Dynamic modeling and control of transcritical vapor compression system for battery electric vehicle thermal management

Electrification is an increasing trend among vehicle systems such as aircrafts, heavy machinery, and civilian transportation. Battery electric vehicles (BEVs) are one such development that use a battery pack to generate electrical energy used to propel the vehicle and power its auxiliaries. However, the battery pack also generates thermal energy as a byproduct which affects the electrical performance of the battery pack. The inherent coupling between electrical and thermal performance creates a challenge in design and control of these complex systems. Furthermore, phase-out of common refrigerants drives interest in CO2 refrigerant, an environmentally friendly and safe alternative. However, these vapor compression systems operate transcritical, thus requiring novel control techniques. This thesis develops a framework for architecture and control design of BEV subsystems. The foundation of this process is the development of multi-domain models. Models for the transcritical vapor compression system and the vehicle cabin are derived from a first principles analysis. A model for a battery pack is derived from an equivalent circuit electrical model and a conservation of energy thermal model. All of the models capture dynamic, nonlinear behaviors important for control development and understanding of coupling between variables. Additionally, the models are scalable and able to be parameterized in order to represent many variations of system architectures. An air-cooled cabin and air-cooled battery pack configuration is demonstrated in open-loop and closed-loop simulations. For closed loop simulation, a model predictive controller (MPC) is compared to baseline decentralized, proportional-integral controllers. The model predictive control makes control decisions based on the minimization of a cost function that weights the regulation of specific variables (such as temperature of the battery pack and cabin) and power consumption of the actuators. It will be shown that the MPC, in the face of disturbances, is able to maintain outputs within their bounds while consuming less energy than baseline controllers

Developing a model for analysis of the cooling loads of a hybrid electric vehicle by using co-simulations of verified submodels

The requirement for including the air-conditioning and the battery-cooling loads within the energy efficiency analyses of a hybrid electric vehicle is widely recognized and has promoted system-level simulations and integrated modelling, escalating the challenge of balancing the accuracy and the speed of simulations. In this paper, a hybrid electric vehicle model is created through co-simulation of the passenger cabin, the air conditioning, the battery cooling, and the powertrai. Calibration and verification of the submodels help determine their accuracy in representing the target vehicle and achieve a balance between the model fidelity and the simulation speed. The result is a model which has a higher accuracy and a higher speed than those of similar models developed previously and which provides a reliable tool for a thorough investigation of the cooling loads for different ambient conditions and different duty cycles

performances of an orc power unit for waste heat recovery on heavy duty engine

Abstract Reciprocating internal combustion engines (ICE) are still the most used in the sector of the on-the-road transportation, both for passengers and freight. CO2 reduction is the actual technological driver, considering the worldwide greenhouse reduction targets committed by most governments. In ICE more than one third of the fuel energy used is rejected to the environment as thermal waste through the exhaust gases. Therefore, a greater fuel economy could be achieved, if this energy was recovered and converted into useful mechanical or electrical power. This recovery appears very interesting, in particular for those engines that run at almost steady working conditions, like marine, agricultural, industrial or long-hauling vehicle applications. In this paper, an ORC-based power unit was tested on a heavy duty diesel engine. Energetic and exergetic analyses have been carried out in order to assess the real performances of the ORC unit and to individuate differences with the theoretical ones. A single stage impulse axial turbine has been tested in this work, complete with an electric variable speed generator and an AC/DC converter. The tests demonstrated that the energy conversion chain is not negligible at all and an overall net efficiency of the power unit was around 2-3 % with respect to a 10% of thermodynamic efficiency

