scholarly journals Modelling of an Existing Neutral Temperature District Heating Network: Detailed and Approximate Approaches

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 379
Author(s):  
Selva Calixto ◽  
Marco Cozzini ◽  
Giampaolo Manzolini
Keyword(s):  
Waste Heat ◽  
District Heating ◽  
Approximate Model ◽  
Primary Energy ◽  
Heat Pumps ◽  
The Other ◽  
Heat Sources ◽  
Detailed Model ◽  
Neutral Temperature ◽  
Energy Balances

This paper deals with the modelling of an existing neutral-temperature district heating network, meaning that the distribution temperature is close to the ambient temperature, with decentralised heat pumps. The considered case is located in Ospitaletto, Italy. Heat sources are given by industrial waste heat at about 25 °C and aquifer wells at about 15 °C. Two models are used to analyse the network: a detailed model able to calculate local values of operating parameters and an approximate model focused on energy balances aggregating all users with a lumped demand. Both models include the behaviour of heat pumps, a feature not available in other district heating modelling tools. An entire year of operation is considered, with an hourly time resolution. Load profiles are provided as inputs, while the main outputs consist of energy balances and primary energy consumptions. The corresponding results are compared, showing a reasonable agreement, where the approximate model underestimates the overall electricity consumptions by about 15% with respect to the detailed model. On the other hand, the different information levels and execution times (the detailed model requires about 30 min to solve the considered network for a full year with hourly time steps, while the approximate model is almost immediate) make the two models suitable for different purposes, like the simulation of control solutions for the detailed one and scenario analysis for the other.

scholarly journals Local Heating Networks with Waste Heat Utilization: Low or Medium Temperature Supply?

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 954 ◽  
Author(s):  
Hanne Kauko ◽  
Daniel Rohde ◽  
Armin Hafner
Keyword(s):  
Low Temperature ◽  
Heat Pump ◽  
Urban Areas ◽  
Waste Heat ◽  
Local Heating ◽  
District Heating ◽  
Heat Pumps ◽  
Hot Water ◽  
Local Network ◽  
Medium Temperature

District heating enables an economical use of energy sources that would otherwise be wasted to cover the heating demands of buildings in urban areas. For efficient utilization of local waste heat and renewable heat sources, low distribution temperatures are of crucial importance. This study evaluates a local heating network being planned for a new building area in Trondheim, Norway, with waste heat available from a nearby ice skating rink. Two alternative supply temperature levels have been evaluated with dynamic simulations: low temperature (40 °C), with direct utilization of waste heat and decentralized domestic hot water (DHW) production using heat pumps; and medium temperature (70 °C), applying a centralized heat pump to lift the temperature of the waste heat. The local network will be connected to the primary district heating network to cover the remaining heat demand. The simulation results show that with a medium temperature supply, the peak power demand is up to three times higher than with a low temperature supply. This results from the fact that the centralized heat pump lifts the temperature for the entire network, including space and DHW heating demands. With a low temperature supply, heat pumps are applied only for DHW production, which enables a low and even electricity demand. On the other hand, with a low temperature supply, the district heating demand is high in the wintertime, in particular if the waste heat temperature is low. The choice of a suitable supply temperature level for a local heating network is hence strongly dependent on the temperature of the available waste heat, but also on the costs and emissions related to the production of district heating and electricity in the different seasons.

Reduction of Primary Energy Consumption Through Distributed Thermal Storage in Buildings Connected With a District Heating Network

2014 ◽  
Author(s):  
Giorgia Baccino ◽  
Sara Cosentino ◽  
Elisa Guelpa ◽  
Adriano Sciacovelli ◽  
Vittorio Verda
Keyword(s):  
Energy Consumption ◽  
Thermal Load ◽  
Waste Heat ◽  
Distributed Storage ◽  
Fluid Dynamic ◽  
District Heating ◽  
Thermal Storage ◽  
Primary Energy ◽  
Operating Conditions ◽  
Primary Energy Consumption

