This article focuses on the influence of social geographic factors on possible installation of renewable heating solutions in Serbia. Therefore, it takes in account legacies of post-socialist transitional society. Crucial point of interest is also air pollution which Serbia and neighbouring countries face every winter and which are largely caused by individual heating solutions powered by fossil fuels. Report of Serbian Environmental Protection Agency shows that small and individual heating solutions participate in emitting 57% of PM10 particles, as well as 75% of PM2.5 particles in Serbia [1
]. Their replacement by renewable heating solutions would be an important step in reducing air pollution.
Thus, there are two layers that should be considered. First, most of Serbian households do not have district heating and are therefore suitable terrain for introducing new heating systems. Mainly, those households are located in smaller Serbian towns and rural areas. Second, socio-economic development of Serbia is heterogeneous. This article tends to present results for an average environment which can be representative for other Serbian towns, as well as for countries with similar socio-economic structure. These two stances revealed Ub as a representative case-study for this research. Ub is a town which does not have district heating system, but mostly various individual heating solutions. According to the socio-economic spatial differentiation of Serbia, Ub is a municipality placed around average [2
]. Additionally, on the traditional regional inequality gradients in the Republic of Serbia (These gradients include the following directions: (I) north-south; (II) centre-periphery; (III) and urban areas with closer surroundings—rural areas [2
] (p. 97)) the municipality of Ub, with its geographical location and structural characteristics, is placed between extreme values.
Ub is a small town in Serbia with population of around 6000. The entire Municipality of Ub which includes surrounding settlements has population of just over 29,000. While post-socialist geographical studies mostly address post-socialist capitals and major cities, this article tends to explore post-socialist trajectories in a small (semi-)peripheral town in a transitional environment. The example of Ub shows tendencies which should be applicable to other similar settings.
Accordingly, this article elaborates possible utilization of very shallow geothermal potentials in the field of space (and district) heating. In addition to scientific literature and statistical reports, websites and online reports are used as sources for the purpose of this article. Authors conducted a survey with 40 households in Ub concerning their opinion about actual heating status and potentials for geothermal heating. Such approach was necessary in order to get an actual overview of the situation. Soil analysis was provided by the ThermoMap
] which offered results presented in the article.
After a brief presentation of geothermal energy potentials, as well as district heating systems worldwide and in Serbia, this article focuses on the case-study of Ub. One specific test field in the town of Ub is selected to examine possibilities for utilization of (very) shallow geothermal energy in the terms of heat conductivity. Finally, there is a discussion about the advantages, but also about the limits that must be overcome in order to build and exploit such a system. Results are presented through three level analysis—technical, economic, as well as social and political limitations. Some general courses and patterns, valid for the most transitional cases, are extracted at the end.
2. Energetic Stability and Renewable Energy Sources
Adequate global energy consumption is one of the most important factors for achieving an adequate global average level of quality of life. However, this is not an easy goal to achieve, as the current global energy mix is 80% fossil fuel based [4
]. Such massive dependence of fossil fuels rises issues which are not of newer date such as accessibility to fossil fuel and its uneven distribution, as well as altering the climate [5
]. Fossil fuel is a negative solution for climate with respect to its greenhouse gases emission [6
]. The extraction of fossil fuels is the biggest cause of climate change, which is furthermore not only an environmental issue, but also a social one [7
]. Discussions regarding reducing CO2
emissions and restraining climate change are of global significance, and one of the very important topics the society faces.
