After 166 Yrs, the Combustion Engine Still Has Untapped Potential

One of the greatest discoveries of our time has been the invention of internal combustion engines, which played a significant role in the development of industrialization and, in turn, human civilization.

These engines were first invented in the 19th century, though scientists and engineers started contributing to their development a decade before the onset of this period. 

A gas turbine was developed in 1791, and a gas engine was patented a few years after that. A patent for an internal combustion engine, which was also the first to use liquid fuel, was filed in 1794, and before the century was over, the first American ICE was built.

While the first automobile to run on an ICE was created in 1862, the first modern combustion engine didn’t come more than a decade later, in 1876. In 1885, Gottlieb Daimler and Wilhelm Maybach improved on the design and invented the first practical ICE and carburetor.

Now, how does a combustion engine exactly work? Well, to start with, combustion is a chemical process under which energy is released from igniting a mixture of fuel and air. Internal combustion engines (ICE) partially convert this energy into mechanical work.  

When the mixture of fuel and air is ignited, thousands of small, controlled explosions happen, which are combustion or burning.

In ICE, fuel ignition and combustion both occur within the engine, which consists of a fixed cylinder and a moving piston. The burning causes the expansion of gases as well as the release of heat, which pushes the piston up and down. This, in turn, rotates the crankshaft through a system of gears in the powertrain, driving the vehicle’s wheels forward.

There are two kinds of internal combustion engines: the spark ignition gasoline engine and the compression ignition diesel engine, with the difference being the way the fuel is supplied and ignited.

Combustion Engines Rules But Faces Challenges

Now, more than a century and a half after their invention, over a billion internal combustion engines (ICE) are still running on the roads globally today.

The global combustion engine market, meanwhile, is currently valued at around $200 billion and is still expected to grow at a CAGR of 9.2% and reach $300 billion by 2033, driven by increasing demand for vehicles in emerging markets and technological advancements in engine design.

However, the biggest challenge to combustion engines is the rise of electric vehicles (EVs) and stricter emission regulations.

But while EVs are now becoming more common, accounting for about 18% of all new car sales globally, up from a mere 2% in 2018, EVs continue to be a really small percentage of total combustion engine vehicles on the road. With an estimated market share of 3-5%, of every 100 combustion engine vehicles, only every third or fifth vehicle is an EV.

The growing EV trend is driven by the rising demand for engines, which is leading to the depletion of fossil fuels as well as a dramatic increase in pollution all around the world. 

Due to gasoline and diesel being the most dominant fuel in the automotive sector, environmental pollution continues to be the main concern with combustion engines. The major emissions from these engines are unburned hydrocarbons, carbon monoxide, oxides of nitrogen, and particulate matter. 

This is resulting in severe health risks and global warming, as a result of which countries across the world have begun to implement stringent regulations to tackle the emissions from the automobile sector. This has led automobile engineers and researchers to experiment with various engine technologies as well as renewable and greener fuels.

With some nations even going for a complete ban on internal combustion engines, researchers are also advancing these engines to improve their performance and reduce their environmental impact.

Making Combustions Engines Efficient by Converting Wasted Heat into Energy

Internal combustion engines produce powerful energy, but not all the energy that is created is utilized. In fact, only about 25% to 30%of the chemical energy is converted into usable power. 

Most of it is stored in fuel that gets lost as heat through the exhaust and engine cooling systems. However, there is a way to use all the lost energy, and scientists are working on finding solutions to make productive use of them. 

A study published¹ this year in ACS Applied Materials & Interfaces has demonstrated just how exhaust heat can be converted into electricity, providing a sustainable energy source.

With funding from the Office of Naval Research, the Army Rapid Innovation Fund Program, and the National Science Foundation Industry, researchers from Pennsylvania State University’s Department of Mechanical Engineering have presented a prototype for a thermoelectric generator system.

The thermoelectric generator (TEG) can reduce fuel consumption as well as carbon dioxide (CO2) emissions. Fuel inefficiency is a major contributor to greenhouse gas (GHG) emissions and emphasizes the need for innovative waste-heat recovery systems like TEG.

These heat-recovery TEG systems utilize semiconductor materials to transform heat into electricity. 

Invented over two hundred years ago, TEG systems can be used in electronic devices, medical devices, and aerospace. These systems have no moving parts or chemical byproducts, allowing them to operate silently and remain environmentally friendly. They are also durable, don’t require any unnecessary maintenance, and are suitable for integration into bulk and flexible devices.

According to the research:

“Thermal energy harvesting for high-speed moving objects is particularly promising in providing an efficient and sustainable energy source to enhance operational capabilities and endurance.”

