Frequently asked questions
Read the most frequently asked questions
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:
- Open loop (groundwater)
- Closed loop Horizontal
- Closed loop Vertical
- 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:
- An underground piping system (ground or underground/surface water).
- A geothermal heat pump (mechanical room)
- 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:
- They draw water from a aquifer that is at a constant temperature (usually in Crete 17-20oC).
- This water passes through the heat exchanger which is located inside the engine room.
- Through the heat exchanger the constant temperature of the water is transferred to the geothermal heat pump.
- 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.
- 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:
- Pipes filled with water are placed in the subsoil.
- These pipes are connected to the geothermal heat pump.
- The water inside the pipes is circulated and thus transfers the constant temperature of the geological formations to the geothermal heat pump.
- 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.
- 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.
During summer in Crete, geothermy compared to any air source heat pump can save up to 40% in cooling.
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.
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.
In mountainous areas of Crete a geothermal system works without problems even in frost conditions as it is not located outside the building.
Because we want to promote green tourism in our owned property, using the most environmentally friendly heating-cooling system.
Because we have an environmental consciousness and we do not want to pollute.
Because a geothermal heat pump has twice the lifespan of an air source heat pump.
Geothermal energy improves the aesthetics of the building, as it does not have external equipment (eg pipes and cables).
Because the combination of geothermal and photovoltaics turns our building into a zero energy building.
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.