Switching the district heating of Szeged to geothermal

Szetav - The city

The municipally owned District Heating Company of Szeged supplies heat and domestic hot water to 27,256 apartments (predominantly in 4-10 storey blocks of housing projects) and 433 public buildings (schools, kindergartens, retail units) in Szeged, Hungary – a city of 162,593 inhabitants near the Hungarian-Serbian-Romanian tri-border. Since 2018 SZETAV and its partners have carried out the largest geothermal district heating overhaul in Europe. When complete, the district heating in Szeged will be 60% less polluting, its energy supply will be local and its operation will be more economical.

Szetav - The company

SZETAV has 3 departments (operations, finance and energy) and 154 employees. The district heating system of Szeged has 23 heating circuits powered by 1-12 mW boilers with 204.17 MW installed capacity, providing an 843,700 GJ/year total energy output to the end-users via 239 heating substations and 215 km’s of subsurface pipelines. Even though the city and its vicinity have exceptional hydrogeological features, and geothermal based bathing, heating and DHW production are all well-established in the region, until very recently 100% imported natural gas has been the sole energy source of the system, making the company the single largest local emitter of CO₂.

Geothermal Energy - Europe

Geothermal energy refers to the inner heat content of the Earth, which originates from the decay of radioactive elements in the core: heat flows towards the surface and presents a great source of energy for us. Geothermal heat and water have been used in bathing and agriculture for a long time – and more recently in district heating systems as well. The main benefits of geothermal heating and cooling are the provision of local, base load and flexible renewable energy, diversification of the energy mix, and protection against volatile fossil fuel prices. There are more than 250 geothermal DH systems in place in Europe.

Geothermal Energy - Southern great plain

Temperature is increasing with respect to depth towards the centre of Earth by 30°C per kilometre on average, but the distribution is not consistent. The ratio of the increase in heat and depth (geothermal gradient) is higher at places where the Earth’s crust is thinner and the heat source is closer to the surface. The Southern Great Plain region is one such place, presenting an excellent opportunity to utilize geothermal energy. Besides balneological and agricultural uses 9 municipalities utilize geothermal energy in their district heating systems in a 50km radius. These systems are based on favourable medium enthalpy resources. Most rely on the doublet or triplet concept (1 production and 1 or 2 injection wells) of heat extraction, with some utilizing the thermal water for heating and for bathing too.

Geothermal Energy - Szeged

Installing geothermal DH systems in areas of high urban density improves project economics, as both resources and demand need to be geographically matched for an economically sound system. For this reason, Szeged is an excellent site for deep geothermal utilization: the city has good geothermal potential, vast heat demand, an existing DH infrastructure, a supporting municipality and a critical mass of grey matter capable of managing and running such projects. In 2015 the City Hall appointed a new expert team to manage SZETAV and to initiate the integration of renewables into district heating. The aim was to reduce the emissions of the gas-powered heating plants, and to improve the economy of the system with the help of renewables. Day-to-day communication with a number of local, regional and national organizations, stakeholders and professionals started: InnoGeo Ltd, GEOSZ Ltd, Geo Hőterm Ltd, Hansa-Kontakt Invest Ltd, Project Admin Ltd (all companies of the Southern Great Plain Thermal Energy Cluster), as well as the Department of Mineralogy, Geochemistry and Petrology of the University of Szeged have advised SZETAV’s management and technical teams on geothermal utilization and renewable project development.

GEOTHERMAL DH IN SZEGED – THE BEGINNINGS

After a few half-hearted attempts at integrating the heat of the Earth into district heating in the 1980’s (and drawing on some long-operating balneological and agricultural systems in and around the city) deep geothermal utilization in Szeged gained real momentum in the early 2000’s. Following a long planning and project development phase, InnoGeo Ltd designed, GEOSZ Ltd built 2 systems that have, since 2013, provided heat for municipal and university buildings in the city centre and in New-Szeged, on the left bank of Tisza. Besides being successful energetical projects in their own right these two developments paved the way for future projects too. They eased the anxieties of the decision makers and the public alike and the lessons learnt while implementing them have come handy for the key players in switching the municipal district heating system of Szeged to geothermal.