One of the possible options for increasing the primary energy efficiency in district heating networks (DHNs) consists in flattening the thermal load diagram of the plants. This can be obtained through thermal storage. Storage generally allows one to increase the percentage of heat produced through CHP plants, waste heat or renewable systems. In this work, a numerical approach to analyze possible effects of distributed storage on the primary energy consumption is presented. This is based on the availability of detailed information about the thermal substations that connect the users to the DHN and a thermo-fluid dynamic model of the network. First, the analysis of a user of the district heating network is proposed in order to show the operating conditions of the heat exchanger in the thermal substation. Then the model of the network is presented and an application is proposed. This application allows us to discuss how the thermal request of a user modifies along the network because of the heat capacity of the network itself and mixing with the mass flow rates at different temperatures. Therefore, the thermal load that the plants should fulfill is different than the simple summation of the thermal request of the users. This tool allows one to link the thermal thermal request of the users to the thermal load of the plant and thus to the global primary energy consumption. It can be then applied to the evaluation of possible variation of thermal request profile of the users.

scholarly journals Synthesis and Optimal Operation of Smart Microgrids Serving a Cluster of Buildings on a Campus with Centralized and Distributed Hybrid Renewable Energy Units

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 745 ◽  
Author(s):  
Daniele Testi ◽  
Paolo Conti ◽  
Eva Schito ◽  
Luca Urbanucci ◽  
Francesco D’Ettorre
Keyword(s):  
Renewable Energy ◽  
Combustion Engine ◽  
District Heating ◽  
Energy System ◽  
Primary Energy ◽  
Heat Pumps ◽  
Optimal Operation ◽  
Optimal Control Strategy ◽  
Renewable Energy Technologies ◽  
Energy Technologies

Micro-district heating networks based on cogeneration plants and renewable energy technologies are considered efficient, viable and environmentally-friendly solutions to realizing smart multi-energy microgrids. Nonetheless, the energy production from renewable sources is intermittent and stochastic, and cogeneration units are characterized by fixed power-to-heat ratios, which are incompatible with fluctuating thermal and electric demands. These drawbacks can be partially overcome by smart operational controls that are capable of maximizing the energy system performance. Moreover, electrically driven heat pumps may add flexibility to the system, by shifting thermal loads into electric loads. In this paper, a novel configuration for smart multi-energy microgrids, which combines centralized and distributed energy units is proposed. A centralized cogeneration system, consisting of an internal combustion engine is connected to a micro-district heating network. Distributed electric heat pumps assist the thermal production at the building level, giving operational flexibility to the system and supporting the integration of renewable energy technologies, i.e., wind turbines, photovoltaic panels, and solar thermal collectors. The proposed configuration was tested in a hypothetical case study, namely, a University Campus located in Trieste, Italy. The system operation is based on a cost-optimal control strategy and the effect of the size of the cogeneration unit and heat pumps was investigated. A comparison with a conventional configuration, without distributed heat pumps, was also performed. The results show that the proposed configuration outperformed the conventional one, leading to a total-cost saving of around 8%, a carbon emission reduction of 11%, and a primary energy saving of 8%.

District Heating Network Modelling for the Analysis of Low-Exergy Sources

2017 ◽  
Author(s):  
Vittorio Verda ◽  
Elisa Guelpa
Keyword(s):  
Power Plants ◽  
Waste Heat ◽  
Fluid Dynamic ◽  
Renewable Energy Sources ◽  
Variable Mass ◽  
District Heating ◽  
Conservation Equation ◽  
Operating Conditions ◽  
Heat Sources ◽  
District Heating System

