Application of Thermal Batteries in district heating systems

The HeatTank Intelligent Thermal Battery has been integrated into the secondary system of an existing substation, where it can serve the heating and domestic hot water needs.

Sizing parameters:

· Maximum heating power demand: 50 kW,

· Base load: 15 kW,

· Variable load: 35 kW,

Data of the installed Thermal Battery:

· Capacity: 60 kWh

· Maximum performance: 200 kW

· External volume: 1,84 m3

· Connection size: DN 42

· Total weight: 1316 kg

With the Thermal Battery, we examined the following benefits: increasing peak output/reducing peak load, optimizing heat sources, improving supply security and availability, reducing heat losses, and enabling intermittent operation.

Peak shaving

Without a Thermal Battery, the district heating system must continuously meet the instantaneous demand. In the daily distribution of domestic hot water (DHW) demand, the experience is that the district heating system must meet to higher peak demands in the morning and evening.

By integrating a Thermal Battery into the system, peak loads can be reduced, and the district heating system only needs to provide a base load. During peak demand, the Thermal Battery and the district heating system together meet the requirements. When there is no peak demand, the Thermal Battery can be charged and regenerated.

The diagram shows that with the help of a Thermal Battery, the peak demand can be reduced from 50 kW to 22.5 kW.

Heat source optimization

With a Thermal Battery, the mix of heat sources can be optimized, meaning the share of non-controllable renewable energy sources (such as solar energy, intermittently available industrial waste heat, heat pumps, etc.) can be increased. From an economic perspective, the mix of heat sources can be optimized based on unit costs, thus avoiding the operation of expensive peak heat sources.

The diagram shows that the Thermal Battery was charged from a source that was available during the day (solar energy, industrial waste heat, heat pump operated more efficiently than at night).

Increasing supply security and availability

In the event of a failure in the primary system, the Thermal Battery ensures the necessary heating/DHW demand. This security is particularly important in industrial processes and social institutions. With Thermal Battery, penalties due to outages can be avoided, as well as the risk of consumers leaving the system due to dissatisfaction.

Reducing heat losses and intermittent operation of substations

During continuous heat supply, the heat loss remains nearly constant (the heat loss is proportional to the difference between the temperature of the water flowing through the district heating pipes and the external air temperature). In the case where a substation is disconnected from the system and the demands are met using the integrated Thermal Battery, the flow of water in the primary branch can be stopped (since the substation no longer requires heat energy from the primary system). The temperature of the water in the pipe starts to decrease, and its heat loss becomes progressively smaller. When the flow is restarted, a heating loss occurs, but this is negligible compared to the saved thermal energy.