The way thermoelectric (TE) technology works is by utilizing temperature differences between a heat source and ambient temperature. This allows TE technology to provide a constant supply of power to such systems, reducing the dependence on traditional batteries while extending operation times.

While promising, the designs of many current thermoelectric devices are complex and heavy and, as such, need more cooling water to keep the necessary temperature difference. However, as the research noted, the integrated TEG system design research is far behind materials development.

So, guided by Wenjie Li and Bed Poudel, Penn State researchers built a compact TEG system to recover thermal energy. These TEG systems can efficiently convert exhaust waste heat from not just cars but also other high-speed vehicles such as unmanned aerial vehicles or drones and helicopters into energy.

This new TEG makes use of bismuth-telluride for its semiconductor. Bi2Te3 is a gray powder made of bismuth and tellurium and has excellent low-temperature thermoelectric performance.

Additionally, the research used triangular plate-fin heat exchangers, much like those used in air conditioners, to capture heat from vehicle exhaust pipelines like engine exhaust gas. 

A heatsink has also been incorporated to regulate temperature. This longitudinal trapezoidal fin cylindrical piece of hardware increases the temperature difference significantly, which has a direct impact on the TEG system’s electrical output.

This heatsink is designed to disperse heat through forced convection, but the team further optimized the design using finite element analysis (FEA) simulations to boost the temperature gradient and electrical output power.

With that, the team’s TEG prototype attained an output power of 40 Watts under a temperature gradient of 190 degrees Celsius with bismuth telluride-based TE modules. This much power is enough to power a lightbulb. 

Notably, the research results showed that high airflow conditions present in exhaust pipes boost efficiency and increase the system’s electrical output. 

The team tested the TEG system in simulations imitating high-speed environments, and it demonstrated great flexibility. Their waste-heat system produced as much as 56 W for exhaust speeds like that of a car, which is equivalent to five lithium-ion (Li) 18650 batteries. These numbers went as high as 146 W for exhaust speeds similar to helicopters, which is equivalent to 12 Li-ion 18650 batteries. 

Li-ion 18650 batteries offer the benefits of large capacity, long life, high voltage, and high safety performance. They are most commonly used in electronic devices, EVs, and energy storage devices.

The latest study’s TEG system, according to the researchers, can be integrated into current exhaust outlets directly and eliminate the requirement for additional cooling systems. 

The researchers further believe this work could open the door to the practical integration of thermoelectric devices into high-speed vehicles amid the growing demand for clean energy solutions.

Click here to learn how hydrogen vehicles are making a comeback.

Combustion Engines Continue to Evolve

Exhaust heat recovery from combustion engines has actually been seeing growing interest in increasing efficiency and reducing fuel consumption. These efforts help reduce the environmental pollution and global warming.

Besides TEG, bottoming cycles, electric turbo-compounding (ETC) devices, vapor absorption, Stirling engine (SE), and thermo-acoustic generators (TAGs) are utilized to harvest heat from automobile and industrial exhaust systems.

Thermoelectric generators, however, have been most adopted as reliable, compact, and solid-state technology, which can convert heat directly into electricity without any mechanical motion. They are also lightweight and vibration-free, with no orientation limitations and zero emission.

In addition to these fuel efficiency methods, combustion engines have also been seeing other advancements to enhance their performance, efficiency, and environmental sustainability.

This includes direct fuel injection, a technology that delivers fuel directly into the combustion chamber, hence allowing for precise control over the fuel-air mixture. Turbochargers, meanwhile, compress the intake air, enabling smaller engines to generate power that is comparable to their larger counterparts. 

An interesting development has been the combination of internal combustion engines with electric motors, which has resulted in hybrid systems. A hybrid powertrain offers the flexibility to utilize electric power for low-speed driving and the combustion engine for higher speeds.

Led by the likes of Honda, Hyundai, Lexus, BYD, and Porsche, hybrid vehicles have been gaining a lot of traction worldwide, but they still face challenges in terms of higher cost and less power compared to traditional cars.

Yet another development has been seen in the fuel that powers internal combustion engine vehicles. The exploration of alternative fuels like ethanol, natural gas, propane, and biodiesel aims to reduce the environmental impact of combustion engines by lowering GHG emissions and reducing their reliance on fossil fuels.

Among these alternative fuels, hydrogen, in particular, is attracting a lot of attention from researchers and companies who want to save combustion engines.

One of the simplest molecules, hydrogen in gas form, has extremely low energy density unless at very high pressure and/or at very low temperature, and even then, its energy density is much lower than most other liquid fuels. This causes fuel storage problems. It also has higher nitrogen oxide (NOx) emissions.

