District Heat Network (DHN) systems could play an important role in providing heat in a Net Zero energy system.

DHN allow a range of low-carbon heat sources, including renewable energy, heat pumps and otherwise wasted heat from power stations, to be used individually, or in combination in a single network. Thermal Energy Storage (TES) could be used to better match heat supply to heat demand in heat networks, improving the efficiency and flexibility of the DHN.

The Storage and Flexibility: Thermal Energy Storage for Heat Networks report has reviewed existing and innovative thermal storage technologies and investigated policy and regulatory barriers to TES alongside DHNs. An Excel-based modelling tool was developed and used to assess the feasibility of TES in DHNs.

This report is part of the Innovating to Net Zero programme. Energy Systems Catapult has carried out a number of deep dives into the technologies potentially needed to achieve the UK government’s 2050 net zero emissions targets – such as nuclear, digitalisation and storage and flexibility.

Key points

The key findings from Storage and Flexibility: Thermal Energy Storage for Heat Networks analysis are:

• Centrally located thermal energy storage (TES) can provide value to DHNs by reducing the size of heat generation.
• In the example explored, for a centrally based store within a high temperature heat network, sensible heat thermal energy storage (STES) was found to be a cost effective solution. However, at small capacities, the cost difference between STES and latent heat thermal energy storage was small and if space is a premium and/or land value is high, then the higher energy density of phase change material-based storage technologies could make them cost-competitive and/or preferable to STES.
• There is a direct relationship between peaking plant requirement and size of TES, with peaking plant required even at high storage volumes. The cross-vector nature of heat networks means this peaking plant could come from any source, but it needs to be low carbon to be compatible with a net zero energy system.

Barriers to deployment of TES include:

• High investment costs
• Space constraints
• Consumer acceptance

A series of policy recommendations to overcome barriers to TES within DHNs were identified including:

• Increased RD&D support for TES
• Clear guidance and minimum requirements for the design and planning of TES within heat networks
• Improved cross-vector integration of heat and power systems to exploit the link between district heating and the grid offered by certain large-scale technologies e.g. co‑generation of electricity and heat, power‑to‑heat production.