A Comparison of Geothermal Systems
Which System Is Best Suited for Which Application?
Not all geothermal energy is the same.
Different systems are used depending on the location, energy needs, and intended use.
Some solutions primarily harness geothermal heat as an energy source for a heat pump, while others use groundwater directly; still others are integrated into the building’s structure or combine cooling, heat supply, and thermal buffering in a single system.
Which solution makes sense therefore does not depend solely on the available space or the desired capacity. Decisive factors include, among others, the geological and hydrogeological conditions, the annual heating and cooling profile, the required temperature levels, the permitting situation, and the existing system infrastructure.
The following overview categorizes the most important systems and shows how the Geo-HEP high-performance energy pile differs from conventional solutions.
An Overview of the Most Important Geothermal Systems
As a general guide, geothermal systems can be classified based on the type of heat extraction and their integration into building or facility systems. The boundaries between individual categories may overlap depending on the project; the specific technical design is always the deciding factor.
System | Basic Principle | Typical Strength | Points to Note |
Ground collectors / near-surface ground-source systems | Heat exchange via pipes laid horizontally in the soil near the surface. | Easy utilization of geothermal energy near the surface provided there is sufficient available land area. | Require a relatively large amount of land; performance depends heavily on the soil and system design. |
Traditional geothermal probes | Slim vertical boreholes with a closed-loop pipe system for heat exchange with the subsurface. | A proven heat source for heat pumps and, depending on the design, also for passive cooling. | Drilling depth, geology, spacing, and permits determine the design; thermal mass in the system is limited. |
Conventional energy piles | Components of a pile foundation are additionally thermally activated using piping. | Combination of structural building function and geothermal utilization. | The number and location are often dictated by the building’s foundation. |
Groundwater/hydrothermal systems | Groundwater is used as a heat source or heat sink and is accessed via wells. | Direct use of a thermally favorable groundwater reservoir can enable high heat transfer rates. | Hydrogeology, water quality, and permits under water laws are particularly important. |
Deep geothermal energy | Exploitation of deep geological formations with higher temperature levels. | Suitable for larger heat supply systems and—depending on the reservoir—other energy applications. | Significantly different project scale, drilling depths, investment requirements, and permitting requirements compared to near-surface systems. |
Geo-HEP High-Performance Energy Pile | Large-volume high-performance energy pile with a heat transfer system and integrated thermal storage mass. | Combines high heat exchange, thermal load buffering, passive cooling, and use as a heat source for heat pumps. | Design is project-specific, based on load profile, geology, hydrogeology, and existing system technology. |
Traditional Geothermal Probe – A Simple, Proven Principle
The classic geothermal probe typically consists of a vertical borehole in which a closed-loop pipe system is installed. A heat transfer fluid absorbs heat from the ground or transfers heat to it.
The strength of these systems lies in their proven design and their use as a heat source for heat pumps. Depending on the system design, passive cooling may also be possible.
In contrast to the Geo-HEP high-performance energy pile, however, this is a comparatively slim probe with low integrated storage mass and a smaller heat exchange surface area per individual element. Targeted buffering of short-term thermal load peaks within the probe element is not the central design principle.
Conventional Energy Piles – Geothermal Energy as Part of the Foundation
Conventional energy piles utilize the piles that are already required for the structural foundation of a building to also facilitate heat exchange with the ground. To this end, piping is integrated into the foundation piles.
This principle can be very practical when a pile foundation is planned anyway. The thermal application is thus combined with a structurally necessary building component.
With the Geo-HEP high-performance energy pile, however, the thermal function takes center stage. The large-volume pile combines heat exchange with integrated thermal storage mass and is designed according to the energy and load profile of the specific project.
Groundwater Systems – Actively Using Groundwater as a Heat Source
In open groundwater systems, groundwater is extracted via wells, used for heating, and then returned to the ground. The groundwater is thus an integral part of the heating system.
This fundamentally distinguishes these systems from the Geo-HEP system. Geo-HEP operates as a closed heat exchange system: groundwater is neither extracted nor integrated into the system’s circuit.
Nevertheless, existing flowing groundwater can be very beneficial for Geo-HEP. It transports the heat introduced into the subsurface and thereby supports thermal regeneration around the high-performance energy piles. The extent to which this effect can be utilized depends on the hydrogeological conditions of the site.
Deep Geothermal Energy—A Whole Different Scale
Deep geothermal energy taps into geological formations at significantly greater depths and thus pursues different technical and economic goals than near-surface systems.
It can, for example, be of interest for larger heat supply structures. However, planning, drilling techniques, investment volumes, and permitting requirements differ fundamentally from those of systems that supply buildings, production facilities, or individual business sites.
Geo-HEP should therefore not be viewed as an alternative to every deep geothermal project. The systems are designed for different project sizes and purposes.
What makes the Geo-HEP system different?
The Geo-HEP high-performance energy pile combines several features that are often considered separately in traditional solutions.
- A high-performance energy pile with a large volume instead of a slender probe
- Large heat exchange surface area with the surrounding ground
- Integrated thermal storage mass—preferably approximately 43 m³ of water
- Buffering of short-term thermal load peaks
- Passive cooling under suitable conditions
- Use as a heat source for heat pumps
- Cooling and heating operations within a shared geothermal infrastructure
- Closed heat exchange system without active groundwater extraction
- Technical components accessible for maintenance
- Project-specific design based on energy demand and site conditions
These features do not mean that Geo-HEP is automatically the better solution for every project. The most suitable technology must be evaluated based on the actual load profile, geology, groundwater conditions, available space, required temperatures, and existing plant infrastructure.
Heat storage is not the same as geothermal energy
Geothermal heat sources and thermal storage systems serve different purposes. Therefore, geothermal probes, energy piles, or groundwater systems should not be equated with standalone seasonal storage systems.
This distinction is also important within the Geo-HEP high-performance energy pile: The integrated water mass primarily serves to absorb and buffer short-term thermal loads within the HEP.
In contrast, the seasonal storage system developed by Geo-HEP Systems is designed to specifically store heat or cooling over extended periods and make it available again later. It is a standalone system and is described separately.
Evaluating Geo-HEP on a Project-by-Project Basis
Geo-HEP Systems therefore considers not only the individual high-performance energy pile, but also the interplay between energy demand, system technology, geology, and hydrogeology.
This allows for an assessment of which geothermal solution is suitable for the specific site and what potential the Geo-HEP high-performance energy pile offers, particularly in cases of high or continuous cooling demand, combined heating and cooling loads, and limited available space.
Which solution is right for which project?
A sound system selection process does not begin with the question of a specific technology, but rather with the actual energy requirements and site conditions.
For the preliminary assessment, the following questions, among others, should be answered:
- Is the primary need for heating, cooling, or both?
- How many operating hours are there per year?
- Do short-term load peaks occur?
- What flow and return temperatures are required?
- How much land is available?
- What is the composition of the subsoil?
- What are the groundwater conditions?
- What heating and cooling systems are already in place?
- What regulatory requirements apply at the site?
Only after considering all these factors can we determine whether a conventional geothermal probe, another geothermal system, or a Geo-HEP concept is technically and economically viable.
Have the technical feasibility of your project evaluated.
There is no one-size-fits-all answer to whether Geo-HEP is technically and economically viable for a specific application. The key is to consider the heating and cooling demands, load profile, system technology, and the geological and hydrogeological conditions of the site as a whole.
Based on this analysis, the system configuration and the required number of high-performance energy piles are determined on a project-specific basis.