It is well known that, thanks to its favorable balneological and geothermal conditions, Hungary is a country rich in thermal waters. Although the demand for the energy utilization of thermal water is increasing, geothermal energy remains our largest untapped energy source, due to the unique geological characteristics of the Carpathian Basin. The average domestic heat flux is high—one and a half times the European average—at 90 mW/m² [1]. This may not seem like a large number, but when multiplied by the country’s area, it amounts to 8,400 MW, which is more than four times the output of the Paks Nuclear Power Plant. Naturally—as we shall see—this cannot all be utilized for several reasons.
Origin and Emergence of Thermal Water
For sustainable utilization of thermal water and geothermal energy production, we must understand the mechanism of thermal water formation and the extent of its replenishment. During the opening of the Pannonian Basin in the Middle Miocene, extensional forces caused significant thinning of the lithosphere in Hungary; therefore, the slowly flowing, heat-transporting asthenosphere beneath the lithosphere is closer to the surface here than under most continental regions elsewhere on Earth. This explains the higher-than-usual values of the geothermal gradient and heat flow. In addition, the country’s excellent geothermal potential is also due to the presence of geological formations with good aquifer properties. Hungarian thermal waters are primarily associated with two different types of geological formations. In the Great Plain, the Little Hungarian Plain, and the Drava Basin, they occur in Pannonian shallow-water porous sandstones, while in the forelands of the mountain ranges, they are mostly linked to fractured Mesozoic carbonate layers, forming thermal karsts.
Hungary is not Iceland or Kamchatka; there are no hot springs here producing dry steam at 150–180 °C. Water warmer than 30 °C is classified as thermal water, and at present, there are about a thousand wells in the country that yield such water. When considering utilization, it must be taken into account that although water warmer than 30 °C can be extracted almost everywhere except in the mountainous regions, water warmer than 50 °C occurs in less than half of the country’s territory. Thermal waters are found at highly variable depths across different parts of the country. Upper Pannonian sandstones, which have particularly good water storage and transmission capacity, lie as deep as 2,500 meters at their deepest points, and from them, water at 90–100 °C can be obtained. In the Great Plain, water at 70 °C can be drawn from a depth of 1,000 meters, and water hotter than 120 °C from 2,000 meters. In theory, even hotter water could be obtained from greater depths, but in practice, technological and economic challenges increase exponentially with depth. As water ascends in thermal wells, it cools, which is why at the surface its temperature rarely exceeds 100 °C [2].
Thermal water is younger than the sediments it resides in and is of meteoric origin. Its formation can be illustrated by the following figure for the thermal springs of Buda:
The amount of infiltrating water depends on annual precipitation and the quality of the rock. The springs associated with the Buda thermal fault line, which appear from Óbuda to the Gellért Bath, have a very significant discharge, and it is still not precisely known where this large volume of water originates. It is likely that it comes from a substantial part of the Dunazug Mountains and possibly even from the fault blocks on the left bank of the Danube. After seeping down to the depths of the Triassic carbonate layers, the infiltrating water heats up and, as ascending water, reaches the springs—probably within a few decades. Part of this water may travel under the Danube into the basin of the Pest Plain and, under the pressure of clay cover layers, return to the right-bank springs of the Danube from greater depths and along a longer path [3].
In the porous Pannonian sandstone reservoirs of the Great Plain, a mechanism similar to that of thermal karsts can be observed. Due to the morphology and geological structure of the Carpathian Basin, two flow systems have developed at depth. One is the upper hydrostatic system (down to a depth of about 2,000 m), where water movement is primarily governed by gravity. The other is the lower overpressured system (mainly around Szolnok, Szeged, Algyő, and in the Makó Trough area, at depths of approximately 2,500–5,000 m). These two flow systems are interconnected and also linked to surface and near-surface waters [4].
The foundation of sustainable thermal water management is that both the extracted heat and the extracted water must be replenished. As a rule of thumb, for heat, the recovery time after production stops can be considered equal to the duration of production, or in the case of high-temperature waters (>150 °C), two to five times longer. For water extraction, the replenishment period is similar to that of heat recovery [5].
In summary, the most important principle regarding the sustainability of thermal water and geothermal energy utilization is that, in the long term, only as much water should be extracted as can be replenished through surface infiltration.
