Thermal Energy Storage

Storing large amounts of energy for long periods of time, so renewables can heat homes.

Last updated: 1st December 2021

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Innovation Lead: Dr Robert Barthorpe

Website:
abc-rp.com/what-we-do/technology/thermal-storage/


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Summary

Heating UK homes accounts for nearly 68 million tonnes of carbon emissions. The electrification of heat, using energy from renewables, is critical if the UK is to achieve its target of being net zero by 2050. But this will place an increased strain on national and local energy networks to balance daily fluctuations in generation and demand. The Active Building Centre Research Programmes is working with teams from Loughborough University and the University of Birmingham, who have thermal energy storage solutions that could deliver the flexibility required for the electrification of heat. These technologies have the potential to reduce energy bills for residents, maximise the utilisation of available renewable sources and reduce pressures on the energy distribution network.

Innovation type: Energy
Organisation type: Research centre

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Project pioneers

Dr Robert Barthorpe heads up the Active Building Centre Research Programmes (ABC-RP) thermal storage work package, bringing together academic collaborators to drive forward innovative new technologies that could enable the decarbonisation of domestic heating.
This project has seen the ABC-RP work with researchers from Loughborough University, led by Professor Philip Eames, developing Phase Change Material (PCM) capable of absorbing and releasing large amounts of energy; and a team at the University of Birmingham, led by Professor Yulong Ding, spearheading the development of Thermochemical technologies to deliver longer-term thermal energy storage.

The problem

UK domestic heating accounts for around 68 million tonnes of carbon emissions per year, with fossil fuel burning boilers producing nitrogen oxides that contribute to smog and ground level ozone in urban areas. Using renewables for electric heating is critical to the UK achieving its target of being net zero by 2050. Because renewable generation doesn't always match the times or seasons when the need for heating is highest, storing this energy is going to be key.
Large-scale storage technologies such as pumped hydropower and electrochemical batteries are hugely capital-intensive, can create distribution issues for grids getting energy from point-of-storage to point-of-use, and may present negative environmental impacts of their own. Distributed domestic storage can play a role in solving these issues. Currently, lithium-ion batteries are the fastest growing technology for this; but they come with limits to the energy that can be stored, significantly reducing performance over the life of the product, concerns over the availability and sustainability of the materials used, and costs that remain stubbornly high.

Vision

Thermal energy storage technologies that can store large amounts of energy for long periods of time can provide the distributed and flexible model needed to electrify heating with renewables, helping the UK achieve its goal of being net zero by 2050. Enabling residents to store energy at off-peak times when prices are low; to meet their daily, weekly and seasonal usage peaks; will reduce their energy bills. Domestic thermal energy storage systems replacing fossil fuel burning boilers, will also reduce the nitrogen oxides that contribute to smog and ground level ozone in urban areas by up to 20%. Distributed thermal energy storage, close to the point-of-use, will help to reduce the need for large-scale, grid-level storage investments; while avoiding some of the downsides of lithium-ion battery technologies.

Key Insight

The team were inspired by the potential for Phase Change Material (PCM) and Thermochemical Storage (TCS) to store large amounts of energy for long periods. The team had a shared belief that these two technologies could play a major role in decarbonising heating, if tailored to domestic use, with the integrated controls needed to operate alongside other assets like heat pumps, electrical storage, and solar photovoltaic-thermal (PV-T) panels.

First step

Independently, the Loughborough University and University of Birmingham teams had made great progress in demonstrating the theoretical potential of their respective thermal storage units. By bringing them together within a large, multidisciplinary research ecosystem, not only were they able to learn from one another, but benefit from the knowledge of other research groups within the ABC-RP consortium. Experts in control engineering have helped the teams understand how their systems can be designed to work within a wider intelligently controlled home energy system. Grid modelling expertise has supported them in demonstrating how distributed thermal storage using the developed modules could reduce energy grid stresses.

Barrier

Commercialising the Phase Change Material (PCM) and Thermochemical Storage (TCS) technologies being developed by Loughborough University and University of Birmingham, required designing modules that work in a domestic setting, potential alongside other technologies in a home energy system. This was critical to try to ensure the adoption that will be needed to provide distributed storage for the grid.

