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Simulation and Optimization models to unlock the evolution of existing District Heating towards next-generation systems
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Integration of Groundwater Storage and Heat Pumps in Second-Generation District Heating Systems
Full text linkDistrict heating (DH) systems in Europe predominantly belong to the second and third generations,
operating at temperatures often exceeding 100°C, which poses challenges for integrating renewable energy sources
(RES). The feasibility of incorporating large-scale groundwater heat pumps into such systems was explored in this
study, with a focus on adjusting the supply water temperature to thermal substations. This adjustment, achieved by
lowering the temperature below design values in response to rising outdoor temperatures, facilitated the integration
of RES and improved system efficiency. Additionally, groundwater or geothermal heat pumps enabled the effective
utilisation of waste heat (WH) from industrial processes or excess heat from renewable sources, particularly during
periods when the thermal demand of the DH system was insufficient to justify direct supply. This excess heat, once
collected, can be stored in the ground and later retrieved for use during the heating season, contributing to the system’s
overall sustainability. The integration of seasonal thermal storage further enhances the operational flexibility of DH
systems by allowing for the balancing of supply and demand over extended periods. The findings underscore the
technical viability and environmental benefits of such integration, providing a pathway for the modernisation of DH
infrastructure and the advancement of energy transition goal
Simulation and Analysis of a Groundwater Seasonal Storage Coupled with a District Heating System
No full textMulti-objective optimization of district energy systems with demand response
Full text linkIn district energy applications, implementation of management strategies is crucial to achieve reductions in primary energy consumption and carbon dioxide emissions. The development of optimization tools to upgrade the operation of smart energy systems should take into account all the relevant elements of these complex infrastructures. In this paper, a global optimization approach, applied to district heating, cooling and electricity networks interconnected to each other, is proposed. The suggested approach combines the optimization of the production side, useful to understand how it is convenient to produce heat, cold and electricity, with demand-side management for district heating customers. This is reached by using a bi-level optimization structure, exploiting the genetic algorithm and linear programming. A physical model of the district heating network is included in the procedure to accurately reproduce the effects of demand-side management. The tool can be applied to different objective functions. In this paper, a multi-objective optimization is carried out with two different objective functions: the operation cost and the carbon dioxide emissions. Results show that, by choosing an intermediate trade-off among the two goals, it would be possible to have a 12% reduction in the emissions at the expense of a 25% increase in the operating cost
Exploring opportunities for temperature reduction in existing district heating infrastructures
Full text linkThe integration of renewable energy sources into existing district heating systems is imperative for the decar-
bonization of the global energy system. This transition is particularly challenging in existing systems that were
originally supplied by fossil fuel plants and designed to operate with high supply temperatures. Reducing supply
temperatures to facilitate the integration of low exergy heat may not be suitable for the existing infrastructure,
due to both the heating devices or the thermal substations that may not support significant reductions or to the
distribution infrastructure that can be unable to handle the required mass flow rate increases. To address these
challenges, this paper focuses on the distribution infrastructure by introducing a physical-based approach to
explore the current potential for supply temperature reduction of existing district heating infrastructures, taking
into account the hydraulics of the system. Indeed, being able to identify the possible hydraulic bottlenecks arising
in the network is essential to enable the transition of the networks and requires an accurate modelling of the fluid
dynamic of the system. The methodology is fast and versatile, making it suitable for applications from small-scale
to large-scale systems. An application to a real large-scale network is presented, proving the wide applicability of
the methodology. Promising results in terms of temperature reduction are shown to be possible: the analyzed
infrastructure is currently capable of shifting its operation from 120 ◦C to about 102 ◦C without considering
invasive structural interventions on the network, and further reductions up to 90 ◦ C are conceivable by assuming
some adjustments to the system configuratio
Integration of storage and thermal demand response to unlock flexibility in district multi-energy systems
Full text linkPotential for supply temperature reduction of existing district heating substations
Full text linkReducing operating temperatures is a crucial goal for transforming district heating networks into sustainable systems as it allows the integration of low exergy heat (e.g. renewable, waste heat). Many criticalities arise when reducing operating temperatures in existing networks that are not designed to operate in these conditions. The criticalities occur at different levels: in the building, in the thermal substations, in the pipelines and in the production plants. In this paper, the reduction of supply temperature in existing district heating substations is analyzed. A methodology including a model of the thermal substation and a data analysis software is developed to estimate the potential temperature reduction that could be applied to existing substations. The application of the model to an existing large-scale district heating network in Northern Italy shows that all the analyzed substations are currently able to shift their operation from 120 °C to 104 °C, and that district heating supply temperatures around 90 °C can be realistically achieved with few improvements on the system
Optimal operation of district heating networks through demand response
Full text linkIn this paper, an optimization method aiming at minimizing the thermal peaks in district heating networks is proposed. The method relies on a thermo-fluid dynamic model of both the supply and return networks and permits to analyze the opportunities for thermal peak shaving through “virtual storage”. The latter is obtained through variation of the thermal request profiles of the users. The presence of a peak in the morning is due to the shut-down or attenuation of the heating systems during the night, which lead to a dramatical increase of the thermal request early in the morning. The peak compromises a full exploitation of cogeneration and renewable plants that are able to cover just a portion of the maximum load. Consequently, boilers have to be used, leading the system to a performance reduction and to an increase of primary energy consumption. Moreover, the peak makes the possibility of network extension quite difficult, because of the limitation on mass flow rates in the pipes. For this reason, a model is developed to make the thermal profile as flat as possible. The model is applied to a portion of the Turin district heating network, which is the largest network in Italy. Results show that reductions between 20% and 42% are possible, depending on the maximum changes in the possible schedules
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