Finite element modeling of geothermal source of heat pump in long-term operation

Heat pumps become more and more popular heat source. They can be an alternative choice for obsolete coal fired boilers which are emissive and not ecological. During heat pump installation designing process, especially for heat pumps with higher heating capacity (for example those suppling larger buildings), a simulation of heat balance of ground heat source must be provided. A 3D heat transport model and groundwater flow in the geothermal heat source for heat pump (GSHP) installation was developed in FEFLOW according to Finite Element Modelling Method. The model consists of 25 borehole heat exchangers, arranged with spacing recommended by heat pump branch guidelines. The model consists of both a homogeneous, non-layered domain and a layered domain, which reflected differences in thermal properties of the ground and hydrogeological factors. The initial temperature distribution in the ground was simulating according to conditions typical for Europe in steady state heat flow. Optimal mesh refinement for nodes around borehole heat exchangers were calculated according to Nillert method. The aim of this work is to present influence of geological, hydrogeological factors and borehole arrangement in the energy balance and long term sustainability of the ground source. The thermal changes in the subsurface have been determined for a long term operation (30 years of operation period). Some thermal energy storage applications have also been considered

Main geothermal water resources that can be used in balneology in the Polish Lowlands abstract /

Tyt. z nagłówka.Bibliogr. s. 479.Geothermal waters can be used in two ways: for direct utilisation and for indirect utilization - electricity generation. Direct utilization of geothermal waters is mainly considered for space heating. But geothermal waters could be widely use in balneology and recreation too. The Polish Lowlands covers huge area, which is about 80% of Poland's territory. The most perspective disposable resources of geothermal waters are accumulated in the Lower Jurassic aquifers containing about 1.88E + 18 J/year = 4.48E + 07 TOE/year (TOE -tons of oil equivalent, 1 TOE = 4.18 · 1010 J) (Górecki 2006). The two main types of water occurring in the area are chloride waters, which are the most common and sulphate-sulphide waters, both used in balneology. Geothermal waters when used for balneology must fulfil some specific conditions. Water must contain appropriate chemical composition and TDS level. Also temperature of water for baths is very important and it is determined in connection to human's body temperature. Additionally, waters, which are labelled as healing waters must be accepted by the Ministry of Health. In the Polish Lowlands there are a very few geothermal health resorts, such as Ciechocinek, Konstancin and Grudziądz. There are also a few geothermal recreation and spa centres. However, the possibility of geothermal waters utilization in balneology is much better. Some the most perspective localizations of waters for geothermal balneology are shown in the presentation.Dostępny również w formie drukowanej.KEYWORDS: geothermal waters, Polish Lowlands, geothermal resources

Examples of applications of geothermal waters for recreation, heating and bottling in selected regions of Hungary

Tyt. z nagłówka.Bibliogr. s. 32.Due to the favourable geothermal conditions in Hungary, where the geothermal gradient is about 1.5 times greater than the world average, the country has numerous centers, which use geothermal waters directly for heating, recreation, or bottling purposes. There are plenty of thermal and mineral water springs, most of which were known even 4000 years ago. This article presents different applications of geothermal waters, illustrated with examples of spas, recreation and balneology centers like the largest spa complexes in Europe - Széchenyi Spa and 500 years old Rudas Spa located in Budapest, Egerszalók with unique travertine deposit or Miscolctapolca in the area of Miskolc where a thermal karstic cave system originally carved and dissolved by the water in karstified Triassic limestone was transformed into a complex of geothermal swimming pools. The dynamic development of the geothermal energy uses system in Veresegyház, which total installed thermal capacity is nearly 13 MW with the total track length of 15 km geothermal pipe line, classify the Veresegyház as one of the most extended geothermal systems in Hungary.Dostępny również w formie drukowanej.KEYWORDS: geothermal energy, geothermal waters, geothermal recreation, mineral waters, Hungary

Finite Element Modeling of Geothermal Source of Heat Pump in Long-Term Operation

Model simulation allows to present the time-varying temperature distribution of the ground source for heat pumps. A system of 25 double U-shape borehole heat exchangers (BHEs) in long-term operation and three scenarios were created. In these scenarios, the difference between balanced and non-balanced energy load was considered as well as the influence of the hydrogeological factors on the temperature of the ground source. The aim of the study was to compare different thermal regimes of BHEs operation and examine the influence of small-scale and short-time thermal energy storage on ground source thermal balance. To present the performance of the system according to geological and hydrogeological factors, a Feflow® software (MIKE Powered by DHI Software) was used. The temperature for the scenarios was visualized after 10 and 30 years of the system’s operation. In this paper, a case is presented in which waste thermal energy from space cooling applications during summer months was used to upgrade thermal performance of the ground (geothermal) source of a heat pump. The study shows differences in the temperature in the ground around different Borehole Heat Exchangers. The cold plume from the not-balanced energy scenario is the most developed and might influence the future installations in the vicinity. Moreover, seasonal storage can partially overcome the negative influence of the travel of a cold plume. The most exposed to freezing were BHEs located in the core of the cold plumes. Moreover, the influence of the groundwater flow on the thermal recovery of the several BHEs is visible. The proper energy load of the geothermal source heat pump installation is crucial and it can benefit from small-scale storage. After 30 years of operation, the minimum average temperature at 50 m depth in the system with waste heat from space cooling was 2.1 °C higher than in the system without storage and 1.6 °C higher than in the layered model in which storage was not applied