Digital Innovation

Phase Change Material (PCM) is capable of absorbing or releasing large amounts of energy when it moves between a solid and a liquid state. Thermochemical Storage (TCS), which uses reversible thermochemical reactions, has the potential to store heat indefinitely without any losses.
To maximise the benefits of these technologies within the home, integrated control methods are being developed to intelligently manage storage modules alongside generation and conversion technologies, such as heat pumps, electrical storage, and solar photovoltaic-thermal (PV-T) panels. These methods make use of forecasts of user demand and other key variables, like ambient temperatures and PV-T availability, over different timescales. Machine learning plays a valuable role in adapting to key demand parameters, simplifying control for users.  As the modules are developed towards commercial application attention will be paid to the use of communication standards that enable interoperability with existing and future domestic energy systems, for example working to the new PAS 1879:2021 for the demand side response (DSR) activities of energy smart appliances (ESA).

Whole life innovation

PCM and TCS technologies break the link between the instantaneous supply and demand of energy within the home, with energy being stored for when it is needed. As a result of demand shifting (residents using stored energy to meet their usage peaks) and demand side response (shifting energy use through the incentive of lower prices at off-peak times) homes will be cheaper and more carbon-efficient to heat throughout the day and between the seasons. If storage is aggregated across many homes, significant environmental benefits can be achieved. These technologies enable heating to be delivered more efficiently from renewable electricity; while mitigating the need for dirty backup generation, typically diesel generator sets, which contribute significantly to particulate matter (PM) 2.5 emissions. Renewable energy can be stored for when it's needed, avoiding wind and solar curtailment - the deliberate reduction in output, below what could have been produced, in order to balance energy supply and demand or due to transmission constraints. Local distribution constraints can also be overcome, by storing energy closer to where it is needed.
The modular designs of the thermal stores will enable them to be seamlessly integrated into new or existing homes, providing distributed energy storage. This supports the electrification of heat needed for the UK to achieve net zero, while using existing infrastructure, reducing the need for large-scale, grid-level storage investments.

Collaborators

This project has seen the Active Building Centre Research Programmes (ABC-RP) work with researchers from Loughborough University, developing Phase Change Material (PCM) for heat storage, and a team at the University of Birmingham, spearheading the development of Thermochemical Storage (TCS) to deliver longer-term thermal energy storage.
While these teams had made great progress in demonstrating the theoretical potential of their respective thermal storage units; bringing them together within a large, multidisciplinary research ecosystem, enabled them to learn from each other and gain a greater understanding of the wider implications of their work.
By working with research groups within the ABC-RP consortium that have leading expertise in control engineering, they have been able to understand how their energy storage systems may be designed for inclusion within a broader, intelligently controlled home energy system. Other teams within the consortium have been able to contribute grid modelling expertise, demonstrating how distributed thermal storage using the developed modules may enable a reduction in energy grid stresses.

  • University of Birmingham
  • University of Loughborough

Lead support

Active Building Centre Research Programme (ABC-RP) is a large-scale programme that brings the expertise of ten leading UK universities together to solve new and existing energy challenges.
Without the support of ABC-RP, through the Transforming Construction Challenge, the Loughborough University and University of Birmingham teams would not have been able to accelerate the development of their modular technologies, and the cutting-edge research underpinning them, with such pace and scale.

Long Term Vision

Moving to a model where energy is stored close to where it is needed, will address the distribution issue for renewable storage. Using thermal energy storage technologies to deliver this, will provide significant benefits through demand shifting, with residents using stored energy to meet their usage peaks, and demand side response, through the incentive of lower prices at off-peak times.  The modular nature of the solutions being developed will enable the rapid deployment of thermal storage into different domestic settings, providing distributed energy storage to a broad range of UK housing types. This will empower residents to drive down their energy bills by benefiting from off-peak tariffs; while contributing to improved local air quality, by reducing the number of fossil fuel burning boilers. Distributed energy storage of this kind will also support the electrification of heat needed for the UK to achieve net zero; providing the flexibility needed for energy networks to balance daily fluctuations in generation and demand with their existing infrastructure, reducing the need for large-scale, grid-level storage investments.

