MUSE – Closed-loop systems requirements & advantages

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Estelle Petitclerc, 4 September 2020

Applications of shallow geothermal energy either use closed-loop or open-loop systems. Here we explain the requirements and advantages of closed-loop systems and in follow-up blog we dive into open-loop systems. In closed-loop systems a heat carrier fluid circulates in pipes to harness heat from or store it in the ground. These heat exchanger pipes can be integrated in (1) borehole heat exchangers, (2) horizontal closed-loop systems and (3) thermo-active building foundations.

Requirements of the systems change in terms of access, space as well as function and type of the chosen application but undeniably an efficient designof the geothermal system is important to guarantee an optimized system according to the energy demand and to prevent thermal interference between adjacent installations in urban areas. An efficient design must consider thermal, hydrogeological and geological conditions on-site.

1 – Borehole heat exchangers (BHEs)

These vertical systems use boreholes, which go down to a depth of around 200 meters. They consume little space and do not depend on specific underground settings. As single BHEs they provide enough energy for heating and cooling of single-family houses. In a field up to hundreds of BHEs can heat and cool an entire neighborhood and even serve as seasonal storage of energy from other renewable sources.

2 – Horizontal closed-loop systems

There are many different types, such as horizontal or trench collectors and slinky coil loops. Basically those systems work like buried solar panels, which use solar radiation stored in the uppermost soil (1 to 4 m depths). This upper soil layer has to be easily removable for a smooth construction. Because they require more space than other shallow geothermal energy systems, horizontal systems are mostly used for single-family houses.

3 – Thermo-active building foundations

Heat carrier pipes get implemented into building foundations directly during construction. Neither additional space nor an additional installation to exchange heat with the ground is required.

Left: Horizontal closed-loop system. Middle: Thermo-active building foundation. Right: Borehole heat exchanger. © GRETA – Interreg Alpine Space ERDF

Similar to other geothermal systems, closed-loop systems are

  • Reliable – shallow geothermal energy is stable and capable of providing heating and cooling 24/7 throughout the year.
  • All-rounders – Covering heating and / or cooling and / or domestic hot water needs with sustainable energy, from single-family houses to entire neighborhoods.
  • Green – Reducing emissions such as smog and greenhouse gases. Combined with renewable electricity the technology produces zero emissions. This supports climate environmental policies.
  • Efficient – Advantageous overall cost thanks to high energy performance.

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