Possibilities for Utilizing Geothermal Energy
Balneological Use
The simplest way of utilizing geothermal energy—known since the Stone Age—is the use of naturally emerging warm water for bathing. This has a long tradition in Hungary as well; there are about 150 thermal baths in the country, including 36 special baths containing waters that are radioactive, sulfuric-acidic, saline-bromide-carbonate, or iodine-rich.
For direct balneological purposes, waters with a temperature of 30–50 °C are typically used. It is worth noting that thermal waters only slightly warmer than 30 °C are not always ideal for operating baths. A good example is the Cave Bath in Miskolctapolca, where the spring barely reaches this temperature [6], so the water must be heated. Even so, bathers often complain that the pool water feels cool.
Even in areas where thermal water is abundant, it is not possible to open new baths indefinitely or increase water withdrawal without limit. One only needs to recall the well-known case of Lake Hévíz, where, due to water extraction associated with the Nyirád bauxite mining, the spring’s discharge decreased by nearly 40% by the end of the 1980s.
Horticultural and Agricultural Use
The traditional way of utilizing thermal waters with temperatures of 50–100 °C is for heating greenhouses and foil-covered tunnels. In Hungary, this practice also has a long-standing tradition: currently, heating for more than 70 hectares of greenhouses and 260 hectares of soil-heated foil tunnels is provided by about 500 wells. In addition, thermal water heats fishing ponds, fish farms, and even poultry, turkey, pig, and snail farms at more than fifty locations. The estimated capacity of thermal water used for agricultural purposes is 3,413 TJ [7]. Although waters of 20–50 °C are typically used in bathing culture, it should be noted here that these waters are also excellent for heating breeding and spawning ponds for fish fry that require lukewarm water.
Heating of Buildings Intended for Human Occupancy
The usual method of direct (non-converted) energy extraction from thermal water is its use for heating purposes. A good example of district heating systems installed on Pannonian porous sandstone reservoirs is the system operated by Szentes Városi Szolgáltató Kft., which provides nearly 100% of the city’s district heating from geothermal energy [8]. For urban geothermal heating systems tapping Mesozoic carbonate reservoirs, the system in Veresegyház, commissioned in 1993, can be mentioned as an example, which will be discussed in more detail later.
A special case of geothermal heating is heat extraction using heat pumps from shallow (on average 100 m) closed-loop boreholes. These systems operate with a high COP value (7–8) compared to air-water heat pumps, and their operation does not involve water extraction, so this technology is not relevant from the perspective of thermal water resource management.
Complex Utilization and Cascade Systems
Under appropriate conditions, thermal waters and geothermal energy can also be used in a complex manner. In practice, this means the seasonal integration or parallel operation of different application areas. Such developments are becoming increasingly common today.
An example is the district heating system of Hódmezővásárhely, where water from production wells with temperatures of 50–80 °C supplies heating to downtown public institutions, a shopping center, and 2,800 apartments. After this, the now cooler water is used to heat the water of a swimming pool and an open-air bath.
Here, the thermal water only comes into contact with the bath water through a heat exchanger; it does not become contaminated, and there is no mixing between the two. Finally, the water—by then cooled to about 20 °C—is returned to two reinjection wells [9].
Electricity Generation
In Hungary, geothermal resources are primarily suitable for direct heat production; however, in recent decades, research and experiments aimed at electricity generation have also been carried out—for example, in the Tótkomlós and Gádoros areas, and most recently near Jászberény, where MOL Nyrt. conducted investigations. There is little publicly available information about these projects, but it is known that due to extreme overpressure, significant gas content, high salinity, strong scaling tendency, and corrosion risk, these projects could not be realized.
The first—and so far only—geothermal power plant generating electricity in Hungary is the 2.7 MW facility in Tura, supplied by a well 1,500 meters deep that provides water at 125–126 °C. The returning water, at 50–60 °C, is currently reinjected into the reservoir with the help of pumps, although earlier plans envisioned using it to heat a greenhouse.
Under typical Hungarian conditions, using steam turbines directly is not feasible, as this would require a minimum of 150 °C, preferably much higher temperatures. While geothermal steam power plants operate in places such as California, this technology cannot be applied in Hungary.
Geothermal power plants that operate with lower-temperature water (even as low as 50–60 °C) are combined-cycle plants. In these systems, the heat of the thermal water is used to vaporize a secondary medium with a lower boiling point (typically a high-molecular-weight organic fluid), and the vapor of this medium drives the turbines. The Tura plant is of this type, operating on an Organic Rankine Cycle (ORC). The efficiency of such plants is rather modest, at around 10–13% [10].