One of the main advantages of district heating system technology is the possibility of integrating multiple heat sources for domestic heating. In particular, it is often possible exploit low-exergy sources, such as waste heat recovered from industry or from renewable energy sources, that are often affected by time variation of the temperature. A very convenient and useful opportunity for predicting and analyzing district heating network behavior is modelling. Modelling allows to quantify opportunities related to changes in DH (district heating) network design or management, before real implementation. Therefore an important point is the creation of models able to simulate network, also very large and linked to many power plants, working at variable heat production conditions (i.e. variable mass flow rates and temperatures). The goal of this work is to propose a novel approach which combines exergy analysis with a DH network model for evaluating the best DH operating conditions. A thermo-fluid dynamic model based on conservation equation has been adapted for the discussed aims and applied to a network involving different low-exergy heat sources with variable temperatures. An evaluation of the implementation of these sources is provided for the Turin district heating network, which is the largest network in Italy.

scholarly journals Assessment of a combination of three heat sources for heat pumps to supply district heating

Energy ◽  
2019 ◽  
Vol 176 ◽  
pp. 156-170 ◽  
Author(s):  
Henrik Pieper ◽  
Torben Ommen ◽  
Brian Elmegaard ◽  
Wiebke Brix Markussen
Keyword(s):  
District Heating ◽  
Heat Pumps ◽  
Heat Sources

scholarly journals Analysis of Different Strategies for Lowering the Operation Temperature in Existing District Heating Networks

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 321 ◽  
Author(s):  
Francesco Neirotti ◽  
Michel Noussan ◽  
Stefano Riverso ◽  
Giorgio Manganini
Keyword(s):  
Energy Efficiency ◽  
Power Plants ◽  
Waste Heat ◽  
Control Strategies ◽  
Renewable Energy Sources ◽  
District Heating ◽  
Heating System ◽  
Heat Pumps ◽  
Critical Parameters ◽  
District Heating System

District heating systems have an important role in increasing the efficiency of the heating and cooling sector, especially when coupled to combined heat and power plants. However, in the transition towards decarbonization, current systems show some challenges for the integration of Renewable Energy Sources and Waste Heat. In particular, a crucial aspect is represented by the operating temperatures of the network. This paper analyzes two different approaches for the decrease of operation temperatures of existing networks, which are often supplying old buildings with a low degree of insulation. A simulation model was applied to some case studies to evaluate how a low-temperature operation of an existing district heating system performs compared to the standard operation, by considering two different approaches: (1) a different control strategy involving nighttime operation to avoid the morning peak demand; and (2) the partial insulation of the buildings to decrease operation temperatures without the need of modifying the heating system of the users. Different temperatures were considered to evaluate a threshold based on the characteristics of the buildings supplied by the network. The results highlight an interesting potential for optimization of existing systems by tuning the control strategies and performing some energy efficiency operation. The network temperature can be decreased with a continuous operation of the system, or with energy efficiency intervention in buildings, and distributed heat pumps used as integration could provide significant advantages. Each solution has its own limitations and critical parameters, which are discussed in detail.

Optimization of the Thermal Request Profiles of Buildings Connected With a Large District Heating Network

2016 ◽  
Author(s):  
Vittorio Verda ◽  
Elisa Guelpa ◽  
Giulia Barbero ◽  
Francesco Brundu ◽  
Andrea Acquaviva ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Waste Heat ◽  
Central Area ◽  
District Heating ◽  
Thermal Storage ◽  
Primary Energy ◽  
Physical Models ◽  
Primary Energy Consumption ◽  
Peak Shaving ◽  
Start Up

