A geothermal system uses the technology of heat pumps that pump heat from one source. We all have in mind the classic heat pump with the outdoor unit and the fan which is called air source heat pump. In the case of geothermal heat we have a ground source heat pump which uses the soil as a source of pumping. The ways in which it can take advantage of the constant soil temperature are:

1. Open loop (groundwater)
2. Closed loop Horizontal
3. Closed loop Vertical
4. Closed pond loop

In the case of a closed-loop system, we place boreholes in the subsoil (geo-exchangers) filled with water and grout (if required) which, by circulating the fluid inside them, achieve the exchange of heat with the ground. While in the case of an open-loop system we take advantage of the existence of an aquifer by pumping the water at a constant temperature and then return it back. Finally, in the case of the closed-pond loop we have a closed system immersed in water. So we replace the outdoor fan-coil unit with a heat pump inside the building connected to the ground.

A geothermal system consists of three main parts:

1. An underground piping system (ground or underground/surface water).
2. A geothermal heat pump (mechanical room)
3. A distribution system inside the building (eg Fan coil, Radiant, A/C etc.)

Shallow geothermal system in a building works as follows:

Open loop: Open loop geothermal systems follow these steps:

1. They draw water from a aquifer that is at a constant temperature (usually in Crete 17-20^oC).
2. This water passes through the heat exchanger which is located inside the engine room.
3. Through the heat exchanger the constant temperature of the water is transferred to the geothermal heat pump.
4. The geothermal heat pump in turn interacts with the distribution system of the building and returns the highest temperature (during cooling) to the heat exchanger and this in turn to the water that is pumped.
5. After the completion of the heat exchange, the water of the aquifer is discharged at a higher temperature (cooling) back to its place.

Closed loop: Closed loop geothermal systems follow these steps:

1. Pipes filled with water are placed in the subsoil.
2. These pipes are connected to the geothermal heat pump.
3. The water inside the pipes is circulated and thus transfers the constant temperature of the geological formations to the geothermal heat pump.
4. The geothermal heat pump in turn interacts with the distribution system of the building and returns the highest temperature (during cooling) to the water of the pipes located underground.
5. So through the geo-exchangers (pipes in the subsoil) the temperature of the water circulating inside them is transferred to the subsoil offering cooling to the building.

The answer is no!

With a geothermal system we can fully meet the needs of our building in heating, cooling and hot water.

The answer is No!

As analyzed in the section What is Geothermy, shallow Geothermy does not require the existence of a geothermal field as it takes advantage of the constant temperature of geological formations a few meters below the Earth’s surface. It does not seek high temperatures nor does it require great depths to offer us heating and cooling.

Geothermal systems have been applied for 60 years internationally, while in Greece they count more than 25 years of applications. It is therefore reliable; provided that the design and installation will be undertaken by people specialized in this technology.

The cost of a geothermal system is proportional to its value and what it offers to its user. Therefore, when we talk about geothermal energy and its cost, we need to consider all the data and not just the initial installation cost. If for example someone does the calculations including the installation, operation and maintenance costs based on 15% for both geothermal and air source heat pump then he will come to the conclusion that Geothermal costs less.

1st Reason

During summer in Crete, geothermy compared to any air source heat pump can save up to 40% in cooling.

2nd Reason

In homes near the sea, geothermal systems have the advantage of not having any exposed equipment thus preventing the premature replacement of the heat pump due to corrosion.

3rd Reason

A hotel by the sea applying an open geothermal system reaches its depreciation within 4 years. Saving from 40-60% in comparison to air source heat pumps.

4th Reason

In mountainous areas of Crete a geothermal system works without problems even in frost conditions as it is not located outside the building.

5th Reason

Because we want to promote green tourism in our owned property, using the most environmentally friendly heating-cooling system.

6th Reason

Because we have an environmental consciousness and we do not want to pollute.

7th Reason
Because a geothermal heat pump has twice the lifespan of an air source heat pump.

8th Reason
Geothermal energy improves the aesthetics of the building, as it does not have external equipment (eg pipes and cables).

9th Reason
Because the combination of geothermal and photovoltaics turns our building into a zero energy building.

10th Reason
The temperatures may not be low enough, but the humidity levels on the island create the need for quality heating.

When we say we cannot drill, we need to bear in mind that oil drilling extraction is carried out at a depth of 10km. Therefore, each drilling requires specific equipment and the corresponding knowledge and experience.

Applying the closed-loop vertical system, all that is needed are holes in the ground with a diameter of 12cm. In addition, an open-loop system does not require space but the existence of water.

We can certainly use seawater for geothermal applications, provided that the correct design and special equipment and materials are selected.

