A smarter, cleaner way to store and use renewable energy
Nick Diepstraten defended his PhD thesis at the Department of Mechanical Engineering on December 3rd.
Renewable energy fluctuates. On sunny or windy days, we often produce more energy than we can use. During calm nights, we produce too little. Storing excess energy in hydrogen is a powerful solution 鈥� but to make this work on a large scale, we need engines that can convert hydrogen back into useful power without wasting energy or producing emissions.
Traditional combustion engines use air, which contains nitrogen that forms pollutants during combustion. They are also not optimized for burning hydrogen efficiently. The APC, however, is designed specifically for hydrogen 鈥� and it makes a fundamental change: it replaces air with a controlled mixture of argon and oxygen.
Argon: the secret ingredient for high efficiency
Argon is a chemically non-reactive gas with properties that give the APC a significant advantage. When hydrogen burns in argon and oxygen, the only products are water and argon. Once the water is condensed out, the argon can be reused endlessly. The result is a closed-loop, emission-free system.
Even more importantly, argon鈥檚 thermodynamic characteristics allow the engine to reach much higher efficiencies than conventional engines. The research confirms that using argon makes a direct-injection, compression-ignition strategy for hydrogen possible 鈥� something that isn鈥檛 feasible with air.
Simulating an engine of the future
To understand every detail happening inside the APC, used advanced computer simulations. These digital experiments make it possible to test extreme pressures, temperatures, and fuel-injection conditions that would be too expensive or complex to measure physically.
A new Global Conservation Model was developed to predict how hydrogen behaves at high pressure and how it flows into the combustion chamber. This model accurately predicts the inflow conditions of gaseous hydrogen injections and significantly reduces simulation time.
After validating the combustion models, the simulations revealed how different engine settings influence performance. One key insight is that increasing the intake pressure can greatly boost efficiency. Oxygen concentration is less critical, as long as hydrogen burns completely. Despite the extremely high temperatures inside the engine, only a small portion of energy is lost as heat, which helps the overall efficiency.
A clean, efficient bridge to a renewable future
The main conclusion is clear: the Argon Power Cycle is not just a theoretical idea. It works 鈥� and it works well. The research demonstrates that using argon instead of nitrogen makes clean, efficient hydrogen combustion possible; that the APC can achieve high efficiencies and overcome key drawbacks of traditional engines; that the new simulation model offers accurate predictions while saving development time; that higher system pressures can further increase efficiency; and that the APC could play an important role in restoring the balance between fluctuating renewable energy production and our constant energy demand.
The researcher summarizes its societal relevance in one striking sentence:
鈥淲e have developed a hydrogen engine that is far more efficient than existing diesel engines 鈥� and completely emission-free.鈥�
If brought to market, the Argon Power Cycle could become a key technology in a future powered by renewable energy, helping us turn fluctuating green power into steady, dependable, and sustainable energy for all.
Title of PhD thesis: . Supervisors: Prof. Jeroen van Oijen, and Dr. Bart Somers.