Thermal management systems of passenger vehicles are fundamental to provide adequate cabin thermal comfort. However, for battery electric vehicles they can use a significant amount of battery energy ...and thus reduce the real driving range. Indeed, when heating or cooling the vehicle cabin the thermal management system can consume up to 84% of the battery capacity. This study proposes a model-based approach to design an energy-efficient control strategy for heating electric vehicles, considering the entire climate control system at different ambient conditions. Specifically, the study aims at reducing the energy demand of the compressor and water pumps when operating in heat pump mode. At this scope, the climate control system of the reference vehicle is modelled and validated, enabling a system efficiency analysis in different operating points. Based on the system performance assessment, the optimized operating strategy for the compressor and the water pumps is elaborated and the results show that the demand-based control achieves up to 34% energy reduction when compared to the standard control.
Climate control systems have a largely negative effect on the energy consumption of electric vehicles and consequently on their real driving range. Improving the efficiency of climate control systems ...requires advanced simulation tools for an accurate evaluation of both the energy savings and thermal comfort of innovative heating and cooling solutions. In this study, the advancements beyond the state of the art consists primarily of the methodology tackling the reduction of computational costs of intensive computational fluid dynamics (CFD) simulations and/or time-consuming experimental investigations and the simultaneous assessment of vehicle cabin thermal comfort and energy flows. The approach was validated against climatized chassis dyno measurements from the EU Horizon 2020 research project QUIET. Indeed, all the considered locations within the cabin were properly validated, both in steady state and transient conditions with the largest deviations at steady state below 3 °C. Additionally, the validation results show a perfect agreement for the average cabin predicted mean vote (PMV) value and a largest deviation in terms of the PMV for the other locations below 0.3. Furthermore, the applicability of the methodology is proved with the help of its application on a parametric study for which various cabin temperature setpoints and heating, ventilation and air conditioning (HVAC) modes were simulated in winter operation.
Innovations in today’s energy grids are mainly driven by the need to reduce carbon emissions and the necessary integration of decentralized renewable energy sources. In this context, a transition ...towards hybrid distribution systems, which effectively couple thermal and electrical networks, promises to exploit hitherto unused synergies for increasing efficiency and flexibility. However, this transition poses practical challenges, starting already in the design phase where established design optimization approaches struggle to capture the technical details of control and operation of such systems. This work addresses these obstacles by introducing a design approach that enables the analysis and optimization of hybrid thermal-electrical distribution systems with explicit consideration of control. Based on a set of key prerequisites and modeling requirements, co-simulation is identified as the most appropriate method to facilitate the detailed analysis of such systems. Furthermore, a methodology is presented that links the design process with the implementation of different operational strategies. The approach is then successfully applied to two real-world applications, proving its suitability for design optimization under realistic conditions. This provides a significant extension of established tools for the design optimization of multi-energy systems.
•Efficient simulation model for district heating and cooling pipes.•Copes with highly variable mass flow rates and temperature profiles.•Good correspondence between simulations and various ...measurements.•Simulation time decreased substantially.
Simulation and optimisation of district heating and cooling networks requires efficient and realistic models of the individual network elements in order to correctly represent heat losses or gains, temperature propagation and pressure drops. Due to more recent thermal networks incorporating meshing decentralised heat and cold sources, the system often has to deal with variable temperatures and mass flow rates, with flow reversal occurring more frequently. This paper presents the mathematical derivation and software implementation in Modelica of a thermo-hydraulic model for thermal networks that meets the above requirements and compares it to both experimental data and a commonly used model. Good correspondence between experimental data from a controlled test set-up and simulations using the presented model was found. Compared to measurement data from a real district heating network, the simulation results led to a larger error than in the controlled test set-up, but the general trend is still approximated closely and the model yields results similar to a pipe model from the Modelica Standard Library. However, the presented model simulates 1.7 (for low number of volumes) to 68 (for highly discretized pipes) times faster than a conventional model for a realistic test case. A working implementation of the presented model is made openly available within the IBPSA Modelica Library. The model is robust in the sense that grid size and time step do not need to be adapted to the flow rate, as is the case in finite volume models.
Integrated operation of distribution grids for multiple energy carriers promises hitherto unused synergies in terms of efficient generation, storage, and consumption. A major obstacle to the ...investment in such systems is their increased complexity, as conventional tools and methods were not designed to capture all relevant technical and economic aspects of hybrid grids. To address this obstacle, this work proposes a methodology to systematically assess multi-carrier energy grids under a holistic scope. By adopting a simulation-based approach that relies on detailed technical and economic models, an efficient and precise evaluation of both short-term (operational) and long-term (strategic) aspects is supported. The methodology enables the assessment of system configurations, control strategies, business models, and regulatory conditions in one coherent approach. As a proof-of-concept, the new methodology is applied to a real-world use case of a hybrid thermal-electrical distribution grid in a central European city. The results are comprehensively discussed to showcase how the various aspects of hybrid energy systems are addressed. The outcomes also demonstrate how this methodology aids the involved stakeholders in understanding the associated risks and potentials, paving the way for early adopters to realize multi-carrier energy distribution grids.
