Spotlight on a student: Xiaoying Gu

Xiaoying Gu, known to friends and colleagues as Annie, wants to build renewable energy solutions from the ground up. A PhD student in Infrastructure Engineering at the University of Melbourne, Annie through her research is crunching the numbers on how we can better use urban roads and footpaths to reduce our energy footprint.

In simple terms, can you tell us what your research is about?

The focus of my research is geothermal pavement systems – in other words, roads and footpaths that can heat and cool buildings. This is a fairly new area of research with huge potential for reducing energy consumption and greenhouse gas emissions.

So far, the technology has mainly been used in vertical applications on buildings, or in roads to melt snow and control surface temperatures. My research proposes broader application through urban roads and footpaths, using the thermal energy to heat and cool indoor spaces. This has the potential to substantially reduce global energy consumption, 50% of which is currently accounted for by indoor heating and cooling, mostly powered by burning fossil fuels.

Rather than testing the technology through costly trials, I developed a mathematical model that could weigh up the costs and benefits of various systems. My findings confirm the energy and economic efficiency of these systems, which should be further explored as renewable energy solutions.

OK, now give us the technical detail!

Geothermal pavement systems are a kind of ground source heat pump (GSHP) system, also known as shallow geothermal heat pumps, because they use energy from just the upper few metres of the ground. These systems make use of the earth as a heat source or sink, and through ground heat exchangers (GHEs) can use the thermal energy as a renewable source of energy, for example, to power indoor heating and cooling systems.

Because geothermal pavements are a relatively recent technology, there is limited understanding of their costs and benefits. My research aims to use numerical techniques to further improve understanding of the technology and contribute to its wider design and application by geotechnical and road engineers. To achieve this, I am exploring several different aspects of its potential.

I have developed a detailed 3D finite element model – turning our questions about the technology into solvable maths problems – which has been successfully validated with data from a full-scale experiment carried out by the University of Melbourne in South Australia, involving another PhD candidate from my group, Yaser Motamedi.

My numerical model further gives insight into the thermal performance of the technology in residential applications and gives cost predictions. Due to the complex nature of the heat transfer between the pavement and the surrounding environment, numerical models like mine can also help us assess the system’s behaviour under various design configurations and climate conditions, including those found around Australia.

Furthermore, to keep up with the development of new sustainable solutions, my research considers the combination of GHEs with permeable pavement systems, which are designed to allow rainwater to infiltrate, reducing stormwater run-off. We know that incorporating GHEs into pavement provides other benefits as well: it’s cheaper than the usual method of drilling boreholes into vertical structures, it enhances the structural stability of roads, and it resolves the land availability issues commonly faced by conventional GSHP systems, because it combines land uses over a single area.

Overall, the outcomes of my research intend to provide deeper knowledge about geothermal pavement systems and offer preliminary design options for their residential application. The broader utilisation of geothermal pavements will promote a more sustainable lifestyle and help with climate change adaptation and mitigation.

Why did you choose this area of research? What interests you about it?

Since taking my bachelor’s degree in Civil Engineering, words like “climate change”, “sustainability” and “renewable energy” have become increasingly popular and important in my discipline. Through my own experience, I have seen an increasing number of extreme weather events from my childhood until now. This further brought home the imperative of finding stable and efficient energy solutions.

When I first joined the Porous Media Research Laboratory (PMRL) group at the University of Melbourne, I was surprised to hear about the concept of using energy geo-structures for space heating and cooling. Since delving into this area, I now strongly believe that this technology can be one of the most economically efficient and viable energy solutions that we can apply extensively in our daily lives, helping all of us move towards a more sustainable world.

I am proud to be part of a research group that is contributing to the development and uptake of a system like geothermal pavements, accelerating its deeper understanding and wider application through my learnings.

What did you study to get here?

Before embarking on a PhD, I completed a master’s degree in civil engineering with an environmental focus here at the University of Melbourne. My undergraduate background is in civil engineering, awarded with honours at Monash University.

Have you received any other honours or awards for your work so far, and can you point us to any recent publications?

I have received a Melbourne Research Scholarship, which has helped to support my PhD. In 2021, I also received the PMRL’s Author of the Year Award for my research publications. This year, I received a Best Paper Award (Civil Engineering) at the Infrastructure Engineering Postgraduate Conference for my work published in Géotechnique, a top journal in our discipline, on geothermal pavement.

When do you plan to complete your studies? And what do you want to do next?

I hope to graduate in early 2023. After graduation, I would like to continue working on renewable projects that can help to build a sustainable future. I want to use my knowledge to protect our community and appeal to more people to devote their attention to building a prosperous, clean, and beautiful world.

What’s the bigger picture? How will your work contribute to the transition to a clean energy system?

The bigger picture, of course, is to introduce geothermal pavement as a renewable solution that can contribute to better management of energy resources and the use of cleaner sources of energy.

Currently, the potential of geothermal pavements is not widely understood. Through my work I want to highlight the merits of the technology and provide design solutions under various environmental conditions. My work so far can assist in the preliminary design of geothermal pavements, using numerical techniques to show the significance of design parameters and conditions, making the technology more accessible in the real world.

Further information

Annie and her supervisor, Prof Guillermo Narsilio, may be contacted via email with further questions about this research.