Session: 3.3 - Open Source CFD

Paper Number: 168065

168065 - A Study on Aerodynamic Analysis of a Photovoltaic Electric Vehicle With a Pair of Built-in Diffusers During Motion 

Abstract: 

Responding to the dramatic global climate anomalies, net-zero emission has become an important goal of global sustainable development. “Renewable energy” and “vehicle electrification” are the most important strategies for the worldwide net-zero transition. The automotive manufacturers are on a voyage to achieving 100% of sales volume for Battery-Powered Electric Vehicle (BEV) by 2050. It is more necessary to prioritize improving the energy efficiency of electric vehicles as a development goal.

To enhance the energy efficiency of BEV, the most sought-after way is to improve the aerodynamics of the vehicles. Currently, many studies focus on installing different add on devices, such as spoilers, diffusers, and flaps on vehicles. This study uniquely integrates diffuser devices that can enhance the aerodynamics of vehicles into the body design of the Apollo IX solar car. The groundbreaking next-generation concept car participated in Bridgestone World Solar Car Challenge 2023, successfully traversing 3,000-kilometer rugged terrain across Australian continent. At high speeds, its low drag body not only ensures high energy efficiency but also incorporates built-in diffuser devices within the vehicle body, enabling the car to maintain a qualified dynamic stability and balance rear-end forces even in strong winds. Therefore, it achieved the prestigious second place globally for practicality.

The study takes the section above the rear wheels as the reference position for the diffuser device, considering various wheelbase lengths and the configuration of the diffuser (including its length and the width formed by a pair of diffusers at the rear of the vehicle). To explain the aerodynamic drag reduction mechanism of Apollo IX car cruising at high speed via a pair of built-in rear diffusers, Computational Fluid Dynamics (CFD) analyses is performed to obtain velocity vectors, streamlines, and pressure distribution at the instantaneous flow field around the vehicle's periphery, internal diffuser devices, and wake observation zone under moving ground and rotating wheel conditions. According to the CFD results, it can be observed that the built-in diffusers of Apollo IX helps generate relatively stable vortices in the wake flow at the rear of the vehicle, aiding airflow attachment around the vehicle. This effectively reduces the wake region at the rear, thereby lowering the pressure difference between the front and rear of the vehicle, which in turn decreases aerodynamic drag and improves driving performance.

The findings from this research can serve as guidelines for designing electric vehicle models with low energy consumption and excellent high-speed handling. In addition, this project not only in line with government’s “Five Plus Two” policy on green energy and EV, but also accelerate the revenue on PVEV industries, along with global net zero emission, new EV era, green energy, and sustainable future.

Keywords: Aerodynamics, CFD, PIV, PVEV

Presenting Author: Herchang Ay National Kaohsiung University of Science and Technology

Presenting Author Biography: Dr. Ay graduated from Department of Mechanical Engineering at University of Michigan, and had served
as the President of St. John's University, Taiwan and a member of the Atomic Energy Council of the
Executive Yuan. He is currently a Distinguished Professor at the National Kaohsiung University of
Science and Technology and the CEO of the Southern Solar School under the Ministry of Education.
In recent years, Dr. Ay has actively participated in community services, serving as the President of the
Taiwan Solar Energy and New Energy Society as well as the Chinese Society of Visualization Science
and Art. Over the past 27 years, he has led the Apollo Solar Car Team, completing the development of
nine generations of solar electric vehicles, participating in 16 international competitions, and achieving
multiple second-place world rankings.
The latest Apollo IX solar car, which is a prototype ready for mass production, represented Taiwan in the
World Solar Challenge (BWSC2023). With its groundbreaking futuristic design, it successfully won the
Precision Lightweight Award, second place in practicality, third place in total travel distance, and fourth
place overall in the Cruiser Class.
As a Principal Investigator of the Alliance of Key Components for Photovoltaic Electric Vehicle Industry
(AKCPVEV) under NSTC, the project progressively links companies in Taiwan engaged in electric
vehicle power testing, power/energy storage systems, G2V/V2G charging stations, smart energy
management, solar photovoltaic power generation, and automotive component design/manufacturing. So
far, the alliance has successfully recruited 153 members, including 53 corporate members, 5
association/institution members, and 95 individual members.
Additionally, the "Photovoltaic Module Production and Testing Laboratory" at the Southern Solar School
focuses on the development of photovoltaic products and is equipped with complete solar module
(production-grade) manufacturing facilities. The lab has long been involved in numerous industry-
academia collaboration projects. Dr. Ay’s research achievements have resulted in 20 approved intellectual
property patents, more than half of which are invention patents (including patents from the U.S., Japan,
the UK, Germany, and France). He has also authored 150 journal and conference papers as well as two
books.