Comparing Internal Combustion Engines and Electric Engines: Efficiency and Design Differences

Introduction

The question of why an internal combustion (IC) engine has less efficiency than an electric engine is a fundamental one in the study of modern transportation systems. This article delves into the mechanics and inefficiencies of IC engines compared to the design and efficiency of electric motors.

Exothermic Reaction and Waste Energy

The burning of hydrocarbon fuel in an IC engine is an exothermic reaction, releasing a significant amount of energy in the form of heat. A large portion of the stored chemical energy in gasoline or diesel fuel is converted into heat rather than usable mechanical energy. This inefficiency is exacerbated by the incomplete combustion of hydrocarbons, which further reduces the engine's efficiency.

IC Engine Efficiency Breakdown

In a typical petrol engine, energy is wasted in several key stages. The piston first descends to draw in air through a small gap, then changes direction to compress air and fuel. Finally, the piston changes direction again to release energy from the expanding gas. However, much of this energy is lost to heat, which is why we see coolant systems and exhaust systems in many engines. Additionally, the combustion process itself is not 100% efficient, and some energy is lost to the friction and moving parts of the engine. This results in an efficiency of around 30% for modern petrol engines, as seen in engines like the Fordtronics Beyron.

Efficacy of Electric Motors

In contrast, electric motors operate with minimal wasted motion and energy. They convert electrical energy directly into mechanical energy through the attraction and repulsion of magnetic fields. The process is much more straightforward, with only a few minor inefficiencies such as bearing wear, copper losses, and small gaps in the rotor design. Electric motors typically have an efficiency of around 95%, meaning that only a small portion of the energy is lost as heat.

Factors Contributing to Engine Efficiency

The differences in efficiency between IC engines and electric motors can be attributed to several factors. One of the key differences is the Otto Cycle, which is the standard working principle for many automotive IC engines. The Otto Cycle is limited in its efficiency and can only convert a fraction of the thermally generated power into mechanical energy. For example, a Beyron engine, even with a high thermal power output of 3000 Thermal HP, can only deliver approximately 1000 Brake HP at the wheels due to various inefficiencies in the engine design and operations.

Cooling Systems and Cooling Losses

IC engines also face significant cooling losses. Much of the heat generated during combustion is expelled through the exhaust system and absorbed by the cooling system. This further reduces the amount of usable energy output. Electric motors, on the other hand, have much lower cooling losses, as the electrical energy is converted directly into mechanical energy with minimal heat generation.

Moving Parts and Friction

The IC engine is much more complex in terms of the number of moving parts and the associated friction. From the pistons and cams to the valves, crankshafts, and transmission gearing, each of these components contributes to the overall inefficiency of the engine. In contrast, electric motors have far fewer moving parts, which means less friction and higher overall efficiency. Additionally, the electric motor does not require a transmission, further reducing the energy losses that can occur in the transmission system.

Conclusion

From the exothermic nature of hydrocarbon fuel combustion to the complex mechanics of moving parts in IC engines, the path of energy conversion in internal combustion engines is fraught with inefficiencies. Electric motors, on the other hand, represent a much more straightforward and efficient path, converting electrical energy directly into mechanical energy with minimal losses. The differences in efficiency between these two types of engines are significant, making electric motors a highly efficient alternative for modern transportation needs.