Six different strategies have recently been proposed for the European Union (EU) energy system in the European Commission's report, Energy Roadmap 2050. The objective for these strategies is to ...identify how the EU can reach its target of an 80% reduction in annual greenhouse gas emissions in 2050 compared to 1990 levels. None of these scenarios involve the large-scale implementation of district heating, but instead they focus on the electrification of the heating sector (primarily using heat pumps) and/or the large-scale implementation of electricity and heat savings. In this paper, the potential for district heating in the EU between now and 2050 is identified, based on extensive and detailed mapping of the EU heat demand and various supply options. Subsequently, a new ‘district heating plus heat savings’ scenario is technically and economically assessed from an energy systems perspective. The results indicate that with district heating, the EU energy system will be able to achieve the same reductions in primary energy supply and carbon dioxide emissions as the existing alternatives proposed. However, with district heating these goals can be achieved at a lower cost, with heating and cooling costs reduced by approximately 15%.
•A new heat atlas is created for the EU27.•District heating and renewable heat potentials are determined for 2030 and 2050.•A new heat strategy based on district heating and individual heat pumps is designed for the EU27.•This new heat strategy is compared to the energy efficiency scenario proposed by the European Commission.•Results indicate that this new heat strategy can reduce heating and cooling costs by ~15%, which is €100 billion per year.
Lowering the temperatures in heating systems is the key to decarbonizing the heat supply in the building sector, because it is a door opener to greater integration of renewable heat, the use of ...excess heat and to improve compatibility for heat pumps. This often fails because heating systems, especially in unrenovated building stock, usually require high supply temperatures. Previous studies on temperature reduction in existing buildings are performed mainly numerically, whereas in this research the numeric calculations are validated by measurements. For this purpose, a demonstrator with two different ceiling heating systems is integrated in the listed architecture building of the Technical University of Darmstadt and the achievable temperature reduction is investigated. Based on this, parameter variations are conducted through a simulation model in order to test the feasibility of the concept for the entire building. The results show that even with an unrenovated building envelope, a significant temperature reduction to below 45 °C is possible without exceeding the normative limits of thermal comfort. With moderate building envelope renovation, the reduction is possible even to below 36 °C. The measures investigated can make the building compatible with renewable heat potentials without negative impacts on the cultural heritage.
Representing unresolved moist convection in coarse‐scale climate models remains one of the main bottlenecks of current climate simulations. Many of the biases present with parameterized convection ...are strongly reduced when convection is explicitly resolved (i.e., in cloud resolving models at high spatial resolution approximately a kilometer or so). We here present a novel approach to convective parameterization based on machine learning, using an aquaplanet with prescribed sea surface temperatures as a proof of concept. A deep neural network is trained with a superparameterized version of a climate model in which convection is resolved by thousands of embedded 2‐D cloud resolving models. The machine learning representation of convection, which we call the Cloud Brain (CBRAIN), can skillfully predict many of the convective heating, moistening, and radiative features of superparameterization that are most important to climate simulation, although an unintended side effect is to reduce some of the superparameterization's inherent variance. Since as few as three months' high‐frequency global training data prove sufficient to provide this skill, the approach presented here opens up a new possibility for a future class of convection parameterizations in climate models that are built “top‐down,” that is, by learning salient features of convection from unusually explicit simulations.
Plain Language Summary
The representation of cloud radiative effects and the atmospheric heating and moistening due to moist convection remains a major challenge in current generation climate models, leading to a large spread in climate prediction. Here we show that neural networks trained on a high‐resolution model in which moist convection is resolved can be an appealing technique to tackle and better represent moist convection in coarse resolution climate models.