It is also crucial to keep stable energetic supply. Renewable energy sources (RES) are considered as a suitable alternative which minimizes environmental impacts and generates minimum secondary waste [8
], as well as offers efficient solution for sustainable development [9
Even though most of energy consumption in the world is provided by fossil fuels [10
], part is still supplied from energy sources such as renewables and nuclear energy [11
]. Nuclear energy is produced without CO2
or methane emission, but is still not a sustainable energy source as it is not clear how to deal with the nuclear waste [12
]. That leaves renewable energy sources as a choice for sustainable energy future [14
]. Reports show that share of renewables in a global energy production is growing every year e.g., [15
]. Renewable energy mix include solar, thermal, photovoltaic, bioenergy, hydro, tidal, wind, wave and geothermal energy [16
As it is always clearer that humans and their actions are the primary cause of climate change (There is almost unanimous consensus regarding this topic among climate scientists. More than 97 percent of them understand that humans are the primary cause of climate change [18
]), renewable energy sources permanently rise the attention of general public, policy makers, as well as scientific community. Renewable energy sources provide energy in different areas. One of their most valuable contribution is in electricity generation [19
]. Technologies regarding storage and supply of electricity got in this way are constantly improving [21
]. Furthermore, solutions including renewable energy and transportation are increasing [24
]. Renewable energy solutions are also contributing in heating and cooling systems [25
According to data of REN21 [15
], participation of renewables in general global energy consumption was around 18%: 7.5% is covered by traditional biomass, while 10.6% is covered by modern renewables. Further division within modern renewables shows that 4.2% of total final energy consumption comes from biomass/solar/geothermal heat, 3.6% hydropower, 2% wind/solar/biomass/geothermal/ocean power and 1% comes from biofuels for transport. The rest is covered from fossil fuels (around 80%) and nuclear energy (around 2%). The share of renewables in total final energy consumption rose in period 2006–2016 for 2.3% (Traditional biomass did not increase its share, while modern renewables increased their share for 4.5%) [15
] (p. 32). Renewable energy is mostly contributing in the sector of power consumption with at around a quarter of total power consumption. Renewables participated with around 10% in total energy used for heating and cooling, as well as with around 3% in the energy used for transport [15
] (pp. 32–33).
3. Geothermal Energy and How Is It Used
Geothermal energy is the energy stored as heat in Earth’s interior [26
]. It can be used in various fields—electrification, space and district heating, space and district cooling, greenhouse heating, in aquaculture and in industry [27
]. Geothermal energy for electricity generation has been produced commercially since 1913, and its utilization increased rapidly in the last decades [10
]. The earliest known commercial use of geothermal energy through district heating system originates from 14th century in Chaudes-Aigues Cantal, France [28
]. Geothermal energy supports agriculture around the world by greenhouse heating [29
Geothermal energy can be captured from different depths and layers of the Earth. Normally, one can make a distinction between deep and shallow geothermal energy [32
] (p. 38). Antics and Sanner [33
] suggest a classification which comprises the following geothermal categories: geothermal power, deep geothermal resources (direct use) and shallow geothermal resources (mainly heat pumps). Shallow geothermal energy is energy acquired from sources on less than 400 m depth [34
]. It is mostly captured from Earth’s layers no deeper than 150 m, and definitely no deeper than 400 m. Layers deeper than 400 m belong to the category of deep geothermal energy [32
] (p. 38). Shallow geothermal energy is a good alternative for fossil fuels in heating and cooling of buildings [35
]. Very shallow geothermal potentials (up to 10 m deep) are gaining more attention in the last years (This layer can be further divided into three depth layers: first (0–3 m), second (3–6 m) and third (6–10 m) [36
] (pp. 227–228)) [36
]. In general, every soil is suitable for very shallow geothermal applications [3
]. Several parameters, such as thermal conductivity of soil, water content, pore size distribution and bulk density, have crucial influence on efficiency of very shallow geothermal applications and create different local potentials related to the prevailing soil conditions [36
Installed thermal power for direct geothermal utilization is growing every year at a compound rate (In the period 2005–2009 it grew at a rate of 11.4% annually) [38
]. Most of geothermal power capacities in 2018 were located in the United States, Indonesia, Philippines, Turkey, New Zealand, Mexico, Italy and Iceland [15
] (pp. 80–83). New capacities in 2018 are installed mostly in Turkey and Indonesia. United States and Iceland are countries which are following. Except Turkey, Italy and Iceland, European countries generally do not use geothermal energy for producing electric power. They use it mostly for heating systems, and shallow geothermal applications are the largest sector of geothermal energy use in Europe [39
Geothermal heating can be used in two ways—as a direct heating, and as indirect heating and cooling via geothermal heat pumps [40
