xEV thermal system control

The increasing electrification of vehicle powertrains has resulted in complex thermal systems. The performance of the thermal system has a strong impact on the electric range. This paper will discuss different thermal system concepts and the related control strategies to optimise their performance. The control algorithm complexity has increased with multi-variable systems and temperature limits that result in a challenging control problem. This paper will discuss the use of model predictive control and optimal control approaches to develop the control solution for this problem. These techniques have the additional benefit of reducing calibration effort whilst delivering efficiency gains

Overview of the Activities on Heavy Duty Diesel Engines Waste Heat Recovery with Organic Rankine Cycles (ORC) in the Frame of the ECCO-MATE EU FP7 Project

The ECCO-MATE Project is a European Union funded project aimed to develop a synergistic framework for cutting edge research on novel engine technologies for higher energy efficiency and lower emissions. The project partners, Ricardo plc, an engineering consulting company, and the University of Trieste, focus the research attention on waste heat recovery systems, such as Organic Rankine Cycles (ORC), which are gaining increasing interest by engine manufacturers, vehicles and ships fleet operators, because of their potential for further increasing engine efficiency and decreasing fuel consumption. In particular, in the frame of the developed research activity, the 1-D Ricardo engine simulation software WAVE has been used in order to assess novel engine concepts, both in the commercial vehicles and marine sectors. A combined engine-ORC system First and Second Law of Thermodynamics analysis has been proposed in order to study where system inefficiencies are concentrated and propose improvements, with particular focus on commercial vehicle heavy duty diesel engines. A thermo-economic analysis has been also considered. In collaboration with the project partners National Technical University of Athens (NTUA) and Winterthur Gas & Diesel, an innovative low pressure Exhaust Gas Recirculation (EGR) configuration for low speed 2-stroke ship propulsion units has also been studied with the aim of reducing NOx in order to meet IMO Tier III emissions limits. ORC systems are, in this application also, a promising technology that can be used, in synergy with emission reduction systems, to recover, in particular, low temperature heat sources such as engine coolant and scavenging air, always with the aim of improving overall system efficiency while respecting new stringent emission reduction targets. The first results of the research activity show that a fuel consumption improvement up to 10% could be achieved both for commercial vehicles off-highway applications and in the marine sector, depending on the type of ORC and waste heat recovery architecture chosen and the engine considered

A Novel Loop Heat Pipe Based Cooling System for Battery Packs in Electric Vehicles

A novel cooling method for Electric Vehicles battery modules by means of Loop Heat Pipe and graphite sheets is proposed. The Loop Heat Pipe is a passive two-phase system and as such it reduces the parasitic power consumed by the EV thermal management. A validated lumped parameter mathematical model has been created describing the thermo-fluid-dynamic problem and used to simulate the performance of the cooling system during highway driving and ultra-fast charging conditions. The numerical predictions show a clear potential to contain the cells’ temperature below 40°C even during ultra-fast charging, with a 3.3K peak temperature reduction in comparison to a conventional liquid cooling method. Moreover, this system adds only 8% of the battery pack mass and it shows potential parasitic power reductions of one order of magnitude

Numerical investigation on a combined loop heat pipe and graphite sheets cooling system for automotive applications

An innovative Battery Thermal Management System for a 3-cell Electric Vehicle module is proposed, involving Loop Heat Pipes and graphite sheets, with the particular aim of fast charging and reacting to automotive requirements. The design feasibility is verified through a Lumped Parameter Model, which has been validated comparing the data from an experimental demonstrator which included a copper/copper flat plate Loop Heat Pipe running ethanol. Results show that this solution is able to maintain the maximum temperature below 32°C after a 10 min fast charge cycle. System performance with a standard working fluid such as ethanol are compared with the system performance using a novel fluid, Novec™ 649, which has desirable features for the automotive industry, such as non-flammability, non-toxicity, below-zero freezing point and outstanding environmental properties (GWP = 1, ODP = 0). Nevertheless, comparison between the results with the two fluids reported no significant difference in thermal performance showing no contraindication in the use of the novel working fluid. Moreover, the model was used to estimate the effect of the Loop Heat Pipe building material, resulting in no sensible difference between the utilization of copper and aluminium, de facto justifying the choice of the lighter material for future applications

Performance of an Environmentally Friendly Alternative Fluid in a Loop Heat Pipe-Based Battery Thermal Management System

