Introduction to Hybrid Drive Development

The transportation sector accounts for approximately 15% of global greenhouse gas emissions. 29% of the USA’s emissions come from the transportation sector, whereas 9% of India’s emissions come from this sector. The transportation industry around the world runs on Fossil fuels that will run out eventually, there is a need to find alternatives. Traditional petrol and diesel engines also produce byproducts such as unburnt hydrocarbons and nitroxide which cause acid rain, pollution, and smog, leading to deteriorating health among the population who live in cities. 

 

Need for Electrification

Internal Combustion Engines produce Carbon DiOxide which, along with methane, are one of the contributing gases to the greenhouse effect which is increasing Global temperature. This has started to have real-world implications, the freak weather incidents around the world - bushfires in Australia, swarm of locusts invading India can be attributed to an increase in ocean temperature which changes the direction of seasonal winds. If Climate Change is not contained, there is a very real chance that Global systems that make up modern society will crumble. To prevent this, most countries entered the Paris Climate Agreement to reduce their greenhouse gas emissions. India has pledged to reduce emissions by 35% by 2030 compared to 2005.

Vehicle electrification is a way to improve the operational efficiency of a vehicle, resulting in lower energy consumption, and reduce or completely stop emissions. 

 

Hybrid vehicles

A hybrid vehicle is a vehicle that uses two energy sources to propel the vehicle. 

One of the energy sources is the conventional Internal Combustion Engine that is powered by petroleum and the other will be one among the many substitutes for ICE. These can be electric, fuel cells, or even a fly-wheel. The most popular variants on the market right now are hybrid vehicles that are powered by an ICE and electricity, like the Toyota Prius, which is one of the top-selling hybrid vehicles in the market. 

 

Current Scenario

In order to meet the Paris Agreement deadlines, the Government is providing incentives to customers and manufacturers to buy a hybrid vehicle. For example, they might have to pay less tax on a hybrid car than a normal car. Indian Government in a way to make the Hybrid Electric Vehicle attractive for the consumer has approved $1.4billion USD towards electric and hybrid incentives, providing an incentive of around 1Lakh upon the purchase of electric vehicles. 

Not all manufacturers are investing in hybrids, however. General Motors and Volkswagen decided against hybrids due to low demand. They saw them as a stepping stone between normal and electric vehicles so they are focusing on electric but Ford, Toyota, and Honda are still investing in hybrid. Volvo has announced that they are planning to completely phase out conventional cars and fully electric in a couple of years. 

 

Predictions for the future

Electric Vehicles and Hybrid Electic Vehicles will amount to 30% of car sales by 2025. HEVs are estimated to account for 23% of sales by 2030. ICE vehicles are estimated to make up 40% of total sales. However, the exact figures will differ from country to country, as per LMC Automotive 

69% of sales in the US will still be pure ICE cars. The Indian Government, for its part, plans to have 30% EVs by 2030. 

 

Research trends

• Optimized structure and using different alloys and composite materials to reduce weight while improving the strength of the vehicle, reducing weight saves on costs and increases efficiency. 

• Battery technology - the current issue is that batteries need to have improved life, store more, and charge quicker, leading to reduction in weight and cost of the battery.

• Charging infrastructure - For electric vehicles to function properly, there needs to be a network of charging stations across a city, if not the country. There is research being conducted on how to better improve charging infrastructure, to increase efficiency. 

• Vehicle intelligence and autonomy: Autonomous vehicles don’t require a driver or only need a driver for certain cases, which increases the safety and efficiency of a vehicle. There can also be a vehicle to vehicle communication which overall makes the system more efficient and safe. 

• Low carbon fuels: This field focuses on making the current carbon-based fuel systems more efficient while also focusing on bio and synthetic fuels which don’t have as many emissions as fossil fuels

• Improving engines: Improving the electric engine by investing in new electric motor designs, people are going to want smaller engines using different cycles for combustion 

• Revamping the entire transportation sector and implementing new mobility solutions and traffic management, for example, people won’t need their own vehicle with ride-sharing.

 

State of Art Technologies

 

• Engines: You can now find turbocharged petrol and diesel engines to improve efficiency and to reduce the size of the engine. Atkinson-cycle based engines are used by Toyota in their vehicles, these engineers do suffer a little power loss and but makes up for it in efficiency gains. Combining these with hybrids gives the best of both worlds. 