1D Modelling and Analysis of Thermal Conditioning Systems for Electric Vehicles

The limited driving range, due to the poor storage capability of electric batteries, represents one of the greatest challenges in the development of electric vehicles. This concern leads to an extremely demanding design of every component within the vehicle powertrain in order to achieve their maximum energy efficiency and decrease the demand on the battery. Additionally, in cold climate conditions, the efficiency of the heating system of an electric vehicle decreases and it can result in further reducing its driving range. In this thesis, 1D modelling in Amesim will be used to analyze different concepts of thermal management for an electric vehicle. Firstly, a 1D model of the original refrigeration system of the chosen vehicle (Fiat 500e) was built by implementing the data of each component. The components were individually modelled, then assembled within a system level model and the final model was validated. Secondly, starting with the validated system, a 1D model of a heat pump system was proposed as a replacement for the commonly used positive temperature coefficient heater (PTC). This model was obtained exploiting the information available on the refrigeration system and assuming all the unknown characteristics. An energy and exergy analysis was carried out to determine the individual components and overall system performance. Finally, the vehicle cabin was modelled exploiting a new Embedded CFD tool of Amesim capable of combining the advantages of 1D and 3D modelling, hence providing lower CPU resources and time consumption required to perform a simulation due to the lower effort to model the temperature distribution inside the cabin. This approach gives also the chance to study zonal heating and cooling of the cabin in order to reduce the energy demand on the battery. Numerous simulations were performed to analyze the impact of different settings and parameters validating each of them through comparison with experimental data

CO2 HEAT PUMPS FOR COMMERCIAL BUILDING APPLICATIONS WITH SIMULTANEOUS HEATING AND COOLING DEMAND

Many commercial buildings, including data centers, hotels and hospitals, have a simultaneous heating and cooling demand depending on the season, occupation and auxiliary equipment. A data center on the Purdue University, West Lafayette campus is used as a case study. The electrical equipment in data centers produce heat, which must be removed to prevent the equipment temperature from rising to a certain level. With proper integration, this heat has the potential to be used as a cost-effective energy source for heating the building in which the data center resides or the near-by buildings. The proposed heat pump system utilizes carbon dioxide with global warming potential of 1, as the refrigerant. System simulations are carried out to determine the feasibility of the system for a 12-month period. In addition, energy, environmental and economic analyses are carried out to show the benefits of this alternative technology when compared to the conventional system currently installed in the facility. Primary energy savings of ~28% to ~61%, a payback period of 3 to 4.5 years and a decrease in the environmental impact value by ~36% makes this system an attractive option. The results are then extended to other commercial buildings

A cleaner and more efficient energy system achieving a sustainable future for road transport

A novel integrated cooling system is developed for future medium to large electric vehicles by integrating the fuel cell, battery, metal-hydride, heat pump, and liquid desiccant dehumidification system to reduce power consumption and extend vehicle's driving range. The system benefits from the reuse of the normally wasted energy in the form of pressure difference and wasted thermal energy, from the hydrogen vessel, the fuel cell stack, and the battery pack. A numerical model for the proposed system and a finite element model for the dehumidifier and regenerator are developed and validated by experimental results from published data. A comprehensive evaluation of the impacts of the ambient air temperature and humidity, fuel cell current output, battery discharging C rate, and air mass flow rate on the Coefficient of Performance (COP), outlet air temperature, and cooling capacity is conducted. Two operating modes, namely non-compressive mode and heat pump supplemental mode are investigated and a detailed comparison between these two modes is undertaken. Furthermore, the proposed system under heat pump supplemental mode has been compared to other published cooling systems and dehumidification systems. Under non-compressive mode, results indicate that the proposed system can provide sufficient cooling capacity without the need of the compressor when the supply air mass flow rate is lower than 0.03kg/s, under the specific operating situation. Under the heat pump supplemental mode, the proposed system can operate at 36 °C with a COP greater than 4, which is 56% higher than the cited published results, although the COP of the proposed system also considers battery cooling. Heat pump supplemental mode drastically reduces the 12-second insufficient cooling period that occurs at the beginning of the charging to discharging transition between the two metal hydrides to 2 seconds compared to non-compressed mode. Overall, this study provides a potential solution for future zero-emission vehicles by utilizing the heat and electric co-generation characteristic of the fuel cell, the isothermal characteristic of the metal hydride, and dehumidification and cooling characteristics of the liquid desiccant dehumidification system to extend the driving range of the electric vehicles and reduce energy consumption for cooling. Moreover, the proposed system can also provide domestic cooling loads and power by integrating the system into residential buildings

Soft computing based controllers for automotive air conditioning system with variable speed compressor