Geothermal DH in Szeged - Extraction

Within the framework of the Szeged project 1,700 - 2,000 m deep thermal wells are drilled in the Upper Town, in Odessa housing estate, in the northern part of the city, in Tarján, in Rókus, and in the city centre, to produce 70 m³/h thermal water at 90°C. Altogether 27 new wells are being drilled in the city, 2 drilling rigs are working night and day. 9 of the boreholes being dug will be used as extraction wells.

Geothermal DH in Szeged - Transportation

Extracted water is transported to 9 heating plants via 30 km’s of newly laid pre-insulated pipeline connecting each point of utilisation, ensuring that the heat loss between the stations is minimal. In most cases the pipes run below the surface, deep enough for the ground to have a fairly consistent year-round temperature, which further helps in reducing heat loss.

Geothermal DH in Szeged - Utilization

Once the water is in the heating plant, its heat energy is utilized via heat exchangers. Geothermal water serves as a heating medium, so it does not enter the district heating network, nor is it used as domestic hot water. According to the plans, with the help of deep geothermal energy a total of nearly 20 million m³ of natural gas would be replaced with 606,958 GJ of geothermal energy per annum, reducing the greenhouse gas load of the city of Szeged by 39,299 tons/year, improving air quality and security of supply. Geothermal in the DH will result in saving 595,887 GJ/year (82%) or 17,525,718 m3/year (68%) natural gas, provide 606,958 GJ/year thermal energy in district heating and 39,299 t/year (65%) CO2 emission saving.

Geothermal DH in Szeged - Injection

With its energy content utilized in the heating plants, the fluid is injected back into the reservoir. After being pumped down, the fluid enters the natural water cycle and gets heated up again by the Earth’s heat and may be extracted again. Without injection, geothermal energy would not be a sustainable resource in the long run.

System operation - financing

Geothermal in the DH will result in saving 595,887 GJ/year (82%) or 17,525,718 m³/year (68%) natural gas, provide 536,298 GJ/year thermal energy in district heating and 34,699 t/year (65%) CO2 emission saving.

North town

Basic data

Number of apartments served: 4,049
Number of public institutions served: 76
Heating plants and heating circuits: Észak I/A, Észak I/B

Energy balance before switching to geothermal

Natural gas used: 4,114,458 m³/year
Energy output: 122,076 GJ/year
CO₂ output: 7,936 t

Energy balance with geothermal

Natural gas saved: 81,480 GJ/year, 2,361,739 m³/year
CO₂ emission decreased by: 4,748 t/year
Geothermal energy output: 73,332 GJ/year

Makkoshaza

Basic data

Number of apartments served: 3,033
Number of public institutions served: 17
Heating plants and heating circuits: Makkosháza

Energy balance before switching to geothermal

Natural gas used: 3,076,706 m³/year
Energy output: 91,286 GJ/year
CO₂ output: 5,934 t

Energy balance with geothermal

Natural gas saved: 69,999 GJ/year, 2,028,954 m³/year
CO₂ emission decreased by: 2,028,954 t/year
Geothermal energy output: 63,000 GJ/year

Uptown

Basic data

Number of apartments served: 3,353
Number of public institutions served: 26
Heating plants and heating circuits: Felsőváros II.

Energy balance before switching to geothermal

Natural gas used: 3,355,000 m³/year
Energy output: 93,775 GJ/year
CO₂ output: 6,755 t

Energy balance with geothermal

Natural gas saved: 75,781 GJ/year, 2,228,853 m³/year
CO₂ emission decreased by: 4,416 t/year
Geothermal energy output: 68,203 GJ/year

Odessa

Basic data

Number of apartments served: 2,353
Number of public institutions served: 29
Heating plants and heating circuits: Odessza I. Odessza II.