At the given time in our country the program for houses that exists (Εξοικονομώ-Αυτονομώ) does not favor geothermy as it subsidizes only the heat pump and not the ground system. We hope that this omission will be rectified in the future.

The answer is no!

There are some rules in geothermal energy that we must follow. Practically, no one forbids us from digging and laying pipes in the subsoil. However, some parameters such as the distance between the pipes or their overlap with correct granulometry soil, as well as the perfection of the geothermal system require study by an engineer and installation by people experienced in such applications.

The installation of a geothermal system requires a permit issued by the peripheral unit to which the property belongs.

The cost of a geothermal system is influenced by many factors which mainly concern the underground. The costing of a shallow geothermal system results from the preliminary study, which is carried out by engineers specialized in the geothermal field.
Factors that affect the cost of a geothermal system and require a preliminary study:

    1.   In closed type horizontal systems, excavation is done, so in case we have rock, it is necessary to use a hammer and transport the fragmented rocks outside the construction site.

    2.   Hard rocks combined with aquifers which increase drilling costs.

    3.   Low subsoil thermal conductivity increases the cost of the well filling material (grout) in the closed type vertical systems.

    4.   In open type systems the chemistry of the water affects the installation cost (e.g. poor quality water requires highly resistant equipment and special specifications, which increases the cost).

Thus, it is easy to understand that a geothermal system is not only priced according to the climatic data of the area, but also according to the volume of the building that we want to cool or heat.

A vertical Geothermal system requires 1 borehole of 100m depth for every 3-3.5kw of cooling or heating capacity with single U geo-exchanger type installation. The precise determination of the number of boreholes varies from region to region due to fluctuations in the thermal conductivity value of soil.

The minimum allowable distance between boreholes in a closed Loop vertical geothermal system is 4.5-5m. However, this is different depending on the study area as well as simulation to accurately determine the difference radius between boreholes.

• It can be included in energy upgrading actions gathering more possibilities for access to financing.
• Payback Period (5-7 years)
• Does not require free space (place even within the urban fabric)
• Energy saving up to 75%
• Reduces the required installed power and therefore the size-area of ​​the Photovoltaic system (solar).
• No regular maintenance required
• Twice the lifespan compared to Air Source Heat Pump
• Silent Mode
• Does not burn (unpleasant odors – cleanliness – possibility of fire)
• Improves the aesthetics of the building (no units with fans, pipes, cables)

• The total installation cost is shared among the owners and thus the final cost is too low for each owner.
• Payback Period (5-7 years)
• Does not require free space (place even within the urban fabric)
• Energy saving up to 75%
• Reduces the required installed power and therefore the size-area of ​​the Photovoltaic system (solar).
• No regular maintenance required
• Twice the lifespan compared to Air Source Heat Pump
• Silent Mode
• Does not burn (unpleasant odors – cleanliness – possibility of fire)
• Improves the aesthetics of the building (no units with fans, pipes, cables)

• There is no free area for horizontal placement of the Geo-exchanger
• Payback Period (10-15 years)
• Does not require free space (place even within the urban fabric)
• Energy saving up to 75%
• Reduces the required installed power and therefore the size-area of ​​the Photovoltaic system (solar).
• No regular maintenance required
• Twice the lifespan compared to Air Source Heat Pump
• Silent Mode
• Does not burn (unpleasant odors – cleanliness – possibility of fire)
• Improves the aesthetics of the building (no units with fans, pipes, cables)

Our company recommends closed loop horizontal geothermal system in residential buildings smaller than 400m² which are located in off-plan plots larger than 1 acre for the following reasons:

• • Energy saving up to 75%
  • Reduced installation costs compared to other types of geothermal systems
  • Reduces the required installed power and therefore the size-area of ​​the Photovoltaic system (solar).
  • Payback Period (5-7 years)
  • No regular maintenance required
  • Twice the lifespan compared to Air Source Heat Pump
  • Silent Mode
  • Does not burn (unpleasant odors – cleanliness – possibility of fire)
  • Improves the aesthetics of the building (no units with fans, pipes, cables)

• Does not require free space (place even within the urban fabric)
• Energy saving up to 75%
• Reduces the required installed power and therefore the size-area of ​​the Photovoltaic system (solar).
• No regular maintenance required
• Twice the lifespan compared to Air Source Heat Pump
• Silent Mode
• Does not burn (unpleasant odors – cleanliness – possibility of fire)
• Improves the aesthetics of the building (no units with fans, pipes, cables)

The payback period of geothermal system is different for each type of geothermal system but also for each type/use of building (e.g. a country house, seasonal hotel, etc.) below we present the payback periods of different types of geothermal systems in basic categories of buildings with climate Crete data.

