To slow climate change and mitigate its effects, we need to find new ways to make our living environment greener. When it comes to carbon emissions and carbon neutrality, the energy sector has a key role to play, particularly when it comes to heating buildings. For a building as large and architecturally complex and interesting as the TalTech complex, developing an environmentally friendly and fully carbon neutral solution is a challenge. One of the key objectives is finding a carbon neutral heat supply.

When people think of energy, electricity and solar panels as a green energy technology come to mind. Nevertheless, electricity accounts for only 15% of the total energy consumption of buildings in the EU. On the other hand, the energy used for heating accounts for as much as 63%, and the energy used for hot water production (which is also thermal in nature) accounts for 15% of the total energy consumption of buildings. Thus, heat production accounts for as much as 78% of the total energy consumption of buildings in the European Union.

We found several options

The campus of TalTech has previously been heated by a natural gas boiler plant located on the territory of the university, which is certainly not compatible with TalTech’s climate and carbon neutrality goals, and therefore, a search began for more environmentally friendly solutions for providing heat. There are 26 buildings on the university campus, 12 of which were previously heated by the boiler plant of the university. The university campus is comparable in size and heat consumption to some of the smaller settlements in Estonia, so making its heating system more energy-efficient and carbon-neutral has significant implications. A number of options were identified for meeting the heating requirements of the campus and different scenarios were developed. Among the different options analysed, the most technically feasible and environmentally friendly option was to connect the campus to the district heating network of the city of Tallinn. Connecting the university to the district heating network was not particularly complicated, as no additional piping or other facilities had to be built for the connection. District heating also benefits from the fact that most of the district heating of Tallinn is green, with three wood chip-fuelled combined heat and power (CHP) plants and one waste-fuelled CHP plant. Only 29% of the city’s total heat is produced by boiler plants using natural gas or shale oil.

Collaboration with Finnish researchers paid off

In order to further increase energy savings, researchers Anna Volkova, Eduard Latõšov, and Kertu Lepiksaar from the TalTech Research Group of Smart District Heating Systems of the Department of Energy Technology together with Aalto University researchers Pauli Hiltunen and Sanna Syri analysed different ways for connecting the university to the district heating network. The solutions found, along with their pros and cons, are described in greater detail in the article ‘Transition towards university campus carbon neutrality by connecting to city district heating network’, published in the prestigious scientific journal Energy Reports. This cooperation was made possible by the international smart city development programme FinEst Centre for Smart Cities. The research article written as a result of the cooperation analysed in detail the impact of different district heating temperature levels on primary energy savings.

Energy cascade solution

One option would be to use low-temperature district heating at the university through an energy cascade solution, as described in more detail here. In this case, the heat used for heating the campus comes mainly from the return flow of the large district heating network with a little water from the upstream flow of the large district heating network mixed in at the mixing node to achieve the right temperature. This way, it is possible to move a step further towards a universal low-temperature district heating network and achieve significant primary energy savings.

However, the downside of this solution is that the entire campus would also need to be ready to use low-temperature heating, which would require most buildings to make significant energy efficiency improvements and reconstruct their internal heating systems.

Another option analysed in the article was to connect the campus to the district heating network of the city in the classic manner. This is technologically the easiest way for establishing a connection and it will also produce around 70% less of carbon emissions.

Overall, district heating reduced the carbon emissions of the campus as well as the cost of keeping the campus warm. In addition, merging the systems will also have a positive impact on the district heating network of Tallinn and the nearby Mustamäe CHP plant.