• Electric motors: PMSM (Permanent-Magnet Synchronous Motor) are in almost all-electric vehicles. Induction motors are conventional types of electric motors, and early Tesla’s are based on these providing high power density at high speeds, but they are less efficient than PMSM’s. Switched Reluctance Motors have issues in terms of vibrations and how you can control them, but they are cheaper because they don’t use expensive magnets. 

• Batteries: Battery cells are made up of different chemistries. All current generations of electric vehicles run on Lithium-Ion batteries because they have the highest power density and also have an extended shelf life. Super-Capacitors, they are not chemical-based batteries but are just a large capacitor, they can be used to store energy. 

• Vehicle Architecture: Plug-in hybrids, for example, the Prius Prime which runs on electricity and has an engine that can plug into a wall socket to get power, fuel cell EV’s are filled with hydrogen and the fuel cells convert it into electricity.

 

Leading System Providers

• Vehicles: Toyota, Honda, Tesla, GM. Toyota and Honda make systems themselves but there are supply companies like ZF.

• Hybrid systems/e-motors: ZF, Borgwarner, Bosch, Schaeffler. Recently BMW has placed an order with ZF for their upcoming SUV. 

• Batteries suppliers: CATL, Panasonic who create Tesla batteries, BYD, LG Chem supplies to Volkswagen, Samsung

• System controls developers: Delphi, Bosch, Denso 

• Engineering service/consulting, they work with the OEMs to help them develop these vehicles: FEV, AVL 

 

Hybrid Electric Vehicles

HEVs combine energy from petroleum and electric for propulsion. Their primary energy source is petroleum and an IC engine, and the secondary energy source is electricity, batteries, and an e-motor. There are multiple architectures and levels of electrification the architecture and system voltage determines vehicle capacity and efficiency. 

 

Sub-systems of HEVs

• Internal combustion engine: Converts fuel into energy, but the issue is that it produces greenhouse gas and carbon dioxide and other harmful emissions. 

• Electric drive unit: Uses electric energy for propulsion, but also converts kinetic energy into electricity. Based on the architecture there can be 1 or 2 EMs, they are highly efficient with around 90-95% efficiency and produce no emissions.

• Transmission: Links the power units to the wheels. It transfers power from propulsion unites to the wheels.

• Fuel tanks: Storage system for Petroleum.

• Battery:  To store electric energy form wall socket or engine 

• Power Electronics: The link between the battery and electric motor and the other electric systems, it is used to control the electric drive unit as a motor or generator, charging system for plugins, converts high voltage to low for accessories.

Advantages of HEVs

• Reduce idle losses: With conventional vehicles when you stop, your engine doesn’t stop so it still uses fuel which is wasted, which is not the case with HEVs.

• Regenerative braking: Kinetic energy from braking is converted into electric energy and stored where it is later used. 

• Engine efficiency improvement/load point shifting: Engines are only efficient at a very low operating region, generally, at low speeds and high torque, when the throttle valve is completely open. In HEV, through load point shifting the efficiency of the engine can be improved, using an electric motor the engine can be pushed to capacity and the excess energy generated can be stored in the battery. 

• Sailing: If you go at 50km/h and you let go of pedal, the engine will slow the vehicle, so you lose energy when you do engine braking but with HEVs you can disconnect from the engine and save on that energy loss, the electric motor will convert that energy back into electricity. 

• Downsizing: You can put in a small engine that runs at a high load point but is very efficient. 

• Improved performance: Electric motors provide higher torque at low speeds, you can get better performance. 

• Reduced dependency on fossil fuels: Less Petroleum, less emissions. 

• Reduced operational 

 

Disadvantages of HEVs 

• They’re expensive - Since they come with an engine and a battery and the associated wiring. 

• Increases complexity: More parts means more chances of it breaking down 

• Increased weight: Batteries don’t have as much energy density, to have the same output as an ICE you need a big battery, and a bigger battery is expensive and increases the weight of the vehicle.

• It requires knowledge of a complex control system if things break down, putting a premium on the after-sales market. 

 

This ends part one of a two-part series, you can read about the career opportunities along with some case studies in HEVs and System Design

 

Skill-Lync offer you a Post Graduate Program in Hybrid Electric Vehicle Design and Analysis.