Degassing
For Hungarian thermal waters, the issue of gas content must also be addressed. In many places, the high methane content poses a serious hazard if the gas accumulates in machine rooms, well shafts, water reservoirs, or in the airspace of baths. In the 1980s, several accidents occurred for this reason, the most recent notable case being the explosion of the Fehérgyarmat water tower in 2010.
According to the MSZ 15285:1998 standard, appropriate degassing equipment must be used to remove gas from water, and adequate ventilation must be ensured in hazardous spaces.
One problem with the currently widespread use of vacuum degassers is that they simply release methane into the atmosphere (a greenhouse gas!). Another issue is that they are not particularly suitable for degassing hot and corrosive thermal waters. An alternative solution could be burning methane in a gas engine, which would allow for the generation of additional energy.
The Issue of Reinjection
The reinjection of thermal water is fundamentally necessary for two reasons. First, to prevent contamination of surface recipients, and second, to replenish the extracted water and counterbalance the reduction in reservoir pressure.
The extracted thermal water, due to its temperature, pH, and the dissolved minerals it contains, is generally harmful to ecosystems and poses a disposal challenge. In many cases, it cannot be discharged directly into natural recipients, or there is no suitable surface recipient available. In such cases, it is advisable to return the water to the same layers from which it was extracted.
Reinjection is also strongly justified if the groundwater body that supplied the thermal water is in an unsatisfactory quantitative state. A glance at the following maps clearly shows that, in many places, the extraction of our thermal water resources exceeds sustainable levels. In these areas, continuous declines in water level have been observed. This is why reinjection is extremely important for geothermal extractions intended for energy purposes.
The Water Management Act of 1995 (Act LVII) mandated reinjection; however, under pressure from the agricultural sector, the law was amended in 2013, and instead of expanding the obligation, it was abolished. Currently, it depends on the first-instance water authority (the Disaster Management Authority) whether reinjection is prescribed during the permitting process.
Following the amendment, other legal regulations were also changed: the permissible limit for the salt content of wastewater or used water was increased (exceeding which incurs fines), and the economic multiplier for the water resource fee payable for the utilization of geothermal energy was reduced (as per Decree 43/1999 (XII.6) KHVM). As a result, economic regulation no longer provides an incentive for reinjection.
We increasingly hear claims that “reinjection is cumbersome and expensive,” or that “in the Great Plain, due to soil porosity, it makes no sense.” However, it must be noted that the technology required for reinjection is not new. The oil industry has been injecting water into Pannonian sandstones for hydrocarbon production for over half a century, and the first effectively operating thermal water reinjection well in Hungary was built in Hódmezővásárhely in 1993. Thus, the technology exists—though it is undeniable that its reliability and economic efficiency can always be improved.
There are indeed concerns related to reinjection, particularly the risks of colmatation and so-called thermal breakthrough. A risk arises if the temperature and chemical composition of the reinjected water differ significantly from those of the water in the receiving layer. When cooled and degassed water mixes with the deep formation waters, various chemical processes may begin, potentially leading to scale formation. Scale clogs the pores of the porous rock, which is essentially a form of colmatation.
Colmatation can also occur when fine rock particles are mobilized by the flowing fluid and block the pores of the rock. As colmatation progresses, the reinjection well becomes “clogged,” requiring increasingly higher pressure for reinjection, which significantly increases costs.
It is no coincidence that long-term experience with reinjection into the cavity systems of karstic and/or fractured rocks has been more favorable than in the case of fine-pored sandstones. However, for such fractured systems, thermal breakthrough can present a problem. Because fracture or cavity networks have better water conductivity, there is a risk that the effect of the reinjected cooler water will reach the production wells, causing a drop in temperature in the extracted water.
This risk is particularly significant in EGS (Enhanced Geothermal System) power plants built for direct electricity generation using hydraulic fracturing technology [11]. In the case of fractured karstic rocks, far less energy is required for reinjection compared to porous reservoirs; however, due to the injected cooler water, a decline in the production well temperature must be expected sooner.
Water used for bathing becomes heavily contaminated during use—primarily with microorganisms living on the human body (including microbes carrying antibiotic resistance genes), as well as with cosmetics, pharmaceutical residues (e.g., diclofenac), lubricants from mechanical equipment, flame retardants, and plasticizers (including those from swimsuits!). For this reason, used bathwater must be treated as wastewater and, by law, may not be reinjected into the aquifer.
