calculated by TEKNOsim 6 are also in good agreement with CIBSE TM33 for most test cases. Some discrepancies are however observed between TEKNOsim 6 and CIBSE TM33, especially for test cases involving certain building elements. Nevertheless, TEKNOsim 6 is shown to be a fast and reliable program for performing early-design stage simulations.
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| 8. |
- Arghand, Taha, 1982, et al.
(författare)
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A comparative study on borehole heat exchanger size for direct ground coupled cooling systems using active chilled beams and TABS
- 2021
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788. ; 240
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Tidskriftsartikel (refereegranskat)abstract
- Direct ground cooling is a method for cooling buildings whereby free cooling is provided by circulating water through borehole heat exchangers (BHEs). Since no refrigeration cooling is involved, supply water temperature to the building’s cooling system is dependent mainly on BHE sizing. This study investigates the sizing of BHEs for direct ground cooling systems, with a particular focus on the influence of terminal unit types and their operating strategies. Experimental results using a direct ground-coupled active chilled beam (ACB) system are used to develop a simulation model for an office building. The model is also modified for thermally activated building systems (TABS). The simulation results show that using TABS instead of ACBs for a similar BHE reduced the ground peak hourly loads, resulting in a lower borehole outlet temperature. Resizing BHE depth to reach similar maximum borehole outlet temperatures according to the actual heat extraction rate from the cooling systems resulted in a significantly shorter BHE depth with TABS compared to ACBs. However, indoor temperature was generally warmer with TABS, due to their slower heat extraction rate from the room. The findings are practical for analysing the design and operation of BHEs for different types of terminal units.
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| 9. |
- Arghand, Taha, 1982, et al.
(författare)
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Combining direct ground cooling with ground-source heat pumps and district heating: Borehole sizing and land area requirements
- 2022
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Ingår i: Geothermics. - : Elsevier BV. - 0375-6505. ; 106
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Tidskriftsartikel (refereegranskat)abstract
- This article studies the potential combination of direct ground cooling (DGC) with district heating (DH) and ground source heat pumps (GSHP) to compare the required borehole depths and needed drilling areas. It also examines two different borehole sizing approaches to optimize investment costs and drilling areas. The results show that the required borehole depths in most cases are shorter for the DGC and DH combination than for the DGC and GSHP combination. It is also demonstrated that the optimal range of borehole outlet temperatures could be chosen based on the trade-off between borehole installation and terminal units’ costs.
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| 10. |
- Arghand, Taha, 1982, et al.
(författare)
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Combining direct ground cooling with ground-source heat pumps and district heating: Energy and economic analysis
- 2023
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 270
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Tidskriftsartikel (refereegranskat)abstract
- Direct ground cooling (DGC) is a method used in cold climates to provide cooling to buildings without the use of any mechanical refrigeration. When DGC is utilized for providing cooling, ground-source heat pumps (GSHPs) and district heating (DH) are the two commonly used technologies for providing heating to the buildings. This article investigates the coupling of DGC with GSHPs and DH in terms of purchased energy and lifecycle costs. An office building equipped with active chilled beams for cooling and radiators for heating is used as a reference. Six cases based on different combinations of building envelope characteristics and thus different building heating and cooling loads are considered. The results show that using DGC-DH significantly reduces the amount of purchased electricity. However, the total energy cost is lower when DGC-GSHP is used. In addition, the DGC-GSHP can be more viable when the ground loads are well balanced. Investment costs, including borehole installation and equipment costs, are lower for the DGC-DH in the majority of the investigated cases. The lifecycle cost is lower for the DGC-DH in most of the investigated cases due to lower equipment costs.
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