Steam engines drove the industrial revolution on little more than 10 horsepower each, whilst the earliest reciprocating engines operated with less than 2% efficiency.
We’ve come a long way since then, thanks to more than 300 years of research into increasing power and improving efficiency, none of which would have been possible without the discovery of one of nature’s fundamental laws, entropy.
Understanding Energy and Engines
To understand why entropy is so important we first need to look at how our understanding of energy has evolved. At the start of the 17th century, despite the invention of steam engines, our understanding of the energy that drove them was very limited – resulting in machines that were inefficient and underpowered.
In 1712, Thomas Newcomen’s five horsepower steam engine was the pinnacle of engine design, and it became the first commercially successful steam engine.
By 1781, James Watt had radically improved Newcomen’s design, doubling power output and improving efficiency. This engine would be a driving force behind the industrial revolution.
In 1794, the first ball bearing patent was issued to Philip Vaughan – and the dramatic reduction in friction that bearings offered would go on to revolutionise efficiency.
In the years that followed engineers and scientists tried to build more powerful engines that were cheaper to run. They discovered that at least some portion of the energy from combustion is always lost.
By burning a mass of fuel, energy is released as heat and light, as well as sound and vibration. In a steam engine, the heat would be used to boil water into steam, driving a piston or turbine with the resulting change in pressure. These multiple exchanges of energy only served to reduce efficiency further, with almost all the energy escaping.
As inventors and industrial titans experimented, they found new answers to the efficiency problem. They imagined ideal engines that eliminated friction and retained heat, turning 100% of the energy input into useful output.
By the 19th century, physicists (most notably Rudolf Clausius) were beginning to understand that nothing can be 100% efficient. They were discovering the fundamental properties of heat and energy exchange. They were establishing the laws of thermodynamics.
Heat, Entropy and Thermodynamics
Engineers working to improve efficiency by diminishing waste, uncovered and developed the theory of entropy: the irreversible flow of action and constant process of decay.
The laws of thermodynamics and entropy say that in a system (anything containing matter and energy), everything tends to decay, irreversibly, from its original state. Even in the most optimum engine, the fuel can’t be unburned, the chemical reaction can’t be undone – and the energy is never going back into its source.
Energy tends to decay into heat – the most disordered form of energy. A big problem with heat is, it radiates away, balancing with surrounding matter. Ultimately, the universe wants to be in thermodynamic equilibrium – no highs, no lows, all the same temperature distributed evenly.
This understanding of entropy can help us to make engines more efficient. The first internal combustion engines (ICE) were a radical step forward from what came before. By using the expansion of combusted fuel to drive the pistons directly, fewer transformations of energy are required and therefore efficiency is improved.
Yet, even the most optimum ICEs can still lose more than 60% of their input energy to heat, friction, vibration and secondary functions. There is much more that can be done.
We Understand Energy
Although it’s impossible to achieve 100% efficiency, that hasn’t stopped continual progress in improving the efficiency of engines. From reducing friction, to cutting leakages and minimising heat loss, there are many different approaches. Several companies have also developed technologies that can be fitted to engines, to provide additional engine efficiency uplift.
One such technology is our Electric Turbo Compounding system that delivers a drastic step change in the efficiency of reciprocating engines by converting some of the heat normally exhausted and lost to atmosphere back into useful energy.