] (p. 341). The direct use of geothermal energy refers to geothermal direct heating plants, geothermal heat in agriculture, geothermal heat in balneology, as well as geothermal heat in other and individual buildings. European countries exploiting most of geothermal direct use in 2018 were Iceland, Italy, Hungary, France and Germany [39
Leading countries using geothermal heat pumps in 2004 were the United States, Sweden, Germany, Switzerland, Canada and Australia, respectively [40
] (p. 345). Ground source heat pumps in Europe in 2018 were mostly installed in Sweden, Germany, France, Finland and Switzerland [39
4. District Heating Systems
District heating systems are efficient and centralized systems for heating residential buildings. They are generally considered to be an ecologically efficient way of heating [41
], and can be also operated by using geothermal sources [42
]. “District Heating (DH) systems provide continuous heating through pipes from heat generators which are located away from individual apartment units” [43
] (p. 73). In addition to district heating, there are also individual heating options [44
District heating systems went through various forms [45
]. As Lund et al. [46
] wrote, there are four generations of district heating. The first generation (1880s–1930s) used steam as the heat carrier. The second generation (1930s–1970s) used pressurised hot water, while the third generation (since 1970s) still used pressurised water as the heat carrier, but often on temperatures below 100 °C. The fourth generation of district heating is characterized by low working temperature and a low heating loss, and aspire to connect to renewable energy resources [47
The number of district heating systems, especially in Northern Europe, is raising since the beginning of the 21st century [48
]. It is estimated that there are around 6000 of such systems in Europe, while those in Iceland are the most representative examples—they cover more than 50% of dwellings, and thanks to a geothermal source they have no CO2
]. Nevertheless, around 13% of EU27 heat market for buildings is covered by district heating systems [50
Still, there are numerous barriers for spreading geothermal district heating systems. As the experiences from the United States showed, most prominent barriers are relatively affordable prices of gas and oil, as well as already developed electricity and fuel delivery infrastructure [51
] (p. 804). Additionally, Thorsteinsson and Tester [51
] (pp. 811–812) distinguish three groups of barriers for its development such as technical, economic and social/political feasibility.
5. Heating Systems and Renewable Energy Solutions in Serbia
After the fall of the Berlin wall, socialistic countries focused on political and economic transition. Part of transition included also the transition of the energy sector, which needed legislation, restructuring, liberalization and privatization, as well as investment [52
]. Indeed, the transition in the energy sector did not contain different elements from those in other sectors. Compared to many other ex-socialist countries, transition in Serbia started later because of complex issues regarding territorial conflicts, civil war, economic embargo and political crisis. Even though transitional process started in 2000, there are still legacies originating from socialist era, as well as new-developed trends from transitional era, which strongly influence actual social, political and economic dynamics in Serbia [53
The biggest part of energy consumption in Serbia goes to residential and commercial buildings with around 46%, and they are followed by industry and transport [55
] (p. 36). Energy in buildings is mostly used for heating (around 62%), followed by energy spent for lighting and warm water [55
] (p. 37).
Many post-socialist countries still rely on district heating systems operating on fuel oil and are built during socialist era [56
]. Cities with a high population density are more favourable places for district heating because of lower distribution costs per household.
“With higher number of heating consumers and a small object density, i.e., large number of apartments per object, district heating system is a better solution”.
It is also expected that post-socialist states reduce plant-level CO2
emission during the transitional process [58
]. Investing in RES can also be motivated by reducing citizens’ energy bills [59
Cost approach was not always considered in socialist states and their former planned economies [49
] (p. 626). Most local heating plants in former Yugoslavia were fuelled by heavy oil and/or natural gas [60
]. District heating systems are present in bigger Serbian cities, while individual heating solutions prevail in small towns [62
]. District heating in Belgrade for instance [63
] is in the phase of renovation and gains the importance again after the turbulent 1990s. Still, district heating systems, not only in Serbia, but in the whole region of Western Balkans, are based on using fossil fuels [64
] (p. 30).
District heating in the Republic of Serbia is used in the bigger urban centres, and is supplied by heat produced by larger heating plants. This heating systems mostly uses coal, wood, oil fuels and gaseous fuels as primary energy source [65
]. District heating plants were built in the socialist era, as a heating solution for growing cities. District heating systems are located in 55 cities, towns and municipalities in Serbia [66
The situation in small Serbian cities is different because they are not dependent on huge heating systems. Their heating structure is very heterogeneous, but also more flexible than in residential complex of big cities. Smaller towns in Serbia, like Ub for instance, do not have such large heating plants, and they are not dependent on district heating systems. Therefore, smaller cities in Serbia are favourable areas for introduction and usage of renewable energy solutions.