Some experts consider this restriction unnecessary, arguing that, first, “Danube water is perfectly purified when passing through gravel beds in bank filtration wells,” and second, “at depth, the water heats above its boiling point, killing all microbes.” However, this reasoning is flawed for several reasons.
The purification process in bank filtration wells is still not fully understood, but it is known that the removal efficiency for organic micropollutants and pharmaceutical residues is only 30–40%, and for some chemicals, less than 10%, meaning the water does not become completely clean [12].
Moreover, even at great depth, due to high pressure, water does not “heat above its boiling point”; at 140–150 °C, it remains in liquid state, and it is well known that some microorganisms survive under such conditions. Recent research has shown that a wide variety of microbes live in hot, saline waters at depths of 1,500–4,000 m.
Unknown biochemical processes may occur in reinjected water, and—unlike in surface waters—we have practically no means to influence these processes or eliminate any contamination that develops within the deep rock formations.
Three Examples of Thermal Water Utilization
The Göd Thermal Bath
The Göd Thermal Bath operates three outdoor pools that are open year-round to visitors. The thermal pool with warm water operates at 34–36 °C and is 25 meters long. The swimming pool is also 25 meters in length, with a water temperature of 26–28 °C. The children’s pool has a temperature of 32–34 °C [13].
The bath’s water is supplied by the Alsógöd Strand I well, whose water is recognized as natural medicinal water by the National Directorate for Medicinal and Thermal Baths. Classification permit number: 490/GYF/2002, registry number: VII/78. [14]
The coordinates of the thermal well are N47° 41′ 30.21″, E19° 09′ 04.98″. Its total depth is 695 m, with a yield of 250 liters per minute. The outflowing water temperature is 51.3 °C, and its pH is slightly acidic (6.37). The water is a low-salinity calcium-magnesium-hydrogen-carbonate thermal water that also contains sodium and has a significant fluoride ion content.
Generally, this type of medicinal water is used in balneotherapy for treating musculoskeletal disorders and for post-injury rehabilitation. Additionally, when used as a drinking cure, it can aid in the treatment of cardiovascular diseases and, due to its fluoride content, in the prevention of tooth decay.
Currently, no therapeutic treatments are conducted at the Göd bath; the thermal water is used exclusively for filling the pools and heating the bath building. The use of this medicinal water is permitted for external application only.
Here is the translated table in English:
| Dissolved ion or compound | Strand 1 thermal well | Municipal tap water |
|---|---|---|
| Na⁺ (mg/L) | 96.0 | 19 |
| K⁺ (mg/L) | 11.2 | 2.6 |
| Ca²⁺ (mg/L) | 171.0 | 73 |
| Cl⁻ (mg/L) | 82 | 36 |
| SO₄²⁻ (mg/L) | 125 | 86 |
| HCO₃⁻ (mg/L) | 787 | 250 |
| CO₂ (mg/L) | 614 | – |
| pH | 6.34 | 7.6 |
| Temperature (°C) | 51.3 | 14.4 |
(Source: Szabó, 2009; DMRV, 2017)
Due to its temperature, the water extracted from the well is not suitable for directly filling the pools; it must be cooled. In 2011, the municipal council decided to utilize the heat for heating purposes within the bath area. The net cost of the investment was HUF 9,175,000, and it was completed in 2012.
Previously, domestic hot water production and heating were provided by gas, which amounted to an annual expense of HUF 3.2 million. In the new system, the water drawn from the thermal well passes through heat exchangers located in the boiler house, supplying both domestic hot water production and the heating system. The cooled return water flows into the reservoir that supplies the pools, so no additional water extraction from the thermal well is required.
This solution also reduced the amount of mains water previously used for cooling, resulting in further cost savings. After use, the thermal water is discharged into the municipal sewer system. The temperature of the used thermal water does not pose a significant problem, but its chemical composition causes a considerable mineral load.
According to the Integrated Urban Development Strategy of Göd for 2008–2013, “A portion of the water resource will be utilized as mineral water. Negotiations regarding the location of the bottling plant are ongoing.” [15] The idea of a bottling plant is interesting, if only because Göd’s medicinal water is approved for external use (as bath water), but internal use (for drinking, bottling, or inhalation) is not recommended.
