Demystifying Battery Storage: How these systems power up the UK

Written By: The Field Team
Posted 03 Oct 2023
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This is the second instalment of our series Demystifying Battery Storage. This fast-growing industry is vital for the energy transition and reaching net zero carbon emissions. But we’re aware that as an industry, it has its fair share of technical jargon.

The first post in this series explained the main principles of how one of our battery storage sites works, and some of the key terms used when describing them. Now, it’s time to explore how these systems contribute to powering the UK, and to lowering carbon emissions.

How do battery storage sites power the UK?

In many ways, the battery storage systems we operate work along similar principles to the AA or AAA batteries you use at home. Only, instead of using our batteries to power a single torch, TV remote or toy car, we use them to provide electricity to thousands of homes and businesses at once.

In particular, our storage sites are designed to fill gaps in the UK’s electricity supply when wind levels are low or the sun doesn’t shine. At these times, our batteries release the electricity stored to meet electricity demand. This ensures plenty of energy is available for people to make their morning cuppa, even on an overcast, calm winter’s day.

Our batteries also help ensure that more of the renewable electricity wind and solar farms produce is stored, rather than wasted when there's an excess of supply. At the moment, the electricity grid often has to turn down supplies from renewable sites because energy isn’t needed at that particular moment.

So, we charge our batteries up at these times (when energy is plentiful), releasing it later (when energy is more in demand and supply is lower). The more storage we build, the more effective wind and solar farms become. And the less electricity we need to generate by burning fossil fuels.

To show how this works in practise, here’s what an average day might look like at one of our sites:


What else can batteries do?

Battery storage isn’t just a one-trick pony. Batteries also provide critical services to the electricity grid that help it function effectively and efficiently. These Ancillary Services, as they’re known, help keep the grid stable and maintain a constant, predictable supply of electricity.

A good example of this is called Frequency Response. To operate effectively, the electricity grid needs to be maintained within a specific frequency rate (there’s a good explanation of this here). The constant changes in electricity demand across the UK mean this frequency varies constantly.

Frequency Response is when a battery storage site quickly adjusts the level of its power output onto the grid in response to these variations. Our batteries can either absorb or release electricity based on what the grid needs at any given moment. This helps keep the whole system stable and lowers the risk of power cuts.

How can batteries cut energy bills?

Electricity is like any other market for goods and services. When there’s excess supply, prices fall. And when there’s excess demand, prices rise. Our batteries charge up when there’s excess electricity supply - usually on a sunny or windy day when renewables generate excess energy. They then discharge when demand surges, providing extra electricity when it’s most needed.

This kind of energy arbitrage will reduce electricity bills over time and improve the overall efficiency of the grid. The more storage capacity we build, the more excess, cheap electricity supply can be captured and then released at times of expensive, peak demand. In some ways, it’s no different to stocking up on something at the supermarket when it’s on special offer, only to use it down the line when you’re ready to.

This idea of energy arbitrage is starting to be offered by domestic energy companies as well. Some suppliers now offer customers tariffs that set a lower cost per unit of electricity at off-peak times of the day. By delaying energy-intensive activities in the house until this point (using the washing machine for example), households take advantage of cheaper electricity.

How powerful are our energy storage systems?

The measure of the capacity of a battery storage system uses two terms: megawatt-hour (MWh) and megawatt (MW).

  • A megawatt is a simple measure of power - a million watts or 1,000 kilowatts.
  • A megawatt-hour is a unit of energy - one megawatt, for an hour, or the same as 1,000 kilowatt-hours (kWh). You may be familiar with kWh as that’s the unit you will see on your electricity meter when you check it at home, or when the bill comes through.

Field’s Newport site, which is currently in construction, is a 40 MWh site. When fully charged, this means it has enough capacity to supply power to 80,000 homes for one hour. In practice, the actual number of homes it supplies during that hour will vary depending on a variety of factors.

For example, if a surge of people pop their kettles on before Eastenders while others are in the middle of cooking dinner, they’ll collectively need more power.

Feeling demystified?

Battery energy storage systems are going to be a key part of reducing carbon emissions from electricity usage, and over time, lowering electricity bills as well. Hopefully, this article and the previous one we posted, have given a good sense of exactly how this technology works and why it’s a vital part of reaching net zero.