Examples of applications of geothermal waters for recreation, heating and bottling in selected regions of Hungary

Due to the favourable geothermal conditions in Hungary, where the geothermal gradient is about 1.5 times greater than the world average, the country has numerous centers, which use geothermal waters directly for heating, recreation, or bottling purposes. There are plenty of thermal and mineral water springs, most of which were known even 4000 years ago. This article presents different applications of geothermal waters, illustrated with examples of spas, recreation and balneology centers like the largest spa complexes in Europe - Szechenyi Spa and 500 years old Rudas Spa located in Budapest, Egerszalók with unique travertine deposit or Miscolctapolca in the area of Miskolc where a thermal karstic cave system originally carved and dissolved by the water in karstified Triassic limestone was transformed into a complex of geothermal swimming pools. The dynamic development of the geothermal energy uses system in Veresegyhaz, which total installed thermal capacity is nearly 13 MW with the total track length of 15 km geothermal pipe line, classify the Veresegyhaz as one of the most extended geothermal systems in Hungary

Upgrading a District Heating System by Means of the Integration of Modular Heat Pumps, Geothermal Waters, and PVs for Resilient and Sustainable Urban Energy

Krakow has an extensive district heating network, which is approximately 900 km long. It is the second largest city in terms of the number of inhabitants in Poland, resulting in a high demand for energy—for both heating and cooling. The district heating of the city is based on coal. The paper presents the conception of using the available renewable sources to integrate them into the city’s heating system, increasing the flexibility of the system and its decentralization. An innovative solution of the use of hybrid, modular heat pumps with power dependent on the needs of customers in a given location and combining them with geothermal waters and photovoltaics is presented. The potential of deep geothermal waters is based on two reservoirs built of carbonate rocks, namely Devonian and Upper Jurassic, which mainly consist of dolomite and limestone. The theoretical potential of water intake equal to the nominal heating capacity of a geothermal installation is estimated at 3.3 and 2.0 MW, respectively. Shallow geothermal energy potential varies within the city, reflecting the complex geological structure of the city. Apart from typical borehole heat exchangers (BHEs), the shallower water levels may represent a significant potential source for both heating and cooling by means of water heat pumps. For the heating network, it has been proposed to use modular heat pumps with hybrid sources, which will allow for the flexible development of the network in places previously unavailable or unprofitable. In the case of balancing production and demand, a photovoltaic installation can be an effective and sufficient source of electricity that will cover the annual electricity demand generated by the heat pump installation, when it is used for both heating and cooling. The alternating demand of facilities for heating and cooling energy, caused by changes in the seasons, suggests potential for using seasonal cold and heat storage

Education and research in the field of renewable sources of energy in the Centre Of Sustainable Development And Energy Savings WGGIOS AGH in Miekinia

The Centre of Sustainable Development and Energy Savings of the Faculty of Geology, Geophysics and Environmental Protection of AGH University of Science and Technology in Miekinia conducts research and educational activities in the field of renewable sources of energy, geothermal heat pumps especially. Growing interest in using the renewable energy sources (RES) is reflected upon the interest in such a discipline of studies. Many people declare intention of studying RES. This is a modern discipline, opened at AGH University of Science and Technology in 2003 as the first in Poland. Since 2012, when the Centre was open ca. 8000 people (including students, pupils, local governments and communities) were educated here. Not only geothermal energy is a main focus attention field. In the Centre other renewable sources of energy are also researched. This include solar energy (both photovoltaic and thermal), solid fuel boilers and wind energy. The Centre is heated by heat pumps with ground sources which are simultaneously use by students for practice and measurements. There are didactic heat pumps with temperature and pressure sensors and electric meters to be used by students during measurements. The Centre is in disposal of self-constructed Thermal Response Test device for thermal parameters measurements. In a stand for testing ground-source brine heat pumps for central heating and hot domestic water preparation research are conducted on the COP heat pump efficiency in accordance with the PN-EN 14511 standard. The Centre works on the prototyping of new, innovative heat pumps