Human Stories

This project has seen the Active Building Centre Research Programmes (ABC-RP) work with researchers from Loughborough University, led by Professor Philip Eames, developing Phase Change Material (PCM) for heat storage; and a team at the University of Birmingham, led by Professor Yulong Ding, spearheading the development of Thermochemical technologies, to deliver longer-term thermal energy storage.
While these teams had made great progress in demonstrating the theoretical potential of their respective thermal storage units; bringing them together within a large, multidisciplinary research ecosystem, enabled them to learn from one another and gain a greater understanding of the wider implications of their work.
By working with research groups within the ABC-RP consortium that have leading expertise in control engineering, they have been able to understand how their energy storage systems may be designed for inclusion within a broader, intelligently controlled home energy system. Other teams within the consortium have been able to contribute grid modelling expertise, demonstrating how distributed thermal storage using the developed modules may enable a reduction in energy grid stresses.

Powerful Processes

Phase Change Material (PCM) is capable of absorbing or releasing large amounts of energy when the material changes between a solid and a liquid state. Thermochemical Storage (TCS), which uses reversible thermochemical reactions, has the potential to store heat indefinitely without any losses.
In order to maximise the value and benefits of these technologies within the home, integrated control methods are being developed to intelligently manage storage modules alongside generation and conversion technologies, such as heat pumps, electrical storage, and solar photovoltaic-thermal (PV-T) panels. These methods make use of forecasts of user demand and other key variables, like ambient temperatures and PV-T availability, over different timescales. Machine learning plays a valuable role in adapting to key demand parameters, simplifying control for users.  As the modules are developed towards commercial application attention will be paid to the use of communication standards that enable interoperability with existing and future domestic energy systems, for example working to the new PAS 1879:2021 for the demand side response (DSR) activities of energy smart appliances (ESA).

Fascinating Facts

This research project is showing that the distributed deployment of Thermochemical Storage (TCS) and Phase Change Material (PCM) solutions have the potential to act as a catalyst for the decarbonisation of domestic energy consumption by maximising the flexibility of use.
Based on the capacities of the storage systems currently being prototyped, and an estimated deployment in 180,000 homes by 2030 (noting the UK government target of over 60,000 heat pump installations per year from 2025); PCM could deliver a net 1.8GWh  of rapidly deployable thermal energy storage; and TCS could provide a further 25.9GWh of long-term (potentially inter-seasonal) storage. The deployment of these thermal storage technologies could also benefit local air quality, reducing NOx in urban areas by around 20%. 

Benefits

Active Energy
The thermal energy storage technologies being developed improve the capacity to store energy locally providing grid flexibility through deferral of demand. PCM can store energy for hours or days, with much smaller standing losses than traditional hot water stores. Once charged TCS can store thermal energy for days or months with zero standing losses. When combined with smart controls to optimise energy consumption at an individual dwelling level, these technologies can deliver up to 50% energy savings where solar PV is installed.

Cost
Internal modeling has shown that the levelised cost of storage is approximate 8.4 p/kWh and 9.3 p/kWh PA respectively for PCM and TCS when installed in conjunction with a heat pump. This compares to 16.9 p/kWh for a Lithium-Ion battery. Distributed thermal energy storage can present fewer risks and earlier returns for potential investors than large scale grid storage. By reducing the need for the immediate consumption of energy being generated by renewables, it can also improve the cost-effectiveness and attractiveness of these generation technologies which could help to stimulate greater private investment. As well as empowering residents to drive down their energy bills by benefiting from off-peak tariffs, these technologies open up the potential for homeowners to be paid for providing grid flexibility services to distribution network operators (DNOs). For local and national grids, the deployment at scale of distributed energy storage technologies could deliver huge savings by avoiding large-scale investments in centralised generation capacity and the subsequent grid reinforcement costs that come with such projects. For housing developers, there are also potential savings by mitigating connection costs. Research by Newcastle University indicates demand management combined with energy storage can yield up to £140,000 savings for a 500 unit development. 

Emissions
Modeling has also shown that, through smart control , these storage technologies could save 218kgCO2 (PCM) and 210kgCO2 (TCS) per year for a typical semi-detached home by optimising charge/discharge cycles for carbon reduction using grid carbon intensity predictions.

Whole-life Value
Distributed thermal energy storage technologies can:

  • Reduce fuel poverty by enabling cost-effective energy consumption and storage periods
  • Reduce reliance on fossil fuels for homeowners to meet space heating and domestic hot water demand
  • Reduce gas consumption and reliance on gas imports
  • Increase UK research in this area by demonstrating the viability and commercial demand for such innovative technological research
  • Help avoid long consultation times associated with large-scale developments
  • Replace large initial capital investments, particularly challenging given uncertain returns, with sequenced small investments that achieve returns over shorter timescales for smaller developers