Keeping us balanced – beyond batteries

Published: 11 June 2020

By Dr Alex Buckman, Networks and Energy Storage Practice Manager, Energy Systems Catapult

Balancing energy supply and demand in a net zero energy system will be a world away from how we balance our current system. Batteries will be important, whether they are in our cars, in our homes or elsewhere – but batteries can’t do it alone.

Energy storage and other flexible technologies can take many forms – everything from the heat stored in the bricks and mortar in our homes to underground gas storage, from liquid fuel in your car to large banks of batteries. Currently, most of the UK’s energy storage is fossil fuel based, and as demand changes, we dispatch more fossil fuels either directly into our homes (e.g. gas into our boilers) or into power stations (e.g. gas into thermal power stations).

Although basic energy services  – such as those that ensure a comfortable home, mobility, the manufacture and transportation of goods  –  will be similar; the types of storage, how we control it and where it is located within our energy system will need to change. We discussed some of these challenges here.

Using Modelling to Understand the Role of Storage and Flexibility

Our new Storage and Flexibility Model is one of the most comprehensive representations of storage and flexibility within net zero energy systems. It lets us compare different storage and flexibility technologies on a level playing field, to see which provide most value to the energy system – no markets, no policies, just the cheapest way to make a reliable net zero energy system.

Whilst we do see an important role for batteries, one of the insights that we’re seeing is the value of those storage and flexibility technologies that are less ‘glamorous’ than lithium-ion batteries – think hot water tanks, medium to long duration thermo-mechanical technologies and gas storage.

Which non-battery technologies have potential?

We’ve taken a deep dive into four technologies that we see as having a high potential impact within future energy systems:

  • Non-battery electricity storage
  • Vehicle-to-Grid
  • Thermal energy storage within heat networks
  • Second-life batteries

In each of the four ‘reports’ for the respective storage types, we carried out a literature review to understand the technology landscape and the policy and regulatory challenges. We then used bespoke models and analysis to explore the potential of each technology. This understanding of the sector is an important prerequisite to incorporating them into our whole energy systems models – such as the Storage and Flexibility Model.

1. Non-Battery Electricity Storage

We assessed a diverse set of non-battery electricity storage technologies before focussing our modelling on those with a medium-long duration. These are. technologies that generally store larger volumes of energy and dispatch this energy over longer durations than batteries typically do.  There are a diverse range of solutions in this space, at a range of technology readiness levels, ranging from traditional pumped hydro to liquid air energy storage.

Some of the key findings from this work were:

  • There is clear value in medium to long duration non-battery electrical storage technologies within a net zero energy system. There are several non-battery storage technologies in development – with no clear frontrunner.
  • The capital costs of non-battery electrical storage need to reduce before it becomes competitive within a least cost energy system.
  • Non-battery electrical storage technologies have several market, policy, and regulatory barriers. Recommendations to remove some of these barriers include:
    • improved capacity market design by reflecting time-limited delivery of storage
    • ensure ancillary services reflect breadth of characteristics of storage technologies and better reflect performance accuracy
    • further improvements in market design flexibility for reserve markets
    • further development and improvement of new markets (e.g. inertia, voltage, network investment deferral).

2. Vehicle to Grid (V2G)

Electric vehicles (EV) are expected to form a big part of a decarbonised energy system – each of which uses a battery instead of a fuel tank. Whilst parked at home or at work, these batteries are not being used, but could be. This report builds upon the V2GB project to assess the potential value of V2G within energy arbitrage markets.

Some of the key findings were:

  • V2G could provide significant value to a Net Zero energy system; providing over 50GWh of flexible capacity by 2050.
  • V2G is most favourable when compared to unmanaged charging of EVs; it can reduce the need for grid-connected electrical storage capacity.
  • The value of V2G is less certain when compared to the benefits of managed charging although V2G does appear to provide additional value by reducing the requirement for grid connected energy storage technologies. This should be investigated further with consideration also given to the other value that V2G could provide over shorter timescales not represented within this modelling.

3. Thermal Energy Storage in Heat Networks

Regardless of where you look, district heat networks (DHNs) are expected to play an increasingly important role within future energy systems. They currently provide about 2% of space heat demand in the UK, but could provide close to 20% by 2050. They can provide low cost heating and, importantly for energy system stability, they can store energy at lower costs than batteries can.

Some of the key findings were:

  • 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.

4. Second Life Batteries

Batteries that are deemed no longer usable within a vehicle face three options: dispose of it, recycle it or re-use it. Re-using them in static storage applications has the potential to extend their usable life whilst reducing whole system costs in expensive electricity storage. This report picks through the practicalities of second life batteries before testing them within a bespoke simulation against other batteries.

Some of the key findings were:

  • The second life battery market could benefit from current lithium ion battery recycling infrastructure being ill-suited (in terms of maturity and cost-effectiveness) to deal with large volumes of retired first life batteries.
  • Second life batteries are likely to be cheaper than new batteries.
  • Other factors, such as EV supply chain, must also be considered. For example, there are unlikely to be enough second life batteries from UK-based EVs to meet peak demand until around 2040.

How can we help you?

Creating a resilient and reliable Net Zero energy system is a huge challenge and will require lots of innovation across a diverse set of storage and flexibility technologies. Many of them already exist, some need to be developed further and there is plenty of scope for new disruptive innovations to challenge our existing thinking. Batteries will be important, but let’s not forget the other forms of energy storage crucial to keeping us balanced in net zero.

Each of the technologies we have explored in this work has shown potential to have disruptive effects on the storage and flexibility sector within a Net Zero energy systems. For each we’ve identified areas for further research and development, and Energy Systems Catapult is keen to work with innovators in these areas to help you: 

  • Understand your potential value to Net Zero energy systems using our modelling tools
  • Frame business models and service propositions to maximise storage value to investors
  • Understand how different energy systems could impact upon your role and deployment strategy