In 2009, considering the planned expansions, the municipality applied for permission to extract an additional 54,000 m³ of thermal water per year, which the Central Danube Valley Environmental and Water Management Directorate rejected. The municipality cited this decision as the reason for the failure of its development plans, even though the same authority had granted permission a year earlier to extract 90,000 m³ annually from the existing K-8 well—after it was revealed that the beach bath had been drawing significantly more water than the previously authorized 30,000 m³/year for years.
It appears that the ambitious plans concerning the bath have since subsided. There is also no visible effort to drill an additional well, although establishing a backup well would be timely. The lifespan of a deep drilled well can be estimated at 40–50 years, and aging issues such as “sand production” and significant yield reduction must be expected. If the well becomes unusable for any reason, it must either be refurbished or replaced by drilling a new well (a so-called side-drilling refurbishment).
The municipality holds a permit to construct a backup thermal well approximately 170 meters west of the current well. According to the permit, the quantity of water extractable from the backup well is 0 m³, and if the backup well is implemented, the combined amount extractable from the current and backup wells must equal the amount currently permitted for the existing well (90,000 m³/year). However, the backup well has not been constructed to this day. To reach the aquifer in question in Göd, a well of approximately 700 meters in depth must be drilled. The estimated cost of drilling such a well at this depth and diameter is about HUF 80 million.
The Veresegyház Bath and Geothermal District Heating
The bath and its connected geothermal heating system are entirely owned and operated by the municipality. The wells are managed by the Gazdasági Műszaki Ellátó Szervezet (GAMESZ), a partially independent institution of the Mayor’s Office.
The system, commissioned in 1993, operates with three production wells and one reinjection well, with a total thermal capacity of 12.1 MWth. The first well, designated B-15, with a bottom depth of 1,462 m, was drilled in 1987. It yielded thermal water with an average temperature of 64 °C, alkaline-hydrocarbonate, chloride-type, and medicinal in character, with a maximum yield of 53 m³/h at the time.
Until 1992, its water was used in a temporary bath, after which the current facility was built on the site of a former student camp, featuring two fill-and-drain system pools. The thermal pool has a water depth of 80 cm and a temperature of 36–38 °C. The shallow, concrete pool is essentially a sitting pool, with a bench running along its sides for sitting; it is not really suitable for swimming.
The composition of water from the B-15 well is similar to that of the Széchenyi Bath water:
| Dissolved ion or compound | B–15 thermal well | Municipal tap water |
|---|---|---|
| Na⁺ (mg/L) | 138.0 | 19 |
| K⁺ (mg/L) | 2.4 | 2.6 |
| Ca²⁺ (mg/L) | 174.0 | 73 |
| Mg²⁺ (mg/L) | 44.7 | 26 |
| Cl⁻ (mg/L) | 82 | 36 |
| F⁻ (mg/L) | 2.9 | – |
| SO₄²⁻ (mg/L) | 155 | 86 |
| HCO₃⁻ (mg/L) | 689 | 250 |
| CO₂ (mg/L) | 425 | – |
| H₂SiO₃ (mg/L) | 63 | – |
| HBO₂ (mg/L) | 3.9 | – |
| pH | 6.4 | 7.6 |
| Temperature (°C) | 64.0 | 14.4 |
(Source: B-15 Expert Report, undated; DMRV, 2017)
The production well is artesian-negative, with the static water level of the thermal water at –33.5 m. For the permitted maximum yield of 100 m³/h, the corresponding water level is –70.0 m. The amount of water that can be extracted for balneological purposes is 103,000 m³/year, while the amount extracted for energy purposes and reinjected is 220,000 m³/year.
The thermal water is pumped from the well using a submersible pump and flows into a horizontal degassing tank. The separated methane gas is not utilized; it is released freely into the atmosphere. From the tank, booster pumps located in the pump house deliver the thermal water via a deep-laid pipeline network to the bath and heat exchange stations [16].
The energy utilization of thermal water began in 1993, when the heating system of the Fő Street Primary School (now Fabriczius) was connected to the thermal water through a heat exchanger. To this day, the school is heated exclusively with thermal energy from the thermal water, resulting in an annual saving equivalent to 100 tons of oil in fossil fuel consumption.
Initially, the cost-effectiveness of the investment for the school was questionable, as was the operability of the system due to the highly corrosive nature of the thermal water. However, after this pilot project delivered positive results, a number of institutions were connected to the system, including the Reformed Parish, the Cinema, the Main Square Business Center, the Innovation Center, the Post Office, the Mission Health Center, the Gyermekliget Kindergarten, the Town Hall, the Retirement Home, the Catholic Church, the Parish, and the Saint Pio Home.