•A holistic methodology to study multi-carrier energy systems is presented.•Operational technical and strategic economic perspectives are considered.•Established tools for different domains are coupled in a co-simulation framework.•Multiple market participants and opposing objectives are taken into account.•The methodology is demonstrated by a comprehensive study in a central European city.
High return temperatures in district heating networks are a significant barrier for the transformation into 4th generation systems. In order to transport high amount of heat in winter times, there is ...the need of increased supply temperatures (>120 °C) or mass flow rates due to high return temperatures. This leads to an inefficient operation of the system. High heat losses, decreased efficiency of heat production units, reduced potential of alternative heat sources and increased pumping costs are the consequences. Further is the connection of new customers often linked with high investment costs due to limited transport capacities in an existing system.
The aim of this paper is to analyse potentials and to develop concepts to reduce return temperatures by implementing thermal energy cascades between different building types in order to improve the performance of the system. This is related to the use of the return flow of high-temperature consumers (e.g. buildings with high-temperature heating systems) for supplying low-temperature consumers (e.g. buildings with floor heating and direct domestic hot water preparation). Based on available data from existing buildings, energy suppliers and network structures, potentials for energy-cascades for representative case studies have been evaluated. To enable energy cascaded interconnections, the temperature and heat load profiles of the investigated buildings in characteristic districts were analysed and different connection scenarios were developed and evaluated. Special attention was given to the hygienic preparation of domestic hot water in the low-temperature consumers and the security of the heat supply.
As a result, the temperature level of the local return line could be reduced (up to >10 K) and transport capacities in the districts were increased (up to 16 %). By implementing this approach in several districts of an urban network, the overall system efficiency can be increased.
The current study presents model based predictions of a desiccant wheel performance using the transient measurements obtained from a real system. The model is based on a set of equations to simulate ...the optimal and measured transient performance as a function of measurable input variables related to the desiccant wheel material and structure. The model is adapted to analyze the influence of different working conditions on the desiccant wheel performance: rotation speeds, air velocity, inlet temperature, and inlet air humidity for both process and regeneration air. The model is capable of estimating the optimal rotation speed and pressure drop of the desiccant wheel. Moreover, the developed model can be applied in both, dehumidification and enthalpy modes. The model is validated in comparison to the published data and measurements from the real building desiccant wheel installation. The specific enthalpy at the outlet of process air is considered performance parameter. The obtained results are in agreement with the published data, while the resulting maximum and minimum validation root mean square error (mean percentage error) between the simulated and measured transient performance is 3.6 kJ/kg (4.6%) and 1.9 kJ/kg (0.2%), respectively.
•Developed a desiccant wheel model in equation-based object-oriented program, Dymola/Modelica.•The model is calibrated and validated using the transient measurements of a real system.•Model estimates the actual and optimal performance in both dehumidification and enthalpy modes.•Resulted max and min RMSE (PME) validation error is 3.6 kJ/kg (4.6%) and 1.9 kJ/kg (0.2%), respectively.
We present two case studies on energy grid hybridization, where the distribution networks of multiple energy sectors are more tightly coupled together to increase their flexibility via mutual ...transfer of energy. The hybridization approaches were developed in cooperation with the local stakeholder in a northern European city, comprising of a short-term setup with a low adoption barrier as well as a long-term scenario with more involved grid coupling using more efficient devices. For a range of coupling device configurations, device locations, control algorithms, and assumptions on utility prices and energy demand, we investigate the influence of the hybridization on the energy mix, CO 2 emissions, and energy costs. The studies have been conducted using a co-simulation toolchain developed by the European Project OrPHEuS specifically for fine-grained technical simulation of multi-carrier grids. Our results confirm that the hybrid grid approach is an effective means to increase the share of renewable energies and reduce operational costs. It also turns out that precise forecasts of energy demand and utility prices are essential for appropriate dimensioning of the coupling points.
Recent advancements in the domain of modeling physical processes offer opportunities to use equation based modeling environments, such as Modelica, for the simulation of building heating, ...ventilation, and air-conditioning (HVAC) systems. The current work demonstrates Modelica capabilities in a case study of real building solar thermal system simulation. The simulated system is part of an innovative ENERGYbase building, designed according to the so called Passivhaus standard. Model calibration and validation procedure is developed to include optimization based parametric adjustments of component models using the monitoring data during a single week. The calibrated system adequately reproduces half a year of real system operation. Future work will concentrate on application of the developed calibration and validation methodology in the whole year overall building energy simulation.
Building automation is the key to exploiting flexibilities in building operation with regard to integration of renewable energy sources, load shifting and general optimization for energy efficiency. ...Based on thermal and electric models of building physics and the energy producers and consumers in the building it is possible to assess the current state of the building and its systems and make predictions about the expected future behavior, which can be exploited to be beneficial for the electric and thermal grid.
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