Tallinn University of Technology

A recently study shows that the Baltic countries have a huge potential in using rivers, seawater, sewage water treatment plants and industrial excess heat to provide sustainable district heating. The study was conducted by a small group of researchers in the field of smart energy systems from TalTech University, Department of Energy Technology.


The article was published on the Estonian news portal Novaator.

The researchers have developed an online available GIS map containing information about the location and capacity of the mentioned heat sources and existing district heating areas. “In this way, district heating areas can be matched with the most suitable and available heat sources in the area. These sources are then used by large electrically driven heat pumps to provide heat to the local district heating networks,” explains author Henrik Pieper, and continues: “If we want to become carbon neutral in the heating sector, there is no cost-effective way around heat pumps that use renewable electricity.”

The Danish pathway towards climate neutrality

A good example and possible pathway towards climate neutrality is Copenhagen as a city and Denmark as a country, which is described in the case study report of the ESPON LOCATE project. Denmark managed to increase its production of renewable energy from 2000 until 2015 by 72%, from which biomass and wind power were the largest contributors. The consumption of renewable energy has increased by 249% during the same period. This shows that locally produced renewable energy could be used locally using for instance the existing district heating infrastructure. In fact, more than 64% of the Danish citizens are supplied by district heating, enabling the efficient use of biomass to a large degree.

Over the last decade, large heat pumps have experienced an enormous growth in Denmark, because they are seen as the key technology to increase the share of renewable energy sources further. Senior researcher and co-author of the present study, Anna Volkova, explains: “In the Baltic countries, a similar trend as in Denmark can be observed, namely a high share of citizens supplied by district heating and a large share of biomass usage. If a similar pathway as described in the ESPON report for Denmark as a country and for Copenhagen as a major city is followed, the Baltics may be on a good way for a sustainable supply of power and heat.”

Visualisation of heat sources near district heating

In the Baltics, the majority of the residents are also supplied by district heating (62% in EE, 65% in LV, and 58% in LT). In 2018, the share of renewable energy sources in the Baltic states in the heating and cooling sector was 46-56%, which was far more than the EU average of 29%.

For the current study, over 350 high-temperature heat sources from boilers, CHP plants and industrial sites have been identified in the Baltics and their excess heat potential has been quantified. In addition, seawater, rivers, lakes, and sewage water treatment plants were analysed in depth as potential heat sources. The proximity of all of these heat sources to over 350 district heating areas has been analysed to identify synergy regions where heat sources can be used for sustainable heating.

Since no existing database about regions with district heating was available for all Baltic states, it was developed within this project based on geospatial data from settlement units or densely populated areas. “This general data was then filtered according to information about the district heating supply in cities collected over the past years from our research group. Then, we compared the GIS data visualising the district heating areas to the data on the heat demand density areas from the Hotmaps project,” explains PhD student and co-author Kertu Lepiksaar.

The results show that settlement units can well represent district heating areas, in particular in larger cities. In rural areas, the size of the potential district heating area is typically overestimated, because of the large amounts of agricultural and forest land as part of the settlement units.

Pärnu’s untapped heat source potential

Pärnu and its surrounding settlements Sauga, Sindi and Paikuse can be used as an example of how to use the GIS map. In total, nine high-temperature heat sources were identified. One of them, a pellet factory up North with 15.5 GWh of potential excess heat, is located further away. Paikuse has one boiler house that can potentially generate 9 GWh of heat per year from flue gases. All other high-temperature heat sources are in Pärnu, including two sources located on the outskirts of the city: an asphalt factory and a CHP plant. The remaining ones are two additional asphalt factories, a larger fibreboard factory and two boiler houses. Asphalt factories are often out of operation during the winter, making it more difficult to make use of such excess heat sources during times of high demand for heat.

In addition, there are several low-temperature heat sources in and around Pärnu. The large Pärnu river flows through the city and can serve as a heat source for Pärnu, Sindi, and Paikuse. Pärnu is located by the sea, so that district heating could be supplied using also seawater. Moreover, a sewage water treatment plant can serve as a potential heat source for large heat pumps, since it maintains higher temperatures in winter, as opposed to sea and river water. As a result, a higher heat pump performance can be achieved, which results in a lower electricity consumption.

High-temperature excess heat potential in the Baltics

From the 350 high-temperature heat sources in the Baltics, TalTech’s research group identified 13 major industrial sectors. They used available data of primary energy consumption and applied sector-specific factors to calculate the theoretical potential of these sources. In addition, they performed a geospatial analysis to identify the heat sources near district heating areas. “This identified the heat sources we should really look at first, since the piping costs to make use of these heat sources are cheaper,“ says Lepiksaar.  

In Estonia, the chemical industry has an excess heat potential of 1351 GWh. In Lithuania, it has an excess heat potential of 1804 GWh, from which Achema, a massive fertilizer manufacturing plant near Jonava, contributes the most. Other important industrial sectors are: Cement (EE, LV, LT), refineries (EE), wood (EE, LV), asphalt (EE), and food (EE, LV, LT), as well as boilers and CHP plants in all three countries.

Volkova explains: “Considering a maximum proximity of 1 km to areas with district heating, our analysis showed that we can make use of 3.400 GWh/a of excess heat in Estonia, 1.400 GWh annually in Latvia and 2.500 GWh per year in Lithuania. If the full potential is used, around 1/3 of the annual district heating demand will be supplied by these sources. The heat from seawater, river and sewage water plants will come on top.”

The future supply of heat in the Baltics

Currently, all Baltic states have invested in biomass-based plants to provide heating, power or both. In 2018, heat in Estonia, Latvia and Lithuania was produced by 47%, 61% and 80% using biomass. In addition, biomass is also used for other purposes, such as construction inside the countries and as export product abroad. “If we look at the ESPON HyperAtlas REGICO, we can compare the share of forest area to the total land area (ha/ha) per country. In 2018 this ratio was 0.49 in Estonia, 0.39 in Latvia and 0.31 in Lithuania. Since the forest area ratio in Lithuania is much smaller, the biomass usage for different purposes, such as providing heating, should be carefully overseen,“ says Pieper.

Therefore, the usage of biomass for may need to be reduced in the future, but should still play a role in the district heating sector in combination with large heat pumps using a variety of heat sources, such as industrial excess heat, sewage water, rivers and seawater.

This article received funding from the ESPON 2020 Cooperation Programme within the framework of the initiative to support young researchers and dissemination of ESPON results among the scientific community.