Decentralised Heating: How Small Batteries Slash Costs and Boost Energy Efficiency

By Antonia Egli and Radhika Deorukhkar (Dublin City University) and edited by Evangelos Bellos, Petros Iliadis, Christos Papalexis, Renos Rotas, Nikos Nikolopoulos, Elias Kosmatopoulos, Christian Halmdienst

Imagine stepping into your home on a cold evening, confident that your heating system is running smarter, not harder. For decades, we’ve relied on large, centralised power sources, including the massive thermal storage tanks that feed district heating networks. These systems are essential to manage energy supply and demand, but they often require significant infrastructure investment. This study on the “Dynamic investigation of centralised and decentralised storage systems for a district heating network” explores a revolutionary alternative: what if the key to a greener, more cost-effective heating future isn’t a giant facility, but a small, smart thermal battery right at your doorstep? This question is vital as countries across Europe push to decarbonise their heat supply and move toward sustainable urban energy solutions.

What Did the Study Investigate in District Heating?

This RINNO study investigates the dynamic performance of different thermal energy storage (TES) strategies within a district heating (DH) network. The network was modelled as being supplied by a biomass boiler, providing heat for residential space heating and domestic hot water (DHW).

The authors compared distinct storage approaches: a traditional Centralised Storage (CS) system with a single large tank and a fully Decentralised Storage (DS) system using novel, small thermal units (‘enerboxx’) installed at each user’s home. Using dynamic energy simulation tools (Modelica/Dymola), the research scrutinised how each setup impacts network operations, focusing intensely on energy consumption, operational costs, and the overall efficiency of the biomass boiler. The findings offer a compelling look at how decentralised storage could fundamentally redesign future district heating infrastructure across the EU and beyond.

What Were the Key Performance Differences?

The system’s reduced thermal losses within the decentralised scenario were found to be largely influenced by a reduction of the mean operating water temperature in the network. The comparison between the centralised and decentralised systems yielded several significant, actionable insights for future district heating design:

• The decentralized storage and control strategy reliably met both space-heating and DHW demand while enabling substantial efficiency gains. By keeping network temperatures near 39 °C for most of the day and separating heating and DHW charging periods, the system cut annual energy use by roughly 11-21%. This approach also smoothed peak loads, limiting high-demand intervals to short charging windows in the morning and afternoon.
  
• Operating temperatures at the dwelling entrance dropped from ~56 °C in the reference setup to ~39 °C in the proposed configuration, rising to ~62 °C only during charging. These lower average temperatures were key to the observed savings and support better scalability across future district-heating generations.
  
• Compared to centralized storage, the decentralized scenario showed 22% lower thermal losses and an 18% lower annual heat demand from the grid. These improvements stemmed directly from the optimised control strategy and reduced mean network temperature.
  
• Seasonally, energy savings peaked in winter at about 21%, falling to around 11% in summer, and remaining near 18% during transitional seasons. This is consistent with the smaller improvement margin when baseline demand is low.

Why Should Utility Companies Invest in Decentralised Heat Storage?

These findings carry significant weight for utility companies, urban planners, and policy makers, particularly in countries like Ireland and across the EU, which are heavily invested in the transition towards greener heat. The traditional model for district heating often demands massive, costly infrastructure upgrades to handle growing urban heat loads and meet mandated efficiency targets.

By adopting decentralised storage, utility companies can achieve two critical goals simultaneously: lower capital expenditure (due to the feasibility of smaller, cheaper pipes) and lower operational expenditure (due to reduced electricity use for pumping). This decentralised model offers a highly scalable solution. Instead of being limited by the size and physical location of a central storage tank, utility providers can roll out the ‘enerboxx’ concept incrementally. This allows for easier connection of new buildings or the retrofitting of existing ones with less disruption and risk.

For example, imagine a large university campus or a new housing development; by integrating these small, smart storage units from the start, the developer can install a cheaper, smaller central plant while maintaining a higher quality of service and lower long-term operating costs for the network operator.

However, the study also highlights a necessary area for future optimisation: the DS system resulted in slightly higher average return temperatures to the central plant (‘50.3°C vs 45.6°C for CS). Future research must focus on further optimising the DS control strategy to lower this return temperature and maximise the benefits across all types of modern networks.

What Is the Ultimate Takeaway from This Research?

The move towards decentralised thermal storage systems represents more than a technical refinement; it is a paradigm shift towards truly smart, flexible, and resilient energy networks. The research clearly indicates that moving the ‘battery’ closer to the user can unlock substantial cost savings and improve the overall system efficiency of district heating, accelerating our vital transition away from reliance on fossil fuels. It shows that sometimes, the biggest, most impactful change comes from thinking small.

Reference:

Bellos, E., Iliadis, P., Papalexis, C., Rotas, R., Nikolopoulos, N., Kosmatopoulos, E. and Halmdienst, C. (2022) ‘Dynamic investigation of centralized and decentralized storage systems for a district heating network’, Journal of Energy Storage, 56, p. 106072. https://doi.org/10.1016/j.est.2022.106072.