INTEGRATE: Integrating seasoNal Thermal storagE with multiple enerGy souRces to decArbonise Thermal Energy

This project evaluates the potential of Seasonal Thermal Energy Storage (STES) systems to facilitate the decarbonisation of heating and cooling while at the same time providing flexibility services for the future net-zero energy system.

The Committee on Climate Change's recent report highlighted that a complete decarbonisation of the building, industry and electricity sectors is required to reach net-zero. Current estimates are that 44% of the total energy demand in the UK is due to heat demand which has large seasonal variations (about 6 times higher in winter compared to summer) and high morning peak ramp-up rates (increase in heat demand is 10 times faster than the increase in electricity demand). Currently, around 80% of the heat is supplied through the natural gas grid which provides the flexibility and capacity to handle the large and fast variations but causes large greenhouse gas emissions. While cooling demand is currently very small in the UK, it is expected to increase significantly: National Grid estimates an increase of up to 100% of summer peak electricity demand due to air conditioning by 2050.

In countries such as Denmark, district energy systems with Seasonal Thermal Energy Storage (STES) are already proving to be affordable and more sustainable alternatives to fossil fuel-based heating that are able to handle the high ramp-up rates and seasonal variations. However, the existing systems are usually designed and operated independently from the wider energy system (electricity, cooling, industry and transport sectors), while it has been shown that the best solution (in terms of emissions reduction and cost) can only be found if all energy sectors are combined and coordinated. In particular, large STES systems which are around 100 times cheaper per installed kWh compared to both electricity and small scale domestic thermal storage, can unlock synergies between heating and cooling demand on one side, and industrial, geothermal and waste heat, and variable renewable electricity generation on the other side. However, the existing systems cannot be directly translated to the UK due to different subsurface characteristics and different wider energy system contexts. In addition, the multi-sector integration is still an open challenge due to the complex and nonlinear interactions between the different sectors.

This project will develop a holistic and integrated design of district energy systems with STES by considering the interplay and coordination between energy supply and demand, seasonal thermal storage characteristics, and regulation and market frameworks. The results and models from the individual areas will be combined in a whole system model for the design and operation of smart district energy systems with STES. The whole system model will be used to develop representative case studies and guidelines for urban, suburban and campus thermal energy systems based around the smart integration of STES systems.

The results will enable the development and deployment of low carbon heating and cooling systems that provide affordable, flexible and reliable thermal energy for the customers while also improving the utilisation of the grid infrastructure and the integration of renewable generation assets and other heat sources.

Scotland and the UK have set targets to reach net-zero by 2045 and 2050, respectively. According to the recent report of the Committee on Climate Change these targets are possible but require a complete decarbonisation of the building, industry and electricity sectors. Currently, around 80% of heat is supplied by natural gas and heating is responsible for around a third of the greenhouse gas emissions in the UK. In addition, cooling demand is expected to rise quickly and could increase the summer peak electricity demand in 2050 by up to 100%.

It is widely accepted that district energy systems need to play an important role in the decarbonisation and that the integration of multiple energy sectors will produce environmental and economic benefits. However, the actual design and operation of these integrated systems is still an open question. The INTEGRATE project will evaluate the interplay between regulation and market frameworks, demand (heating and cooling), storage (short and long term) and different energy sources (some of which are non-dispatchable) and design integrated Seasonal Thermal Energy Storage (STES) systems. This is a first step towards developing and deploying low carbon heating and cooling systems that provide affordable, flexible and reliable thermal energy for the customers while also improving the utilisation of the grid infrastructure and the integration of renewable generation assets and other heat sources.

Environmental, economic and energy benefit: This research enables the development and deployment of Smart Thermal Grids (STG) with STES which are tailored to provide affordable, secure and low carbon thermal energy for the consumers as well as flexibility services for the wider energy system, e.g. use of otherwise curtailed renewable energy. Therefore, this research addresses the energy trilemma: STG with STES enable a better utilisation of renewable generation, and industrial, waste and geothermal heat which increases the energy security and environmental sustainability and reduces the heating and cooling costs.

Society: Policy makers planning for net-zero need accurate information on new low carbon thermal energy technologies. The proposed research will provide guidance on the potential but also on the barriers of STES to act as a vital part of the future, net-zero energy system. In addition, we will develop regulation and market frameworks which facilitate the deployment of these systems. This information will guide policy, regulation and market development and future standards for the integration of STES with multiple energy sources. The general public will benefit from the deployment of integrated STG with STES which will lower emissions (replacement of gas and oil boilers) and reduce costs. This will increase the quality of life through better air quality and more comfortable homes (warmer in winter and cooler in summer).

Commercial and industry benefit: Integrated STES systems are at an early stage of development but are recognised as a technology that could facilitate the transition to net-zero due to the large storage size and low cost compared to other storage technologies. A significant portion of the research has been performed in continental Europe but there are gaps in the integration of STES with multiple energy vectors, subsurface characterisation and design, and development of effective market and regulation frameworks. Taking a lead in these areas can produce clear benefits in terms of international competitiveness. Direct beneficiaries are the industrial companies and organisations supporting the INTEGRATE project as partners. In addition, councils and organisations with large campuses, e.g. universities and NHS, will benefit from the guidelines and case studies in the drive to decarbonise their heating and cooling systems.

Academia: The project will be beneficial for many researchers in thermal energy systems as outlined in the Academic Beneficiaries section.