The inefficient On/Off control for the compressor operation has long been regarded as the major factor contributing to energy loss and poor cabin temperature control of an automotive air conditioning (AAC) system. In this study, two soft computing based controllers, namely the proportional-integral-derivative (PID) based controllers tuned using differential evolution (DE) algorithm and an adaptive neural network based model predictive controller (A-NNMPC), are proposed to be used in the regulation of cabin temperature through proper compressor speed modulation. The implementation of the control schemes in conjunction with DE and neural network aims to improve the AAC performance in terms of reference tracking and power efficiency in comparison to the conventional On/Off operation. An AAC experimental rig equipped with variable speed compressor has been developed for the implementation of the proposed controllers. The dynamics of the AAC system is modelled using a nonlinear autoregressive with exogenous inputs (NARX) neural network. Based on the plant model, the PID gains are offline optimized using the DE algorithm. Experimental results show that the DE tuned PID based controller gives better tracking performance than the Ziegler-Nichols tuning method. For A-NNMPC, the identified NARX model is incorporated as a predictive model in the control system. It is trained in real time throughout the control process and therefore able to adaptively capture the time varying dynamics of the AAC system. Consequently, optimal performance can be achieved even when the operating point is drifted away from the nominal condition. Finally, the comparative assessment indicates clearly that A-NNMPC outperforms its counterparts, followed by DE tuned PID based controller and the On/Off controller. Both proposed control schemes achieve up to 47% power saving over the On/Off operation, indicating that the proposed control schemes can be potential alternatives to replace the On/Off operation in an AAC system

Waste Heat Recovery From a Compression Ignition Engine using a Combined Diesel Particulate Filter Heat Exchanger

Compression ignition (CI) engines have been a figurehead in the transportation industry for decades. However, as environmental regulations dictate increasingly strict emissions guidelines for engines, technologies must accordingly advance. To this end, this thesis describes the work of validating a combined diesel particulate filter heat exchanger (DPFHX) for CI engine exhaust waste heat recovery (WHR) in a Rankine Cycle (RC), a concept introduced in the first chapter of this thesis. The second chapter includes a comprehensive literature review, indicating the increasing prevalence of WHR in the literature. Additionally, with RC as the principal system for WHR and engine exhaust as the primary heat source, this research is exceptionally relevant. Furthermore, the primary aspects of an RC WHR system requiring individual optimization are the heat exchangers and expanders along with working fluid selection. As such, the third chapter discusses experiments to analyze and compare the DPFHX with various working fluids; thus, incorporating the literature trends of working fluid comparison and component specificity in the methodology. Consequently, in the DPFHX, water achieved a higher heat transfer rate by over 60% than the 50% by volume mixture of water and ethylene glycol, the two optimal working fluids in the apparatus without DPF cores. However, alterations made to the DPF cores’ outer diameters and lengths when installing them in the heat exchanger tubes prevented them from achieving the expected outcome (i.e., improving apparatus performance). Finally, the fourth chapter links the conclusions from this work to recommendations for future efforts to investigate DPFHXs

THIESEL 2022. Conference on Thermo-and Fluid Dynamics of Clean Propulsion Powerplants

The THIESEL 2022. Conference on Thermo-and Fluid Dynamic Processes in Direct Injection Engines planned in Valencia (Spain) for 8th to 11th September 2020 has been successfully held in a virtual format, due to the COVID19 pandemic. In spite of the very tough environmental demands, combustion engines will probably remain the main propulsion system in transport for the next 20 to 50 years, at least for as long as alternative solutions cannot provide the flexibility expected by customers of the 21st century. But it needs to adapt to the new times, and so research in combustion engines is nowadays mostly focused on the new challenges posed by hybridization and downsizing. The topics presented in the papers of the conference include traditional ones, such as Injection & Sprays, Combustion, but also Alternative Fuels, as well as papers dedicated specifically to CO2 Reduction and Emissions Abatement.Papers stem from the Academic Research sector as well as from the IndustryXandra Marcelle, M.; Payri Marín, R.; Serrano Cruz, JR. (2022). THIESEL 2022. Conference on Thermo-and Fluid Dynamics of Clean Propulsion Powerplants. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thiesel.2022.632801EDITORIA