1.Closed Loop-Horizontal for

• Residential building with free area (5-7 Years)

2. Closed Loop-Vertical for

• Apartment Buildings (5-7 Years)
• Public Buildings (5-7 Years)
• Residential building without free area (10-15 years)

3. Open Loop for

• • Commercial Buildings /Hotels in seaside area (4-6 years)

In applications with a maximum cooling or heating capacity of less than 75 Kw where significant heterogeneities are observed in the local formations.

In applications with a maximum heating or cooling capacity greater than or equal to 75 Kw it is considered economically appropriate.

The reasons that Thermal Response Test is performed are:

• Most accurate method for determining average thermal properties of borehole
• Accurate thermal property knowledge helps prevent over/under sizing loop field
• Provides knowledge of drilling conditions
• Improves contractor knowledge of subsoil conditions, taking uncertainties out of bid process.

Stage 1 Preliminary Study-Total Cost

• Visit to the site of project- data collection
• Topographical
• Building Load Calculations (if exists)
• Geological formations of the application area
• Preliminary study which includes:
• Data analysis project description.
• Assessment of the geology at study area includes Geological section.
• Initial system design and dimensioning of its individual elements.
• Simulation of the geothermal system to verify it’s completeness
• Detailed description of the system and its installation process.
• All stages of the project with detailed costs.
• Financial feasibility study of the project and its payback period.

Stage 2  Issue of Permit (in Greece)-Final Design – Project supervision

• Simulation of the geothermal system to verify it’s completeness
• Completion of the Geothermal System Study.
• Collections of supporting documents for the issuance of the permit of install geothermal system.
• Completing the file and submitting it for the issuance of the permit (1-2 months usually).
• Supply of equipment-materials for the construction of the project.
• Issuance of the permit and installation of the geothermal system under our supervision (includes issuance of a paravolo (GR) from a financial cost of 300 euro).

Stage 3  Procedure for the installation of the geothermal system (under our supervision)

• Construction of Geo-exchanger
• Excavation – Backfilling
• Geo-exchanger pressure test
• Construction of piping networks to connect to the mechanical room.
• Flushing-Purging of the geothermal system.
• Start up the system

Stage 1  Preliminary study-Total Cost

• Visit to the site of project- data collection
• Topographical
• Building Load Calculations (if exists)
• Geological formations of the application area
• Preliminary study which includes:
• Data analysis project description.
• Assessment of the geology at study area includes Geological section.
• Initial system design and dimensioning of its individual elements.
• Simulation of the geothermal system to verify it’s completeness
• Detailed description of the system and its installation process.
• All stages of the project with detailed costs.
• Financial feasibility study of the project and its payback period.

Stage 2  Issue of Permit (in Greece)-Final Design – Project supervision

• Simulation of the geothermal system to verify it’s completeness
• Completion of the Geothermal System Study.
• Collections of supporting documents for the issuance of the permit of install geothermal system.
• Completing the file and submitting it for the issuance of the permit (1-2 months usually).
• Supply of equipment-materials for the construction of the project.
• Issuance of the permit and installation of the geothermal system under our supervision (includes issuance of a paravolo (GR) from a financial cost of 300 euro).

Stage 3  Procedure for the installation of the geothermal system (under our supervision)

• Drilling of boreholes-placement of geo-exchangers- grouting of boreholes.
• Geoexchanger pressure test
• Thermal Response Test (required in large projects)
• Construction of piping networks to connect to the mechanical room.
• Flushing-Purging of the geothermal system.
• Start up the system

Table 1

 **Table 1 (Source : ‘’RETScreen Expert ‘’ Clean Energy Management Software version 8.1)

Total Cost= Kw*GSHP Cost + Kw*Cost (Horizontal or Vertical) Ground Loop

The cost of a closed loop geothermal system depends on:

• The building heating and cooling Loads (peak loads it will need to cover).
• The geology of the area (increases and reductions in drilling and grouting costs).
• The available area (horizontal or vertical).
• The quality of the materials.

The dimensions of the trenches and their number differ depending on the designer of the system and the data in his possession (e.g. in some cases where there is no available area and the geology allows it, the designer can place in one trench more levels by increasing the depth of the trench.

The minimum acceptable distance between trenches is 3-3.5 meters so that each trench is not disturbed by its neighbors.

The installation depth of the geoexchanger in horizontal geothermal systems depends on the designer as the main parameter is the thermal conductivity of the soil in the study area.

