Antoine (Cambridge)
Antoine Koen is a third year PhD student at the University of Cambridge. His research focusses on grid-scale pumped thermal energy storage, an energy storage option to compensate for the intermittency of renewable power.
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Tell me about your journey into academia
I come from Paris and did my undergrad there. I’d always been keen on science, math, and engineering. In France, for a few subjects including engineering, there’s a specific system called the “Grandes Ecoles” with national competitive entry exams that take two years to prepare. I got into one called the École Centrale Paris (now CentraleSupélec), where I started my engineering education properly. The first two years were in general engineering, and then I had the option of staying there or moving somewhere else for my master’s year.
I found a Master’s in Energy Technologies at the University of Cambridge, and fortunately got accepted. We studied everything related to energy engineering, and it was a fast-paced and exciting year for me. At the end of the course, you write a master’s thesis, which was a chance to get a feel for what real research is like. It’s a good stepping-stone into a PhD.
For my master’s thesis, I stumbled upon thermal energy storage. One of the top researchers in the field happened to be in my department at Cambridge. I didn’t have any specific research ideas at the time, but I knew I wanted to work on this because it seemed so interesting.
What is pumped thermal energy storage?
It’s basically an alternative to batteries, for large scales. We’re getting more renewable energy on our electricity grids, and while that’s great for lower emissions, it’s challenging in terms of managing their intermittency: you can’t just turn the sun on and off whenever you want. One of the ways to manage this is by having grid scale storage, i.e. storing energy at levels large enough to power whole cities for hours and hours. It’s a very different challenge to storing energy in your smartphone for example, and yet a lot of people, certainly in the media, they keep batteries at the top of their minds. One alternative is storing electricity as heat.
When you have excess electricity to store, you run that through a special heat pump, converting that electricity into thermal energy, which you can store in a cheap and abundant material. For example, you could have crushed rock or molten salt, which can go up to hundreds of degrees. When you want the electricity back, you convert the heat to electricity with a heat engine, similarly to conventional thermal power plants.
How does your PhD research fit in?
The work that my group does is theory, modelling and computer simulations, to explore different thermodynamic cycles. These cycles are what we use to convert electricity to heat and back in the heat pump and heat engine. They all have different properties and characteristics that you can tweak and optimize.
This research is very exploratory, laying the groundwork for other researchers to then do experiments and gather real-world data. The field is still relatively new, so it’s exciting.
What’s going to be the biggest challenge for the field over the next few years?
I think the field is soon reaching a stage where we can start building these systems, in order to learn by doing. In addition to academics, there are also a few companies tackling this, like Malta in the US and Siemens in Germany. There’s only so much you can foretell with models, so by building prototypes we’ll be able to identify what the most challenging areas are and then figure out how to solve them.
Do you have any reading to recommend people interested in energy?
The main one I’d recommend is Sustainable Energy — without the hot air by David MacKay. It’s a free e-book that came out a couple of years ago now, but still extremely relevant. Even though I read it as an engineer, it’s actually very accessible to any layperson.
It takes the example of the UK, looking at energy consumption and then the physical potential of renewable energy supply, answering how can we square the two. Do we have enough? What do we do with our buildings? What do we do with our cars? What do we do with our power plants? Etc. It’s thorough and enlightening.