According to data from 2002 [67
], dominant energy source for space heating was coal. Around 36% of energy for space heating came from this source. Today natural gas is the most favourable fuel for domestic heating, while traditional fuels dominate in rural and low-income urban households [68
]. Around 22% of occupied dwellings in Serbia are connected to district heating systems, around 21% use central heating, while around 57% are without district and central heating (see Figure 1
). Đurić et al. [55
] (p. 36) wrote that 26% of the households are connected to district heating systems, 30% use electricity for heating, 20% wood, 15% coal, while less than 6% use gas.
Already at the beginning of 21st century it was clear that energy consumption in Serbia is outdated—including low energy efficiency, with high costs, as well as unfavourable influence on the environment and health [69
]. Such findings are still applicable in this region [70
]. Inadequate energetic efficiency of the most houses in Serbia should not be overlooked. Most of the houses have significant heat losses due to unsatisfactory walls, facades, doors and windows [71
“New energy use patterns and technologies need to be adopted if the economy is to grow and poverty is to be reduced”.
Renewable energy solutions have been under discussion as potential solutions in Serbia for some time, but are not yet used in practice at a higher level. For example, in 2012 only 0.1% of Serbian households had installed solar powered domestic hot water systems [72
]. Solar energy development in Serbia dates back to 1970s, but its usage is still limited to not numerous locations [73
]. Potentials of heating systems using geothermal water are not new in Serbia [74
], and geothermal sources could replace significant amount of fossil fuel [75
]. Many articles and researches concerning exploitation of geothermal energy in Serbia are oriented to hydro-thermal potentials [76
]. In general, excluding hydro power (There are two big hydro power production complexes in Serbia [82
]. One is located on the Danube (Hydro power plants Djerdap 1 and Djerdap 2), while the second is on the rivers Drina and Lim (Drinsko-Limske Hydro power plants)), the share of RES in total energy production in Serbia is less than 1% [68
Average age of district heating infrastructure is over 25 years, and the system is based on fossil fuels. There are high heat losses as pipes with 25 years of age cannot have the newest insolation standards too. There are actual plans for reducing the share of liquid fuel and coal, and improving the role of RES [83
6. Ub—Social Geographic and Energetic Overview
Ub is municipality and town in the central part of Serbia. It is located around 60 km south-western from Serbian Capital Belgrade (see Figure 2
). Ub is part of the Kolubara District and is located around 30 km from the Kolubara District’s administrative centre Valjevo. According to the census data from 2011, the municipality population was 29,101 [84
] (p. 60). There were 9176 [85
] (p. 98) households in the municipality, with 3.17 members in average.
According to the same census data, the urban settlement of Ub has a population of 6191 inhabitants [84
] (p. 60). There were 2095 households [85
] (p. 98), with 2.96 average members per household. In the urban settlement there were 2692 [85
] (p. 99) dwellings in total. Only 2078 of them are occupied, while others were temporarily unoccupied, abandoned or used occasionally [86
] (pp. 152–153). The average area of occupied dwelling is around 87 m2
More than half of the municipality’s active workers have agriculture, forestry or fishing as their primary occupation [87
] (p. 122). Other important activities for the local economy are mining, especially lignite mining, as well as manufacturing. According to the data on the official website of the municipality (www.opstinaub.org.rs
), there are huge reserves of lignite in the municipality of Ub. Opening of the open-pit lignite mine is planned in the following years, and should be one of the biggest in Europe.
Available data show that in the municipality of Ub there are 2653 occupied dwellings with central heating, and 6466 occupied dwellings without district and central heating installations [65
] (pp. 36–37). Vast majority of those dwellings use coal and wood for heating. Only energy raw material worth of mentioning beside coal and wood is electricity. Around 5% of dwellings get heating from that source. Other sources are used only by several households. More than 72% of dwellings in the urban settlement of Ub are located in the residential building with one dwelling, around 8% are located in the residential building with two dwellings, while around 20% are in the buildings with three or more dwellings (see Figure 3
). More than 80% of all urban dwellings in Ub are located on the ground floor [88
] (p. 444). A simple look to the facades in the town of Ub shows that many households use air conditioners for cooling and partly heating spaces.
Our survey with the inhabitants of Ub showed that around 73% of the households use wood and coal for heating. The rest use pellet and electricity. An average household in Ub spends around one third of yearly budget only for heating. Doors and windows are in average older than ten years, and it is made mostly of wood and PVC. Around half of the respondents are not satisfied with their insulation, around 40% are satisfied, while around 10% of them do not have insulation (e.g., Figure 4
). Coal and wood heaters cause most of the air pollution in urban areas and are increasing health threats [91
]. Their replacement by sustainable energy solutions should therefore be on the top of the priority lists.
