| 1. |
- Markeby Ljungqvist, Hampus, et al.
(författare)
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A realistic view on heat reuse from direct free air-cooled data centres
- 2023
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Ingår i: Energy Conversion and Management: X. - : Elsevier. - 2590-1745. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- This paper examines the opportunities to reuse excess heat from direct free air-cooled data centres without incorporating heat pumps to upgrade the heat. The operation of a data centre in northern Sweden, Luleå, was simulated for a year. It was established that heat losses through the thermal envelope and from the humidification of the cooling airflow influenced the momentary energy reuse factor, iERF, with up to 7%. However, for the annual energy reuse factor, ERF, the heat losses could be neglected since they annually contributed to an error of less than 1%. It was shown that the ideal heat reuse temperature in Luleå was 13, 17, and 18 °C with an exhaust temperature of 30, 40 and 50 °C. The resulting ERF was 0.50, 0.59 and 0.66, meaning that a higher exhaust temperature resulted in potentially higher heat reuse. It could also be seen that raising the exhaust temperature lowered the power usage effectiveness, PUE, due to more efficient cooling. Using heat reuse applications with different heat reuse temperatures closer to the monthly average instead of an ideal heat reuse temperature for the whole year improved the ERF further. The improvement was 11–31% where a lower exhaust temperature meant a higher relative improvement.
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| 2. |
- Vesterlund, Mattias, et al.
(författare)
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Design optimization of a district heating network expansion : a case study for the town of Kiruna
- 2017
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Ingår i: Applied Sciences. - Basel : MDPI. - 2076-3417. ; 7:5
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Tidskriftsartikel (refereegranskat)abstract
- The urbanization of new areas beyond the existing perimeter of a town implies the expansion of several infrastructures, including the district heating network. The main variables involved in the design of the district heating network expansion are the layout of the new pipes, their diameters, and the capacity of the new heat production sites that are required to satisfy the increased demand of room heating and hot tap water. In this paper, a multi-objective evolutionary algorithm is applied to the minimization of the costs related to the expansion of the district heating network of the town of Kiruna, in northern Sweden. The results show that the spectrum of the optimal design compromises between investment costs for the new pipes and the new heat generation site on one side, and operating costs due to overall fuel consumption and pumping power in the network on the other. The presented methodology is a tool meant for the decision makers in the company who own the district heating network, to evaluate all the possible best design alternatives before making a decision.
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| 3. |
- Vesterlund, Mattias, et al.
(författare)
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Optimization of multi-source complex district heating network : a case study
- 2016
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Ingår i: Proceeding of 29th International Conference on efficiency, Cost, Optimization, Simulation and Enviromental Impact of Energy Systems.
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Konferensbidrag (refereegranskat)abstract
- The level of complexity for a district heating network increases with the maturity of the network, and this affects the pattern of the distribution of the hot water from the heat production sites to the end users. The majority of district heating systems are also multi-source networks, typically supported with heat from one main production site and other smaller satellite sites that are activated when required. In general, local energy companies have a lack of knowledge regarding how a meshed network behaves when different production sites are operated. The schedule of heat generation at the different sites is often based on staff experience and some general rules of thumb.In this paper a method for modeling and simulating complex district networks is further developed in order to optimize the total operating costs of a multi-source network, with constraints on the pressure and temperature levels in the user areas and on the heat generation characteristics at each production site.The optimization results show that the usage of the cheapest resources is preferred to a distributed generation of heat, even if some of the pipes may exceed the recommended thermal load capacity. The main site water supply temperature is found to be the lowest allowed by the constraint on the temperature of the water supplied to the end users, since the decrease of the costs associated with the lower thermal losses in the network is not counterbalanced by the increase of those associated with the pumping power of a larger water mass flow rate.
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| 4. |
- Vesterlund, Mattias, et al.
(författare)
-
Optimization of multi-source complex district heating network, a case study
- 2017
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 126, s. 53-63
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Tidskriftsartikel (refereegranskat)abstract
- The level of complexity for a district heating network increases with the maturity of the network, and this affects the pattern of the distribution of the hot water from the heat production sites to the end users. The majority of district heating systems are also multi-source networks, typically supported with heat from one main production site and other smaller satellite sites that are activated when required. In general, local energy companies have a lack of knowledge regarding how a meshed network behaves when different production sites are operated. The schedule of heat generation at the different sites is often based on staff experience and some general rules of thumb.In this paper a method for modeling and simulating complex district networks is further developed in order to optimize the total operating costs of a multi-source network, with constraints on the pressure and temperature levels in the user areas and on the heat generation characteristics at each production site.The optimization results show that the usage of the cheapest resources is preferred to a distributed generation of heat, even if some of the pipes may exceed the recommended thermal load capacity. The main site water supply temperature is found to be the lowest allowed by the constraint on the temperature of the water supplied to the end users, since the decrease of the costs associated with the lower thermal losses in the network is not counterbalanced by the increase of those associated with the pumping power of a larger water mass flow rate.
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| 5. |
- Vesterlund, Mattias, et al.
(författare)
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Simulation and analysis of a meshed district heating network
- 2015
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Ingår i: ECOS 2015. - : International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. - 9782955553909
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Konferensbidrag (refereegranskat)abstract
- The maturity of a district heating system can be estimated from its complexity. In fact, a mature network has a meshed structure while a younger network is often in the form of small network islands or has a tree structure. When a district heating system is developing and its complexity is increasing the flow distribution in the network is no longer obvious. As a consequence, the network owner, often the local energy company, is in need of a simulation program to have the possibility of analysing it and enlarge their network understanding. In this paper, a simulation tool developed in MATLAB/Simulink is applied in order to analyse the flow distribution in the district heating network of the town of Kiruna (Sweden). The Kiruna network has been developing since the 60s and is today a mature network with the meshed structure. The method has specifically been developed to analyse the flow pattern in such kind of networks without altering their physical structure, and it is expected to be a valuable tool for the redesign of the network in the forthcoming relocation of some of the urban districts. The results about the current network configuration show that only a few pipes in the network are exceeding the recommended level of flow in terms of thermal power. The temperature and pressure drop from heat production site to the nodes serving the main consumer areas is within 1.6 bar and 10°C in the days of highest demand.
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| 6. |
- Vesterlund, Mattias, et al.
(författare)
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Simulation and analysis of a meshed district heating network
- 2016
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 122, s. 63-73
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Tidskriftsartikel (refereegranskat)abstract
- The flow distribution in a district heating network tends to become no longer obvious when system design is developed and its complexity increased. As a consequence, the network owner, often the local energy company, is in need of a simulation program to have the possibility of analysing network behaviour and expand the understanding about the operation of district heating system. In this paper, a simulation tool developed in MATLAB/Simulink is applied in order to analyse the flow distribution in the district heating network of the town of Kiruna (Sweden). The network in Kiruna has been developing since the 60s and is today a complex network with a meshed structure, i.e. it is formed by a set of loops from which secondary branches depart. The simulation tool is part of a methodology that has specifically been developed to analyse the flow pattern in such kind of networks without altering their physical structure, and it is expected to be a valuable tool for the redesign of the network in the forthcoming relocation of some of the urban districts. The results about the current network configuration show that only a few pipes in the network are exceeding the levels of heat flow recommended by pipe manufacturers. The largest drops in pressure and temperature from the heat production site to the nodes serving the main consumer areas are within 1.2 bar and 9 °C in the days of highest demand.
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