Key Points
We use a global atmospheric model with embedded cloud resolving model, as training data set for a machine learning algorithm of convection
The machine learning algorithm can reproduce most of the key features of the embedded cloud resolving model
The machine learning algorithm is much more computationally efficient than a super parameterization, but does not behave stochastically
Based on the case of Denmark, this paper analyses the role of district heating in future Renewable Energy Systems. At present, the share of renewable energy is coming close to 20 per cent. From such ...point of departure, the paper defines a scenario framework in which the Danish system is converted to 100 per cent Renewable Energy Sources (RES) in the year 2060 including reductions in space heating demands by 75 per cent. By use of a detailed energy system analysis of the complete national energy system, the consequences in relation to fuel demand, CO
2 emissions and cost are calculated for various heating options, including district heating as well as individual heat pumps and micro CHPs (Combined Heat and Power). The study includes almost 25 per cent of the Danish building stock, namely those buildings which have individual gas or oil boilers today and could be substituted by district heating or a more efficient individual heat source. In such overall perspective, the best solution will be to combine a gradual expansion of district heating with individual heat pumps in the remaining houses. Such conclusion is valid in the present systems, which are mainly based on fossil fuels, as well as in a potential future system based 100 per cent on renewable energy.
Combined heat, and power dispatch promotes interactions, and synergies between electric power systems, and district heating systems. However, nonlinear, and nonconvex heating flow imposes significant ...challenges on finding qualified solutions efficiently. Most existing methods rely on constant flow assumptions to derive a linear heating flow model, sacrificing optimality for computational simplicity. This paper proposes a novel convex combined heat, and power dispatch model based on model simplification, and constraint relaxations, which improves solution quality, and avoids assumptions on operating regimes of district heating systems. To alleviate mathematical complexity introduced by the commonly used node method, a simplified thermal dynamic model is proposed to capture temperature changes in networked pipelines. Quadratic, and polyhedral relaxations are then applied to convexify the original problem with quadratic equality, and bilinear constraints. Furthermore, an adaptive solution algorithm is developed to successively reduce the relaxation area based on sequential bound tightening, which improves solution optimality with desirable computational efficiency. The proposed method is verified on a distribution-level, and a transmission-level integrated electricity, and heat systems, compared to constant-flow-based solutions, and iterative algorithms.
The competitiveness of present and future district heating systems can be at risk when residential and service sector heat demands are expected to decrease in the future. In this study, the future ...competitiveness of district heating has been examined by an in depth analysis of the distribution capital cost at various city characteristics, city sizes, and heat demands. Hereby, this study explores an important market condition often neglected or badly recognised in traditional comparisons between centralised and decentralised heat supply.
By a new theoretical approach, the traditional and empirical expression for linear heat density is transformed into an analytical expression that allows modelling of future distribution capital cost levels also in areas where no district heating exists today. The independent variables in this new analytical expression are population density, specific building space, specific heat demand and effective width.
Model input data has primarily been collected from national and European statistical sources on heat use, city populations, city districts and residential living areas. Study objects were 83 cities in Belgium, Germany, France, and the Netherlands. The average heat market share for district heat within these cities was 21% during 2006.
The main conclusion is that the future estimated capital costs for district heat distribution in the study cities are rather low, since the cities are very dense. At the current situation, a market share of 60% can be reached with a marginal distribution capital cost of only 2.1
€/GJ, corresponding to an average distribution capital cost of 1.6
€/GJ. The most favourable conditions appear in large cities and in inner city areas. In the future, there is a lower risk for reduced competitiveness due to reduced heat demands in these areas, since the increased distribution capital cost is low compared to the typical prices of district heat and competing heat supply. However, district heating will lose competitiveness in low heat density areas. Hence, reduced heat demands in high heat density areas are not a general barrier for district heating in the future.