With these additions, the B-15 thermal well reached its capacity limit and could not be further loaded. The next thermal well (K-25) and the necessary system expansion were completed in 2011, and this well had a much higher yield than expected. In 2012, a horticultural investor expressed interest in using thermal water heating, and once again, the capacity of the two wells proved insufficient. Consequently, a third well (K-26) was drilled [17].
What Will Happen to the Budaörs Thermal Well?
In 2006, a thermal water source with a temperature of 46 °C was discovered in Budaörs. The well, with a depth of 1,067 meters, extracts water from the Triassic-age Budaörs Dolomite Formation and has a yield of nearly 800 liters per minute. Laboratory analyses show that the water is of almost the same quality as that of Gellérthegy, containing few dissolved substances and classified as calcium-magnesium-sulfate-hydrogen-carbonate type with fluoride content. The water has significant iron content and, based on its total methane content, falls into category “A” (gas-free).
The purchase of the plot—previously used as an illegal waste dump—by the City of Budaörs was criticized by many and by the city’s mayor, Tamás Wittinghoff, even though the deal was not unfavorable at the time, as the city acquired the land well below market value. When it later turned out that thermal water was present there, it became an exceptionally valuable investment.
Members of the city council intended to use the well water to supply water and heat to the City Sports Hall and Swimming Pool, and some even supported opening a thermal bath and establishing a medicinal water bottling plant.
The well utilizes the thermal karst water body in the Budapest area, whose water balance has long been negative, primarily due to large-scale and initially unregulated water withdrawals for balneological purposes.
A preliminary feasibility study prepared in 2012 assumed that the authorities would only permit additional water withdrawal if the extracted water is reinjected (this was also a requirement for the Veresegyház wells). The study concluded that approximately 2.2 MW of thermal power could be obtained from the water, which would cover 80–90% of the heating needs of the current swimming pool and primary school.
However, the extracted low-temperature thermal water cannot be connected directly to the city’s district heating system; economically, it could only be used for heating residential buildings near the swimming pool, with the inclusion of a heat pump. Still, as in the case of the swimming pool and school, gas boilers would also be needed on colder winter days.
The available thermal water cannot provide heating for nearby shopping centers and industrial facilities because the water temperature is too low. Similarly, for balneological use—such as the potential construction of a leisure bath—the limiting factor remains the issue of water withdrawal and reinjection [18].
Summary
We reviewed three examples of thermal water utilization in towns around Budapest. Göd and Veresegyház lie in the Visegrád–Veresegyház thermal karst area, while Budaörs is located in the thermal karst region around Budapest. The conditions and catchments of these two neighboring areas are very similar, and both are overexploited in terms of thermal water extraction.
In Göd, the municipality and local residents had ambitious plans to expand the thermal bath, but since the authorities did not permit an increase in water withdrawal, these ambitions gradually faded after some dispute. In Veresegyház, the municipality moved toward energy utilization, combined with reinjection of the extracted thermal water, which allowed their plans to be realized. In Budaörs, the developments have not yet been implemented, but here too it is evident that ambitious visions from residents and some municipal representatives are constrained by the limitations of water extraction. The feasibility study commissioned by the Budaörs municipality focuses practically on heat energy utilization.
The biggest issue in thermal water utilization is the lack of sufficient domestic experience and knowledge—apart from a narrow circle of experts—as well as the absence of a unified national concept for the use of renewable energy sources in general and geothermal energy in particular.
The protection of our groundwater reserves, including thermal waters, should receive a much higher priority than is currently the case. In the case of thermal baths located on closed karst reservoirs, water extraction cannot be increased further; for energy purposes, utilization is only possible with reinjection. Water extracted for energy purposes can be reinjected into the thermal layer because its quality does not change during use, which means that future demands will not be restricted from a quantitative perspective.
The revised national River Basin Management Plan (VGT2) also states that the current use of thermal water for energy purposes in Hungary represents wasteful and unacceptable exploitation: of the approximately 50 million m³ of thermal water extracted annually for energy purposes, only about 5–6 million m³ is reinjected underground.
To ensure sustainable thermal water production, a legal solution could be an amendment to the Water Management Act that at least favors partial or complete reinjection over other methods of disposing of used water. The economic multiplier of the water resource fee payable for geothermal energy utilization should be increased.