Energy balance before switching to geothermal

Natural gas used: 2,372,000 m³/year
Energy output: 70,102 GJ/year
CO₂ output: 4,874 t

Energy balance with geothermal

Natural gas saved: 66,030 GJ/year, 1,942,059 m³/year
CO₂ emission decreased by: 3,847.78 t/year
Geothermal energy output: 59,427 GJ/year

Rokus

Basic data

Number of apartments served: 3,253
Number of public institutions served: 33
Heating plants and heating circuits: Rókus

Energy balance before switching to geothermal

Natural gas used: 353,244 m³/year
Energy output: 84,742 GJ/year
CO₂ output: 6,809 t

Energy balance with geothermal

Natural gas saved: 75,555 GJ/year, 2,190,016 m³/year
CO₂ emission decreased by: 4,392 t/year
Geothermal energy output: 67,838 GJ/year

Rokus 2

Basic data

Number of apartments served: 1,747
Number of public institutions served: 37
Heating plants and heating circuits: Rókus

Energy balance before switching to geothermal

Natural gas used: 1,895,892 m³/year
Energy output: 76,251 GJ/year
CO₂ output: 3,657 t

Energy balance with geothermal

Natural gas saved: 19,251 GJ/year, 558,000 m³/year
CO₂ emission decreased by: 4,197.55 t/year
Geothermal energy output: 64,829 GJ/year

Szilleri

Basic data

Number of apartments served: 5,792
Number of public institutions served: 51
Heating plants and heating circuits: Felsőváros I., Tarján III, VIII

Energy balance before switching to geothermal

Natural gas used: 4,598,000 m³/year
Energy output: 127,742 GJ/year
CO₂ output: 9,736 t

Energy balance with geothermal

Natural gas saved: 76,921 GJ/year, 2,262,250 m³/year
CO₂ emission decreased by: 4,482.44 t/year
Geothermal energy output: 69,229 GJ/year

Tarjan

Basic data

Number of apartments served: 3,293
Number of public institutions served: 27
Heating plants and heating circuits: Tarján II. IV, V, VI

Energy balance before switching to geothermal

Natural gas used: 2,899,000 m³/year
Energy output: 81,097 GJ/year
CO₂ output: 5,885 t

Energy balance with geothermal

Natural gas saved: 69,514 GJ/year, 2,044,419 m³/year
CO₂ emission decreased by: 4,050.83 t/year
Geothermal energy output: 62,563 GJ/year

City Centre

Basic data

Number of apartments served: 312 + 600 in the Cedrus apartment complex
Number of public institutions served: 32
Heating plants and heating circuits: Tisza Lajos krt 38, Török u. 3.

Energy balance before switching to geothermal

Natural gas used: 435,894 m³/year
Energy output: 13,301 GJ/year
CO₂ output: 977 t

Energy balance with geothermal

Natural gas saved: 16,635 GJ/year, 489,264 m³/year
CO₂ emission decreased by: 4,575 t/year
Geothermal energy output: 14,968 GJ/year + 55,692 in the Cedrus apartment complex

Research and Development

With dozens of geothermal wells operating in the Southern Great Plain, operators have gained significant knowledge about issues the new systems are likely to encounter. During the exploitation of geothermal energy in the region, the following problems have been often encountered and are therefore likely to affect new systems too:

Corrosion and scaling on the pipeline wall
Clogging of injection wells
Interaction of wells
High methane content of the thermal water
Social concerns

To tackle these and similar issues and to aid operators, a Geothermal District Heating Service Hub is being set up in Szeged (with sister offices opening in Krakow and Bratislava) – these knowledge centres will offer high-level system analysis and consultation for operators of existing and planned geothermal DH systems, enhancing their efficiency and maintaining their sustainability. The Hubs will strive to contribute to reducing the adverse effects of human activities on the environment.

Cooperation with Szeged

With a dedicated pool of professionals, SZETAV and its partners engage in H2020, EEA Interreg and other cooperation, including the ongoing CROWDTHERMAL (SZETAV) and User4GeoEnergy (InnoGeo) projects. Always open for participation in ambitious R&D projects, SZETAV and its partners have made Szeged a popular case study for international consortiums in the field of renewable energies and rightly so: switching the district heating of medium size cities to geothermal is a major step towards a carbon neutral, sustainable Europe.

Green Energy in Szeged

The robust development in Szeged is a great opportunity for interested municipalities, stakeholders, students and researchers to gain first-hand experience of a large-scale RES integration programme, sustainable reservoir management and environmentally responsible, as well as economically sound operational protocols. The developments in Szeged may serve as easy-to-duplicate blueprints for future DH overhauls in Central and Eastern Europe and beyond.