Thermal storage is very important in modern district heating networks in order to increase the share of waste heat and heat produced through renewable sources and cogeneration. The role of thermal storage is even more important in the case of Mediterranean areas, where climate and user behavior cause high peak requests in the morning. Nevertheless the installation of large storage volumes is not always feasible, especially in dense urban areas, therefore alternative options are investigated. One of these options is virtual storage. This consists in proposing changes to the thermal request profiles of some of the connected buildings, in order to obtain a peak shaving, which is an effect similar to that obtained using storage. To perform such approach there are two crucial elements: 1) an advanced ICT solution able provide real time information about the thermal request of the buildings and the thermodynamic conditions at the thermal substations; 2) a detailed thermo fluid-dynamic model of the district heating network able to simulate the temperature evolution along the network as the function of time. Using physical models it is possible to examine the effects, obtained by modifying the thermal request of users, on the total load of the thermal plants feeding the network. In particular, the model is applied to the analysis of changes in the start-up time of the buildings as well as possible pauses during the day. The start-up strategy should not produce significant effects on the building temperatures, so that acceptable comfort standard can be guaranteed. This is checked using a compact model of the buildings which parameters are obtained through data measured at the thermal substations. These changes in the request profiles usually involve a larger heat request. Nevertheless, peak shaving is accompanied by a reduction in heat generation of boilers and an increase in the thermal production of efficient systems, such as cogeneration units. This results in a significant reduction in the primary energy consumption. The goal of the analysis is to find the optimal start-up strategy in order to minimize the primary energy consumption at the thermal plants. An application to the Turin district heating network, which is the largest network in Italy, is presented. In particular, a subnetwork connecting the main transport network to about 100 buildings located in the central area of the town is considered. The analysis if performed in selected days where the optimization was conducted the day before on the basis of weather forecasts and then applied to the network. Despite the changes in the request profiles could be applied only to a limited number of buildings, the analysis show that the peak request can be reduced. Simulations performed considering the application of changes to a larger number of buildings show that reduction in the primary energy consumptions of the order of 1.25% can be obtained.

Thermodynamic Heating With Various Types of Cogeneration Plants and Heat Pumps

1995 ◽  
Vol 117 (2) ◽  
pp. 251-258 ◽  
Author(s):  
K. Stachel ◽  
H. U. Frutschi ◽  
H. Haselbacher
Keyword(s):  
Power Plant ◽  
Power Plants ◽  
Primary Energy ◽  
Heat Pumps ◽  
Combined Cycle ◽  
The Other ◽  
Environmental Damage ◽  
Site Conditions ◽  
Fuel Utilization ◽  
Heating Method

The thermodynamic heating method combines cogeneration power plants and heat pumps in order to maximize the heating energy that can be derived from a given amount of fuel. In doing this, unnecessary waste of primary energy and environmental damage can be prevented. In this paper, four cogeneration systems—combined cycle plants, steam and gas turbine power plants, and gas engines—and heat pump systems are investigated and compared with respect to fuel utilization for realistic site conditions. It is shown that the combined cycle cogeneration power plant is superior to the other three types of power plant.

scholarly journals Reuse of Data Center Waste Heat in Nearby Neighborhoods: A Neural Networks-Based Prediction Model

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 814 ◽  
Author(s):  
Marcel Antal ◽  
Tudor Cioara ◽  
Ionut Anghel ◽  
Radoslaw Gorzenski ◽  
Radoslaw Januszewski ◽  
...  
Keyword(s):  
Data Center ◽  
High Performance ◽  
Data Centers ◽  
Waste Heat ◽  
District Heating ◽  
Heat Pumps ◽  
Training Data ◽  
Pump Operation ◽  
Hot Air ◽  
Dynamics Simulations

This paper addresses the problem of data centers’ cost efficiency considering the potential of reusing the generated heat in district heating networks. We started by analyzing the requirements and heat reuse potential of a high performance computing data center and then we had defined a heat reuse model which simulates the thermodynamic processes from the server room. This allows estimating by means of Computational Fluid Dynamics simulations the temperature of the hot air recovered by the heat pumps from the server room allowing them to operate more efficiently. To address the time and space complexity at run-time we have defined a Multi-Layer Perceptron neural network infrastructure to predict the hot air temperature distribution in the server room from the training data generated by means of simulations. For testing purposes, we have modeled a virtual server room having a volume of 48 m3 and two typical 42U racks. The results show that using our model the heat distribution in the server room can be predicted with an error less than 1 °C allowing data centers to accurately estimate in advance the amount of waste heat to be reused and the efficiency of heat pump operation.

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