6.9. Battery energy storage systems

A battery energy storage system (BESS) stores electricity in rechargeable batteries. It allows electricity generated from sources such as solar panels or wind farms to be stored when demand is low and released when demand is high. 

By supporting the integration of renewable energy sources, BESS plays an important role in creating a more stable, efficient and sustainable electricity network.  

A typical BESS consists of battery modules, power conversion equipment, and safety features including cooling and fire protection systems. These systems can respond within seconds to changes in energy demand, making them valuable for applications such as: 

• peak shaving (reducing grid energy use during periods of peak grid energy demand to lower costs) 
• load shifting (rescheduling electricity consumption to off-peak hours to lower costs) 
• frequency regulation (balancing electricity supply and demand to keep the grid stable) 
• renewable energy integration (adding in clean power sources such as solar or wind) 
• emergency power supply (an independent source of power that can keep critical devices online) 

Types of BESS

Most current projects incorporating battery storage with public EV charging use lithium iron phosphate (LFP) batteries. This battery chemistry is well suited to the frequent charging and discharging cycles associated with EV charging hubs because it combines safety, long cycle life, thermal stability, and a relatively low cost.  

Containerised battery storage solutions, which are pre-assembled modular units, are generally the best option for medium-to-large charging hubs due to their scalability and high energy capacity.  For smaller charging locations where space is limited, outdoor cabinets or integrated battery and EV charge point devices may be more appropriate.  

Integrated battery storage DC charging infrastructure solutions can charge from the grid at a steady, low power and then rapidly discharge when vehicles require charging. This approach: 

• Can support high-power charging – 50kW+. 
• Enables multiple vehicles to charge simultaneously. 
• Reduces peak demand on the grid. 
• Can help avoid costly grid connection upgrades. 

Where to deploy BESS

Rapid charging hubs where energy supply is constrained 

Battery storage can provide additional power during peak charging periods, enabling rapid and ultra-rapid chargers to operate where local network capacity is limited. This can reduce the need for immediate grid reinforcement.  

Rural trunk road and tourism locations 

Battery storage is particularly beneficial in rural areas where grid infrastructure is less robust. It can support high power EV charging demand without requiring major network upgrades and can improve service reliability for residents and visitors. 

Sites with local renewable generation 

Co-locating battery storage with solar or wind generation and EV charging infrastructure allows excess renewable electricity to be stored and used later for vehicle charging. This can improve the use of renewable energy and reduce energy costs.  

Capacity charges 

Sites with electricity connections above a certain capacity must pay monthly capacity charges levied by the DNO. These charges increase as connection size increases. 

Battery storage can enable charge points to operate at higher power ratings than would otherwise be possible based on grid connection capacity alone. This can reduce the scale of grid reinforcement works required and the associated capacity charges. 

Financial modelling can then be used to assess whether these savings outweigh the capital cost of supplying and installing the battery system. Battery storage can also improve the operational economics of EV charging hubs by reducing peak electricity demand from the grid. 

Compounding benefits 

Battery storage delivers the greatest value when serves multiple purposes. These can include supporting EV charging, storing renewable energy, reducing peak electricity costs, improving energy resilience, and optimising site energy management. 

Where BESS may not be appropriate

Sites with sustained high usage 

Battery storage is generally less effective at locations where chargers see consistently high usage throughout the day. In these circumstances, the battery may be unable to fully recharge between charging sessions, limiting its ability to support EV charging infrastructure operating at its rated capacity.  

Sites with low-power AC charging 

Locations that primarily provide low-power AC charging, such as destination, workplace, or overnight locations, typically have lower peak power requirements and place less strain on the local electricity network. The benefits of energy storage at these site types may be insufficient to justify the additional cost and complexity of a BESS installation.  

Sites that lack capital or space  

Battery storage systems typically require high-cost investments and have large physical footprints. For smaller sites or where budgets are limited, cost and space constraints may outweigh the operational benefits of these systems. 

Sites with readily available grid capacity 

Where the local electricity network already provides sufficient capacity to support current and future charging demand, a BESS may offer limited additional value compared with investing directly in charging infrastructure. 

Very low traffic locations 

At sites with very low charging demand, charging revenue may be too low to deliver a sufficient return on the high investment costs a BESS would require. 

Temporary or short-term charging installations 

Where a charging site is expected to operate for only a limited period, the cost and resources required to deploy a BESS may not be justified unless there are significant grid constraints or additional energy management requirements. 

BESS in Scotland

In Scotland, battery storage can play a significant role in supporting the rollout of public EV charging infrastructure. Particularly in more remote areas where grid capacity is more likely to be constrained, such as in the Highlands and Islands.  

Battery storage allows for faster deployment of charging hubs where grid upgrades are likely to take a long time. Thereby enabling sites to become operational while longer-term network improvements are planned and delivered. In many cases, a BESS can defer or reduce the need for costly grid reinforcement, by providing part of the power required by high-capacity chargers rather than relying solely on an upgraded grid connection. This is especially valuable in Scotland, as the country has many geographically remote areas where network upgrades can be expensive and time-consuming.  

Critically, battery storage can facilitate increased use of Scotland’s abundant wind resource, by creating a buffer between when the energy is generated and when it is used.