District cooling station that uses residual heat (Tartu)

Main sector:

• District energy
• Smart electricity

Overview/Plan:

In the past, the heating system of the pilot area panel buildings was based on district heating networks with heat exchangers in boiler rooms. Hot water was produced locally with individual boilers that used electricity. The new district cooling system that is using residual heat for producing water, which is supplied through the existing district heating network. More specifically, this system is based on a heat pump that, installed to return the flow of the district cooling system, produces heat for the district heating system by using residual heat from cooling.

The district cooling station uses free solar energy from PV panels to cover a part of the cooling system’s energy demand. As such, the use of fossil electric energy for producing hot water with electric boilers is replaced with residual heat and electricity produced by PV panels. The solution meets consumer demands for thermal indoor comfort and domestic hot water while retaining high energy efficiency and share of renewable energy. Piloting this district cooling system is accompanied by an in-depth monitoring application (see more under ICT solutions) based on smart meters that collect real-time data on energy consumption and thus demonstrate the effectiveness of the solution. 

The construction works of Fortum Tartu’s district cooling plant and network were completed in May 2016. The first customer who joined the network was a shopping mall. The plant is located next to river Emajõgi, allowing to use river-cooled chillers that are a part of the high-performance production solution. Water from the river is used for free cooling from October to April.

At the moment, the length of the current district cooling network in the downtown area is about six kilometers. The district cooling project decreases the need of electricity up to 70% annually compared to local cooling solutions. The decrease in electricity use will benefit the environment by reducing CO₂ emissions up to approximately 70%.

Outcome/successful implementation:

The district cooling has been successfully implemented and over 10 km of cooling pipelines have been built in three years. The number of customers is steadily increasing.
Over three years, over 7,000 MWh of cooling energy has been produced and the share of solar energy in the plant's energy consumption has increased.

Business model:

The main industry partner of this solution, AS Fortum Tartu, has a biofuel CHP plant in Tartu that ensures that most of the heat used in district heating is produced from renewable fuels. The total cost of the new cooling system investment is ca. EUR 6.4 million, including a new cooling plant with the capacity of 13 MW. In cooperation with the SmartEnCity project, solar panels were installed to produce electricity from the plant’s own energy needs

Citizen engagement:

Informing the pilot area residents about the renovation activities and discussing any issues with them has been a crucial part of the planning and implementation process. For boosting participation and interest in the project, several measures have been taken into use, including regular information meetings, technical consultations and forum discussions (see more under citizen engagement solutions).

Process:

Benefits:

• Connecting a (commercial) property to the district cooling network removes the need for refrigeration equipment and additional cooling units on rooftops
• Increased resource and energy efficiency
• Transferring thermal energy that is in the wrong place to the place where it is needed
• Increased business reputation from using an environmentally friendly cooling solution
• Job creation
• Autonomy of fossil fuels and independence of energy supply
• Reduction of carbon emissions
• Reduction in the usage of F-gases
• Increase in grid stability
• Stable long-term return on investments

Stakeholders:

Investment/Finance:

Ca. 6.4 million €

Potential for replication:

District cooling systems are very beneficial in areas with dense population and high cooling demand. Besides residential buildings, there are plenty of businesses and shopping centers that all need cooling. In Tartu alone, Fortum has approximately 800 business customers and 75,000 residential customers in district heating who now have the opportunity to benefit from district cooling. The factors that contribute to the solution’s success in Tartu include

• Tartu’s city center is sufficiently populated;
• New buildings ensure the area’s high energy density (ca. 7 kW/m);
• Fortum Tartu owns a riverside property; 

Picture source:
AS Fortum Tartu