The present investigation aims to devise a thermal management system (TMS) for electric vehicles able to improve on limitations like charging time and all-electric range, together with the safety and environmental impact of the chosen thermal medium. A research gap is identified, as focus is often on addressing system thermal performance without considering that the thermal medium must not only provide suitable performances, but also must not add risks to both passengers and the environment. Thus, this work proposes an innovative cooling system including graphite sheets and a Loop Heat Pipe, filled with Novec™ 649 as working fluid, due to its exceptional environmental properties (GWP = 1 − ODP = 0) and safety features (non-flammable, non-toxic, dielectric). A three-cell module experimental demonstrator was built to compare temperatures when the proposed TMS is run with Novec™ 649 and ethanol. Results of testing over a bespoke fast charge driving cycle show that Novec™ 649 gave a faster start-up and a slightly higher maximum temperature (0.7 °C), meaning that the gains in safety and lower environmental impact brought by Novec™ 649 came without lowering the thermal performance. Finally, the TMS was tested under three different fast charge conditions (1C, 2C, 3C), obtaining maximum temperatures of 28.4 °C, 36.3 °C and 46.4 °C, respectively

Numerical investigation on a combined loop heat pipe and graphite sheets cooling system for automotive applications

An innovative Battery Thermal Management System for a 3-cell Electric Vehicle module is proposed, involving Loop Heat Pipes and graphite sheets, with the particular aim of fast charging and reacting to automotive requirements. The design feasibility is verified through a Lumped Parameter Model, which has been validated comparing the data from an experimental demonstrator which included a copper/copper flat plate Loop Heat Pipe running ethanol. Results show that this solution is able to maintain the maximum temperature below 32°C after a 10 min fast charge cycle. System performance with a standard working fluid such as ethanol are compared with the system performance using a novel fluid, Novec™ 649, which has desirable features for the automotive industry, such as non-flammability, non-toxicity, below-zero freezing point and outstanding environmental properties (GWP = 1, ODP = 0). Nevertheless, comparison between the results with the two fluids reported no significant difference in thermal performance showing no contraindication in the use of the novel working fluid. Moreover, the model was used to estimate the effect of the Loop Heat Pipe building material, resulting in no sensible difference between the utilization of copper and aluminium, de facto justifying the choice of the lighter material for future applications

COMPARISON BETWEEN DIFFERENT BATTERY THERMAL MANAGEMENT SYSTEMS DURING FAST CHARGE CYCLES

Aiming to improve on fast charge timings, all-electric range and to reduce costs and complexity, a Battery Thermal Management System (BTMS) with Loop Heat Pipes (LHPs) and graphite sheets is proposed. The LHP placed at the bottom of a prismatic cell module will transfer heat from the cells to a chiller, already part of the HVAC system of the vehicle (hence reducing complexity). Graphite, due its woven structure, provides excellent heat transfer in one direction, and insulation from cell to cell. LHPs do not need pumps or moving parts, nor they need additional energy sources to transfer heat, contrarily to an active forced convection system using fans or pumps. This work investigates the performance between the passive BTMS proposed by the Authors, another passive cooling method (free convection) and an active BTMS (liquid cold plate), thanks to a previously validated code. It resulted that free convection, compared to the LHP-based and cold plate BTMS, can contain maximum cell temperature at low values of C-rates, but is not able to reduce the temperature once the vehicle returns to normal driving conditions. Furthermore, results showed potential for the LHP BTMS to contain the cell temperature below 50°C at 5C fast charge conditions (7 minutes) and to reduce the maximum cell temperature by 7.9ºC compared to free convection and even by 2ºC compared to the active liquid cold plate

A review of waste heat recovery and Organic Rankine Cycles (ORC) in on-off highway vehicle Heavy Duty Diesel Engine applications

Heavy Duty Diesel Engine (HDDE) are between the biggest contributors to CO2 emission and ambient pollution as they are the most widely used technology for commercial vehicles and ship propulsion applications, as well as, together with reciprocating gas engines, for small medium-size distributed stationary power generation. New emission legislations in the on and off highway sectors, such as for example EURO VI and Tier 4 final, regarding NOx and Particulate Matter (PM), are also becoming year by year more stringent. For these reasons, in the last years, concerns about further engine development and efficiency improvement are of primary importance and several technologies have been studied and implemented. This review is meant to give an overview of the Organic Rankine Cycle (ORC) technology to recover wasted thermal energy in Heavy Duty Diesel Engines (e.g. exhaust gas, EGR, coolant circuit, charge air cooling, oil circuit) with particular focus on vehicle applications for on and off highway sectors (e.g. long-haul trucks, earthmoving machines, agricultural tractors). In addition, multiple different engine operating profiles in terms of torque and speed are gathered and reported for a variety of typical vehicles, in order to characterize the best system design point for the chosen application