Energy Transition Priorities of Zagreb City Centre – Development vision after the 2020 earthquake

The earthquake on March 22nd caused extensive damage to the Zagreb City Centre largely due to the destruction of chimneys, which then pulled parts of the roofs and facades with them. In addition to the damage being disproportionate to the magnitude of the earthquake, a substantial part of the area called the Lower Town became uninhabitable because the gas was switched off, meaning that heating was disabled.

How to respond to this challenge? Should we be investing in meeting the conditions before the earthquake or can we think of a new and better solution?

Gas has no future in a decarbonized European Union

Natural gas is a fossil fuel that emits greenhouse gases during production, transportation and use. The EU plans to reduce greenhouse gas emissions by 50 to 55 percent by 2030 and achieve climate neutrality by 2050. According to a 1.5 °C compatible trajectory, natural gas will generally have to be pulled out of heating by 2040. This means that we consider natural gas exclusively transitional fuel without giving it a spotlight in the EU’s energy future for heating purposes. As the lifetime of gas equipment is around 20 years, and their decommissioning should be no later than 2040, it is time to invest very judiciously and limitedly into gas.

EU heating and cooling strategy

In its strategy for heating and cooling the EU has recognized that district heating systems (DHS) are the optimal technical solution for densely populated urban areas, as they can be easily decarbonized using waste heat, geothermal and solar energy. It is also necessary to invest in energy and static renovation of buildings.

Zagreb Centre District Heating Project

The Government of the Republic of Croatia and the City of Zagreb need to define, as soon as possible, a common concept of reconstruction of the earthquake distressed area, which is an unprecedented national project, but also an opportunity for generations to make an advanced step. Therefore, as a part of the reconstruction project, a solution for sustainable heating of Upper and Lower Town is proposed. It is necessary to run the hot water through the streets of the Lower and Upper Town (now passing along the edge of the Lower Town), to push the vertices through the stairs, and to set up heat substations in each apartment. The optimal location for a heat substation is where the gas boiler is located in the apartment today, which is why the installation of centralized heating and hot water in the apartment goes further. In case there is no centralized heating installation in the apartment, it should be carried out. The question is which part of the investment to socialize and which to leave to the citizens? Certainly, the investment in street ducts needs to be socialized, the cost of verticals in buildings plus the cost of heat substations can be divided optimally, and the part that would be borne by the tenants could be paid through the future heating costs. For any necessary changes and upgrades to the floor heating and hot water systems, a subsidy should be provided to cover a significant part of this cost. This approach is proposed for all buildings that are undergoing major reconstruction or new construction. For buildings that do not need significant renovation and that will be occupied, a transitional solution in the form of condensing boilers or electric heaters should be planned, but with the prospect of switching to DH as soon as possible and by 2040 at the latest.

What do we suggest?

We got a solution to the chimney issue, partly immediately and partly phase-wise, which will always be a threat in the shaky area where Zagreb was built. We have received a solution to the decarbonization issue and an open opportunity for a valuable investment cycle. Zagreb also lies in large geothermal energy sites – this is a resource that can fully provide heat for the future. This proposal brings a high-quality heating system in the city centre of Zagreb, which is based on domestic energy sources and reduces dependence on energy imports.

In order to ensure a long-term sustainable and secure energy supply in the city centre of Zagreb, it is necessary to build a hot water network (Figure 1 shows the potential distribution of such a network – in green, as well as the possibility of connecting to the existing grid – in blue). The proposed network is only one of the possible options – in this configuration, its total length is 17.4 km, the estimated cost of this configuration could be approximately EUR 15-19 million. The inner centre of Zagreb is an area of ​​an extremely high density of construction and thus the demand for heat, which makes it ideal for the application of such technology. (Figure 2 shows the heat demand in the City of Zagreb, planned and existing main pipelines and pipelines – in blue, and the proposed district heating network for the district of Lower Town – in green).

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Figure 1. Proposal for the expansion of DH network in Lower Town District

Can we finance this?

As a potential source of funding for the preparation phase (study and project documentation), specific objective 4c3 from OPCC may be used. The specific objective relates to increasing the impact of the district heating system, and with minimal changes to the criteria for project selection and redistribution of the total allocation foreseen for the stated objective, the amount needed to finance this project may be reached. The funds for the implementation of this specific objective are foreseen for use through the Integrated Territorial Investment Mechanism, which is already in use in the area of ​​Urban agglomeration Zagreb. At the national level, total allocation for 4c3 (EUR 80 million) can be redistributed under the ITU mechanism. It is also possible to use technical assistance funds (SC10) to prepare the project or combine both specific objectives. The share of the co-financing rate should be determined subsequently, and the project may be co-financed by the heat distribution system operator, HEP Toplinarstvo.

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Figure 2. Heat demand and district heating network in Upper and Lower Town
Figure 3. Heat demand and district heating network – existing, planned and proposed configuration