Energy/fuel consumption and associated emissions are major concerns of transport sector. During the fiscal year (FY) of 2018, Pakistan’s transport sector consumed 22 million tons of oil equivalent (TOE) energy from burning of fossil fuels and emitted 52.8 million metric tons (MMT) of CO₂, which accounted for 30% of country’s overall carbon emissions. Different scenarios, such as business as usual (BAU), International Energy Agency Vision 2030 (IEA V30), International Energy Agency Vision 2050 (IEA V50), China Pakistan Economic Corridor (CPEC) and newly developed Pakistan National Electric Vehicle Policy (NEVP), are analyzed for Pakistan’s transport sector and results are forecasted for the next 17 years. The results show that effective electric vehicle (EV) adoption can cause significant reductions in energy/fuel consumption as well as atmospheric emissions. The distinctive outputs are important parameters in analyzing future energy demands, emissions and introducing effective sustainable energy policies for the transport sector of developing countries.

We study the multimodal breakup of a double emulsion droplet under a uniform direct current electric field.

The field of droplet electrohydrodynamics (EHD) emerged with a seminal work of G.I. Taylor in 1966, who presented the so-called leaky dielectric model (LDM) to predict the droplet shapes undergoing distortions under an electric field. Since then, the droplet EHD has evolved in many ways over the next 55 years with numerous intriguing phenomena reported, such as tip and equatorial streaming, Quincke rotation, double droplet breakup modes, particle assemblies at the emulsion interface, and many more. These phenomena have a potential of vast applications in different areas of science and technology. This paper presents a review of prominent droplet EHD studies pertaining to the essential physical insight of various EHD phenomena. Here, we discuss the dynamics of a single-phase emulsion droplet under weak and strong electric fields. Moreover, the effect of the presence of particles and surfactants at the emulsion interface is covered in detail. Furthermore, the EHD of multi-phase double emulsion droplet is included. We focus on features such as deformation, instabilities, and breakups under varying electrical and physical properties. At the end of the review, we also discuss the potential applications of droplet EHD and various challenges with their future perspectives.

We study the mechanism of stretching and breaking of a mono-emulsion droplet under a direct current electric field using theoretical and experimental approaches aided by numerical simulation. Axisymmetric straining flow driven by an electric field results in the equilibrium deformation of the droplet along the direction of the electric field if the electric capillary number Ca_e that is the ratio of electric stresses to capillary stresses, is less than a critical value (Ca_e)_crit. At (Ca_e)_crit, the droplet breaks either before showing the slow deformation stage or rapidly. Furthermore, we developed a theoretical model to understand the mechanism of the transition from equilibrium deformation to non-equilibrium breaking. The Ca_e that can induce Taylor's deformation D = (α − β)/(α + β) ≈ 0.295; where α and β are the lengths of semi-major and semi-minor axes of the droplet, corresponds to (Ca_e)_crit. At this stage, the maximum flow velocity shifts to the outside of the droplet along the electric field direction and large electric stresses are mainly concentrated at the droplet's side apex causing daughter droplet ejection. Finally, we compare the values of (Ca_e)_crit obtained from the theoretical model ((Ca_e)_crit ≈ 0.25) for which the conductivity ratio (R) between the droplet and ambient liquid i.e., R ∼ O(10) with our experimental results ((Ca_e)_crit ≈ 0.245) and realize that (Ca_e)_crit decreases as R increases. We also observe that even though the viscosity ratio can alter the emulsion breakup modes, it has no effect on (Ca_e)_crit for the onset of breaking.