Résultats de recherche pour « District heating »

In the present paper an optimal control problem for a system of differential-algebraic equations (DAEs) is considered. This problem arises in the dynamic optimization of unsteady district heating networks. Based on the Carathéodory theory existence of a unique solution to the DAE system is proved using specific properties of the district heating network model. Moreover, it is shown that the optimal control problem possesses optimal solutions. For the numerical experiments different networks are considered including also data from a real district heating network.

The purpose with this review is to provide a presentation of the background for the current position for district heating and cooling in the world, with some deeper insights into European conditions. The review structure considers the market, technical, supply, environmental, institutional, and future contexts. The main global conclusions are low utilisation of district heating in buildings, varying implementation rates with respect to countries, moderate commitment to the fundamental idea of district heating, low recognition of possible carbon dioxide emission reductions, and low awareness in general of the district heating and cooling benefits. The cold deliveries from district cooling systems are much smaller than heat deliveries from district heating systems. The European situation can be characterised by higher commitment to the fundamental idea of district heating, lower specific carbon dioxide emissions, and higher awareness of the district heating and cooling benefits. The conclusions obtained from the six contexts analysed show that district heating and cooling systems have strong potentials to be viable heat and cold supply options in a future world. However, more efforts are required for identification, assessment, and implementation of these potentials in order to harvest the global benefits with district heating and cooling. • Low utilisation of district heating in buildings. • Low awareness of the district heating and cooling benefits. • Variation in reaching the fundamental idea of district heating. • Promising tool for further mitigation of climate change. • District cold deliveries are still small.

Current developments in heat pumps, supported by innovative business models, are driving several industry sectors to take a proactive role in future district heating and cooling networks in cities. For instance, supermarkets and data centers have been assessing the reuse of waste heat as an extra source for the district heating network, which would offset the additional investment in heat pumps. This innovative business model requires complete deregulation of the district heating market to allow industrial heat producers to provide waste heat as an additional source in the district heating network. This work proposes the application of innovative market designs for district heating networks, inspired by new practices seen in the electricity sector. More precisely, pool and market designs are addressed, comparing centralized and decentralized market proposals. An illustrative case of a Nordic district heating network is used to assess the performance of each market design, as well as the potential revenue that different heat producers can obtain by participating in the market. An important conclusion of this work is that the proposed market designs are in line with the new trends, encouraging the inclusion of new excess heat recovery players in district heating networks.

The purpose with this review is to provide a presentation of the background and current position for district heating and cooling in Sweden. The review structure considers the market, technical, supply, environmental, institutional, and future contexts. The main conclusions are high utilisation of district heating in Swedish buildings, commitment to the third generation of district heating technology, high proportions of heat recycling and renewable supply, high compliance to European definition of efficient district heating, considerable reductions of fossil carbon dioxide emissions, strong national driving forces from high fossil fuel taxes, and soft district heating regulation based on transparency. District cooling systems are small compared to district heating systems. From strong legislative driving forces, the Swedish heat market became a testing ground for a market situation when fossil fuels are expensive in a heat market. The long-term market solutions have then become district heating in dense urban areas and local heat pumps in suburban and rural areas.

Using hydraulic models in control design in district heating networks can increase pumping efficiency and reduce sensitivity to hydraulic bottlenecks. These models are usually white-box, as they are obtained based on full knowledge of the district heating network and its parameters. This type of model is time-consuming to obtain, and might differ from the actual behavior of the system. In this paper, a method is proposed to obtain a grey-box hydraulic model for tree-shaped district heating systems: hydraulic parameters are estimated based on pressure measurements in only two locations. While previous works only estimate parameters related to pressure losses in pipes, this work also includes customers valves in the grey-box model structure, an important inclusion for control-oriented applications. Finally, a numerical example illustrates the proposed method on a small district heating network, showing its ability to obtain an accurate model on the basis of noisy measurements.

District heating is a network of pipes through which heat is delivered from a centralised source. It is expected to play an important role in the decarbonisation of the energy sector in the coming years. In district heating, heat is traditionally generated through fossil fuels, often with combined heat and power (CHP) units. However, increasingly, waste heat is being used as a low carbon alternative, either directly or, for low temperature sources, via a heat pump. The design of district heating often has competing objectives: the need for inexpensive energy and meeting low carbon targets. In addition, the planning of district heating schemes is subject to multiple sources of uncertainty such as variability in heat demand and energy prices. This paper proposes a decision support tool to analyse and compare system designs for district heating under uncertainty using stochastic ordering (dominance). Contrary to traditional uncertainty metrics that provide statistical summaries and impose total ordering, stochastic ordering is a partial ordering and operates with full probability distributions. In our analysis, we apply the orderings in the mean and dispersion to the waste heat recovery problem in Brunswick, Germany.

Modern district heating technologies have a great potential to make the energy sector more flexible and sustainable due to their capabilities to use energy sources of varied nature and to efficiently store energy for subsequent use. Central control tasks within these systems for the efficient and safe distribution of heat refer to the stabilization of overall system temperatures and the regulation of storage units state of charge. These are challenging goals when the networked and nonlinear nature of district heating system models is taken into consideration. In this letter, for district heating systems with multiple, distributed heat producers, we propose a decentralized control scheme to provably meet said tasks stably.

Current temperature levels in European district heating networks are still too high with respect to future conditions as customer heat demands decrease and new possible heat source options emerge. A considerable reduction of temperature levels can be accomplished by eliminating current faults in substations and customer heating systems. These faults do not receive proper attention today, because neither substations nor customer heating systems are centrally supervised. The focus of this paper has been to identify these faults by annual series of hourly meter readings obtained from automatic meter reading systems at 135 substations in two Swedish district heating systems. Based on threshold methods, various faults were identified in 74% of the substations. The identified faults were divided into three different fault groups: Unsuitable heat load pattern, low average annual temperature difference, and poor substation control. The most important conclusion from this early study of big data volumes is that automatic meter reading systems can provide proactive fault detection by continuous commissioning of district heating substations in the future. A complete reduction of current faults corresponds to approximately half the required reduction of the current temperature levels in the effort toward future low-temperature district heating networks.