The minimum acceptable coating thickness to protect the geoexchanger is 10-30 cm to protect against any contact with spikes.

• Doesnotrequirefreespace
• Can use sea water
• Energy saving up to 75%
• Payback Period (4-6 years)
• Reduces the required installed power and therefore the size-area of ​​the Photovoltaic system (solar).
• Can be combined in desalination units (reducing the energy cost of desalination by increasing the water temperature during cooling).
• It can contribute to the production of domestic hot water as well as to the heating of the swimming pool as a supporting system through heat recovery.
• Maintenance required (depends on water-chemistry)
• Twice the lifespan compared to Air Source Heat Pump
• Silent Mode
• Does not burn (unpleasant odors – cleanliness – possibility of fire)
• Improves the aesthetics of the building (no units with fans, pipes, cables)

In open Loop geothermal system applications the use of a tank is prohibited due to the fact that it allows oxygen to enter the system, it also allows dissolved carbon dioxide (CO2) to escape, lowering the pH and worsening scaling. The above is written in the international bibliography of geothermal energy (excerpt from bibliography ‘’ The use of open tanks for storing the groundwater is unacceptable, because, in addition to allowing oxygen to enter the system, this also lets dissolved car- bon dioxide (CO2) escape, lowering pH and exacerbating scaling’’.

Stage 1  Preliminary study-Total Cost

• Visit to the site of project- data collection
• Topographical
• Building Load Calculations (if exists)
• Geological formations of the application area
• Preliminary study which includes:
• Data analysis project description.
• Assessment of the geology at study area includes Geological section.
• Initial system design and dimensioning of its individual elements.
• Detailed description of the system and its installation process.
• All stages of the project with detailed costs.
• Financial feasibility study of the project and its payback period.

Stage 2  Issue of Permit (in Greece)

• Collections of supporting documents for the issuance of the permit of install geothermal system.
• Completing the file and submitting it for the issuance of the permit (2-3 months usually).
• Issuance of the permit and installation of the geothermal system under our supervision (includes issuance of a paravolo (GR) from a financial cost of 300 euro).

Stage 3  Final Design – Project supervision-Procedure for the installation of the geothermal system (under our supervision)

• Drilling of boreholes or well construction (includes wellbore cleaning and test pumping by the well manufacturer)
• Take a water sample and send it for chemical analysis (included in the cost of the study for permit)
• Simulation of the geothermal system to verify it’s completeness
• Final system design which results from wells flow testing data and the chemical analysis of the water
• Supply of equipment-materials for the construction of the project.
• Construction of piping networks to connect to the mechanical room.
• Start up the system

Our company recommends the application of open loop Geothermal systems in the following cases:

• In applications that require at least 18Kw of cooling or heating power.
• In cases where the quantity of water resources is guaranteed (e.g. coastal areas).
• In cases where poor water chemistry can be dealt with by special equipment and normal maintenance.

 Table 1

 Table 1 (Source: https://unfccc.int/resource/cd_roms/na1/mitigation/Module_5/Module_5_1/b_tools/RETScreen/Manuals/Ground_Source_Heat_Pumps.pdf  & Estimations from Whelve Energy team based on real projects at the island of Crete)

Total Cost= Kw*GWHP Cost + Kw*Well Pump Cost + Kw*Plate HEX Cost + Kw*Well Construction                                  

The cost of open loop geothermal system depends on:

• The building heating and cooling Loads (peak loads it will need to cover).
• The geology & hydrology of the area (increases and reductions in drilling cost).
• The water chemistry.
• The quality of the materials.

The maintenance of an open loop geothermal system is considered necessary and its frequency depends on the chemistry of the water used.

• Doesnotrequirefreespace
• Can use sea water
• Energy saving up to 75%
• Payback Period (4-6 years)
• Reduces the required installed power and therefore the size-area of ​​the Photovoltaic system (solar).
• Can be combined in desalination units (reducing the energy cost of desalination by increasing the water temperature during cooling).
• It can contribute to the production of domestic hot water as well as to the heating of the swimming pool as a supporting system through heat recovery.
• Maintenance required (depends on water-chemistry)
• Twice the lifespan compared to Air Source Heat Pump
• Silent Mode
• Does not burn (unpleasant odors – cleanliness – possibility of fire)
• Improves the aesthetics of the building (no units with fans, pipes, cables)

• Geothermal systems can provide, through heat recovery during the cooling process, a higher temperature for the production of domestic hot water/swimming pool heating, achieving energy savings.

• Silent Mode
• Does not burn (unpleasant odors – cleanliness – possibility of fire)
• Improves the aesthetics of the building (no units with fans, pipes, cables)