7. Very Shallow Geothermal Potentials of Ub
Geothermal based heating (and cooling) solutions require certain favourable characteristics of the soil. Very shallow geothermal systems for instance require favourable petrophysical parameters realized in thermal heat conductivity of the soil. In order to explore thermal heat conductivity in Ub, the soil was analysed by ThermoMap
Viewer (Results presented in this part of the paper were obtained through ThermoMap
Viewer and its option vSGP Report. ThermoMap
Viewer is available at www.thermomap.eu
was a project funded by European Commission with the aim of mapping the very Shallow Geothermal Potentials (vSGP) in Europe [3
]. It shows that the territory of the urban area of Ub splits almost equally in soil with 1.07 W/(mK) thermal conductivity, and soil with 1.21 W/(mK) thermal conductivity (These values are calculated by using Kersten formulas [93
]) (see Figure 5
One area in the eastern part of the urban area of Ub is located, and chosen as a potential test field (see Figure 6
). This test field is used for the purposes of this article to present an estimated model and show how very shallow geothermal potentials in Ub could be activated. This test field has around 26,000 m2
. It is surrounded by around 90 households, and located on the edge of the urban settlement. Most of the houses on the potential network consist of one or two households. It would make the planning process and eventual connection to the network less complicated, because of less parties involved in a process.
According to ThermoMap,
a slope on the test field which is less than 15° is a favourable condition for very shallow geothermal system in a hydraulic point of view for e.g., horizontal collectors or special forms like heat baskets (see Figure 7
reveals also climatic conditions for the test field (see Table 1
). Mean annual air temperature for the chosen site is 12.08 °C, while annual precipitation is 760 mm with maximal monthly precipitation in June. The nearest official meteorological station of the Serbian Hydrometeorological Service [95
] shows similar results (see Table 1
). Accordingly, climatic conditions of the selected area are favourable for utilization of vSGP—there are humid conditions.
The following results from the ThermoMap
Viewer Report for the Test field in Ub also show no limitations for the utilization of the vSGP. Dominant soil type according to the World Reference Base is Luvisol (“Luvisols have a higher clay content in the subsoil than in the topsoil, as a result of pedogenetic processes (especially clay migration) leading to an argic subsoil horizon. Luvisols have high-activity clays throughout the argic horizon and a high base saturation in the 50–100 cm depth” [96
] (p. 165)). This soil type should not have restrictions regarding the installation of (very) shallow geothermal systems. The dominant grain size distribution is medium according to the European Soil Data Centre (ESDAC) soil texture classification.
Thermal heat conductivity is defined essentially by texture, water content and bulk density of the soil [37
predefines bulk density (relation between mass and volume) for selected area at 1.3 g/m3
. On the basis of humid conditions, a possible thermal conductivity value is 1.07 W/(mK). In general, these petrophysical parameters indicate that the possible test field is suitable for the utilisation of the very shallow geothermal potential in terms of heat conductivity.
It is assumed that average consumption of energy for heating in Serbia is 150 kWh/m3
. Estimation of the Energy Agency of the Republic of Serbia [97
] shows that one household needs an energy of around 9000 kWh annually (For this analysis are taken following characteristics: 60 m2
apartment—average insulation, 180 days of heating, 20 °C during 16 h per day in the whole apartment). If the potential test field in Ub (Figure 6
) would be covered with horizontal collectors, it is assumed that it could receive around 1,300,000 kWh of energy annually (Here is estimated that horizontal collector provides 50 kWh/m2
annually. This estimation is based on relevant literature [98
], as well as our practical experience on various locations). Estimated annual energy heating consumption of 9000 kWh allows an assumption that this field could provide enough energy for heating (and cooling) around 140 households (The calculation is based on the following values: area covered by the test field (26,000 m2
), potential energy provided by the test field if it would be covered by a (very) shallow geothermal system (around 50 kWh/m2
annually or around 1,300,000 kWh in total), as well as estimated annual energy consumption by household (9000 kWh)). Investment in the insulation and improving energetic efficiency of the houses would increase possible number of households in the system’s network.