But where hydrogen shines is in combustion speed, which is very high, much higher than petrol. Also, the zero carbon property of hydrogen, when burned with oxygen, makes it an attractive alternative fuel. This is why hydrogen internal combustion engines and hydrogen fuel cells are seeing so much traction. 

Both of these power vehicles use hydrogen. In ICEV, hydrogen is burned much like gasoline, while fuel cell hydrogen vehicles (FCEVs) use hydrogen in a device to generate electricity.

Last year, researchers from the University of Alberta introduced a new aluminum-nickel alloy to revolutionize hydrogen combustion engines. The alloy AlCrTiVNi5 offers high stability in extreme heat conditions, low thermal expansion, and superior durability, making it ideal for enduring the extreme temperatures of hydrogen combustion. 

Toyota also revealed several ICE prototypes last year that can run on hydrogen in addition to gasoline and other fuels.

Leading the New Approaches to Combustion Engines

Currently, combustion engines are facing rising pressure from EVs and emission regulations, but despite all that, they continue to dominate the transportation sector. This is primarily due to established infrastructure and widespread availability, but that’s not all. Companies are also making a lot of headway in addressing the key problem of emissions.

For instance, Cummins (CMI +1.21%) and Ford Motor (F +1.39%) are investing in hydrogen combustion engine technology, while ClearSign Technologies Corporation (CLIR +3.16%) has created Duplex Burner Architecture to enhance energy efficiency and meet stringent emissions standards.

So, let’s take a deeper look at the investing potential of an innovator who is still developing new approaches to the combustion engine and helping it thrive.

1. Westport Fuel Systems Inc. (WPRT +3.39%) (NASDAQ: WPRT)

A leading supplier of advanced alternative fuel systems, Westport Fuel Systems operates through several segments, including Light-Duty, High-Pressure Controls & Systems, Cespira, Heavy-Duty OEM, and Corporate. 

With a market cap of $72.5 million, Westport shares are currently trading at $4.70, up 27.93% YTD. Its EPS (TTM) is -1.57, and the P/E (TTM) ratio is -2.91.

The company reported revenue of $66.2 million in Q3 2024, which was a decrease of 14% from the same quarter last year. The revenue was driven by the transition of the Heavy-Duty OEM assets into Cespira, a joint venture between Volvo Group and Westport. 

With this joint venture, Westport Fuel Systems and Volvo Group aim to develop, promote, and accelerate the commercialization of the HPDI technology. This will help them focus on driving the progress of affordable, sustainable transportation solutions using the internal combustion engine that operates on renewable fuels, for now, and hydrogen in the future.

In particular, the joint venture is expected to have a significant impact on global long-haul and off-road heavy-duty applications. HPDI-powered internal combustion engines, Volvo CTO Lars Stenqvist said, are believed to “play a crucial role in global decarbonization efforts in commercial transportation.”

During the quarter-third, the company’s net loss was $3.9 million, and cash and cash equivalents at the end of it were $33.3 million.

“We remain confident in the role that alternative fuels will play in driving sustainability in the future of the transportation and industrial application space.”

– CEO Dan Sceli

While talking about hydrogen, he noted a slowdown in global infrastructure development, which, in turn, affected the adoption of automotive and industrial applications powered by hydrogen. According to Dan:

“The success of this market depends on the installation of infrastructure and the production of clean hydrogen, both of which have been slow to materialize.”

Despite this, the company still believes that hydrogen as a fuel will prevail but expects its worldwide adoption as a clean fuel source to be a gradual process rather than immediate.

In the meantime, Westport will continue to deliver a wide range of affordable alternative low-carbon fuels like propane, natural gas, renewable natural gas, and hydrogen.

“We are driving cleaner performance by addressing lower emissions regulations with practical applications using innovation available today.”

– Dan

Conclusion 

Combustion engines are where the mobility revolution started. However, such an engine only operates with about 40% efficiency range while having a significant negative impact on the environment due to the use of fossil fuels. The transportation sector is actually the second-largest source of greenhouse gas emissions globally. 

This has led the world to make a shift towards greener alternatives such as electric vehicles. But this is not the extent of it; even combustion engines are evolving to keep up with the changing environment, showing their untapped potential even after a century. 

Breakthroughs such as thermoelectric generators (TEGs) for waste-heat recovery, hybrid powertrains, and alternative fuels like hydrogen are currently driving this transformation. With ongoing research and innovation, combustion engines are poised to become more efficient and environmentally friendly. And as the world embraces cleaner technologies, they will not only coexist with EVs but may even contribute meaningfully to a more sustainable future.

Click here for a list of top 5 hydrogen combustion engines set to break the mold.