Renewable Energy Research Group @ CUT

Energy Geo-structures: what are they, and testing in WAGEs project

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Lazaros
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In-Short: Energy Geo-structures (EGs) turn foundation elements of a building; such as piles, retaining walls, slabs, and tunnel linings, into hidden heat exchangers that feed highly efficient heat pumps. They cut emissions and running costs by using the steady underground temperatures, without additional land requirements and with only a fraction of the boreholes costs. WAGEs project is aimed to test and showcase these systems for Cyprus.

What are Energy Geo-structures?

Energy geo-structures are regular geotechnical elements—piles, diaphragm/retaining walls, slabs, even tunnel segments—that have plastic pipes embedded in the concrete. A fluid (medium) circulates through the pipes, exchanging heat with the surrounding ground. Coupled to a ground-source heat pump (GSHP), the same network can deliver heating in winter and cooling in summer. EGs do double duty: they carry structural loads and provide renewable heating/cooling.

Why this matters: compared with conventional air-source systems, EGs benefit from the ground’s relatively stable temperature, improving seasonal efficiency and comfort while shrinking the visible footprint of plant on site. In many projects, EGs can avoid additional borehole fields altogether because the foundations become the heat exchanger.

Where do EGs fit in modern energy systems?

EGs integrate naturally with 5th-generation district heating and cooling (5GDHC)—low-temperature, ambient-loop networks that connect buildings which share heating and cooling and use the ground (often via boreholes or EGs) as a long-term thermal buffer. This approach helps balance neighborhoods and store seasonal surplus energy.

Typical EG types you’ll see

  • Energy piles: reinforcement cages carry pipe loops before the pour; very common under mid-rise buildings.
  • Energy walls: slurry/diaphragm or secant pile walls with embedded pipes; attractive in basement or cut-and-cover projects.
  • Energy slabs: foundation slabs fitted with pipe grids; promising for low-rise or where piles aren’t needed.

The WAGEs project in a nutshell

WAGEs:  “Towards the Wide Adoption of shallow Geothermal Energy systems in Cyprus.” Our goal is to expand local infrastructure, hands-on testing, training, and knowledge sharing so that businesses, public authorities, and universities can deploy shallow geothermal solutions — like EGs — more confidently and at scale.

What that looks like in practice:

  1. Testbeds & demonstrations. We’re evaluating ground-source solutions—including EG variants—on real and simulated sites typical of Cyprus (soil/rock conditions, climate, and building practices).
  2. Monitoring & analytics. We instrument systems to track temperatures, flows, and performance so designers can size and operate EGs correctly over the long term. (For energy slabs specifically, recent work by our team explores performance under Cyprus building typologies.) link: ktisis.cut.ac.cy
  3. Design guidance & training. We translate results into practical guidance for local engineers, contractors, and authorities through workshops and open resources.
  4. Integration with future-ready grids. We study how EGs pair with GSHPs, PV, and ambient-loop (5GDHC) concepts to cut peak demand and enable thermal storage.

What we’re testing (high level)

  • Thermal performance under Cyprus conditions. How do ground stratigraphy and conductivity affect EG output? What flow/temperature setpoints keep efficiency high across seasons? link: https://doi.org/10.1007/s12053-025-10307-3
  • Energy slabs as EGs. Using realistic house designs, we simulate and analyze slab-integrated pipe grids and their impact on comfort, heat-pump sizing, and lifecycle cost.
  • Comparisons across exchanger types. Side-by-side assessments of different ground heat exchanger (GHE) configurations inform when to choose piles, slabs, walls, or classic boreholes. link: https://doi.org/10.3390/en17184621
  • District-scale operation. How EGs participate in ambient loops and seasonal storage to balance neighborhoods—key to scaling renewables in dense urban areas.

Benefits for Cyprus

  • Lower energy bills & emissions via efficient GSHPs matched to our climate.
  • Minimal land take — EGs use structures we’re already building.
  • Urban friendliness — works well in tight plots where drilling a full borehole field is hard.
  • Future-proofing — EGs plug into 5GDHC and building-to-grid strategies as these expand.

What’s next

Over the project’s lifetime we’ll publish case studies, datasets, and design notes tailored to Cyprus. If you’re an engineer, developer, or public authority exploring EGs for a new build or retrofit, reach out — WAGEs can help with measured data, design considerations, and training resources.

Further reading

  • Energy geo-structures overview & definitions. A compact overview of EG forms (piles, walls, slabs, tunnels) and their dual structural–thermal role.
  • Why integrate with 5GDHC? Reviews and case studies on ambient-loop networks and shallow geothermal storage.
  • Energy slabs under Cyprus conditions. Foundation slabs as EGs in a typical nZEB dwelling—modeling insights from CUT researchers.
  • Project overview (WAGEs). A lay summary of goals, activities, and how industry can get involved.