Currently, the economy of Middle Eastern countries relies heavily on fossil fuel sources. The direct and indirect adverse consequences of fossil fuel utilization for power generation enforce the ...region’s countries to raise the share of renewable energy. In this context, various incentive policies have been developed to encourage the residential and industrial sectors to support a portion of energy needs through renewable energy resources. In this case, a solar water heating system (SWHS) as an application of solar thermal technology provides some of the heat energy requirements for domestic hot water (DHW) and space heating, supported conventionally by electricity or natural gas, or even other fossil fuels. This paper reviews the feasibility of the SWHS in the Middle East region from technical and economical standpoints and investigates some of the progress, challenges, and barriers toward this market. The pay-back times and CO2 emission reduction under different incentive frameworks and configurations of each system have been assessed in this context. Furthermore, the advantages and weaknesses of the SWHS in several countries have been reported. Finally, various guidelines have been proposed to enhance the development of this technology.
The German Federal Government identifies the integration of industrial waste heat and solar thermal energy into district heating systems as two measures to decarbonize the heating and cooling market ...in The Climate Action Plan 2050. This work determines the theoretical potential of industrial waste heat and solar thermal power within the cities’ boundaries and in relation to the cities’ district heating systems. A prognosis for the year 2030 and 2050 will be given. Poor information about industrial waste heat is bypassed by taking industrial emission from the dehst and by calculating the overall installed energy by stoichiometry. 10 %, 20 %, 30 % of the so calculated primary energy input is assumed to be meaningful integrable waste heat. The potential of solar thermal power is estimated by the solar fraction that is given with 1 %, 5 % and 15 %. The results show a high, currently unused potential of industrial waste heat sources and solar thermal power for the integration into district heating. In some cities, these energy sources can supply the heat demand of the city’s district heating system completely.
•Waste heat from industrial sectors has great potential to cover district heating demand.•In 2050, the waste heat from industrial sectors of the cities under consideration will still be roughly 36 TWh⁄a @ 20 °C.•Solar thermal energy can cover up to 15% of the district heating needs with less than 1% of the city area.
A large fraction of the energy demand is due to space heating. Direct solar heating might reduce the need of fossil fuels. However the poor solar collector efficiency when outside temperature and ...solar radiation are low, as in the heating season, limit most of solar collectors application to domestic hot water heating. Similarly air source heat pumps are penalized just when the heating demand is higher. Then a possible solar contribution to the outside air as a heat pump cold source was first analyzed, evaluating different integration modes of the two sources. Subsequently the coupling of a ground source and a solar section appeared a more favourable application, also because solar heat could recharge the ground in periods of low or no heating demand. At the same time the solar section might reduce the length of the expensive boreholes. Solar assisted absorption heat pumps were successfully experimented. Recently studies were devoted to a solar assistance of heat pumps by PV/T collectors, that offer both a fraction of the electricity to drive the heat pump and a solar assistance to the heat pump cold source, be it the ground or the outside air.
•Performance of triple-pipes in a district heating system with two supply temperatures is analyzed.•Various arrangements of the supply and the return lines are considered in the simulations.•A ...triangular arrangement of the supply and return lines is found as the best case among all.•The triple-pipe system is compared with a twin-pipe system, being found a more efficient solution.
Employing triple-pipes for simultaneous yet separate supply of space heating and domestic hot water demands of district heating network is an interesting solution for decreasing the rate of losses and increasing the cost-effectiveness of district heating systems. Although the thermodynamic performance of triple-pipes has been studied before, there is not any detailed performance analysis of such pipes, especially for the specific two-supply-temperature district heating design. This study employs computational fluid dynamic methods to investigate the feasibility of using triple-pipes for this district heating scheme and presents a detailed report of the thermal behavior of such pipes under different operational conditions including different pipe arrangements within the casing. For better understanding the effect of using triple-pipes in such a district heating system, the results obtained for this type of pipe is compared to those given for a twin-pipe in a regular district heating system. The results show that a triple-pipe with any arrangement is better than a twin-pipe supply method while this enhancement can be much better with a triangular arrangement of the three lines within the casing. With certain supply and return temperatures for a 10 km long pipeline, the rate of heat loss from the most efficient triple-pipe design is only 80 kW while it is about 145 kW for the twin-pipe system.
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