Given the economic significance of greenhouse and foil vegetable-fruit production, and recognizing agricultural demand for thermal water and geothermal energy, the economic multiplier of the water resource fee payable after geothermal utilization should be increased to at least double the current rate to encourage farmers to reinject water.
Significant assistance for farmers would also include financial and technological support from the state for the construction of reinjection wells. While reinjection is a routine practice in the oil industry, the technology for reinjecting into sandstones could also be improved, primarily by applying more efficient and reliable well-completion technologies.
Refenrences
[1] Szanyi, János, Dr., et al. (eds.) (2008): A komplex geotermikus hasznosítási rendszer és a magyar–szerb termálvízbázis-monitoring. Geotermikus Koordinációs és Innovációs Alapítvány, Szeged. http://www2.sci.u-szeged.hu/geotermika/dokumentumok/magyar-szerb.pdf. Last accessed: 2023-11-20.
[2] Dr. Horváth, József (2011): Megújuló energia. http://www.tankonyvtar.hu/hu/tartalom/tamop425/0021_Megujulo_energia/ch05.html. Last accessed: 2017-12-20.
[3] Kovács, J. és Müller, P. (1980): A Budai hegyek hévizes tevékenységének kialakulása és nyomai. Karszt és Barlang 1980/II., 93-98.
[4] Mádl-Szőnyi, J. & Tóth, Á. (2015): Basin-scale conceptual groundwater flow model for an unconfined and confined thick carbonateregion. Hydrogeology Journal 23, 1359–1380. https://doi.org/10.1007/s10040-015-1274-x Last accessed: 2023-11-20.
[5] Harsh K. Gupta, Sukanta Roy (2012): Geothermal Energy: An Alternative Resource for the 21st Century. https://doi.org/10.1016/B978-0-444-52875-9.X5000-X Last accessed: 2023-11-20.
[6] Website of the Miskolctapolca Cave Bath: https://barlangfurdo.hu/udito-es-gyogyito-termalviz. Last accessed: 2023-11-20.
[7] Szanyi János, Nádor Annamária, Madarász Tamás (2021): A geotermikus energia kutatása és hasznosítása Magyarországon az elmúlt 150 év tükrében. Földtani Közlöny, 151/1, doi: 10.23928/foldt.kozl.2021.151.1.79 Last accessed: 2023-11-20.
[8] Szentes Városi Szolgáltató Kft official website: https://www.szvszkft.hu/kozerdeku-adatok/beszamolok/ Last accessed: 2023-11-20.
[9] Ádók János (2014): Geotermikus fűtési rendszerek – egy működő rendszer tapasztalatai. Hódmezővásárhelyi Vagyonkezelő és Szolgáltató ZRt. https://rekk.hu/downloads/events/tavho_ws_2015_adok_janos.pdf Last accessed: 2023-11-20.
[10] DiPippo, Ronald (2016). Geothermal Power Plants. Principles, Applications, Case Studies and Environmental Impact (4th ed.). Butterworth-Heinemann. p. 203. ISBN 978-0-08-100879-9. https://books.google.hu/books?id=lMkHBgAAQBAJ
[10] Rybach, Ladislaus [László] – Mongillo. Michael (2006): Geothermal sustainability – A review with identified research needs. Geothermal Research Council Transactions, Vol. 30, 2006.
[12] Goda Zoltán (2022): Szerves mikroszennyezők kockázatbecslése a parti szűrésen alapuló ivóvízellátásban. PhD Dissertation, National University of Public Service, Military Engineering Doctoral School.
[13] Gödi Településellátó Szervezet: http://www.goditesz.hu
[14] OTH által elismert gyógyvizek jegyzéke. (2017). Forrás: http://efrirb.antsz.hu:7778/ogyfi/gyogyviz.jsp
[15] Göd Város Integrált Városfejlesztési Stratégiája 2008-2013. (2008). Forrás: http://www.god.hu/onkormanyzat/tervezet/?doc4_op=detail&doc4_fid=1001&doc4_id=27
[16] Dr. Bártfai, Z. (2011). Fürdőgépészeti rendszerek üzemeltetése. Gödöllő: Szent István Egyetem.
[17] Szőke, S. (2016). Veresegyház: új termelő kút, új fogyasztók. Földhő Hírlevél, 52-53. [XIII/1-2.]
[18] Corex Projektfejlesztési Kft (2012): Geotermikus energiahasznosítás Budaörsön. Előzetes megvalósíthatósági tanulmány.